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  • richardmitnick 9:13 am on September 24, 2022 Permalink | Reply
    Tags: "Star Light Star Bright … But Exactly How Bright?", , , , , , Standard candles, , Type 1A supernovae   

    From The National Institute of Standards and Technology: “Star Light Star Bright … But Exactly How Bright?” 

    From The National Institute of Standards and Technology

    9.22.22

    Technical Contacts

    Susana Deustua
    susana.deustua@nist.gov
    (301) 975-3763

    John T. Woodward IV
    john.woodward@nist.gov
    (301) 975-5495

    1
    NIST researcher John Woodward with the four-inch telescope used to calibrate the luminosity of nearby stars.
    Credit: C. Suplee/NIST.

    2
    Astronomers use the brightness of a type of exploding star known as a Type 1A supernova (seen here as bright blue dot to the left of a remote spiral galaxy) to determine the age and expansion rate of the universe. New calibrations of the luminosity of nearby stars, observed by NIST researchers, could help astronomers refine their measurements.
    Credit: J. DePasquale (STScI), M. Kornmesser and M. Zamani (ESA/Hubble), A. Riess (STScI/JHU)NASA, ESA, and the SH0ES team, and the Digitized Sky Survey.

    3
    The four-inch telescope on Mt. Hopkins in Arizona. Credit: J. Woodward/NIST.

    4
    Side view of the telescope undergoing testing in the laboratory. Credit: C. Suplee/NIST.

    A picture may be worth a thousand words, but for astronomers, simply recording images of stars and galaxies isn’t enough. To measure the true size and absolute brightness (luminosity) of heavenly bodies, astronomers need to accurately gauge the distance to these objects. To do so, the researchers rely on “standard candles”– stars whose luminosities are so well known that they act like light bulbs of known wattage.

    One way to determine a star’s distance from Earth is to compare how bright the star appears in the sky to its luminosity.

    But even standard candles need to be calibrated. For more than a decade, scientists at the National Institute of Standards and Technology (NIST) have been working to improve the methods for calibrating standard stars. They observed two nearby bright stars, Vega and Sirius, in order to calibrate their luminosity over a range of visible-light wavelengths. The researchers are now completing their analysis and plan to release the calibration data to astronomers within the next 12 months.

    The calibration data could aid astronomers who use more distant standard candles–exploded stars known as type Ia supernovas–to determine the age and expansion rate of the universe. (Comparing the brightness of remote type Ia supernovas to nearby ones led to the Nobel-prize winning discovery that the expansion of the universe is not slowing down, as expected, but is actually speeding up.)

    ______________________________________________________________________________

    4 October 2011

    The Royal Swedish Academy of Sciences has decided to award the Nobel Prize in Physics for 2011

    with one half to

    Saul Perlmutter
    The Supernova Cosmology Project
    The DOE’s Lawrence Berkeley National Laboratory and The University of California-Berkeley,

    and the other half jointly to

    Brian P. SchmidtThe High-z Supernova Search Team, The Australian National University, Weston Creek, Australia.

    and

    Adam G. Riess

    The High-z Supernova Search Team,The Johns Hopkins University and The Space Telescope Science Institute, Baltimore, MD.

    Written in the stars

    “Some say the world will end in fire, some say in ice…” *

    What will be the final destiny of the Universe? Probably it will end in ice, if we are to believe this year’s Nobel Laureates in Physics. They have studied several dozen exploding stars, called supernovae, and discovered that the Universe is expanding at an ever-accelerating rate. The discovery came as a complete surprise even to the Laureates themselves.

    In 1998, cosmology was shaken at its foundations as two research teams presented their findings. Headed by Saul Perlmutter, one of the teams had set to work in 1988. Brian Schmidt headed another team, launched at the end of 1994, where Adam Riess was to play a crucial role.

    The research teams raced to map the Universe by locating the most distant supernovae. More sophisticated telescopes on the ground and in space, as well as more powerful computers and new digital imaging sensors (CCD, Nobel Prize in Physics in 2009), opened the possibility in the 1990s to add more pieces to the cosmological puzzle.

    The teams used a particular kind of supernova, called Type 1a supernova. It is an explosion of an old compact star that is as heavy as the Sun but as small as the Earth. A single such supernova can emit as much light as a whole galaxy. All in all, the two research teams found over 50 distant supernovae whose light was weaker than expected – this was a sign that the expansion of the Universe was accelerating. The potential pitfalls had been numerous, and the scientists found reassurance in the fact that both groups had reached the same astonishing conclusion.

    For almost a century, the Universe has been known to be expanding as a consequence of the Big Bang about 14 billion years ago. However, the discovery that this expansion is accelerating is astounding. If the expansion will continue to speed up the Universe will end in ice.

    The acceleration is thought to be driven by dark energy, but what that dark energy is remains an enigma – perhaps the greatest in physics today. What is known is that dark energy constitutes about three quarters of the Universe. Therefore the findings of the 2011 Nobel Laureates in Physics have helped to unveil a Universe that to a large extent is unknown to science. And everything is possible again.

    *Robert Frost, Fire and Ice, 1920
    ______________________________________________________________________________

    Astronomers may be able to use the NIST calibrations of Vega and Sirius to better compare the brightness of nearby and faraway type Ia supernovas, leading to more accurate measurements of the expansion of the universe and its age.

    In the ongoing NIST study, scientists observe the two nearby stars with a four-inch telescope they designed and placed atop Mount Hopkins in the desert of southern Arizona.

    John Woodward, Susana Deustua, and their colleagues have repeatedly observed the spectra, or colors, of light emitted by Vega (25 light-years away) and Sirius (8.6 light-years). One light-year, the distance that light travels through a vacuum is one year, is 9.46 trillion kilometers.

    At the beginning and end of each observing night, the researchers tilt the telescope downwards so that they can compare the stellar spectra to that of an artificial star–a quartz lamp whose luminosity has been exactly measured and placed 100 meters from the telescope.

    Before the scientists can directly make the comparisons, they must account for the effect of Earth’s atmosphere, which scatters and absorbs some of the starlight before it can reach the telescope. Although light from the ground-based lamp does not travel through the full depth of the atmosphere, some of it is scattered by air during its short, horizontal journey to the telescope.

    To assess how much of the ground-based light is scattered from the lamp, the NIST team measures the relative ratio of power generated by a helium-neon laser at its output and 100 m away, at the site of the lamp.

    To determine how much starlight is lost to the Earth’s atmosphere, the researchers record the amount of starlight reaching the telescope as it points in different directions, peering through different thicknesses of the atmosphere during the night. Changes in the amount of light recorded by the telescope as the night progresses allow astronomers to correct for the atmospheric absorption.

    Once Vega and Sirius are calibrated, astronomers can use those stars as steppingstones to calibrate the light from other stars. For instance, by using the same telescope, researchers can observe a set of slightly fainter stars—call them Set 2. The luminosity of those fainter stars can then be calibrated using Vega and Sirius as reference standards.

    Switching to a telescope large enough to observe both the newly calibrated Set 2, and a group of even fainter stars (call them Set 3), astronomers can calibrate the light from Set 3 in terms of Set 2. Astronomers can repeat the process as needed to calibrate light from extremely remote stars. In this way, astronomers will be able to transfer the NIST calibration of Vega and Sirius to stars that lie thousands to millions of light-years away.

    Next year, Deustua and Woodward will move their small telescope, now back at NIST, to the European Southern Observatory’s (ESO’s) Paranal Observatory in the high-altitude desert of northern Chile.

    With drier climate than Mt. Hopkins, the Chilean site promises more clear nights to observe Sirius and Vega and less moisture to absorb or scatter the light. The telescope will reside on a mountaintop away from ESO’s Very Large Telescope, a suite of four 8.2-m telescopes and four 1.2-m telescopes, so that the light from NIST’s quartz lamp won’t interfere with observations of distant galaxies.

    The team also plans to expand its repertoire of bright nearby stars to include Arcturus (37 light-years), Gamma Crucis (89 light-years), and Gamma Trianguli Australis (184 light-years) and to observe stars at longer, infrared wavelengths. The recently launched James Webb Space Telescope and the Roman Space Telescope, set for launch by the end of the decade, are designed to examine the universe at these wavelengths.

    The NIST researchers recently received seed money to build a larger telescope which could observe and calibrate fainter, more distant stars. That would allow astronomers to transfer the NIST calibration to remote standard candles more directly. Reducing the number of steppingstones between the stars observed by NIST and the stars astronomers are studying reduces calibration errors.

    See the full article here.

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    NIST Campus, Gaitherberg, MD.

    The National Institute of Standards and Technology‘s Mission, Vision, Core Competencies, and Core Values

    Mission

    To promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security and improve our quality of life.

    NIST’s vision

    NIST will be the world’s leader in creating critical measurement solutions and promoting equitable standards. Our efforts stimulate innovation, foster industrial competitiveness, and improve the quality of life.

    NIST’s core competencies

    Measurement science
    Rigorous traceability
    Development and use of standards

    NIST’s core values

    NIST is an organization with strong values, reflected both in our history and our current work. NIST leadership and staff will uphold these values to ensure a high performing environment that is safe and respectful of all.

    Perseverance: We take the long view, planning the future with scientific knowledge and imagination to ensure continued impact and relevance for our stakeholders.
    Integrity: We are ethical, honest, independent, and provide an objective perspective.
    Inclusivity: We work collaboratively to harness the diversity of people and ideas, both inside and outside of NIST, to attain the best solutions to multidisciplinary challenges.
    Excellence: We apply rigor and critical thinking to achieve world-class results and continuous improvement in everything we do.

    Background

    The Articles of Confederation, ratified by the colonies in 1781, contained the clause, “The United States in Congress assembled shall also have the sole and exclusive right and power of regulating the alloy and value of coin struck by their own authority, or by that of the respective states—fixing the standards of weights and measures throughout the United States”. Article 1, section 8, of the Constitution of the United States (1789), transferred this power to Congress; “The Congress shall have power…To coin money, regulate the value thereof, and of foreign coin, and fix the standard of weights and measures”.

    In January 1790, President George Washington, in his first annual message to Congress stated that, “Uniformity in the currency, weights, and measures of the United States is an object of great importance, and will, I am persuaded, be duly attended to”, and ordered Secretary of State Thomas Jefferson to prepare a plan for Establishing Uniformity in the Coinage, Weights, and Measures of the United States, afterwards referred to as the Jefferson report. On October 25, 1791, Washington appealed a third time to Congress, “A uniformity of the weights and measures of the country is among the important objects submitted to you by the Constitution and if it can be derived from a standard at once invariable and universal, must be no less honorable to the public council than conducive to the public convenience”, but it was not until 1838, that a uniform set of standards was worked out. In 1821, John Quincy Adams had declared “Weights and measures may be ranked among the necessities of life to every individual of human society”.

    From 1830 until 1901, the role of overseeing weights and measures was carried out by the Office of Standard Weights and Measures, which was part of the U.S. Coast and Geodetic Survey in the Department of the Treasury.

    Bureau of Standards

    In 1901 in response to a bill proposed by Congressman James H. Southard (R- Ohio) the National Bureau of Standards was founded with the mandate to provide standard weights and measures and to serve as the national physical laboratory for the United States. (Southard had previously sponsored a bill for metric conversion of the United States.)

    President Theodore Roosevelt appointed Samuel W. Stratton as the first director. The budget for the first year of operation was $40,000. The Bureau took custody of the copies of the kilogram and meter bars that were the standards for US measures, and set up a program to provide metrology services for United States scientific and commercial users. A laboratory site was constructed in Washington DC (US) and instruments were acquired from the national physical laboratories of Europe. In addition to weights and measures the Bureau developed instruments for electrical units and for measurement of light. In 1905 a meeting was called that would be the first National Conference on Weights and Measures.

    Initially conceived as purely a metrology agency the Bureau of Standards was directed by Herbert Hoover to set up divisions to develop commercial standards for materials and products. Some of these standards were for products intended for government use; but product standards also affected private-sector consumption. Quality standards were developed for products including some types of clothing; automobile brake systems and headlamps; antifreeze; and electrical safety. During World War I, the Bureau worked on multiple problems related to war production even operating its own facility to produce optical glass when European supplies were cut off. Between the wars Harry Diamond of the Bureau developed a blind approach radio aircraft landing system. During World War II military research and development was carried out including development of radio propagation forecast methods; the proximity fuze and the standardized airframe used originally for Project Pigeon; and shortly afterwards the autonomously radar-guided Bat anti-ship guided bomb and the Kingfisher family of torpedo-carrying missiles.

    In 1948, financed by the United States Air Force the Bureau began design and construction of SEAC: the Standards Eastern Automatic Computer. The computer went into operation in May 1950 using a combination of vacuum tubes and solid-state diode logic. About the same time the Standards Western Automatic Computer, was built at the Los Angeles office of the NBS by Harry Huskey and used for research there. A mobile version- DYSEAC- was built for the Signal Corps in 1954.

    Due to a changing mission, the “National Bureau of Standards” became the “ The National Institute of Standards and Technology” in 1988.

    Following September 11, 2001, NIST conducted the official investigation into the collapse of the World Trade Center buildings.

