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  • richardmitnick 1:34 pm on April 24, 2019 Permalink | Reply
    Tags: "Bringing Clarity to What Drives Auroras", , , Basic Research, ,   

    From Eos: “Bringing Clarity to What Drives Auroras” 

    From AGU
    Eos news bloc

    From Eos

    Mark Zastrow

    In this image taken from the International Space Station, both diffuse and intense auroras are visible, produced by charged particles propelled into Earth’s atmosphere. Credit: NASA

    The most spectacular auroras are produced by electrons zipping from space into Earth’s atmosphere. Although Earth’s magnetic field repels most electrons before they reach any wisps of air, under special conditions they can penetrate into the atmosphere, striking air molecules and causing them to glow.

    But how exactly those electrons, which normally circulate in Earth’s magnetic field, are accelerated or pushed down into the atmosphere is not fully clear.

    It’s generally agreed that there are three main ways to generate this “auroral precipitation.” One is small pockets of strong electric field high above Earth—also known as quasi-static potential structures (QSPS)—which can whisk them down. Another is strong waves in Earth’s magnetic field in which field lines vibrate like a plucked string—called Alfvén waves—propelling the charged particles along. These two mechanisms produce the most intense bands, curtains, and sheets of auroras.

    The other main cause is higher-frequency waves in Earth’s magnetic field that don’t increase electrons’ speed but scatter them, nudging the particles into trajectories that carry them down into the atmosphere. Wave scattering produces a less vivid, diffuse auroral glow but is commonly thought to be responsible for the bulk of the total auroral energy.

    But it’s difficult to decipher which of these three is happening at any given time. They can be identified only indirectly by analyzing spacecraft data measurements. Plus, these different mechanisms can occur simultaneously, which researchers have been unable to disentangle.

    Now, Dombeck et al. [JGR Space Physics] have developed a classification scheme that resolves many of these ambiguities and can detect multiple mechanisms. Their method used 13 years of data from NASA’s Fast Auroral Snapshot Explorer (FAST), a satellite launched into Earth orbit in 1996.

    NASA Fast Auroral Snapshot Explorer (FAST)

    Crucially, its instruments can observe electrons traveling both down toward Earth and up into space. In contrast, the previous, widely used scheme was based on data from satellites that could measure only downward traveling electrons and could identify only a single mechanism at a time.

    Being able to see upward traveling electrons makes it easier to determine whether they were accelerated by electric field structures or magnetic field vibrations, as the former reflect upgoing electrons back toward Earth and the latter do not. When the team compared their results, they found that misclassifications were common under the previous scheme.

    Applying their method to FAST data paints a complex picture of electron precipitation: Most of the time, multiple mechanisms contribute, and frequently, all three appear in intense auroral storms.

    Intriguingly, their results may also contradict the view that wave scattering contributes most of the energy of electron precipitation: The authors found that on Earth’s nightside, two thirds of the energy input comes from intense precipitation that is mostly caused by QSPS and Alfvén waves.

    Using this new method to better understand the mechanisms responsible for auroral precipitation will also help scientists better understand how Earth’s magnetic fields interact with the stream of charged particles coming from the Sun and how this interaction produces hazardous solar storms.

    See the full article here .


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    Eos is the leading source for trustworthy news and perspectives about the Earth and space sciences and their impact. Its namesake is Eos, the Greek goddess of the dawn, who represents the light shed on understanding our planet and its environment in space by the Earth and space sciences.

  • richardmitnick 12:15 pm on April 24, 2019 Permalink | Reply
    Tags: "Scientists Use Asteroid to Measure Smallest Star Size to Date", , , Basic Research, , , ,   

    From Harvard-Smithsonian Center for Astrophysics: “Scientists Use Asteroid to Measure Smallest Star Size to Date” 

    Harvard Smithsonian Center for Astrophysics

    From Harvard-Smithsonian Center for Astrophysics

    April 16, 2019

    Amy Oliver
    Public Affairs
    Center for Astrophysics | Harvard & Smithsonian
    Fred Lawrence Whipple Observatory
    +1 617-495-7462

    Tyler Jump
    Public Affairs
    Center for Astrophysics | Harvard & Smithsonian
    +1 617-495-7462


    Scientists in the VERITAS (Very Energetic Radiation Imaging Telescope Array System) Collaboration have published a paper in Nature Astronomy journal detailing the results of their work with the VERITAS array—located at the Center for Astrophysics’ Fred Lawrence Whipple Observatory in Amado, Arizona—to measure the smallest apparent size of stars in the night sky known to date.

    CfA/VERITAS, a major ground-based gamma-ray observatory with an array of four 12m optical reflectors for gamma-ray astronomy in the GeV – TeV energy range. Located at Fred Lawrence Whipple Observatory,Mount Hopkins, Arizona, US in AZ, USA, Altitude 2,606 m (8,550 ft)

    Measurements taken using the VERITAS telescopes revealed the diameter of a giant star located 2,674 light years from Earth. Taken on February 22, 2018, at the Whipple Observatory, data revealed the star to be 11 times the diameter of Earth’s Sun. Using the four 12-m gamma-ray telescopes of VERITAS, the team collected 300 images per second to detect the diffraction pattern in the shadow sweeping past the telescopes as the star TYC 5517-227-1 was occulted by the 60-km asteroid Imprinetta. “From these data, the brightness profile of the diffraction pattern of the star was reconstructed with high accuracy,” said Dr. Michael Daniel, Operations Manager, VERITAS. “This allowed us to determine the actual diameter of the star, and determine it to be a red giant, although it could previously be classified as ambiguous.”

    Three months later, on May 22, 2018, the team repeated the experiment when asteroid Penelope—diameter 88-km—occulted star TYC 278-748-1 located 700 light years from Earth. “Using the same formula for data collection and calculations, we determined this star to be 2.17 times the diameter Earth’s Sun,” said Daniel. “This direct measurement allowed us to correct an earlier estimation that placed the star’s diameter at 1.415 times that of our sun.”

    With almost any star on the night sky too distant from Earth to be directly measured using even the best of optical telescopes, scientists overcame these limitations using diffraction, which occurs when an object, like an asteroid, passes in front of a star, making a shadow called an occultation. “The incredibly faint shadows of asteroids pass over us every day,” explained Dr. Tarek Hassan, DESY. “But the rim of the shadow isn’t perfectly sharp. Instead, wrinkles of light surround the central shadow, like water ripples.”

    For VERITAS scientists, however, the task was not as easy as turning telescopes to the sky. “Asteroid occultations are difficult to predict,” said Daniel. “The only chance to catch the diffraction pattern is to make very fast snapshots when the shadow of the occultation sweeps across the telescope.”

    Astronomers have similarly used this method— which measures to an angular diameter of roughly one milliarcsecond—to measure angular sizes of stars occulted by Earth’s moon. “The trouble is that not many telescopes are large enough for the occultation method to measure the diffraction pattern with confirmed accuracy over the turbulence in the Earth’s atmosphere,” said Daniel. “VERITAS telescopes are uniquely sensitive as we use them primarily for observing faint light from very-high-energy gamma rays and cosmic rays. While they do not produce images as elegant as those from traditional optical telescopes, they see and capture fast variations of light, and we estimate that they can analyze stars up to ten times farther away with extreme accuracy than optical telescopes using the lunar occultation method can.”

    At its conclusion, the pilot study resulted in the direct measurement of the size of a star at the smallest angular scale in the night sky to date, and established a new method to determine the angular diameter of stars.

    About VERITAS

    VERITAS (Very Energetic Radiation Imaging Telescope Array System) is a ground-based array of four, 12-m optical reflectors for gamma-ray astronomy located at the Center for Astrophysics | Harvard & Smithsonian, Fred Lawrence Whipple Observatory in Amado, Arizona. VERITAS is the world’s most sensitive very-high-energy gamma-ray observatory, and it detects gamma rays via the extremely brief flashes of blue “Cherenkov” light they create when they are absorbed in the Earth’s atmosphere.

    VERITAS is supported by grants from the U.S. Department of Energy Office of Science, the U.S. National Science Foundation, and the Smithsonian Institution, and by NSERC in Canada.

    The VERITAS Collaboration consists of about 80 scientists from 20 institutions in the United States, Canada, Germany and Ireland.

    For more information about VERITAS visit http://veritas.sao.arizona.edu

    About DESY

    DESY is one of the world’s leading particle accelerator centers. Researchers use the large‐scale facilities at DESY to explore the microcosm in all its variety – ranging from the interaction of tiny elementary particles to the behavior of innovative nanomaterials and the vital processes that take place between biomolecules to the great mysteries of the universe. The accelerators and detectors that DESY develops and builds at its locations in Hamburg and Zeuthen are unique research tools. DESY is a member of the Helmholtz Association, and receives its funding from the German Federal Ministry of Education and Research (BMBF) (90 per cent) and the German federal states of Hamburg and Brandenburg (10 per cent).

    See the full article here .

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    Stem Education Coalition

    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.

  • richardmitnick 9:07 am on April 24, 2019 Permalink | Reply
    Tags: , , Basic Research, , , ,   

    From JPL-Caltech: “NASA’s InSight Lander Captures Audio of First Likely ‘Quake’ on Mars” 

    NASA JPL Banner

    From JPL-Caltech

    April 23, 2019

    Andrew Good
    Jet Propulsion Laboratory, Pasadena, Calif.

    Dwayne Brown
    Headquarters, Washington

    Alana Johnson
    Headquarters, Washington

    NASA’s Mars InSight lander has measured and recorded for the first time ever a likely “marsquake.”

    NASA/Mars InSight Lander

    The faint seismic signal, detected by the lander’s Seismic Experiment for Interior Structure (SEIS) instrument, was recorded on April 6, the lander’s 128th Martian day, or sol. This is the first recorded trembling that appears to have come from inside the planet, as opposed to being caused by forces above the surface, such as wind. Scientists still are examining the data to determine the exact cause of the signal.

    This image, taken March 19, 2019 by a camera on NASA’s Mars InSight lander, shows the rover’s domed Wind and Thermal Shield, which covers its seismometer, the Seismic Experiment for Interior Structure, and the Martian surface in the background. Credits: NASA/JPL-Caltech

    This video and audio illustrates a seismic event detected by NASA’s Mars InSight rover on April 6, 2019, the 128th Martian day, or sol, of the mission. Three distinct kinds of sounds can be heard, all of them detected as ground vibrations by the spacecraft’s seismometer, called the Seismic Experiment for Interior Structure (SEIS): noise from Martian wind, the seismic event itself, and the spacecraft’s robotic arm as it moves to take pictures. Credits: NASA/JPL-Caltech/CNES/IPGP/Imperial College London

    “InSight’s first readings carry on the science that began with NASA’s Apollo missions,” said InSight Principal Investigator Bruce Banerdt of NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California. “We’ve been collecting background noise up until now, but this first event officially kicks off a new field: Martian seismology!”

    The new seismic event was too small to provide solid data on the Martian interior, which is one of InSight’s main objectives. The Martian surface is extremely quiet, allowing SEIS, InSight’s specially designed seismometer, to pick up faint rumbles. In contrast, Earth’s surface is quivering constantly from seismic noise created by oceans and weather. An event of this size in Southern California would be lost among dozens of tiny crackles that occur every day.

    “The Martian Sol 128 event is exciting because its size and longer duration fit the profile of moonquakes detected on the lunar surface during the Apollo missions,” said Lori Glaze, Planetary Science Division director at NASA Headquarters.

    NASA’s Apollo astronauts installed five seismometers that measured thousands of quakes while operating on the Moon between 1969 and 1977, revealing seismic activity on the Moon. Different materials can change the speed of seismic waves or reflect them, allowing scientists to use these waves to learn about the interior of the Moon and model its formation. NASA currently is planning to return astronauts to the Moon by 2024, laying the foundation that will eventually enable human exploration of Mars.

    InSight’s seismometer, which the lander placed on the planet’s surface on Dec. 19, 2018, will enable scientists to gather similar data about Mars. By studying the deep interior of Mars, they hope to learn how other rocky worlds, including Earth and the Moon, formed.

    This set of images from the Instrument Deployment Camera shows NASA’s InSight lander placing its first instrument onto the surface of Mars, completing a major mission milestone. Image Credit: NASA/JPL-Caltech.

    Three other seismic signals occurred on March 14 (Sol 105), April 10 (Sol 132) and April 11 (Sol 133). Detected by SEIS’ more sensitive Very Broad Band sensors, these signals were even smaller than the Sol 128 event and more ambiguous in origin. The team will continue to study these events to try to determine their cause.

    Regardless of its cause, the Sol 128 signal is an exciting milestone for the team.

    “We’ve been waiting months for a signal like this,” said Philippe Lognonné, SEIS team lead at the Institut de Physique du Globe de Paris (IPGP) in France. “It’s so exciting to finally have proof that Mars is still seismically active. We’re looking forward to sharing detailed results once we’ve had a chance to analyze them.”