    Organization

    NIST is headquartered in Gaithersburg, Maryland, and operates a facility in Boulder, Colorado, which was dedicated by President Eisenhower in 1954. NIST’s activities are organized into laboratory programs and extramural programs. Effective October 1, 2010, NIST was realigned by reducing the number of NIST laboratory units from ten to six. NIST Laboratories include:

    Communications Technology Laboratory (CTL)
    Engineering Laboratory (EL)
    Information Technology Laboratory (ITL)
    Center for Neutron Research (NCNR)
    Material Measurement Laboratory (MML)
    Physical Measurement Laboratory (PML)

    Extramural programs include:

    Hollings Manufacturing Extension Partnership (MEP), a nationwide network of centers to assist small and mid-sized manufacturers to create and retain jobs, improve efficiencies, and minimize waste through process improvements and to increase market penetration with innovation and growth strategies;
    Technology Innovation Program (TIP), a grant program where NIST and industry partners cost share the early-stage development of innovative but high-risk technologies;
    Baldrige Performance Excellence Program, which administers the Malcolm Baldrige National Quality Award, the nation’s highest award for performance and business excellence.

    NIST’s Boulder laboratories are best known for NIST‑F1 which houses an atomic clock.

    NIST‑F1 serves as the source of the nation’s official time. From its measurement of the natural resonance frequency of cesium—which defines the second—NIST broadcasts time signals via longwave radio station WWVB near Fort Collins in Colorado, and shortwave radio stations WWV and WWVH, located near Fort Collins and Kekaha in Hawai’i, respectively.

    NIST also operates a neutron science user facility: the NIST Center for Neutron Research (NCNR).

    The NCNR provides scientists access to a variety of neutron scattering instruments which they use in many research fields (materials science; fuel cells; biotechnology etc.).

    The SURF III Synchrotron Ultraviolet Radiation Facility is a source of synchrotron radiation in continuous operation since 1961.

    SURF III now serves as the US national standard for source-based radiometry throughout the generalized optical spectrum. All NASA-borne extreme-ultraviolet observation instruments have been calibrated at SURF since the 1970s, and SURF is used for measurement and characterization of systems for extreme ultraviolet lithography.

    The Center for Nanoscale Science and Technology performs research in nanotechnology, both through internal research efforts and by running a user-accessible cleanroom nanomanufacturing facility.

    This “NanoFab” is equipped with tools for lithographic patterning and imaging (e.g., electron microscopes and atomic force microscopes).
    Committees

    NIST has seven standing committees:

    Technical Guidelines Development Committee (TGDC)
    Advisory Committee on Earthquake Hazards Reduction (ACEHR)
    National Construction Safety Team Advisory Committee (NCST Advisory Committee)
    Information Security and Privacy Advisory Board (ISPAB)
    Visiting Committee on Advanced Technology (VCAT)
    Board of Overseers for the Malcolm Baldrige National Quality Award (MBNQA Board of Overseers)
    Manufacturing Extension Partnership National Advisory Board (MEPNAB)

    Measurements and standards

    As part of its mission, NIST supplies industry, academia, government, and other users with over 1,300 Standard Reference Materials (SRMs). These artifacts are certified as having specific characteristics or component content, used as calibration standards for measuring equipment and procedures, quality control benchmarks for industrial processes, and experimental control samples.

    Handbook 44

    NIST publishes the Handbook 44 each year after the annual meeting of the National Conference on Weights and Measures (NCWM). Each edition is developed through cooperation of the Committee on Specifications and Tolerances of the NCWM and the Weights and Measures Division (WMD) of the NIST. The purpose of the book is a partial fulfillment of the statutory responsibility for “cooperation with the states in securing uniformity of weights and measures laws and methods of inspection”.

    NIST has been publishing various forms of what is now the Handbook 44 since 1918 and began publication under the current name in 1949. The 2010 edition conforms to the concept of the primary use of the SI (metric) measurements recommended by the Omnibus Foreign Trade and Competitiveness Act of 1988.

     
  • richardmitnick 1:39 pm on August 3, 2021 Permalink | Reply
    Tags: "Newly discovered planetary nebulae could improve cosmic distance measurements", A planetary nebula occurs at the end of a star’s red giant phase when helium has been exhausted and can no-longer be fused to create carbon and oxygen., , , , DELF: differential emission-line filter, , , PNLF could help soon help astronomers solve one of cosmology’s most troubling puzzles: the Hubble Tension., PNLF: planetary nebula luminosity function, Standard candles, The Hubble tension: mismatch between the local rate of expansion using standard candles and the value that is calculated using the lambda-cold-dark-matter (ΛCDM) model of cosmology.   

    From physicsworld.com (UK) : “Newly discovered planetary nebulae could improve cosmic distance measurements” 

    From physicsworld.com (UK)

    02 Aug 2021
    Hamish Johnston

    1
    Eye on the universe: the planetary nebula NGC 7294, or the “Helix Nebula”, is nearby in the Milky Way. However, astronomers have managed to observe similar objects at much greater distances. (Courtesy: National Aeronautics Space Agency (US), National Optical Astronomy Observatory (US), European Space Agency [Agence spatiale européenne][Europäische Weltraumorganisation](EU), the Hubble Helix Nebula Team, M Meixner (Space Telescope Science Institute (US)), and TA Rector (National Radio Astronomy Observatory (US))

    Planetary nebulae as far away as 40 Mpc (about 130 million light–years) have been observed by astronomers for the first time. The objects had been too distant to see until an international team of astronomers used a new filter on data from the Multi-Unit Spectroscopic Explorer (MUSE) instrument – which operates on European Space Agency’s Very Large Telescope (VLT).

    The team was led by Martin Roth at the Leibniz Institute for Astrophysics [Leibniz-Institut für Astrophysik] (DE) in Potsdam, Germany and it applied a differential emission-line filter (DELF) to archival data collected by MUSE. This revealed 15 planetary nebulae that were previously too faint to be seen. The technique could prove to be a useful tool for studying the cosmos and could even help resolve a mystery about the expansion of the universe.

    “Planetary nebulae are like Swiss Army Knives for extragalactic study,” says team member Robin Ciardullo at Penn State University(US). “You can use them to learn about stellar dynamics, dark matter, stellar evolution, galactic chemical evolution, the history of galaxy clusters and, of course, measure extragalactic distances.”

    Shedding layers

    A planetary nebula occurs at the end of a star’s red giant phase when helium has been exhausted and can no-longer be fused to create carbon and oxygen. At this point, a star that began life at less than 8 solar-masses will shed its outer layers leaving behind a stellar core surrounded by a cloud of material. Eventually, the star will become a white dwarf.

    Light emitted by the star will ionize atoms in the cloud, freeing electrons that can then collide with electrons still bound in atoms, kicking them up to higher energy states. When these bound electrons decay to lower energy states they emit light at very specific wavelengths.

    “Now that its outside is gone, the star is very hot. The high-energy light from the star slams into the material that just came off the star and lights it up,” explains Ciardullo. “We see what the star ejected into space — the ‘planetary nebula’. It is a terrible name since it has nothing at all to do with planets!”

    Standard candles

    It is the uniformity of the light emitted by planetary nebulae that make them excellent yardsticks for the measurement of extragalactic distances. Such yardsticks are known as standard candles because they have known luminosities and therefore their distances can be inferred from how bright they appear in the sky.

    Standard Candles to measure age and distance of the universe

    Along with George Jacoby and Holland Ford, Ciardullo introduced the planetary nebula luminosity function (PNLF) in 1989 and it has been used as a distance indicator for galaxies up to around 15 Mpc ever since.

    Using planetary nebulae to look further than about 15 Mpc had not been possible because the luminosity of objects drops as the square of the distance, making more distant objects significantly fainter and therefore harder to observe. Now, however, the application of DELF and the power of MUSE/ VLT has extended this limit considerably allowing precision distance measurements to be made for galaxies up to around 40 Mpc.

    Bigger and better

    “By the turn of the century, we had explored planetary nebulae in nearby galaxies and had pushed the PNLF distance measurement technique about as far into the universe as we could,” says Ciardullo. “Now telescopes are bigger, and the instrumentation is better. Observations that were extremely difficult 20 years ago are trivial, and we can extend the technique out to much larger distances”

    With this boost, PNLF could help soon help astronomers solve one of cosmology’s most troubling puzzles. This is the apparent mismatch between the local rate of expansion of the universe that astronomers observe using standard candles and the value that is calculated using the lambda-cold-dark-matter (ΛCDM) model of cosmology. Dubbed the Hubble Tension, resolving this discrepancy could point to new physics beyond the ΛCDM.

    Lamda Cold Dark Matter Accerated Expansion of The universe http scinotions.com the-cosmic-inflation-suggests-the-existence-of-parallel-universes. Credit: Alex Mittelmann.

    The idea is to use planetary nebulae as a complementary distance measurement to other standard candles.

    “One way to address [the Hubble tension] is to double-check the local measurements with other precision ways of measuring distances,” explains Ciardullo. “Until now, planetary nebulae were not bright enough to observe deep enough into the universe to test this tension. Our [research] shows that with MUSE and the VLT, we can get to these necessary distances.”

    The observations are described The Astrophysical Journal.

    See the full article here .


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    Please help promote STEM in your local schools.

    a href=”http://www.stemedcoalition.org/”>Stem Education Coalition

    PhysicsWorld(UK) is a publication of the Institute of Physics(UK). The Institute of Physics is a leading scientific society. We are a charitable organisation with a worldwide membership of more than 50,000, working together to advance physics education, research and application.

    We engage with policymakers and the general public to develop awareness and understanding of the value of physics and, through IOP Publishing, we are world leaders in professional scientific communications.
    IOP Institute of Physics

     
  • richardmitnick 9:54 pm on April 29, 2021 Permalink | Reply
    Tags: "Black hole-neutron star collisions may settle dispute over Universe’s expansion", , , , , , Standard candles,   

    From University College London (UK) : “Black hole-neutron star collisions may settle dispute over Universe’s expansion” 

    UCL bloc

    From University College London (UK)

    28 April 2021

    Mark Greaves
    +44 (0)7990 675947
    m.greaves@ucl.ac.uk

    Studying the violent collisions of black holes and neutron stars may soon provide a new measurement of the Universe’s expansion rate, helping to resolve a long-standing dispute, suggests a new simulation study led by researchers at University College London (UK).

    1
    A black hole and star. Credit: iStock / Pitris.

    Our two current best ways of estimating the Universe’s rate of expansion – measuring the brightness and speed of pulsating and exploding stars, and looking at fluctuations in radiation from the early Universe – give very different answers, suggesting our theory of the Universe may be wrong.

    A third type of measurement, looking at the explosions of light and ripples in the fabric of space caused by black hole-neutron star collisions, should help to resolve this disagreement and clarify whether our theory of the Universe needs rewriting.

    The new study, published in Physical Review Letters, simulated 25,000 scenarios of black holes and neutron stars colliding, aiming to see how many would likely be detected by instruments on Earth in the mid- to late-2020s.

    The researchers found that, by 2030, instruments on Earth could sense ripples in space-time caused by up to 3,000 such collisions, and that for around 100 of these events, telescopes would also see accompanying explosions of light.

    They concluded that this would be enough data to provide a new, completely independent measurement of the Universe’s rate of expansion, precise and reliable enough to confirm or deny the need for new physics.

    Lead author Dr Stephen Feeney (UCL Physics & Astronomy) said: “A neutron star is a dead star, created when a very large star explodes and then collapses, and it is incredibly dense – typically 10 miles across but with a mass up to twice that of our Sun. Its collision with a black hole is a cataclysmic event, causing ripples of space-time, known as gravitational waves, that we can now detect on Earth with observatories like LIGO and Virgo.

    Caltech/MIT Advanced aLigo at Hanford, WA(US), Livingston, LA(US) and VIRGO Gravitational Wave interferometer, near Pisa(IT).

    “We have not yet detected light from these collisions. But advances in the sensitivity of equipment detecting gravitational waves, together with new detectors in India and Japan, will lead to a huge leap forward in terms of how many of these types of events we can detect. It is incredibly exciting and should open up a new era for astrophysics.”

    To calculate the Universe’s rate of expansion, known as the Hubble constant, astrophysicists need to know the distance of astronomical objects from Earth as well as the speed at which they are moving away. Analysing gravitational waves tells us how far away a collision is, leaving only the speed to be determined.

    To tell how fast the galaxy hosting a collision is moving away, we look at the “redshift” of light – that is, how the wavelength of light produced by a source has been stretched by its motion.

    Explosions of light that may accompany these collisions would help us pinpoint the galaxy where the collision happened, allowing researchers to combine measurements of distance and measurements of redshift in that galaxy.

    Dr Feeney said: “Computer models of these cataclysmic events are incomplete and this study should provide extra motivation to improve them. If our assumptions are correct, many of these collisions will not produce explosions that we can detect – the black hole will swallow the star without leaving a trace. But in some cases a smaller black hole may first rip apart a neutron star before swallowing it, potentially leaving matter outside the hole that emits electromagnetic radiation.”

    Co-author Professor Hiranya Peiris (UCL Physics & Astronomy and Stockholm University [Stockholms universitet](SE)) said: “The disagreement over the Hubble constant is one of the biggest mysteries in cosmology. In addition to helping us unravel this puzzle, the spacetime ripples from these cataclysmic events open a new window on the universe. We can anticipate many exciting discoveries in the coming decade.”

    Gravitational waves are detected at two observatories in the United States (the LIGO Labs), one in Italy (Virgo), and one in Japan (KAGRA). A fifth observatory, LIGO-India, is now under construction.

    Our two best current estimates of the Universe’s expansion are 67 kilometres per second per megaparsec (3.26 million light years) and 74 kilometres per second per megaparsec. The first is derived from analysing the cosmic microwave background [CMB], the radiation left over from the Big Bang, while the second comes from comparing stars at different distances from Earth – specifically Cepheids, which have variable brightness, and exploding stars called type Ia supernovae.