    Most people are familiar with quakes on Earth, which occur on faults created by the motion of tectonic plates. Mars and the Moon do not have tectonic plates, but they still experience quakes – in their cases, caused by a continual process of cooling and contraction that creates stress. This stress builds over time, until it is strong enough to break the crust, causing a quake.

    Detecting these tiny quakes required a huge feat of engineering. On Earth, high-quality seismometers often are sealed in underground vaults to isolate them from changes in temperature and weather. InSight’s instrument has several ingenious insulating barriers, including a cover built by JPL called the Wind and Thermal Shield, to protect it from the planet’s extreme temperature changes and high winds.

    SEIS has surpassed the team’s expectations in terms of its sensitivity. The instrument was provided for InSight by the French space agency, Centre National d’Études Spatiales (CNES), while these first seismic events were identified by InSight’s Marsquake Service team, led by the Swiss Federal Institute of Technology.

    “We are delighted about this first achievement and are eager to make many similar measurements with SEIS in the years to come,” said Charles Yana, SEIS mission operations manager at CNES.

    JPL manages InSight for NASA’s Science Mission Directorate. InSight is part of NASA’s Discovery Program, managed by the agency’s Marshall Space Flight Center in Huntsville, Alabama. Lockheed Martin Space in Denver built the InSight spacecraft, including its cruise stage and lander, and supports spacecraft operations for the mission.

    A number of European partners, including CNES and the German Aerospace Center (DLR), support the InSight mission. CNES provided the SEIS instrument to NASA, with the principal investigator at IPGP. Significant contributions for SEIS came from IPGP; the Max Planck Institute for Solar System Research in Germany; the Swiss Federal Institute of Technology (ETH Zurich) in Switzerland; Imperial College London and Oxford University in the United Kingdom; and JPL. DLR provided the Heat Flow and Physical Properties Package (HP3) instrument, with significant contributions from the Space Research Center of the Polish Academy of Sciences and Astronika in Poland. Spain’s Centro de Astrobiología supplied the temperature and wind sensors.

    For more information about InSight, visit:


    For more information about the agency’s Moon to Mars activities, visit


    See the full article here .


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    NASA JPL Campus

    Jet Propulsion Laboratory (JPL)) is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. Although the facility has a Pasadena postal address, it is actually headquartered in the city of La Cañada Flintridge, on the northwest border of Pasadena. JPL is managed by the nearby California Institute of Technology (Caltech) for the National Aeronautics and Space Administration. The Laboratory’s primary function is the construction and operation of robotic planetary spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA’s Deep Space Network.

    Caltech Logo

    NASA image

  • richardmitnick 8:37 am on April 24, 2019 Permalink | Reply
    Tags: "Omega Centauri’s lost stars", , , “Fimbulthul” contains 309 stars stretching over 18° in the sky, Basic Research, , , We now know that Omega Centauri is the most massive globular cluster in the Milky Way   

    From Canada France Hawaii Telescope: “Omega Centauri’s lost stars” 

    CFHT icon
    From Canada France Hawaii Telescope


    Mary Beth Laychak, Outreach manager
    Canada-France-Hawaii Telescope

    The Milky Way, as seen by the Gaia satellite. Streams of co-moving stars are shown colored according to their motions as measured by Gaia. The “Fimbulthul” stream which is due to stars lost from the omega Centauri globular cluster (white box) has been highlighted. Credit R. Ibata.

    A team of researchers from the Strasbourg Astronomical Observatory, Bologna Observatory and the University of Stockholm has identified a stream of stars that was torn off the globular cluster Omega Centauri. Searching through the 1.7 billion stars observed by the ESA Gaia mission, they have identified 309 stars that suggest that this globular cluster may actually be the remnant of a dwarf galaxy that is being torn apart by the gravitational forces of our Galaxy.

    ESA/GAIA satellite

    In 1677, Edmond Halley gave the name “Omega Centauri” (ω Cen) to what he thought was a star in the Centaurus constellation. Later in 1830 John Herschel realized that it was in fact a globular cluster that could be resolved into individual stars. We now know that Omega Centauri is the most massive globular cluster in the Milky Way: it is about 18,000 light years from us and contains several million stars that are about 12 billion years old. The nature of this object has been the subject of much debate: is it really a globular cluster, or could it be the heart of a dwarf galaxy whose periphery has been dispersed by the Milky Way?

    This last hypothesis is based on the fact that ω Cen contains several stellar populations, with a large range of metallicities (i.e. heavy element content) that betray a formation over an extended period of time. An additional argument in favor of this hypothesis would be to find debris from the cluster scattered along its orbit in the Milky Way. Indeed, when a dwarf galaxy interacts with a massive galaxy like our own, stars are torn off by gravitational tidal forces, and these stars remain visible for a time as stellar streams, before becoming dispersed in the vast volumes of interstellar space surrounding the massive galaxy.

    By analyzing the motions of stars measured by the Gaia satellite with an algorithm called STREAMFINDER developed by the team, the researchers identified several star streams. One of them, named “Fimbulthul” (after one of the rivers in Norse mythology that existed at the beginning of the world), contains 309 stars stretching over 18° in the sky.

    By modeling the trajectories of the stars, the team showed that the Fimbulthul structure is a stellar tidal stream torn off ω Cen, extending up to 28° from the cluster. Spectroscopic observations of 5 stars of this stream with the Canada-France Hawaii Telescope show that their velocities are very similar, and that they have metallicities comparable to the stars of ω Cen itself, which reinforces the idea that the tidal stream is linked to ω Cen.

    “The stars that the team observed were quite faint for the instrument we were using,” says Dr. Nadine Manset, instrument scientist for Espadons and CFHT’s astronomy group manager. “It is great to see such challenging observations reinforce the Fimbulthul structure’s link to ω Cen.”

    The researchers were then able to show that the stream is also present in the very crowded area of sky in the immediate vicinity of the cluster. Further modeling of the tidal stream will constrain the dynamical history of the dwarf galaxy that was the progenitor of ω Cen, and allow us to find even more stars lost by this system into the halo of the Milky Way.

    The team’s paper appeared in the April 22nd edition of Nature.

    See the full article here .


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    The CFH observatory hosts a world-class, 3.6 meter optical/infrared telescope. The observatory is located atop the summit of Mauna Kea, a 4200 meter, dormant volcano located on the island of Hawaii. The CFH Telescope became operational in 1979. The mission of CFHT is to provide for its user community a versatile and state-of-the-art astronomical observing facility which is well matched to the scientific goals of that community and which fully exploits the potential of the Mauna Kea site.