    Dr Feeney explained: “As the microwave background measurement needs a complete theory of the Universe to be made but the stellar method does not, the disagreement offers tantalising evidence of new physics beyond our current understanding. Before we can make such claims, however, we need confirmation of the disagreement from completely independent observations – we believe these can be provided through black hole-neutron star collisions.”

    The study was carried out by researchers at UCL, Imperial College London (UK), Stockholm University and the University of Amsterdam [Universiteit van Amsterdam] (NL). It was supported by the Royal Society, the Swedish Research Council (VR), the Knut and Alice Wallenberg Foundation, and the Netherlands Organisation for Scientific Research (NWO).

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    UCL campus

    University College London (UK) is a public research university located in London, United Kingdom, and a member institution of the federal University of London(UK). It is the largest university in the United Kingdom by total enrollment apart from the Open University, and the largest by postgraduate enrollment.

    Established in 1826, as London University by founders inspired by the radical ideas of Jeremy Bentham, UCL was the first university institution to be established in London, and the first in England to be entirely secular and to admit students regardless of their religion. University College London (UK) also makes contested claims to being the third-oldest university in England and the first to admit women. In 1836, University College London (UK) became one of the two founding colleges of the University of London, which was granted a royal charter in the same year. It has grown through mergers, including with the Institute of Ophthalmology (in 1995); the Institute of Neurology (in 1997); the Royal Free Hospital Medical School (in 1998); the Eastman Dental Institute (in 1999); the School of Slavonic and East European Studies (in 1999); the School of Pharmacy (in 2012) and the Institute of Education (in 2014).

    University College London (UK) has its main campus in the Bloomsbury area of central London, with a number of institutes and teaching hospitals elsewhere in central London and satellite campuses in Queen Elizabeth Olympic Park in Stratford, east London and in Doha, Qatar. University College London (UK) is organised into 11 constituent faculties, within which there are over 100 departments, institutes and research centres. University College London (UK) operates several museums and collections in a wide range of fields, including the Petrie Museum of Egyptian Archaeology and the Grant Museum of Zoology and Comparative Anatomy, and administers the annual Orwell Prize in political writing. In 2019/20, UCL had around 43,840 students and 16,400 staff (including around 7,100 academic staff and 840 professors) and had a total income of £1.54 billion, of which £468 million was from research grants and contracts.

    University College London (UK) is a member of numerous academic organisations, including the Russell Group(UK) and the League of European Research Universities, and is part of UCL Partners, the world’s largest academic health science centre, and is considered part of the “golden triangle” of elite, research-intensive universities in England.

    University College London (UK) has many notable alumni, including the respective “Fathers of the Nation” of India; Kenya and Mauritius; the founders of Ghana; modern Japan; Nigeria; the inventor of the telephone; and one of the co-discoverers of the structure of DNA. UCL academics discovered five of the naturally occurring noble gases; discovered hormones; invented the vacuum tube; and made several foundational advances in modern statistics. As of 2020, 34 Nobel Prize winners and 3 Fields medalists have been affiliated with UCL as alumni, faculty or researchers.

    History

    University College London (UK) was founded on 11 February 1826 under the name London University, as an alternative to the Anglican universities of the University of Oxford(UK) and University of Cambridge(UK). London University’s first Warden was Leonard Horner, who was the first scientist to head a British university.

    Despite the commonly held belief that the philosopher Jeremy Bentham was the founder of University College London (UK), his direct involvement was limited to the purchase of share No. 633, at a cost of £100 paid in nine installments between December 1826 and January 1830. In 1828 he did nominate a friend to sit on the council, and in 1827 attempted to have his disciple John Bowring appointed as the first professor of English or History, but on both occasions his candidates were unsuccessful. This suggests that while his ideas may have been influential, he himself was less so. However, Bentham is today commonly regarded as the “spiritual father” of University College London (UK), as his radical ideas on education and society were the inspiration to the institution’s founders, particularly the Scotsmen James Mill (1773–1836) and Henry Brougham (1778–1868).

    In 1827, the Chair of Political Economy at London University was created, with John Ramsay McCulloch as the first incumbent, establishing one of the first departments of economics in England. In 1828 the university became the first in England to offer English as a subject and the teaching of Classics and medicine began. In 1830, London University founded the London University School, which would later become University College School. In 1833, the university appointed Alexander Maconochie, Secretary to the Royal Geographical Society, as the first professor of geography in the British Isles. In 1834, University College Hospital (originally North London Hospital) opened as a teaching hospital for the university’s medical school.

    1836 to 1900 – University College, London

    In 1836, London University was incorporated by royal charter under the name University College, London. On the same day, the University of London was created by royal charter as a degree-awarding examining board for students from affiliated schools and colleges, with University College and King’s College, London being named in the charter as the first two affiliates.[23]

    The Slade School of Fine Art was founded as part of University College in 1871, following a bequest from Felix Slade.

    In 1878, the University College London (UK) gained a supplemental charter making it the first British university to be allowed to award degrees to women. The same year University College London (UK) admitted women to the faculties of Arts and Law and of Science, although women remained barred from the faculties of Engineering and of Medicine (with the exception of courses on public health and hygiene). While University College London (UK) claims to have been the first university in England to admit women on equal terms to men, from 1878, the University of Bristol(UK) also makes this claim, having admitted women from its foundation (as a college) in 1876. Armstrong College, a predecessor institution of Newcastle University (UK), also allowed women to enter from its foundation in 1871, although none actually enrolled until 1881. Women were finally admitted to medical studies during the First World War in 1917, although limitations were placed on their numbers after the war ended.

    In 1898, Sir William Ramsay discovered the elements krypton; neon; and xenon whilst professor of chemistry at University College London (UK).

    1900 to 1976 – University of London, University College

    In 1900, the University College London (UK) was reconstituted as a federal university with new statutes drawn up under the University of London Act 1898. UCL, along with a number of other colleges in London, became a school of the University of London. While most of the constituent institutions retained their autonomy, University College London (UK) was merged into the University in 1907 under the University College London (Transfer) Act 1905 and lost its legal independence. Its formal name became University College London (UK), University College, although for most informal and external purposes the name “University College, London” (or the initialism UCL) was still used.

    1900 also saw the decision to appoint a salaried head of the college. The first incumbent was Carey Foster, who served as Principal (as the post was originally titled) from 1900 to 1904. He was succeeded by Gregory Foster (no relation), and in 1906 the title was changed to Provost to avoid confusion with the Principal of the University of London. Gregory Foster remained in post until 1929. In 1906, the Cruciform Building was opened as the new home for University College Hospital.

    As it acknowledged and apologized for in 2021, University College London (UK) played “a fundamental role in the development, propagation and legitimisation of eugenics” during the first half of the 20th century. Among the prominent eugenicists who taught at University College London (UK) were Francis Galton, who coined the term “eugenics”, and Karl Pearson, and eugenics conferences were held at UCL until 2017.

    sustained considerable bomb damage during the Second World War, including the complete destruction of the Great Hall and the Carey Foster Physics Laboratory. Fires gutted the library and destroyed much of the main building, including the dome. The departments were dispersed across the country to Aberystwyth; Bangor; Gwynedd; University of Cambridge (UK) ; University of Oxford (UK); Rothamsted near Harpenden; Hertfordshire; and Sheffield, with the administration at Stanstead Bury near Ware, Hertfordshire. The first UCL student magazine, Pi, was published for the first time on 21 February 1946. The Institute of Jewish Studies relocated to UCL in 1959.

    The Mullard Space Science Laboratory(UK) was established in 1967. In 1973, UCL became the first international node to the precursor of the internet, the ARPANET.

    Although University College London (UK) was among the first universities to admit women on the same terms as men, in 1878, the college’s senior common room, the Housman Room, remained men-only until 1969. After two unsuccessful attempts, a motion was passed that ended segregation by sex at University College London (UK). This was achieved by Brian Woledge (Fielden Professor of French at University College London (UK) from 1939 to 1971) and David Colquhoun, at that time a young lecturer in pharmacology.

    1976 to 2005 – University College London (UK)

    In 1976, a new charter restored University College London (UK) ‘s legal independence, although still without the power to award its own degrees. Under this charter the college became formally known as University College London (UK). This name abandoned the comma used in its earlier name of “University College, London”.

    In 1986, University College London (UK) merged with the Institute of Archaeology. In 1988, University College London (UK) merged with the Institute of Laryngology & Otology; the Institute of Orthopaedics; the Institute of Urology & Nephrology; and Middlesex Hospital Medical School.

    In 1993, a reorganisation of the University of London (UK) meant that University College London (UK) and other colleges gained direct access to government funding and the right to confer University of London degrees themselves. This led to University College London (UK) being regarded as a de facto university in its own right.

    In 1994, the University College London (UK) Hospitals NHS Trust was established. University College London (UK) merged with the College of Speech Sciences and the Institute of Ophthalmology in 1995; the Institute of Child Health and the School of Podiatry in 1996; and the Institute of Neurology in 1997. In 1998, UCL merged with the Royal Free Hospital Medical School to create the Royal Free and University College Medical School (renamed the University College London (UK) Medical School in October 2008). In 1999, UCL merged with the School of Slavonic and East European Studies and the Eastman Dental Institute.

    The University College London (UK) Jill Dando Institute of Crime Science, the first university department in the world devoted specifically to reducing crime, was founded in 2001.

    Proposals for a merger between University College London (UK) and Imperial College London(UK) were announced in 2002. The proposal provoked strong opposition from University College London (UK) teaching staff and students and the AUT union, which criticised “the indecent haste and lack of consultation”, leading to its abandonment by University College London (UK) provost Sir Derek Roberts. The blogs that helped to stop the merger are preserved, though some of the links are now broken: see David Colquhoun’s blog and the Save University College London (UK) blog, which was run by David Conway, a postgraduate student in the department of Hebrew and Jewish studies.

    The London Centre for Nanotechnology was established in 2003 as a joint venture between University College London (UK) and Imperial College London (UK). They were later joined by King’s College London(UK) in 2018.

    Since 2003, when University College London (UK) professor David Latchman became master of the neighbouring Birkbeck, he has forged closer relations between these two University of London colleges, and personally maintains departments at both. Joint research centres include the UCL/Birkbeck Institute for Earth and Planetary Sciences; the University College London (UK) /Birkbeck/IoE Centre for Educational Neuroscience; the University College London (UK) /Birkbeck Institute of Structural and Molecular Biology; and the Birkbeck- University College London (UK) Centre for Neuroimaging.

    2005 to 2010

    In 2005, University College London (UK) was finally granted its own taught and research degree awarding powers and all University College London (UK) students registered from 2007/08 qualified with University College London (UK) degrees. Also in 2005, University College London (UK) adopted a new corporate branding under which the name University College London (UK) was replaced by the initialism UCL in all external communications. In the same year, a major new £422 million building was opened for University College Hospital on Euston Road, the University College London (UK) Ear Institute was established and a new building for the University College London (UK) School of Slavonic and East European Studies was opened.

    In 2007, the University College London (UK) Cancer Institute was opened in the newly constructed Paul O’Gorman Building. In August 2008, University College London (UK) formed UCL Partners, an academic health science centre, with Great Ormond Street Hospital for Children NHS Trust; Moorfields Eye Hospital NHS Foundation Trust; Royal Free London NHS Foundation Trust; and University College London Hospitals NHS Foundation Trust. In 2008, University College London (UK) established the University College London (UK) School of Energy & Resources in Adelaide, Australia, the first campus of a British university in the country. The School was based in the historic Torrens Building in Victoria Square and its creation followed negotiations between University College London (UK) Vice Provost Michael Worton and South Australian Premier Mike Rann.

    In 2009, the Yale UCL Collaborative was established between University College London (UK); UCL Partners; Yale University(US); Yale School of Medicine; and Yale – New Haven Hospital. It is the largest collaboration in the history of either university, and its scope has subsequently been extended to the humanities and social sciences.

    2010 to 2015

    In June 2011, the mining company BHP Billiton agreed to donate AU$10 million to University College London (UK) to fund the establishment of two energy institutes – the Energy Policy Institute; based in Adelaide, and the Institute for Sustainable Resources, based in London.

    In November 2011, University College London (UK) announced plans for a £500 million investment in its main Bloomsbury campus over 10 years, as well as the establishment of a new 23-acre campus next to the Olympic Park in Stratford in the East End of London. It revised its plans of expansion in East London and in December 2014 announced to build a campus (UCL East) covering 11 acres and provide up to 125,000m^2 of space on Queen Elizabeth Olympic Park. UCL East will be part of plans to transform the Olympic Park into a cultural and innovation hub, where University College London (UK) will open its first school of design, a centre of experimental engineering and a museum of the future, along with a living space for students.

    The School of Pharmacy, University of London merged with University College London (UK) on 1 January 2012, becoming the University College London (UK) School of Pharmacy within the Faculty of Life Sciences. In May 2012, University College London (UK), Imperial College London and the semiconductor company Intel announced the establishment of the Intel Collaborative Research Institute for Sustainable Connected Cities, a London-based institute for research into the future of cities.

    In August 2012, University College London (UK) received criticism for advertising an unpaid research position; it subsequently withdrew the advert.

    University College London (UK) and the Institute of Education formed a strategic alliance in October 2012, including co-operation in teaching, research and the development of the London schools system. In February 2014, the two institutions announced their intention to merge, and the merger was completed in December 2014.