    CFHT Telescope


  • richardmitnick 4:19 pm on April 23, 2019 Permalink | Reply
    Tags: Basic Research, , GREAT-The proof was obtained using the German Receiver for Astronomy at Terahertz Frequencies a far-infrared spectrometer carried on board SOFIA, , The helium hydride ion to give HeH+ its full name once posed something of a dilemma for science.   

    From NASA/DLR SOFIA: “SOFIA uncovers ones of the building blocks of the early Universe” 

    From From NASA/DLR SOFIA
    NASA SOFIA Banner


    Airborne observatory brings the long search to a successful conclusion.

    The early development of the Universe would have been impossible without a small ion known as HeH+.
    Previously, scientists had been unable to detect this ion in space.
    Thanks to the GREAT far-infrared spectrometer on board the SOFIA airborne observatory, an international team of researchers has now succeeded in obtaining proof of its presence.

    The helium hydride ion, to give HeH+ its full name, once posed something of a dilemma for science. Although its existence has been known from laboratory studies for almost 100 years, it had not been found in space, despite extensive searches. As a result, the chemical model calculations associated with it were called into question. But an international team of researchers led by Rolf Güsten of the Max Planck Institute for Radio Astronomy in Bonn has now succeeded in clearly detecting this ion in the direction of the planetary nebula NGC 7027.

    NGC 7027. William B. Latter (SIRTF Science Center/Caltech) and NASA.

    Max Planck Institute for Radio Astronomy Bonn Germany

    The proof was obtained using the German Receiver for Astronomy at Terahertz Frequencies (GREAT) [image below], a far-infrared spectrometer carried on board the Stratospheric Observatory for Infrared Astronomy (SOFIA). SOFIA is a joint project by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) and NASA, the US space agency. The results were published in the 18 April 2019 issue of the scientific journal Nature.

    “Over the last decade, people have had great hopes for space observatories such as Spitzer (NASA, launched 2003) and Herschel (ESA, launched 2009), but none of these telescopes were able to detect this ion.

    NASA/Spitzer Infrared Telescope

    ESA/Herschel spacecraft active from 2009 to 2013

    SOFIA has provided us with proof that this ion really can form in planetary nebulae. At present, there is no other telescope capable of observing at these wavelengths, so this observation platform will remain unique for many years to come,” says Anke Pagels-Kerp, Head of the Space Science Department at the DLR Space Administration in Bonn.

    In the late 1970s, astrochemical models suggested that a detectable quantity of HeH+ might be present within nebulae in the Milky Way. It was thought most likely to be found in what are known as planetary nebulae, which are shells of gas and dust that have been ejected from a Sun-like star in the last phase of their lifecycle. The high-energy radiation generated by the central star drives ionisation fronts into the envelope of ejected material. According to the model calculations, it is precisely here that the HeH+ ions are supposed to form. Yet despite its undisputed importance in the history of the early Universe, it had long proven impossible to find the HeH+ ion in interstellar space. Although it has been known to exist since 1925, specific searches for it in space have been unsuccessful over recent decades.

    The molecule emits its strongest spectral line at a characteristic wavelength of 149.1 micrometres (corresponding to a frequency of 2.01 terahertz). Earth’s atmosphere blocks all radiation in this wavelength range, preventing searches by ground-based observatories; therefore, the search must be conducted either from space or using high-flying observatories such as SOFIA. At an altitude of 13 to 14 kilometres, SOFIA operates above the absorbing layers of the lower atmosphere.

    “SOFIA offers a unique opportunity to use the very latest technologies at any given time. The ongoing German-led development of the GREAT instrument has now made the detection of helium hydride possible. This underlines the importance of such instruments and the potential that their development holds for SOFIA in future,” explains Heinz Hammes, SOFIA Project Manager at the DLR Space Administration.

    After the Big Bang, chemistry began in the Universe

    The HeH+ ion is very important by virtue of its role in the formation of the Universe; all chemistry began approximately 300,000 years after the Big Bang. Although the Universe was still in its early stages, the temperature had already fallen to under approximately 3700 degrees Celsius. The elements that formed in the Big Bang – such as hydrogen, helium, deuterium and traces of lithium – were ionised at first, due to the high temperatures. As the Universe cooled, they recombined with free electrons to create the first neutral atoms. This happened first with helium. At this point, hydrogen was still ionised and was present in the form of free protons, or hydrogen nuclei. These combined with the helium atoms to form the helium hydride ion HeH+, making it one of the very first molecular compounds in the Universe. As recombination advanced, HeH+ reacted with the newly-formed neutral hydrogen atoms, thus paving the way for the formation of molecular hydrogen and thus the chemical origins of the Universe.

    “Thanks to recent advances in terahertz technology, it is now possible to perform high-resolution spectroscopy at the required far-infrared wavelengths,” explains Rolf Güsten, Lead Author of the article. As a result of measurements performed using the GREAT spectrometer on board the SOFIA airborne observatory, the team can now announce the unambiguous detection of the HeH+ ion in the direction of the planetary nebula NGC 7027.

    NASA SOFIA GREAT [German Receiver for Astronomy at Terahertz Frequencies]

    NASA SOFIA High-resolution Airborne Wideband Camera-Plus HAWC+ Camera

    NASA/SOFIA Forcast

    See the full article here .


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    SOFIA is a Boeing 747SP jetliner modified to carry a 106-inch diameter telescope. It is a joint project of NASA and the German Aerospace Center, DLR. NASA’s Ames Research Center in California’s Silicon Valley manages the SOFIA program, science and mission operations in cooperation with the Universities Space Research Association headquartered in Columbia, Maryland, and the German SOFIA Institute (DSI) at the University of Stuttgart. The aircraft is maintained and operated from NASA’s Armstrong Flight Research Center Hangar 703, in Palmdale, California.
    NASA image

    DLR Bloc

  • richardmitnick 3:29 pm on April 23, 2019 Permalink | Reply
    Tags: Basic Research, , Dimitri Mendeleev's early Periodic Table, FOCS 1- a continuous cold caesium fountain atomic clock in Switzerland started operating in 2004 at an uncertainty of one second in 30 million years., Group I metals also known as alkali metals are very reactive, , , Volatile Group I metals   

    From The Conversation: “Understanding the periodic table through the lens of the volatile Group I metals” 

    From The Conversation

    April 23, 2019
    Erwin Boschmann


    The news broke that a railroad car, loaded with pure sodium, had just derailed and was spilling its contents. A television reporter called me for an explanation of why firefighters were not allowed to use water on the flames bursting from the mangled car. While on the air I added some sodium to a bit of water in a petri dish and we observed the vicious reaction. For further dramatic effect, I also placed some potassium into water and astonished everyone with the explosive bluish flames.

    Because Group I metals, also known as alkali metals, are very reactive, like the sodium from the rail car or the potassium, they are not found in nature in pure form but only as salts. Not only are they very reactive, they are soft and shiny, can easily be cut even with a dull knife and are the most metallic of all known elements.

    I am a chemist who spent his career building new molecules, sometimes using Group I elements. By studying the behavior and trends of Group I elements, we can get a glimpse of how the periodic table is arranged and how to interpret it.

    Periodic Table of the Elements. The Group I metals are on the far left colored red. Humdan/Shutterstock.com

    The basics

    The arrangement of the periodic table and the properties of each element in it is based of the atomic number and the arrangement of the electrons orbiting the nucleus. The atomic number describes the number of protons in the nucleus of the element. Hydrogen’s atomic number is 1, helium’s is 2, lithium’s is 3 and so on.

    Each of the 18 columns in the table is called a group or a family. Elements in the same group share similar properties. And the properties can be assumed based on the location within the group. Going from the top of Group I to the bottom, for example, the atomic radii – the distance from the nucleus to the outer electrons – increases. But the amount of energy needed to rip off an outer electron decreases going from the top to the bottom because the electrons are farther from the nucleus and not held as tightly.

    This is important because how elements interact and react with each other depends on their ability to lose and gain electrons to make new compounds.

    The horizontal rows of the table are called periods. Moving from the left side of the period to the right, the atomic radius becomes smaller because each element has one additional proton and one additional electron. More protons means that electrons are pulled in more tightly toward the nucleus. For the same reason electronegativity – the degree to which an element tends to gain electrons – increases from left to right.

    The force required to remove the outermost electron, known as the ionization potential, also increases from the left-hand side of the table, which has elements with a metallic character, to the right side, which are nonmetals.

    Electronegativity decreases from the top of the column to the bottom. The melting point of the elements within a group also decreases from the top to the bottom of a group.

    Trends of the periodic table. Sandbh/Wikipedia, CC BY-SA

    The outermost electron surrounding the Cesium atom is far from the nucleus and thus easy to remove. That makes cesium highly reactive. gstraub/Shutterstock.com

    Applying the basics to Group I elements

    As its name implies, Group I elements occupy the first column in the periodic table. Each element starts a new period. Lithium is at the top of the group and is followed by sodium, Na; potassium, K; rubidium, Rb; cesium, Cs and ends with the radioactive francium, Fr. Because it is highly radioactive, virtually no chemistry is performed with this element.

    Because each element in this column has a single outer electron in a new shell, the volumes of these elements are large and increase dramatically when moving from the top to the bottom of the group.

    Of all the Group I elements, cesium has the largest volumes because the outermost single electron is loosely held.

    In spite of these trends, the properties of the elements of Group I are more similar to each other than those of any other group.

    Alkali metals through history

    Using chemical properties as his guide, Russian chemist Dimitri Mendeleev correctly ordered the first Group I elements into his 1869 periodic table.

    Dimitri Mendeleev’s early Periodic Table

    It is called periodic because every eighth element repeats the properties of the one above it in the table. After arranging all of the then known elements, Mendeleev took the bold step of leaving blanks where his extrapolation of chemical properties showed that an element should exist. Subsequent discovery of these new elements proved his prediction correct.

    Some alkali metals have been known and put to good use long before Mendeleev created the periodic table. For instance, the Old Testament mentions salt – a combination of the alkali metal sodium with chlorine – 31 times. The New Testament refers to it 10 times and calls sodium carbonate “neter” and potassium nitrate “saltpeter.”

    People have known since antiquity that wood ashes produce a potassium salt which, when combined with animal fat, will yield soap. Samuel Hopkins obtained the first U.S. patent on July 31, 1790, for soap under the new patent statute just signed into law by President George Washington a few months earlier.

    The pyrotechnic industry loves these Group I elements for their vibrant colors and explosive nature.

    Fireworks owe their vivid colors to the Group I metals. elena_prosvirova/Shutterstock.com

    Burning lithium produces a vivid crimson red color; sodium a yellow one; potassium lilac; rubidium red; and cesium violet. These colors are produced as electrons jump from their home environment orbiting the nucleus and returning back again.

    The cesium atomic clock, the most accurate timepiece ever developed, functions by measuring the frequency of cesium electrons jumping back and forth between energy states.

    FOCS 1, a continuous cold caesium fountain atomic clock in Switzerland, started operating in 2004 at an uncertainty of one second in 30 million years.

    Clocks based on electrons jumping provide an extremely precise way to count seconds.

    Other applications include sodium vapor lamps and lithium batteries.

    In my own research I have used Group I metals as tools to perform other chemistry. Once I was in need of absolutely dry alcohol, and the driest I could buy still contained minute traces of water. The only way to get rid of the last remnant of water was by treating the water-containing alcohol with sodium – a rather dramatic way to remove water.

    The alkali elements not only occupy the first column in the periodic table, but they also show the most reactivity of all groups in the entire table and have the most dramatic trends in volume and ionization potential, while maintaining great similarity among themselves.

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    The Conversation launched as a pilot project in October 2014. It is an independent source of news and views from the academic and research community, delivered direct to the public.
    Our team of professional editors work with university and research institute experts to unlock their knowledge for use by the wider public.
    Access to independent, high quality, authenticated, explanatory journalism underpins a functioning democracy. Our aim is to promote better understanding of current affairs and complex issues. And hopefully allow for a better quality of public discourse and conversation.

  • richardmitnick 1:10 pm on April 23, 2019 Permalink | Reply
    Tags: "Scientists find new surprises about Titan’s lakes", , , Basic Research, , NASA/ESA/ISA Cassini-Huygens   

    From NASA/ESA/ISA Cassini Huygens via EarthSky: “Scientists find new surprises about Titan’s lakes” 

    NASA Cassini Spacecraft

    From NASA/ESA/ISA Cassini-Huygens



    April 23, 2019
    Paul Scott Anderson

    Cassini data now reveal that some of Titan’s lakes are surprisingly deep.

    Infrared view of seas and lakes in Titan’s northern hemisphere, taken by Cassini in 2014. Sunlight can be seen glinting off the southern part of Titan’s largest sea, Kraken Mare. Image via NASA/JPL-Caltech/University of Arizona/University of Idaho.

    Kraken Mare, Titan’s largest sea, is the body in black and blue that sprawls from just below and to the right of the north pole down to the bottom.