    In September 2013, a new Department of Science, Technology, Engineering and Public Policy (STEaPP) was established within the Faculty of Engineering, one of several initiatives within the university to increase and reflect upon the links between research and public sector decision-making.

    In October 2013, it was announced that the Translation Studies Unit of Imperial College London would move to University College London (UK), becoming part of the University College London (UK) School of European Languages, Culture and Society. In December 2013, it was announced that University College London (UK) and the academic publishing company Elsevier would collaborate to establish the UCL Big Data Institute. In January 2015, it was announced that University College London (UK) had been selected by the UK government as one of the five founding members of the Alan Turing Institute(UK) (together with the universities of Cambridge, University of Edinburgh(SCL), Oxford and University of Warwick(UK)), an institute to be established at the British Library to promote the development and use of advanced mathematics, computer science, algorithms and big data.

    2015 to 2020

    In August 2015, the Department of Management Science and Innovation was renamed as the School of Management and plans were announced to greatly expand University College London (UK) ‘s activities in the area of business-related teaching and research. The school moved from the Bloomsbury campus to One Canada Square in Canary Wharf in 2016.

    University College London (UK) established the Institute of Advanced Studies (IAS) in 2015 to promote interdisciplinary research in humanities and social sciences. The prestigious annual Orwell Prize for political writing moved to the IAS in 2016.

    In June 2016 it was reported in Times Higher Education that as a result of administrative errors hundreds of students who studied at the UCL Eastman Dental Institute between 2005–06 and 2013–14 had been given the wrong marks, leading to an unknown number of students being attributed with the wrong qualifications and, in some cases, being failed when they should have passed their degrees. A report by University College London (UK) ‘s Academic Committee Review Panel noted that, according to the institute’s own review findings, senior members of University College London (UK) staff had been aware of issues affecting students’ results but had not taken action to address them. The Review Panel concluded that there had been an apparent lack of ownership of these matters amongst the institute’s senior staff.

    In December 2016 it was announced that University College London (UK) would be the hub institution for a new £250 million national dementia research institute, to be funded with £150 million from the Medical Research Council and £50 million each from Alzheimer’s Research UK and the Alzheimer’s Society.

    In May 2017 it was reported that staff morale was at “an all time low”, with 68% of members of the academic board who responded to a survey disagreeing with the statement ” University College London (UK) is well managed” and 86% with “the teaching facilities are adequate for the number of students”. Michael Arthur, the Provost and President, linked the results to the “major change programme” at University College London (UK). He admitted that facilities were under pressure following growth over the past decade, but said that the issues were being addressed through the development of UCL East and rental of other additional space.

    In October 2017 University College London (UK) ‘s council voted to apply for university status while remaining part of the University of London. University College London (UK) ‘s application to become a university was subject to Parliament passing a bill to amend the statutes of the University of London, which received royal assent on 20 December 2018.

    The University College London (UK) Adelaide satellite campus closed in December 2017, with academic staff and student transferring to the University of South Australia(AU). As of 2019 UniSA and University College London (UK) are offering a joint masters qualification in Science in Data Science (international).

    In 2018, University College London (UK) opened UCL at Here East, at the Queen Elizabeth Olympic Park, offering courses jointly between the Bartlett Faculty of the Built Environment and the Faculty of Engineering Sciences. The campus offers a variety of undergraduate and postgraduate master’s degrees, with the first undergraduate students, on a new Engineering and Architectural Design MEng, starting in September 2018. It was announced in August 2018 that a £215 million contract for construction of the largest building in the UCL East development, Marshgate 1, had been awarded to Mace, with building to begin in 2019 and be completed by 2022.

    In 2017 University College London (UK) disciplined an IT administrator who was also the University and College Union (UCU) branch secretary for refusing to take down an unmoderated staff mailing list. An employment tribunal subsequently ruled that he was engaged in union activities and thus this disciplinary action was unlawful. As of June 2019 University College London (UK) is appealing this ruling and the UCU congress has declared this to be a “dispute of national significance”.

    2020 to present

    In 2021 University College London (UK) formed a strategic partnership with Facebook AI Research (FAIR), including the creation of a new PhD programme.

    Research

    University College London (UK) has made cross-disciplinary research a priority and orientates its research around four “Grand Challenges”, Global Health, Sustainable Cities, Intercultural Interaction and Human Wellbeing.

    In 2014/15, University College London (UK) had a total research income of £427.5 million, the third-highest of any British university (after the University of Oxford and Imperial College London). Key sources of research income in that year were BIS research councils (£148.3 million); UK-based charities (£106.5 million); UK central government; local/health authorities and hospitals (£61.5 million); EU government bodies (£45.5 million); and UK industry, commerce and public corporations (£16.2 million). In 2015/16, University College London (UK) was awarded a total of £85.8 million in grants by UK research councils, the second-largest amount of any British university (after the University of Oxford), having achieved a 28% success rate. For the period to June 2015, University College London (UK) was the fifth-largest recipient of Horizon 2020 EU research funding and the largest recipient of any university, with €49.93 million of grants received. University College London (UK) also had the fifth-largest number of projects funded of any organisation, with 94.

    According to a ranking of universities produced by SCImago Research Group University College London (UK) is ranked 12th in the world (and 1st in Europe) in terms of total research output. According to data released in July 2008 by ISI Web of Knowledge, University College London (UK) is the 13th most-cited university in the world (and most-cited in Europe). The analysis covered citations from 1 January 1998 to 30 April 2008, during which 46,166 UCL research papers attracted 803,566 citations. The report covered citations in 21 subject areas and the results revealed some of University College London (UK) ‘s key strengths, including: Clinical Medicine (1st outside North America); Immunology (2nd in Europe); Neuroscience & Behaviour (1st outside North America and 2nd in the world); Pharmacology & Toxicology (1st outside North America and 4th in the world); Psychiatry & Psychology (2nd outside North America); and Social Sciences, General (1st outside North America).

    University College London (UK) submitted a total of 2,566 staff across 36 units of assessment to the 2014 Research Excellence Framework (REF) assessment, in each case the highest number of any UK university (compared with 1,793 UCL staff submitted to the 2008 Research Assessment Exercise (RAE 2008)). In the REF results 43% of University College London (UK) ‘s submitted research was classified as 4* (world-leading); 39% as 3* (internationally excellent); 15% as 2* (recognised internationally) and 2% as 1* (recognised nationally), giving an overall GPA of 3.22 (RAE 2008: 4* – 27%, 3* – 39%, 2* – 27% and 1* – 6%). In rankings produced by Times Higher Education based upon the REF results, University College London (UK) was ranked 1st overall for “research power” and joint 8th for GPA (compared to 4th and 7th respectively in equivalent rankings for the RAE 2008).

     
  • richardmitnick 12:01 pm on July 10, 2020 Permalink | Reply
    Tags: , , , , , Standard candles,   

    From AAS NOVA: “Shining Bright Through the Ages” 

    AASNOVA

    From AAS NOVA

    10 July 2020
    Tarini Konchady

    1
    SN 1994D (lower left), detected at the edge of galaxy NGC 4526, is an example of a Type Ia supernova. [NASA/ESA/The Hubble Key Project Team/The High-Z Supernova Search Team]

    Accurate distance measurements are critical to astronomy. A Type Ia supernova is one of the few objects that we can trust for making distance measurements since they have a fixed peak brightness. But can the brightness of such a supernova change significantly based on the properties of its host galaxy? And what does this mean for our understanding of dark energy?

    Lighthouses in the Distant Universe

    A Type Ia supernovae is what’s known as a “standard candle” — we know what its brightness is at a particular distance, and when we observe these supernovae in distant galaxies, we can extrapolate to determine how far away those galaxies are. Like lighthouses, the fainter a Type Ia supernova is, the further away it is.

    Standard Candles to measure age and distance of the universe from supernovae. NASA

    Accurate distance measurements form the backbone of astronomy, and Type Ia supernovae are especially valuable because they allow us to measure extremely large distances beyond the reach of other standard candles. However, the properties of Type Ia supernovae were and are determined empirically, so a mistaken assumption about a supernova can trickle down and cause miscalculations further down the road.

    Type Ia supernova distances are in play in a rather contentious part of astronomy: measurements of the Hubble constant. The value of the Hubble constant is measured in one of two ways: using the cosmic microwave background (CMB), and using Type Ia supernovae and variable stars called Cepheids to measure the distances and velocities of far-off galaxies. The value measured with supernovae is significantly larger than the value measured with the CMB, however — and it suggests the presence of “dark energy”, a mysterious energy that’s accelerating the expansion of the universe.

    Recently, it’s been hypothesized that the supernova-based measurement is biased by an overlooked relation between peak Type Ia supernova brightnesses and the age of their host galaxies. Accounting for this brightness–age relation, if it holds up, could eliminate the need for dark energy and relieve the discrepancy between the two measurements of the Hubble constant. But a new study led by Benjamin Rose (Space Telescope Science Institute) now refutes this proposed relation.

    Sample Adjustments

    Rose and collaborators started their analysis by examining the sample of 34 Type Ia supernovae that was used to claim the possible brightness–age relation. The authors found that 10 supernovae in the sample fail at least one of the quality cuts typically used for cosmological studies. These include the supernova not being observed prior to its peak brightness, and an overall lack of observations.

    Rose and collaborators also argue that the prior study didn’t correctly account for the error on Type Ia supernova distances. Once these errors are accounted for and quality cuts are made to the supernova sample, the brightness–age relation appears negligible to measurements of the Hubble constant.

    Rose and collaborators also attempted to determine a brightness–age relation using a larger, robust sample of 254 Type Ia supernovae. They found no relation significant enough to suggest that the supernova distances had been misestimated — so there should be no changes to the supernova-based measurement of the Hubble constant.

    While this particular relation may not have borne out, Rose and collaborators agree that the properties of Type Ia supernovae must be constrained as much as possible for reliable distance measurements to be made. For now, however, it looks like dark energy may be here to stay!

    Citation

    “Evidence for Cosmic Acceleration Is Robust to Observed Correlations between Type Ia Supernova Luminosity and Stellar Age,” B. M. Rose et al 2020 ApJL 896 L4.

    https://iopscience.iop.org/article/10.3847/2041-8213/ab94ad

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    1

    AAS Mission and Vision Statement

    The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

    The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
    The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
    The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
    The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
    The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

    Adopted June 7, 2009

     
  • richardmitnick 2:19 pm on January 14, 2020 Permalink | Reply
    Tags: "Have Dark Forces Been Messing With the Cosmos?", Alan Guth MIT "Inflation", , , , , CMB per Planck, , , , Discrepancy in how fast the niverse is expanding., Edwin Hubble in 1929 discovers the Universe is Expanding, , , Saul Perlmutter [The Supernova Cosmology Project] shared the 2006 Shaw Prize in Astronom; the 2011 Nobel Prize in Physics; and the 2015 Breakthrough Prize in Fundamental Physics with Brian P. Schmidt , Standard candles   

    From The New York Times: “Have Dark Forces Been Messing With the Cosmos?” 


    From The New York Times

    Feb. 25, 2019 [Sorry, missed the first time around. Picked up from another article found today by Dennis Overbye]
    Dennis Overbye

    1
    Brian Stauffer

    There was, you might say, a disturbance in the Force.

    Long, long ago, when the universe was only about 100,000 years old — a buzzing, expanding mass of particles and radiation — a strange new energy field switched on. That energy suffused space with a kind of cosmic antigravity, delivering a not-so-gentle boost to the expansion of the universe.

    Then, after another 100,000 years or so, the new field simply winked off, leaving no trace other than a speeded-up universe.

    So goes the strange-sounding story being promulgated by a handful of astronomers from Johns Hopkins University. In a bold and speculative leap into the past, the team has posited the existence of this field to explain an astronomical puzzle: the universe seems to be expanding faster than it should be.

    The cosmos is expanding only about 9 percent more quickly than theory prescribes. But this slight-sounding discrepancy has intrigued astronomers, who think it might be revealing something new about the universe.

    And so, for the last couple of years, they have been gathering in workshops and conferences to search for a mistake or loophole in their previous measurements and calculations, so far to no avail.

    “If we’re going to be serious about cosmology, this is the kind of thing we have to be able to take seriously,” said Lisa Randall, a Harvard theorist who has been pondering the problem.

    At a recent meeting in Chicago, Josh Frieman, a theorist at the Fermi National Accelerator Laboratory [FNAL] in Batavia, Ill., asked: “At what point do we claim the discovery of new physics?”

    Now ideas are popping up. Some researchers say the problem could be solved by inferring the existence of previously unknown subatomic particles. Others, such as the Johns Hopkins group, are invoking new kinds of energy fields.

    Adding to the confusion, there already is a force field — called dark energy — making the universe expand faster.

    Dark Energy Survey


    Dark Energy Camera [DECam], built at FNAL


    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam at an altitude of 7200 feet

    Timeline of the Inflationary Universe WMAP

    The Dark Energy Survey (DES) is an international, collaborative effort to map hundreds of millions of galaxies, detect thousands of supernovae, and find patterns of cosmic structure that will reveal the nature of the mysterious dark energy that is accelerating the expansion of our Universe. DES began searching the Southern skies on August 31, 2013.

    According to Einstein’s theory of General Relativity, gravity should lead to a slowing of the cosmic expansion. Yet, in 1998, two teams of astronomers studying distant supernovae made the remarkable discovery that the expansion of the universe is speeding up. To explain cosmic acceleration, cosmologists are faced with two possibilities: either 70% of the universe exists in an exotic form, now called dark energy, that exhibits a gravitational force opposite to the attractive gravity of ordinary matter, or General Relativity must be replaced by a new theory of gravity on cosmic scales.