    Saturn’s largest moon Titan is the only world in our solar system besides Earth known to have bodies of liquid on its surface. Scientists announced definitive evidence for them in 2007, based on data from NASA’s Cassini spacecraft. The large ones are known as maria (seas) and the small ones as lacus (lakes). It’s now known that Titan’s hydrologic cycle is surprisingly similar to Earth’s, with one big exception: the liquid on Titan is liquid methane/ethane instead of water, due to the extreme cold. The moon’s northern hemisphere, in particular, has dozens of smaller lakes near its pole, and now scientists have found that they are surprisingly deep and sit on the tops of hills and mesas. These observations come from data collected during the last close flyby of Titan during the Cassini mission, which ended in 2017.

    The new peer-reviewed findings were published on April 15, 2019, in the journal Nature Astronomy.

    Scientists had thought that the lakes would be an almost equal mixture of methane and ethane, like the larger seas. This is the case with the one sizable lake in the southern hemisphere called Ontario Lacus.

    This RADAR-image of Ontario Lacus, the largest lake on the southern hemisphere of Saturn’s moon Titan, was obtained by NASA’s Cassini spacecraft on Jan. 12, 2010. North is up in this image.

    But to their surprise, they found that the lakes in the northern hemisphere are composed almost entirely of methane. As lead author Marco Mastrogiuseppe, a Cassini radar scientist at Caltech, explained:

    “Every time we make discoveries on Titan, Titan becomes more and more mysterious. But these new measurements help give an answer to a few key questions. We can actually now better understand the hydrology of Titan.”

    Map of Titan’s seas and lakes in the northern hemisphere. Image via JPL-Caltech/NASA/ASI/USGS.

    But while some questions may be answered, other new ones are also raised. Why the difference between the lakes in the northern and southern hemispheres? Also, the hydrology on one side of the northern hemisphere appears to be very different from that on the other side. Why? On the eastern side, you find larger seas with low elevation, canyons and islands. But the western side is dominated by the smaller lakes perched on top of hills and mesas. Some of those lakes are more than 300 feet (100 meters) deep, a surprise given their small sizes. As noted by Cassini scientist and co-author Jonathan Lunine of Cornell University:

    “It is as if you looked down on the Earth’s North Pole and could see that North America had completely different geologic setting for bodies of liquid than Asia does.”

    The findings show how Titan’s alien yet earthly-ish landscape is even more unusual than first thought. They show very deep lakes sitting atop tall mesas or plateaus, suggesting that they formed when the surrounding bedrock of ice and solid organics chemically dissolved and collapsed. These Titan lakes are reminiscent of karst lakes on Earth, which form when subterranean caves collapse. In the earthly counterparts, however, water dissolves limestone, gypsum or dolomite rock.

    This is a great example of how – much like the hydrologic cycle – geologic processes on Titan can also mimic those on Earth, yet be uniquely Titanian at the same time. In many ways, Titan looks a lot like Earth, but the underlying mechanisms, and composition of materials, are fundamentally different on this world in the much-colder outer solar system.

    Cassini also observed another kind of lake on Titan. Radar and infrared data revealed transient lakes where the level of liquids varies significantly. These results have been published in a separate paper in Nature Astronomy. According to Shannon MacKenzie, a planetary scientist at the Johns Hopkins University Applied Physics Laboratory, those changes may be seasonal:

    “One possibility is that these transient features could have been shallower bodies of liquid that over the course of the season evaporated and infiltrated into the subsurface.”

    Images from Cassini showing new small lakes appearing in Arrakis Planitia between 2004 and 2005. Such lakes seem to be transient, where the liquids fill the lakes before evaporating or seeping into the ground again. Image via NASA/JPL/Space Science Institute.

    Taken together, the results about both the deep lakes and transient lakes support the scenario where methane/ethane rain feeds the lakes, which then evaporate back into the atmosphere or drain into the subsurface, leaving reservoirs of liquid below the surface. It is a complete hydrologic cycle, but, in the colder environment than on Earth, one where methane and ethane can be liquid and water is in the form of rock-hard ice.

    The presence of lakes and seas on Titan brings up another question. Might there possibly be any form of life there? Some scientists think there indeed could be at least microscopic organisms, despite the harsh conditions in contrast to Earth, that use liquid methane/ethane in a similar way that life here uses water. Such life would have to be evolved to exist in conditions unlike any on Earth, but it’s an intriguing possibility.

    Bottom line: Data on Titan’s lakes, collected by the Cassini spacecraft (whose mission ended in 2017), continue to reveal insights into a hydrologic cycle that’s remarkably similar to Earth’s in some ways – but distinctly alien in others. A new finding is that lakes near Titan’s north pole are surprisingly deep and sit on the tops of hills and mesas.

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    The Cassini-Huygens mission was a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology, Pasadena, managed the mission for NASA’s Science Mission Directorate in Washington. The VIMS team is based at the University of Arizona in Tucson. The radar instrument was built by JPL and the Italian Space Agency, working with team members from the US and several European countries.

    Cassini launched in October 1997 with the European Space Agency’s Huygens probe. The probe was equipped with six instruments to study Titan, Saturn’s largest moon. It landed on Titan’s surface on Jan. 14, 2005, and returned spectacular results.

    Meanwhile, Cassini’s 12 instruments returned a daily stream of data from Saturn’s system since arriving at Saturn in 2004.

    Among the most important targets of the mission are the moons Titan and Enceladus, as well as some of Saturn’s other icy moons. Towards the end of the mission, Cassini made closer studies of the planet and its rings.

    Cassini completed its initial four-year mission to explore the Saturn System in June 2008 and the first extended mission, called the Cassini Equinox Mission, in September 2010. Since then the healthy spacecraft was seeking to make exciting new discoveries in a second extended mission called the Cassini Solstice Mission.

    The mission’s extension, which goes through September 2017, is named for the Saturnian summer solstice occurring in May 2017. The northern summer solstice marks the beginning of summer in the northern hemisphere and winter in the southern hemisphere. Since Cassini arrived at Saturn just after the planet’s northern winter solstice, the extension will allow for the first study of a complete seasonal period.

    The mission ended on September 15, 2017, when Cassini’s trajectory took it into Saturn’s upper atmosphere and it burned up.