    DES is designed to probe the origin of the accelerating universe and help uncover the nature of dark energy by measuring the 14-billion-year history of cosmic expansion with high precision. More than 400 scientists from over 25 institutions in the United States, Spain, the United Kingdom, Brazil, Germany, Switzerland, and Australia are working on the project. The collaboration built and is using an extremely sensitive 570-Megapixel digital camera, DECam, mounted on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory, high in the Chilean Andes, to carry out the project.

    Over six years (2013-2019), the DES collaboration used 758 nights of observation to carry out a deep, wide-area survey to record information from 300 million galaxies that are billions of light-years from Earth. The survey imaged 5000 square degrees of the southern sky in five optical filters to obtain detailed information about each galaxy. A fraction of the survey time is used to observe smaller patches of sky roughly once a week to discover and study thousands of supernovae and other astrophysical transients.

    And a new, controversial report suggests that this dark energy might be getting stronger and denser, leading to a future in which atoms are ripped apart and time ends.

    Thus far, there is no evidence for most of these ideas. If any turn out to be right, scientists may have to rewrite the story of the origin, history and, perhaps, fate of the universe.

    Or it could all be a mistake. Astronomers have rigorous methods to estimate the effects of statistical noise and other random errors on their results; not so for the unexamined biases called systematic errors.

    As Wendy L. Freedman, of the University of Chicago, said at the Chicago meeting, “The unknown systematic is what gets you in the end.”

    Edwin Hubble looking through a 100-inch Hooker telescope at Mount Wilson in Southern California, 1929 discovers the Universe is Expanding

    Edwin Hubble in 1949, two decades after he discovered that the universe is expanding.Credit…Boyer/Roger Viollet, via Getty Images (credit: Emilio Segre Visual Archives/AIP/SPL)

    Hubble trouble

    Generations of great astronomers have come to grief trying to measure the universe. At issue is a number called the Hubble constant, named after Edwin Hubble, the Mount Wilson astronomer who in 1929 discovered that the universe is expanding.

    As space expands, it carries galaxies away from each other like the raisins in a rising cake. The farther apart two galaxies are, the faster they will fly away from each other. The Hubble constant simply says by how much.

    But to calibrate the Hubble constant, astronomers depend on so-called standard candles: objects, such as supernova explosions and certain variable stars, whose distances can be estimated by luminosity or some other feature. This is where the arguing begins.

    Standard Candles to measure age and distance of the universe from supernovae. NASA

    Until a few decades ago, astronomers could not agree on the value of the Hubble constant within a factor of two: either 50 or 100 kilometers per second per megaparsec. (A megaparsec is 3.26 million light years.)

    But in 2001, a team using the Hubble Space Telescope, and led by Dr. Freedman, reported a value of 72. For every megaparsec farther away from us that a galaxy is, it is moving 72 kilometers per second faster.

    More recent efforts by Adam G. Riess [The Astrophysical Journal], of Johns Hopkins and the Space Telescope Science Institute, and others have obtained similar numbers, and astronomers now say they have narrowed the uncertainty in the Hubble constant to just 2.4 percent.

    But new precision has brought new trouble. These results are so good that they now disagree with results from the European Planck spacecraft, which predict a Hubble constant of 67.

    The discrepancy — 9 percent — sounds fatal but may not be, astronomers contend, because Planck and human astronomers do very different kinds of observations.

    Planck is considered the gold standard of cosmology. It spent four years studying the cosmic bath of microwaves [CMB] left over from the end of the Big Bang, when the universe was just 380,000 years old.

    CMB per ESA/Planck


    ESA/Planck 2009 to 2013

    But it did not measure the Hubble constant directly. Rather, the Planck group derived the value of the constant, and other cosmic parameters, from a mathematical model largely based on those microwaves.

    In short, Planck’s Hubble constant is based on a cosmic baby picture. In contrast, the classical astronomical value is derived from what cosmologists modestly call “local measurements,” a few billion light-years deep into a middle-aged universe.

    What if that baby picture left out or obscured some important feature of the universe?

    ‘Cosmological Whac-a-Mole’

    And so cosmologists are off to the game that Lloyd Knox, an astrophysicist from the University of California, Davis, called “cosmological Whac-a-Mole” at the recent Chicago meeting: attempting to fix the model of the early universe, to make it expand a little faster without breaking what the model already does well.

    One approach, some astrophysicists suggest, is to add more species of lightweight subatomic particles, such as the ghostlike neutrinos, to the early universe. (Physicists already recognize three kinds of neutrinos, and argue whether there is evidence for a fourth variety.) These would give the universe more room to stash energy, in the same way that more drawers in your dresser allow you to own more pairs of socks. Thus invigorated, the universe would expand faster, according to the Big Bang math, and hopefully not mess up the microwave baby picture.

    A more drastic approach, from the Johns Hopkins group, invokes fields of exotic anti-gravitational energy. The idea exploits an aspect of string theory, the putative but unproven “theory of everything” that posits that the elementary constituents of reality are very tiny, wriggling strings.

    String theory suggests that space could be laced with exotic energy fields associated with lightweight particles or forces yet undiscovered. Those fields, collectively called quintessence, could act in opposition to gravity, and could change over time — popping up, decaying or altering their effect, switching from repulsive to attractive.

    The team focused in particular on the effects of fields associated with hypothetical particles called axions. Had one such field arisen when the universe was about 100,000 years old, it could have produced just the right amount of energy to fix the Hubble discrepancy, the team reported in a paper late last year. They refer to this theoretical force as “early dark energy.”

    “I was surprised how it came out,” said Marc Kamionkowski, a Johns Hopkins cosmologist who was part of the study. “This works.”

    The jury is still out. Dr. Riess said that the idea seems to work, which is not to say that he agrees with it, or that it is right. Nature, manifest in future observations, will have the final say.

    Dr. Knox called the Johns Hopkins paper “an existence proof” that the Hubble problem could be solved. “I think that’s new,” he said.

    Dr. Randall, however, has taken issue with aspects of the Johns Hopkins calculations. She and a trio of Harvard postdocs are working on a similar idea that she says works as well and is mathematically consistent. “It’s novel and very cool,” Dr. Randall said.

    So far, the smart money is still on cosmic confusion. Michael Turner, a veteran cosmologist at the University of Chicago and the organizer of a recent airing of the Hubble tensions, said, “Indeed, all of this is going over all of our heads. We are confused and hoping that the confusion will lead to something good!”

    Doomsday? Nah, nevermind

    Early dark energy appeals to some cosmologists because it hints at a link to, or between, two mysterious episodes in the history of the universe. As Dr. Riess said, “This is not the first time the universe has been expanding too fast.”

    The first episode occurred when the universe was less than a trillionth of a trillionth of a second old. At that moment, cosmologists surmise, a violent ballooning propelled the Big Bang; in a fraction of a trillionth of a second, this event — named “inflation” by the cosmologist Alan Guth, of M.I.T. — smoothed and flattened the initial chaos into the more orderly universe observed today.

    Inflation

    4
    Alan Guth, from Highland Park High School and M.I.T., who first proposed cosmic inflation

    HPHS Owls

    Lamda Cold Dark Matter Accerated Expansion of The universe http scinotions.com the-cosmic-inflation-suggests-the-existence-of-parallel-universes
    Alex Mittelmann, Coldcreation

    Alan Guth’s notes:

    Alan Guth’s original notes on inflation

    Nobody knows what drove inflation.

    The second episode is unfolding today: cosmic expansion is speeding up. But why? The issue came to light in 1998, when two competing teams of astronomers asked whether the collective gravity of the galaxies might be slowing the expansion enough to one day drag everything together into a Big Crunch.

    To great surprise, they discovered the opposite: the expansion was accelerating under the influence of an anti-gravitational force later called dark energy. The two teams won a Nobel Prize.

    Saul Perlmutter [The Supernova Cosmology Project] shared the 2006 Shaw Prize in Astronomy, the 2011 Nobel Prize in Physics, and the 2015 Breakthrough Prize in Fundamental Physics with Brian P. Schmidt and Adam Riess [The High-z Supernova Search Team] for providing evidence that the expansion of the universe is accelerating.

    Dark energy comprises 70 percent of the mass-energy of the universe. And, spookily, it behaves very much like a fudge factor known as the cosmological constant, a cosmic repulsive force that Einstein inserted in his equations a century ago thinking it would keep the universe from collapsing under its own weight. He later abandoned the idea, perhaps too soon.

    Under the influence of dark energy, the cosmos is now doubling in size every 10 billion years — to what end, nobody knows.

    Early dark energy, the force invoked by the Johns Hopkins group, might represent a third episode of antigravity taking over the universe and speeding it up. Perhaps all three episodes are different manifestations of the same underlying tendency of the universe to go rogue and speed up occasionally. In an email, Dr. Riess said, “Maybe the universe does this from time-to-time?”

    If so, it would mean that the current manifestation of dark energy is not Einstein’s constant after all. It might wink off one day. That would relieve astronomers, and everybody else, of an existential nightmare regarding the future of the universe. If dark energy remains constant, everything outside our galaxy eventually will be moving away from us faster than the speed of light, and will no longer be visible. The universe will become lifeless and utterly dark.

    But if dark energy is temporary — if one day it switches off — cosmologists and metaphysicians can all go back to contemplating a sensible tomorrow.

    “An appealing feature of this is that there might be a future for humanity,” said Scott Dodelson, a theorist at Carnegie Mellon who has explored similar scenarios.

    The phantom cosmos

    But the future is still up for grabs.

    Far from switching off, the dark energy currently in the universe actually has increased over cosmic time, according to a recent report in Nature Astronomy. If this keeps up, the universe could end one day in what astronomers call the Big Rip, with atoms and elementary particles torn asunder — perhaps the ultimate cosmic catastrophe.

    This dire scenario emerges from the work of Guido Risaliti, of the University of Florence in Italy, and Elisabeta Lusso, of Durham University in England. For the last four years, they have plumbed the deep history of the universe, using violent, faraway cataclysms called quasars as distance markers.

    Quasars arise from supermassive black holes at the centers of galaxies; they are the brightest objects in nature, and can be seen clear across the universe. As standard candles, quasars aren’t ideal because their masses vary widely. Nevertheless, the researchers identified some regularities in the emissions from quasars, allowing the history of the cosmos to be traced back nearly 12 billion years. The team found that the rate of cosmic expansion deviated from expectations over that time span.

    One interpretation of the results is that dark energy is not constant after all, but is changing, growing denser and thus stronger over cosmic time. It so happens that this increase in dark energy also would be just enough to resolve the discrepancy in measurements of the Hubble constant.

    The bad news is that, if this model is right, dark energy may be in a particularly virulent and — most physicists say — implausible form called phantom energy. Its existence would imply that things can lose energy by speeding up, for instance. Robert Caldwell, a Dartmouth physicist, has referred to it as “bad news stuff.”

    As the universe expands, the push from phantom energy would grow without bounds, eventually overcoming gravity and tearing apart first Earth, then atoms.

    The Hubble-constant community responded to the new report with caution. “If it holds up, this is a very interesting result,” said Dr. Freedman.

    Astronomers have been trying to take the measure of this dark energy for two decades. Two space missions — the European Space Agency’s Euclid and NASA’s Wfirst — have been designed to study dark energy and hopefully deliver definitive answers in the coming decade. The fate of the universe is at stake.

    ESA/Euclid spacecraft depiction

    NASA/WFIRST

    In the meantime, everything, including phantom energy, is up for consideration, according to Dr. Riess.

    “In a list of possible solutions to the tension via new physics, mentioning weird dark energy like this would seem appropriate,” he wrote in an email. “Heck, at least their dark energy goes in the right direction to solve the tension. It could have gone the other way and made it worse!”

    See the full article here .

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    Please help promote STEM in your local schools.

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  • richardmitnick 1:54 pm on December 30, 2019 Permalink | Reply
    Tags: "These Are The Most Distant Astronomical Objects In The Known Universe", , , , , , , , , , , , Our most distant “standard candle” for probing the Universe is SN UDS10Wil located 17 billion light-years (Gly), , , Standard candles,   

    From Ethan Siegel: “These Are The Most Distant Astronomical Objects In The Known Universe” 

    From Ethan Siegel
    Dec 30, 2019

    Astronomy’s enduring quest is to go farther, fainter, and more detailed than ever before. Here’s the edge of the cosmic frontier.

    1
    The distant galaxy MACS1149-JD1 is gravitationally lensed by a foreground cluster, allowing it to be imaged at high resolution and in multiple instruments, even without next-generation technology.

    Gravitational Lensing NASA/ESA

    This galaxy’s light comes to us from 530 million years after the Big Bang, but the stars within it are at least 280 million years old. It is the second-most distant galaxy with a spectroscopically confirmed distance, placing it 30.7 billion light-years away from us. (ALMA (ESO/NAOJ/NRAO), NASA/ESA HUBBLE SPACE TELESCOPE, W. ZHENG (JHU), M. POSTMAN (STSCI), THE CLASH TEAM, HASHIMOTO ET AL.)

    ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres

    NASA/ESA Hubble Telescope

    Astronomers have always sought to push back the viewable distance frontiers.

    2
    Although there are magnified, ultra-distant, very red and even infrared galaxies in the eXtreme Deep Field, there are galaxies that are even more distant out there than what we’ve discovered in our deepest-to-date views. These galaxies will always remain visible to us, but we will never see them as they are today: 13.8 billion years after the Big Bang. (NASA, ESA, R. BOUWENS AND G. ILLINGWORTH (UC, SANTA CRUZ))

    More distant galaxies appear fainter, smaller, bluer, and less evolved overall.

    3
    Galaxies comparable to the present-day Milky Way are numerous, but younger galaxies that are Milky Way-like are inherently smaller, bluer, more chaotic, and richer in gas in general than the galaxies we see today. For the first galaxies of all, this ought to be taken to the extreme, and remains valid as far back as we’ve ever seen. The exceptions, when we encounter them, are both puzzling and rare. (NASA AND ESA)

    Milky Way NASA/JPL-Caltech /ESO R. Hurt. The bar is visible in this image

    Laniakea supercluster. From Nature The Laniakea supercluster of galaxies R. Brent Tully, Hélène Courtois, Yehuda Hoffman & Daniel Pomarède at http://www.nature.com/nature/journal/v513/n7516/full/nature13674.html. Milky Way is the red dot.

    Individual planets and stars are only known relatively nearby, as our tools cannot take us farther.

    Local Group. Andrew Z. Colvin 3 March 2011

    4
    A massive cluster (left) magnified a distant star known as Icarus more than 2,000 times, making it visible from Earth (lower right) even though it is 9 billion light years away, far too distant to be seen individually with current telescopes. It was not visible in 2011 (upper right). The brightening leads us to believe that this was a blue supergiant star, formally named MACS J1149 Lensed Star 1. (NASA, ESA, AND P. KELLY (UNIVERSITY OF MINNESOTA))

    As the 2010s end, here are our presently known most distant astronomical objects.

    4
    The ultra-distant supernova SN UDS10Wil, shown here, is the farthest type Ia supernova ever discovered, whose light arrives today from a position 17 billion light-years away.

    A white dwarf fed by a normal star reaches the critical mass and explodes as a type Ia supernova. Credit: NASA/CXC/M Weiss

    Type Ia supernovae are used as distance indicators because of their standard intrinsic brightnesses, and are some of our strongest evidence for the accelerated expansion best explained by dark energy.

    Standard Candles to measure age and distance of the universe from supernovae NASA

    (NASA, ESA, A. RIESS (STSCI AND JHU), AND D. JONES AND S. RODNEY (JHU))

    The farthest type Ia supernova, our most distant “standard candle” for probing the Universe, is SN UDS10Wil, located 17 billion light-years (Gly) away.

    4
    This illustration of superluminous supernova SN 1000+0216, the most distant supernova ever observed at a redshift of z=3.90, from when the Universe was just 1.6 billion years old, is the current record-holder for individual supernovae. Unlike SN UDS10Wil, this supernova is a Type II (core collapse) supernova, and may have formed via the pair instability mechanism, which would explain its extraordinarily large intrinsic brightness. (ADRIAN MALEC AND MARIE MARTIG (SWINBURNE UNIVERSITY))

    The most distant supernova of all, 2012’s superluminous SN 1000+0216, occurred 23 Gly away.

    6
    The most distant X-ray jet in the Universe, from quasar GB 1428, sends us light from when the Universe was a mere 1.25 billion years old: less than 10% its current age. This jet comes from electrons heating CMB photons, and is over 230,000 light-years in extent: approximately double the size of the Milky Way. (X-RAY: NASA/CXC/NRC/C.CHEUNG ET AL; OPTICAL: NASA/STSCI; RADIO: NSF/NRAO/VLA)

    NASA/Chandra X-ray Telescope

    NRAO/Karl V Jansky Expanded Very Large Array, on the Plains of San Agustin fifty miles west of Socorro, NM, USA, at an elevation of 6970 ft (2124 m)

    The most distant quasar jet, revealed by GB 1428+4217’s X-rays, is 25.4 Gly distant.

    7
    This image of ULAS J1120+0641, a very distant quasar powered by a black hole with a mass two billion times that of the Sun, was created from images taken from surveys made by both the Sloan Digital Sky Survey and the UKIRT Infrared Deep Sky Survey.

    SDSS Telescope at Apache Point Observatory, near Sunspot NM, USA, Altitude2,788 meters (9,147 ft)


    UKIRT, located on Mauna Kea, Hawai’i, USA as part of Mauna Kea Observatory,4,207 m (13,802 ft) above sea level

    The quasar appears as a faint red dot close to the centre. This quasar was the most distant one known from 2011 until 2017, and is seen as it was just 745 million years after the Big Bang. It is the most distant quasar with a visual image available to be viewed by the public. (ESO/UKIDSS/SDSS)

    The first discovered object whose light exceeds 13 billion years in age, quasar ULAS J1120+0641, is 28.8 Gly away.

    9
    This artist’s concept shows the most distant quasar and the most distant supermassive black hole powering it. At a redshift of 7.54, ULAS J1342+0928 corresponds to a distance of some 29.32 billion light-years; it is the most distant quasar/supermassive black hole ever discovered. Its light arrives at our eyes today, in the radio part of the spectrum, because it was emitted just 686 million years after the Big Bang. (ROBIN DIENEL/CARNEGIE INSTITUTION FOR SCIENCE)

    However, quasar ULAS J1342+0928 is even farther at 29.32 Gly: our most distant black hole.

    10
    This illustration of the most distant gamma-ray burst ever detected, GRB 090423, is thought to be typical of most fast gamma-ray bursts. When one or two objects violently form a black hole, such as from a neutron star merger, a brief burst of gamma rays followed by an infrared afterglow (when we’re lucky) allows us to learn more about these events. The gamma rays from this event lasted just 10 seconds, but Nial Tanvir and his team found an infrared afterglow using the UKIRT telescope just 20 minutes after the burst, allowing them to determine a redshift (z=8.2) and distance (29.96 billion light-years) to great precision. (ESO/A. ROQUETTE)

    Gamma-ray bursts exceed even that; GRB 090423’s verified light comes from 29.96 Gly away in the distant Universe, while GRB 090429B might’ve been even farther.

    9
    Here, candidate galaxy UDFj-39546284 appears very faint and red, and from the colors it displays, it has an inferred redshift of 10, giving it an age below 500 million years and a distance greater than 31 billion light-years. Without spectroscopic confirmation, however, this and similar galaxies cannot reliably be said to have a known distance; more data is needed, as photometric redshifts are notoriously unreliable. (NASA, ESA, G. ILLINGWORTH (UNIVERSITY OF CALIFORNIA, SANTA CRUZ), R. BOUWENS (UNIVERSITY OF CALIFORNIA, SANTA CRUZ, AND LEIDEN UNIVERSITY) AND THE HUDF09 TEAM)

    Ultra-distant galaxy candidates abound, including SPT0615-JD, MACS0647-JD, and UDFj-39546284, all lacking spectroscopic confirmation.

    11
    The most distant galaxy ever discovered in the known Universe, GN-z11, has its light come to us from 13.4 billion years ago: when the Universe was only 3% its current age: 407 million years old. The distance from this galaxy to us, taking the expanding Universe into account, is an incredible 32.1 billion light-years. (NASA, ESA, AND G. BACON (STSCI))

    The most distant galaxy of all is GN-z11, located 32.1 Gly away.

    11
    The James Webb Space Telescope vs. Hubble in size (main) and vs. an array of other telescopes (inset) in terms of wavelength and sensitivity. It should be able to see the truly first galaxies, even the ones that no other observatory can see. Its power is truly unprecedented. (NASA / JWST SCIENCE TEAM)

    NASA/ESA/CSA Webb Telescope annotated

    With the 2020s promising revolutionary new observatories, these records may all soon fall.

    12
    Our deepest galaxy surveys can reveal objects tens of billions of light years away, but there are more galaxies within the observable Universe we still have yet to reveal between the most distant galaxies and the cosmic microwave background [CMB], including the very first stars and galaxies of all.

    CMB per ESA/Planck

    It is possible that the coming generation of telescopes will break all of our current distance records. (SLOAN DIGITAL SKY SURVEY (SDSS))

    See the full article here .

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    Please help promote STEM in your local schools.

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    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

     
  • richardmitnick 10:07 am on April 25, 2019 Permalink | Reply
    Tags: "Mystery of the Universe's Expansion Rate Widens with New Hubble Data", Astronomers have already hypothesized that dark energy existed during the first seconds after the big bang and pushed matter throughout space starting the initial expansion., , , , Cepheid variables in the Large Magellanic Cloud, , , Dark energy may also be the reason for the universe's accelerated expansion today., DASH (Drift And Shift) using Hubble as a "point-and-shoot" camera, , , , Proposed by astronomers at Johns Hopkins the theory is dubbed "early dark energy" and suggests that the universe evolved like a three-act play., Standard candles, The new estimate of the Hubble constant is 74 kilometers (46 miles) per second per megaparsec., The new theory suggests that there was a third dark-energy episode not long after the big bang which expanded the universe faster than astronomers had predicted., The true explanation is still a mystery.   

    From NASA/ESA Hubble Telescope: “Mystery of the Universe’s Expansion Rate Widens with New Hubble Data” 

    NASA Hubble Banner

    NASA/ESA Hubble Telescope


    From NASA/ESA Hubble Telescope

    Apr 25, 2019

    Adam Riess
    Space Telescope Science Institute, Baltimore, Maryland
    and Johns Hopkins University, Baltimore, Maryland
    410-338-6707
    ariess@stsci.edu

    Donna Weaver
    Space Telescope Science Institute, Baltimore, Maryland
    410-338-4493
    dweaver@stsci.edu

    Ray Villard
    Space Telescope Science Institute, Baltimore, Maryland
    410-338-4514
    villard@stsci.edu

    1
    Large Magellanic Cloud (DSS View) with Star Cluster Overlay (Hubble). STScI.
    New physics may be needed to rectify the universe’s past and present behavior.

    2
    Three Steps to the Hubble Constant. STScI.

    4
    Three steps to the Hubble constant | ESA/Hubble

    ________________________________________________________________
    There is something wrong with our universe. Or, more specifically, it is outpacing all expectations for its present rate of expansion.

    Something is amiss in astronomers’ efforts to measure the past and predict the present, according to a discrepancy between the two main techniques for measuring the universe’s expansion rate – a key to understanding its history and physical parameters.

    The inconsistency is between the Hubble Space Telescope measurements of today’s expansion rate of the universe (by looking at stellar milepost markers) and the expansion rate as measured by the European Space Agency’s Planck satellite. Planck observes the conditions of the early universe just 380,000 years after the big bang.

    ESA/Planck 2009 to 2013

    For years, astronomers have been assuming this discrepancy would go away due to some instrumental or observational fluke. Instead, as Hubble astronomers continue to “tighten the bolts” on the accuracy of their measurements, the discordant values remain stubbornly at odds.

    The chances of the disagreement being just a fluke have skyrocketed from 1 in 3,000 to 1 in 100,000.

    Theorists must find an explanation for the disparity that could rattle ideas about the very underpinnings of the universe.
    ________________________________________________________________

    Astronomers using NASA’s Hubble Space Telescope say they have crossed an important threshold in revealing a discrepancy between the two key techniques for measuring the universe’s expansion rate. The recent study strengthens the case that new theories may be needed to explain the forces that have shaped the cosmos.

    A brief recap: The universe is getting bigger every second. The space between galaxies is stretching, like dough rising in the oven. But how fast is the universe expanding? As Hubble and other telescopes seek to answer this question, they have run into an intriguing difference between what scientists predict and what they observe.

    Hubble measurements suggest a faster expansion rate in the modern universe than expected, based on how the universe appeared more than 13 billion years ago. These measurements of the early universe come from the European Space Agency’s Planck satellite. This discrepancy has been identified in scientific papers over the last several years, but it has been unclear whether differences in measurement techniques are to blame, or whether the difference could result from unlucky measurements.

    The latest Hubble data lower the possibility that the discrepancy is only a fluke to 1 in 100,000. This is a significant gain from an earlier estimate, less than a year ago, of a chance of 1 in 3,000.

    These most precise Hubble measurements to date bolster the idea that new physics may be needed to explain the mismatch.

    “The Hubble tension between the early and late universe may be the most exciting development in cosmology in decades,” said lead researcher and Nobel laureate Adam Riess of the Space Telescope Science Institute (STScI) and Johns Hopkins University, in Baltimore, Maryland. “This mismatch has been growing and has now reached a point that is really impossible to dismiss as a fluke. This disparity could not plausibly occur just by chance.”

    Tightening the bolts on the ‘cosmic distance ladder’

    Scientists use a “cosmic distance ladder” to determine how far away things are in the universe.

    Cosmic Distance Ladder, skynetblogs

    Standard Candles to measure age and distance of the universe from supernovae NASA

    This method depends on making accurate measurements of distances to nearby galaxies and then moving to galaxies farther and farther away, using their stars as milepost markers. Astronomers use these values, along with other measurements of the galaxies’ light that reddens as it passes through a stretching universe, to calculate how fast the cosmos expands with time, a value known as the Hubble constant.

    Riess and his SH0ES (Supernovae H0 for the Equation of State) team have been on a quest since 2005 to refine those distance measurements with Hubble and fine-tune the Hubble constant.

    In this new study, astronomers used Hubble to observe 70 pulsating stars called Cepheid variables in the Large Magellanic Cloud. The observations helped the astronomers “rebuild” the distance ladder by improving the comparison between those Cepheids and their more distant cousins in the galactic hosts of supernovas. Riess’s team reduced the uncertainty in their Hubble constant value to 1.9% from an earlier estimate of 2.2%.