    NASA image
    ESA50 Logo large

    Italian Space Agency

  • richardmitnick 12:10 pm on April 23, 2019 Permalink | Reply
    Tags: "Falsifiability and physics", , , Basic Research, , , , , Karl Popper (1902-1994) "The Logic of Scientific Discovery", , ,   

    From Symmetry: “Falsifiability and physics” 

    Symmetry Mag
    From Symmetry

    Matthew R. Francis

    Illustration by Sandbox Studio, Chicago with Corinne Mucha

    Can a theory that isn’t completely testable still be useful to physics?

    What determines if an idea is legitimately scientific or not? This question has been debated by philosophers and historians of science, working scientists, and lawyers in courts of law. That’s because it’s not merely an abstract notion: What makes something scientific or not determines if it should be taught in classrooms or supported by government grant money.

    The answer is relatively straightforward in many cases: Despite conspiracy theories to the contrary, the Earth is not flat. Literally all evidence is in favor of a round and rotating Earth, so statements based on a flat-Earth hypothesis are not scientific.

    In other cases, though, people actively debate where and how the demarcation line should be drawn. One such criterion was proposed by philosopher of science Karl Popper (1902-1994), who argued that scientific ideas must be subject to “falsification.”

    Popper wrote in his classic book The Logic of Scientific Discovery that a theory that cannot be proven false—that is, a theory flexible enough to encompass every possible experimental outcome—is scientifically useless. He wrote that a scientific idea must contain the key to its own downfall: It must make predictions that can be tested and, if those predictions are proven false, the theory must be jettisoned.

    When writing this, Popper was less concerned with physics than he was with theories like Freudian psychology and Stalinist history. These, he argued, were not falsifiable because they were vague or flexible enough to incorporate all the available evidence and therefore immune to testing.

    But where does this falsifiability requirement leave certain areas of theoretical physics? String theory, for example, involves physics on extremely small length scales unreachable by any foreseeable experiment.

    String Theory depiction. Cross section of the quintic Calabi–Yau manifold Calabi yau.jpg. Jbourjai (using Mathematica output)

    Cosmic inflation, a theory that explains much about the properties of the observable universe, may itself be untestable through direct observations.

    Some critics believe these theories are unfalsifiable and, for that reason, are of dubious scientific value.

    At the same time, many physicists align with philosophers of science who identified flaws in Popper’s model, saying falsification is most useful in identifying blatant pseudoscience (the flat-Earth hypothesis, again) but relatively unimportant for judging theories growing out of established paradigms in science.

    “I think we should be worried about being arrogant,” says Chanda Prescod-Weinstein of the University of New Hampshire. “Falsifiability is important, but so is remembering that nature does what it wants.”

    Prescod-Weinstein is both a particle cosmologist and researcher in science, technology, and society studies, interested in analyzing the priorities scientists have as a group. “Any particular generation deciding that they’ve worked out all that can be worked out seems like the height of arrogance to me,” she says.

    Tracy Slatyer of MIT agrees, and argues that stringently worrying about falsification can prevent new ideas from germinating, stifling creativity. “In theoretical physics, the vast majority of all the ideas you ever work on are going to be wrong,” she says. “They may be interesting ideas, they may be beautiful ideas, they may be gorgeous structures that are simply not realized in our universe.”

    Particles and practical philosophy

    Take, for example, supersymmetry. SUSY is an extension of the Standard Model in which each known particle is paired with a supersymmetric partner.

    Standard Model of Supersymmetry via DESY

    The theory is a natural outgrowth of a mathematical symmetry of spacetime, in ways similar to the Standard Model itself. It’s well established within particle physics, even though supersymmetric particles, if they exist, may be out of scientists’ experimental reach.

    SUSY could potentially resolve some major mysteries in modern physics. For one, all of those supersymmetric particles could be the reason the mass of the Higgs boson is smaller than quantum mechanics says it should be.

    CERN CMS Higgs Event

    CERN ATLAS Higgs Event

    “Quantum mechanics says that [the Higgs boson] mass should blow up to the largest mass scale possible,” says Howard Baer of the University of Oklahoma. That’s because masses in quantum theory are the result of contributions from many different particles involved in interactions—and the Higgs field, which gives other particles mass, racks up a lot of these interactions. But the Higgs mass isn’t huge, which requires an explanation.

    “Something else would have to be tuned to a huge negative [value] in order to cancel [the huge positive value of those interactions] and give you the observed value,” Baer says. That level of coincidence, known as a “fine-tuning problem,” makes physicists itchy. “It’s like trying to play the lottery. It’s possible you might win, but really you’re almost certain to lose.”

    If SUSY particles turn up in a certain mass range, their contributions to the Higgs mass “naturally” solve this problem, which has been an argument in favor of the theory of supersymmetry. So far, the Large Hadron Collider has not turned up any SUSY particles in the range of “naturalness.”


    CERN map

    CERN LHC Tunnel

    CERN LHC particles

    However, the broad framework of supersymmetry can accommodate even more massive SUSY particles, which may or may not be detectable using the LHC. In fact, if naturalness is abandoned, SUSY doesn’t provide an obvious mass scale at all, meaning SUSY particles might be out of range for discovery with any earthly particle collider. That point has made some critics queasy: If there’s no obvious mass scale at which colliders can hunt for SUSY, is the theory falsifiable?

    A related problem confronts dark matter researchers: Despite strong indirect evidence for a large amount of mass invisible to all forms of light, particle experiments have yet to find any dark matter particles. It could be that dark matter particles are just impossible to directly detect. A small but vocal group of researchers has argued that we need to consider alternative theories of gravity instead.

    Fritz Zwicky, the Father of Dark Matter research.No image credit after long search

    Astronomer Vera Rubin at the Lowell Observatory in 1965, worked on Dark Matter (The Carnegie Institution for Science)

    U Washington ADMX Axion Dark Matter Experiment

    DEAP Dark Matter detector, The DEAP-3600, suspended in the SNOLAB deep in Sudbury’s Creighton Mine

    Dark Side-50 Dark Matter Experiment at Gran Sasso

    Slatyer, whose research involves looking for dark matter, considers the criticism partly as a problem of language. “When you say ‘dark matter,’ [you need] to distinguish dark matter from specific scenarios for what dark matter could be,” she says. “The community has not always done that well.”

    In other words, specific models for dark matter can stand or fall, but the dark matter paradigm as a whole has withstood all tests so far. But as Slatyer points out, no alternative theory of gravity can explain all the phenomena that a simple dark matter model can, from the behavior of galaxies to the structure of the cosmic microwave background.

    Prescod-Weinstein argues that we’re a long way from ruling out all dark matter possibilities. “How will we prove that the dark matter, if it exists, definitively doesn’t interact with the Standard Model?” she says. “Astrophysics is always a bit of a detective game. Without laboratory [detection of] dark matter, it’s hard to make definitive statements about its properties. But we can construct likely narratives based on what we know about its behavior.”