    As the team’s measurements have become more precise, their calculation of the Hubble constant has remained at odds with the expected value derived from observations of the early universe’s expansion. Those measurements were made by Planck, which maps the cosmic microwave background [CMB], a relic afterglow from 380,000 years after the big bang.

    CMB per ESA/Planck

    The measurements have been thoroughly vetted, so astronomers cannot currently dismiss the gap between the two results as due to an error in any single measurement or method. Both values have been tested multiple ways.

    “This is not just two experiments disagreeing,” Riess explained. “We are measuring something fundamentally different. One is a measurement of how fast the universe is expanding today, as we see it. The other is a prediction based on the physics of the early universe and on measurements of how fast it ought to be expanding. If these values don’t agree, there becomes a very strong likelihood that we’re missing something in the cosmological model that connects the two eras.”

    How the new study was done

    Astronomers have been using Cepheid variables as cosmic yardsticks to gauge nearby intergalactic distances for more than a century. But trying to harvest a bunch of these stars was so time-consuming as to be nearly unachievable. So, the team employed a clever new method, called DASH (Drift And Shift), using Hubble as a “point-and-shoot” camera to snap quick images of the extremely bright pulsating stars, which eliminates the time-consuming need for precise pointing.

    “When Hubble uses precise pointing by locking onto guide stars, it can only observe one Cepheid per each 90-minute Hubble orbit around Earth. So, it would be very costly for the telescope to observe each Cepheid,” explained team member Stefano Casertano, also of STScI and Johns Hopkins. “Instead, we searched for groups of Cepheids close enough to each other that we could move between them without recalibrating the telescope pointing. These Cepheids are so bright, we only need to observe them for two seconds. This technique is allowing us to observe a dozen Cepheids for the duration of one orbit. So, we stay on gyroscope control and keep ‘DASHing’ around very fast.”

    The Hubble astronomers then combined their result with another set of observations, made by the Araucaria Project, a collaboration between astronomers from institutions in Chile, the U.S., and Europe. This group made distance measurements to the Large Magellanic Cloud by observing the dimming of light as one star passes in front of its partner in eclipsing binary-star systems.

    The combined measurements helped the SH0ES Team refine the Cepheids’ true brightness. With this more accurate result, the team could then “tighten the bolts” of the rest of the distance ladder that extends deeper into space.

    The new estimate of the Hubble constant is 74 kilometers (46 miles) per second per megaparsec. This means that for every 3.3 million light-years farther away a galaxy is from us, it appears to be moving 74 kilometers (46 miles) per second faster, as a result of the expansion of the universe. The number indicates that the universe is expanding at a 9% faster rate than the prediction of 67 kilometers (41.6 miles) per second per megaparsec, which comes from Planck’s observations of the early universe, coupled with our present understanding of the universe.

    So, what could explain this discrepancy?

    One explanation for the mismatch involves an unexpected appearance of dark energy in the young universe, which is thought to now comprise 70% of the universe’s contents. Proposed by astronomers at Johns Hopkins, the theory is dubbed “early dark energy,” and suggests that the universe evolved like a three-act play.

    Astronomers have already hypothesized that dark energy existed during the first seconds after the big bang and pushed matter throughout space, starting the initial expansion. Dark energy may also be the reason for the universe’s accelerated expansion today. The new theory suggests that there was a third dark-energy episode not long after the big bang, which expanded the universe faster than astronomers had predicted. The existence of this “early dark energy” could account for the tension between the two Hubble constant values, Riess said.

    Another idea is that the universe contains a new subatomic particle that travels close to the speed of light. Such speedy particles are collectively called “dark radiation” and include previously known particles like neutrinos, which are created in nuclear reactions and radioactive decays.

    Yet another attractive possibility is that dark matter (an invisible form of matter not made up of protons, neutrons, and electrons) interacts more strongly with normal matter or radiation than previously assumed.

    But the true explanation is still a mystery.

    Riess doesn’t have an answer to this vexing problem, but his team will continue to use Hubble to reduce the uncertainties in the Hubble constant. Their goal is to decrease the uncertainty to 1%, which should help astronomers identify the cause of the discrepancy.

    The team’s results have been accepted for publication in The Astrophysical Journal.

    See the full HubbleSite article here .
    See the ESA/Hubble article here .


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    The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

    ESA50 Logo large

    AURA Icon

     
  • richardmitnick 1:16 pm on April 4, 2019 Permalink | Reply
    Tags: , , , , , , Standard candles, The Hubble Constant discrepency, UC Banta Barbra   

    From UC Santa Barbara: “The Standard Siren” 

    UC Santa Barbara Name bloc
    From UC Santa Barbara

    Ten years before the detection of gravitational waves, two KITP postdocs at UC Santa Barbara had a novel idea.

    April 2, 2019
    Harrison Tasoff

    1
    Two neutron stars collide, sending out gravitational waves and electromagnetic radiation detected on Earth in 2017. Photo Credit: Fermilab

    2
    Scott Hughesz. Photo Credit: MIT

    The history of science is filled with stories of enthusiastic researchers slowly winning over skeptical colleagues to their point of view. Astrophysicist Scott Hughes can relate to these tales.

    “For the first 15 or 16 years of my career I was speaking to astronomers, and I always had the impression that they were politely interested in what I had to say, but regarded me as a little bit of a wild-eyed enthusiast who was telling them about a herd of unicorns that my friends and I were raising,” said Hughes.

    “Now,” he continued, “there are people who are going, ‘Ooh, all those unicorns you found, can I use them to solve my problem? Do your unicorns have wings? Are they sparkly?’”

    3
    Daniel Holz. Photo Credit: University of Chicago

    These unicorns are gravitational waves, an area of physics in which Hughes specializes. While working as postdoctoral researchers at UC Santa Barbara’s Kavli Institute for Theoretical Physics (KITP), Hughes and his colleague, Daniel Holz, were among the first to propose using the phenomena, in combination with telescope-based observations, to measure the Hubble constant, a fundamental quantity involved in describing the expansion of the universe.

    As the universe expands, it carries celestial objects away from us. This stretches out the wavelength of light we detect from these objects, causing it to drop in frequency just like a siren on a passing ambulance. The faster the object is receding, the more its light will shift toward the red end of the spectrum. The Hubble constant relates an object’s distance from Earth to this redshift, and thus the object’s speed as it’s carried away.

    One of an astronomer’s best tools for calculating this is a standard candle, any class of objects that always have the same, standard brightness.

    Standard Candles to measure age and distance of the universe from supernovae NASA

    If scientists know the brightness of an object, they can determine its distance by measuring how dim it appears to us on Earth.

    For decades scientists have tried to get accurate measurements of the Hubble constant in order to investigate why the universe is expanding, and, in fact, accelerating. This ultimately resolves to measuring objects’ redshifts and matching them with independent measurements of the objects’ distances from us. However, these two most accurate measurements scientists currently have for the Hubble constant disagree — an endless source of frustration for cosmologists.

    A Proposal

    This was the cosmological landscape in the early 2000s when Holz and Hughes held positions as postdoctoral researchers at KITP. “Scott had been thinking about gravitational waves for a while,” said Holz. “He was the expert, and I was much more focused on cosmological questions.” But Hughes’ enthusiasm soon piqued Holz’s curiosity, and the two began to talk about gravitational wave cosmology in the office and on walks along the Santa Barbara bluffs.

    Holz and Hughes credit their close collaboration to the construction of the new wing of Kohn Hall in 2001. Initially, all postdocs at KITP had their own offices, explained Hughes, but the construction forced them to double-up. “Suddenly we were spending a lot more time with each other.”

    A 2002 KITP program on cosmological data fanned the flames of their interest in the topic. By the time Hughes left to join the faculty at MIT, they had finished the first draft of their paper detailing how to calculate the Hubble constant with gravitational waves. After two years gestating they finally published the study in The Astrophysical Journal.

    “I had a great time writing that paper with Scott,” said Holz. “I learned an incredible amount. So much that I was convinced that gravitational waves were the future, and that I should get involved.”

    The idea of using gravitational wave sources to measure the Hubble constant was not new. The concept was first proposed in a visionary paper back in 1986 by Bernard Schutz [Nature]. And a number of other notions regarding gravitational waves were also floating around the literature in the early 2000s. But what Holz and Hughes did was synthesize all these ideas and emphasize the feasibility of combining data from gravitational waves with follow-up observations using light.

    The study also was the first to use the term “standard siren [Nature].” Hughes recalled discussing the paper with Caltech astrophysicist Sterl Phinney, who remarked, “Hmm. Kind of like a standard candle, but you hear it. You should call it a standard siren.” Holz independently had an almost identical conversation with physicist Sean Carroll, a former KITP postdoc himself. Holz and Hughes included the term in their paper, and it stuck. The phrase has since become ubiquitous in cosmology.

    “The term ‘standard siren’ might be our most lasting contribution, Scott,” Holz remarked. “I’ll take it,” laughed Hughes.

    Using gravitational waves to measure the Hubble constant has many advantages over other methods. Certain supernovae provide decent standard candles, “but, as a standard candle, supernovae are not very well understood,” said Holz. “The main thing that makes standard sirens interesting is that they’re understood from first principles, directly from the theory of general relativity.”

    When using standard candles, scientists have to calibrate the distances of certain classes of objects using the information from other ones, effectively leapfrogging their way to a proper distance measurement. Astronomers call this method a “distance ladder,” and errors and uncertainty can creep in at many points in the calculations.

    3
    Getting accurate measurements of distance requires building up a distance ladder using a number of different techniques for various ranges. Photo Credit: MATT PERKO.

    In contrast, gravitational waves can provide a direct measurement of an object’s distance. “You just write down the equations and solve them, and then you’re done,” said Holz. “We’ve tested general relativity for a hundred years; it really works, and it says ‘here’s how far that source is.’ There’s no distance ladder, there’s none of that fiddling around.”

    All the early papers on measuring the Hubble constant using gravitational waves were somewhat speculative, according to Holz. They were proposals for the far future. “We hadn’t even detected gravitational waves yet, much less waves from two neutron stars, much less with an optical counterpart,” he said. But interest and enthusiasm for the technique were growing.

    Hughes remembers colleagues coming up to him after his talks and asking about the likelihood of observing a standard siren in the next decade. He didn’t know, but he did say that with a better understanding of the optical counterpart, they could probably localize an event to within 10-20 square degrees. “And I think if you have that, every piece of large glass on Earth is going to stare at that spot on the sky,” Hughes had said. “And, in the end, that is exactly what happened.”

    And Then It Happened

    On August 17, 2017, less than two years after detecting the first gravitational waves, the LIGO and Virgo observatories recorded a signal from merging neutron stars. Thanks to an alert system, which Holz helped establish, a flurry of activity followed as nearly every major ground and space-based observatory trained their sights on the event. Scientists collected data on the merger in every region of the electromagnetic spectrum.


    VIRGO Gravitational Wave interferometer, near Pisa, Italy


    Caltech/MIT Advanced aLigo Hanford, WA, USA installation


    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

    Gravitational waves. Credit: MPI for Gravitational Physics/W.Benger

    Gravity is talking. Lisa will listen. Dialogos of Eide

    ESA/eLISA the future of gravitational wave research

    Localizations of gravitational-wave signals detected by LIGO in 2015 (GW150914, LVT151012, GW151226, GW170104), more recently, by the LIGO-Virgo network (GW170814, GW170817). After Virgo came online in August 2018


    Skymap showing how adding Virgo to LIGO helps in reducing the size of the source-likely region in the sky. (Credit: Giuseppe Greco (Virgo Urbino group)

    “It really is one of those things where, if it had happened before I retired, I would have been happy,” said Hughes. “But it actually happened before I turned 50.”

    Suddenly, gravitational wave cosmology was a real field, and standard sirens were another part of the toolkit. “But for something to become part of the toolkit so quickly? That’s extraordinarily unusual,” said Holz.

    It turns out that cosmologists need another tool, because they currently have two different values for the Hubble constant. Methods using the cosmic microwave background [CMB] — faint light left over from the big bang — yields a value of around 68. Meanwhile, calculations that use Type Ia supernovae — a variety of standard candle [above] — yield a bit more than 73.

    CMB per ESA/Planck

    Although they appear close, the two values actually differ by three standard deviations, and both have fairly tight error bars. The disagreement has cosmologists increasingly concerned as the error bars on these two values only get tighter. It could signal a fundamental problem in our understanding of the universe, and is the subject of a KITP conference this July.

    There are a few intrinsic differences between the two techniques, though. The cosmic microwave background reflects the conditions of the early universe, while the supernovae paint a picture of the current universe. “There’s a chance that maybe something very strange and unexpected has happened between the early and late days of the universe, and that’s why these values don’t agree,” said Holz. But cosmologists simply don’t know for sure.

    Getting another, independent value for the Hubble constant will help clear up this conundrum. “Because it’s so clean and so direct, that measurement will be a very compelling number,” Holz explained. “At the very least, it’ll inform this discussion, if not just completely resolve it.”

    Holz and his colleagues, Hsin-Yu Chen and Maya Fishbach, have just published a paper in the journal Nature, finding that 20 to 30 observations would allow scientists to calculate the Hubble constant to within 2 percent accuracy, tight enough to begin comparing it to the two values from the cosmic microwave background and supernovae.

    This summer, Holz is co-organizing a KITP program on the new era of gravitational wave physics and astrophysics, and the new field of standard siren cosmology will be a major topic of discussion. In fact, Holz also helped organize the KITP rapid response program that brought researchers together shortly after LIGO’s first detection of gravitational waves.

    Holz and Hughes credit their success to their experiences at KITP. “While working together at the KITP the two of us got excited about measuring the Hubble constant using gravitational waves,” said Holz. “And that’s exactly what the KITP is about: bringing different people together with different backgrounds, stirring the pot and seeing what happens.”

    For the past decade Holz’s career has focused on standard siren cosmology. “And the amazing thing is we’ve actually done it,” he said. “I helped write the paper that did the first standard siren measurement ever. This was exactly what Scott and I had hypothesized about years before.”

    “If both of us hadn’t been at the KITP there’s no way I’d be spending a good fraction of my life on LIGO teleconferences right now,” said Holz. “But I wouldn’t have it any other way.”

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    UC Santa Barbara Seal
    The University of California, Santa Barbara (commonly referred to as UC Santa Barbara or UCSB) is a public research university and one of the 10 general campuses of the University of California system. Founded in 1891 as an independent teachers’ college, UCSB joined the University of California system in 1944 and is the third-oldest general-education campus in the system. The university is a comprehensive doctoral university and is organized into five colleges offering 87 undergraduate degrees and 55 graduate degrees. In 2012, UCSB was ranked 41st among “National Universities” and 10th among public universities by U.S. News & World Report. UCSB houses twelve national research centers, including the renowned Kavli Institute for Theoretical Physics.

     
  • richardmitnick 10:28 am on January 29, 2019 Permalink | Reply
    Tags: , , , , , , Quasars are brilliant enough to be seen from a universe less than a billion years old making them prime targets for reaching earlier epochs, , Standard candles, Two decades ago astronomers discovered that the universe was not only expanding but accelerating in its expansion, Type Ia supernovae have long been the brightest of standard candles, What Quasar Cosmology Can Teach Us About Dark Energy   

    From Sky & Telescope: “What Quasar Cosmology Can Teach Us About Dark Energy” 

    SKY&Telescope bloc

    From Sky & Telescope

    January 28, 2019
    Monica Young

    Astronomers have found a way to turn quasars into standard candles, with potentially far-reaching implications for the nature of mysterious dark energy.

    Standard Candles to measure age and distance of the universe NASA

    National Science Foundation (NASA, JPL, Keck Foundation, Moore Foundation, related) — Funded BICEP2 Program; modifications by E. Siegel.

    Two decades ago astronomers discovered that the universe was not only expanding but accelerating in its expansion. They dubbed the cause of this acceleration dark energy, but what that actually is remains as ineffable now as it was then.

    The weird repulsive force has left its fingerprints on the earliest photons we can see, the ones emitted as part of the cosmic microwave background (CMB), when the infant universe was only 370,000 years old. Yet dark energy only began to dominate expansion as the universe entered middle age, after 9 billion years or so.

    Now, Guido Risaliti (University of Florence and INAF-Astrophysical Observatory of Arcetri, Italy) and Elisabeta Lusso (Durham University, UK) are using quasars to probe the cosmology of our universe’s relatively unexplored adolescence. The results, appearing in the January 28th Nature Astronomy, promise to reveal dark energy’s true nature.

    The leading explanation for dark energy has long been the cosmological constant, also known as vacuum energy. This energy inherent to empty space arises from quantum theory, which says that even when space appears empty of particles, it’s actually filled with quantum fields. These fields exert a negative pressure that counteracts the attractive force of gravity. However, calculations of vacuum energy overpredict the measured dark energy density by an astounding 120 orders of magnitude (that’s a 1 followed by 120 zeroes!). That the cosmological constant remains the favorite theory speaks to how little we understand dark energy — and how difficult the measurements involved are.

    Studying the universe at any age starts with gauging cosmological distance — the farther we look, the further back in time we see­­ ­— but we can’t just roll out a tape measure to the stars. Enter standard candles, objects for which we can measure an intrinsic luminosity. By comparing how bright a standard candle appears to be with how bright it really is, we can determine its distance without knowing anything about cosmology.

    Type Ia supernovae have long been the brightest of standard candles. Observations of these detonating white dwarfs led to the Nobel-winning discovery of accelerating expansion announced back in 1998. The supernovae extended our reach to when the universe was a third of its current age. That’s a pretty good tape measure! Nevertheless, it only probes the era when dark energy began to dominate the universe’s expansion. To see farther back, and probe the era when dark energy overtook matter, astronomers need something even more luminous.

    Quasars as Standard Candles

    2
    Understanding the physics of quasar accretion disks (blue-white) and X-ray-emitting coronae (yellow) can help astronomers use quasars as standard candles.
    NASA / CXC / M. Weiss.

    What’s more luminous than an exploding star? A gas-guzzling supermassive black hole would do the trick. After all, quasars are brilliant enough to be seen from a universe less than a billion years old, making them prime targets for reaching earlier epochs.

    Unfortunately, quasars also exhibit a bewildering variety of forms — astronomers have long thought they were anything but standard. Case in point: Astronomers have known for the past 30 years that more visibly luminous quasars emit relatively fewer X-rays, but there was too much variance from one quasar to another to pin down any one quasar’s intrinsic brightness.

    Risaliti and Lusso realized that this relation between the emission of X-rays and visible light must arise from the physics of quasar accretion disks. The disk itself emits visible light, while a hot, gaseous corona emits the X-rays. The two are intertwined by straightforward physics; it’s just that previously, contaminants had been mucking things up. So for this study, Risaliti and Lusso removed any sources where disk emission is obscured (by dust or gas) or contaminated (by emission from a fast-flowing black hole jet). Their careful selection results in a much tighter, more useful relation. Using data from the Sloan Digital Sky Survey and the XMM-Newton, Chandra, and Swift space telescopes, the duo then apply the relation to turn 1,600 quasars into standard candles.

    SDSS 2.5 meter Telescope at Apache Point Observatory, near Sunspot NM, USA, Altitude 2,788 meters (9,147 ft)

    ESA/XMM Newton

    NASA/Chandra X-ray Telescope

    NASA Neil Gehrels Swift Observatory

    3
    The history of the universe shows a crucial time when the expansion switched from decelerating to accelerating. But the future still hangs in the balance, depending on the behavior of dark energy. If dark energy increases, everything will be torn apart; if it changes direction, the cosmos could end in a big crunch.
    NASA / CXC / M.Weiss

    The quasars help Risaliti and Lusso fill in the gap along the cosmic timeline, looking back to an adolescent universe only a billion years old. From this data, the team finds that dark energy is actually increasing over cosmic time.

    The results appear to rule out the cosmological constant, which predicts a constant energy density. That’s a bit of a relief given that vacuum energy overpredicts the observations so badly. (Did I mention the 120 orders of magnitude?) Evolving dark energy may also help resolve an ongoing tension between measurements of the universe’s current expansion rate.

    Nevertheless, the results are unsettling from a philosophical standpoint: If dark energy density really does increase over time, then so does the repulsive force it exerts, potentially ending our universe in a Big Rip.

    Too Early To Tell

    Let’s not give up on the universe just yet, though. Phil Hopkins (Caltech), who wasn’t involved in the study, urges caution in interpreting its results. The relation that Lusso and Risaliti use to turn quasars into standard candles may itself evolve over time, making those quasars not so standard. For example, if quasars slow their gas-guzzling as mergers become less frequent, that might change the shape of the relation between the emission of X-rays and visible light. “[The relation] only needs to evolve a little bit to explain these observations,” he adds.

    That said, Hopkins agrees the results are interesting and worth following up with even bigger and better samples. The authors also note that other studies probing the adolescent universe are forthcoming. The bar is high these days for disproving the standard cosmological model, and only time and additional study will tell if this is the method that will do it.

    See the full article here .
    See also from Chandra here.

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Sky & Telescope magazine, founded in 1941 by Charles A. Federer Jr. and Helen Spence Federer, has the largest, most experienced staff of any astronomy magazine in the world. Its editors are virtually all amateur or professional astronomers, and every one has built a telescope, written a book, done original research, developed a new product, or otherwise distinguished him or herself.

    Sky & Telescope magazine, now in its eighth decade, came about because of some happy accidents. Its earliest known ancestor was a four-page bulletin called The Amateur Astronomer, which was begun in 1929 by the Amateur Astronomers Association in New York City. Then, in 1935, the American Museum of Natural History opened its Hayden Planetarium and began to issue a monthly bulletin that became a full-size magazine called The Sky within a year. Under the editorship of Hans Christian Adamson, The Sky featured large illustrations and articles from astronomers all over the globe. It immediately absorbed The Amateur Astronomer.

    Despite initial success, by 1939 the planetarium found itself unable to continue financial support of The Sky. Charles A. Federer, who would become the dominant force behind Sky & Telescope, was then working as a lecturer at the planetarium. He was asked to take over publishing The Sky. Federer agreed and started an independent publishing corporation in New York.

    “Our first issue came out in January 1940,” he noted. “We dropped from 32 to 24 pages, used cheaper quality paper…but editorially we further defined the departments and tried to squeeze as much information as possible between the covers.” Federer was The Sky’s editor, and his wife, Helen, served as managing editor. In that January 1940 issue, they stated their goal: “We shall try to make the magazine meet the needs of amateur astronomy, so that amateur astronomers will come to regard it as essential to their pursuit, and professionals to consider it a worthwhile medium in which to bring their work before the public.”

     
  • richardmitnick 3:06 pm on October 24, 2018 Permalink | Reply
    Tags: A double-degenerate model in which a one white dwarf explodes in a binary pair flinging the other one out into space, , , , , , Dynamically driven double-degenerate double-detonation” model — or D6 for short, Speeding White Dwarfs May Point to Past Explosions, Standard candles,   

    From AAS NOVA: “Speeding White Dwarfs May Point to Past Explosions” 

    AASNOVA

    From AAS NOVA

    24 October 2018
    Susanna Kohler

    1
    A new study suggests that binary white dwarfs be the key to understanding Type Ia supernovae like the explosion featured in this artist’s impression. [ESO/M. Kornmesser]

    A recent study has discovered three of the fastest stars known in the Milky Way. But these stars may be more than just speeders — they might also be evidence of how Type Ia supernovae occur.

    1
    Two competing theoretical models for the progenitors of Type Ia supernova explosions: the single-degenerate model (top) and the double-degenerate model (bottom). Today’s study focuses on a double-degenerate model in which a one white dwarf explodes in a binary pair, flinging the other one out into space. [NASA/CXC/SAO and GSFC/D. Berry]

    Seeking a Source

    Given the extent to which we rely on Type Ia supernovae as standard candles used to measure vast distances, you might think that we’ve got them fairly well figured out. But these stellar explosions are complicated, and it turns out that we don’t know some of the most fundamental things about them! Scientists are still working hard to find answers about what systems Type Ia supernovae originate from, and how the explosions are caused.

    Led by astronomer Ken Shen (University of California, Berkeley), a team of astronomers has explored one particular model for Type Ia supernovae further: the “dynamically driven double-degenerate double-detonation” model — or D6, for short. In this scenario, a pair of white dwarfs orbit each other in a binary system. Two back-to-back detonations then cause one of the white dwarfs to explode as a supernova while the other white dwarf survives and is flung free of the explosion site.

    Shen and collaborators note that if the D6 model proves to be the primary means of producing Type Ia supernovae, then there’s an observable outcome: there should be white dwarfs speeding throughout our galaxy that were suddenly liberated by the supernova explosions of their companions.

    2
    Posterior probability distributions for the total galactocentric velocities for estimated for the three hypervelocity white dwarf candidates: D6-1, D6-2, and D6-3. [Shen et al. 2018]

    Hunt for Speeders

    Based on the estimated supernova rate in our galaxy and the properties of binary white dwarfs, Shen and collaborators predict that there should be ~30 hypervelocity white dwarfs within ~3,000 light-years of us. But how to spot these compact stars speeding across the sky? With one of the best tools in the business: Gaia.

    Shen and collaborators combed through the numbers from the Gaia mission’s second data release, which presents the astrometric parameters of more than a billion stars across the sky. In this treasure trove of information, they discovered seven candidates that they then followed up with ground-based observations. After ruling out four as ordinary stars, the authors were left with three candidate hypervelocity white dwarfs.

    Associated Remnant?

    3

    The three candidates have total galactocentric velocities between 1,000 and 3,000 km/s (that’s 2.2 to 6.7 million miles per hour!), making them some of the fastest known stars in the Milky Way. That alone is enough to qualify them as potential progenitors of Type Ia supernovae via the D6 model — but Shen and collaborators look for one more clue: whether they can be tracked back to a supernova remnant.

    Two of the candidates show no sign of having traveled from a nearby remnant — not necessarily surprising, as the remnants could be very faint, or even have already dissipated completely. But the third candidate can be tracked back to a location within the faint, old supernova remnant G70.0–21.5.

    While not yet a smoking gun, these hypervelocity white dwarfs represent important support for the D6 model. And continued follow-up of additional candidates — as well as new candidates discovered in future Gaia releases — may further confirm this model for how Type Ia supernovae occur.

    Citation

    “Three Hypervelocity White Dwarfs in Gaia DR2: Evidence for Dynamically Driven Double-Degenerate Double-Detonation Type Ia Supernovae,” Ken J. Shen et al 2018 ApJ 865 15.
    http://iopscience.iop.org/article/10.3847/1538-4357/aad55b/meta

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    1

    AAS Mission and Vision Statement

    The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

    The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
    The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
    The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
    The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
    The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

    Adopted June 7, 2009

     
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