    Similarly, Baer thinks that we haven’t exhausted all the SUSY possibilities yet. “People say, ‘you’ve been promising supersymmetry for 20 or 30 years,’ but it was based on overly optimistic naturalness calculations,” he says. “I think if one evaluates the naturalness properly, then you find that supersymmetry is still even now very natural. But you’re going to need either an energy upgrade of LHC or an ILC [International Linear Collider] in order to discover it.”

    ILC schematic, being planned for the Kitakami highland, in the Iwate prefecture of northern Japan

    Beyond falsifiability of dark matter or SUSY, physicists are motivated by more mundane concerns. “Even if these individual scenarios are in principle falsifiable, how much money would [it] take and how much time would it take?” Slatyer says. In other words, rather than try to demonstrate or rule out SUSY as a whole, physicists focus on particle experiments that can be performed within a certain number of budgetary cycles. It’s not romantic, but it’s true nevertheless.

    Illustration by Sandbox Studio, Chicago with Corinne Mucha

    Is it science? Who decides?

    Historically, sometimes theories that seem untestable turn out to just need more time. For example, 19th century physicist Ludwig Boltzmann and colleagues showed they could explain many results in thermal physics and chemistry if everything were made up of “atoms”—what we call particles, atoms, and molecules today—governed by Newtonian physics.

    Since atoms were out of reach of experiments of the day, prominent philosophers of science argued that the atomic hypothesis was untestable in principle, and therefore unscientific.

    However, the atomists eventually won the day: J. J. Thompson demonstrated the existence of electrons, while Albert Einstein showed that water molecules could make grains of pollen dance on a pond’s surface.

    Atoms provide a case study for how falsifiability proved to be the wrong criterion. Many other cases are trickier.

    For instance, Einstein’s theory of general relativity is one of the best-tested theories in all of science. At the same time, it allows for physically unrealistic “universes,” such as a “rotating” cosmos where movement back and forth in time is possible, which are contradicted by all observations of the reality we inhabit.

    General relativity also makes predictions about things that are untestable by definition, like how particles move inside the event horizon of a black hole: No information about these trajectories can be determined by experiment.

    The first image of a black hole, Messier 87 Credit Event Horizon Telescope Collaboration, via NSF 4.10.19

    Yet no knowledgeable physicist or philosopher of science would argue that general relativity is unscientific. The success of the theory is due to enough of its predictions being testable.

    Eddington/Einstein exibition of gravitational lensing solar eclipse of 29 May 1919

    Another type of theory may be mostly untestable, but have important consequences. One such theory is cosmic inflation, which (among other things) explains why we don’t see isolated magnetic monopoles and why the universe is a nearly uniform temperature everywhere we look.

    The key property of inflation—the extremely rapid expansion of spacetime during a tiny split second after the Big Bang—cannot be tested directly. Cosmologists look for indirect evidence for inflation, but in the end it may be difficult or impossible to distinguish between different inflationary models, simply because scientists can’t get the data. Does that mean it isn’t scientific?


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

    HPHS Owls

    Lambda-Cold Dark Matter, Accelerated Expansion of the Universe, Big Bang-Inflation (timeline of the universe) Date 2010 Credit: Alex MittelmannColdcreation

    Alan Guth’s notes:

    “A lot of people have personal feelings about inflation and the aesthetics of physical theories,” Prescod-Weinstein says. She’s willing to entertain alternative ideas which have testable consequences, but inflation works well enough for now to keep it around. “It’s also the case that the majority of the cosmology community continues to take inflation seriously as a model, so I have to shrug a little when someone says it’s not science.”

    On that note, Caltech cosmologist Sean M. Carroll argues that many very useful theories have both falsifiable and unfalsifiable predictions. Some aspects may be testable in principle, but not by any experiment or observation we can perform with existing technology. Many particle physics models fall into that category, but that doesn’t stop physicists from finding them useful. SUSY as a concept may not be falsifiable, but many specific models within the broad framework certainly are. All the evidence we have for the existence of dark matter is indirect, which won’t go away even if laboratory experiments never find dark matter particles. Physicists accept the concept of dark matter because it works.

    Slatyer is a practical dark matter hunter. “The questions I’m most interested asking are not even just questions that are in principle falsifiable, but questions that in principle can be tested by data on the timescale of less than my lifetime,” she says. “But it’s not only problems that can be tested by data on a timescale of ‘less than Tracy’s lifetime’ are good scientific questions!”

    Prescod-Weinstein agrees, and argues for keeping an open mind. “There’s a lot we don’t know about the universe, including what’s knowable about it. We are a curious species, and I think we should remain curious.”

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 8:29 am on April 23, 2019 Permalink | Reply
    Tags: "A day in the life of a midnight beam master", , Basic Research, Ben Ripman- operations engineer at the SLAC accelerator control room, , , SLAC SPEAR3, ,   

    From SLAC National Accelerator Lab: “A day in the life of a midnight beam master” 

    From SLAC National Accelerator Lab

    April 16, 2019 [Just today 4.23.19 in social media]
    Angela Anderson

    In SLAC’s accelerator control room, shift lead Ben Ripman and a team of operators fine-tune X-ray beams for science experiments around the clock.

    When is a day not a day? When you work in the central nervous system of the world’s longest linear accelerator, open 24-7.

    “There’s a constant cycle of people coming and going,” says Ben Ripman, an operations engineer at the Department of Energy’s SLAC National Accelerator Laboratory.

    Ben Ripman, operations engineer at the SLAC accelerator control room (Angela Anderson/SLAC National Accelerator Laboratory)

    He might start at 8 a.m., at 4 p.m. or at midnight. But the shift rotations are no barrier to his passion for the job – leading a team of control room operators who deliver brilliant X-ray beams for scientific experiments.

    Control room operators spend most of their workdays (or nights) in a room filled with monitors, three deep and crowded with numbers, charts and graphs. Those displays track the status of thousands of devices and systems in the linear accelerator that runs through a tunnel below Highway 280 and feeds SLAC’s X-ray laser, the Linac Coherent Light Source (LCLS).


    The accelerator boosts electrons to almost the speed of light and then wiggles them between magnets to generate X-rays. That X-ray light is formed into pulses and optimized for materials science, biology, chemistry, and physics experiments.

    The entire operation is monitored in the control room, which also serves SPEAR3, the accelerator that produces X-rays for the Stanford Synchrotron Radiation Lightsource (SSRL).



    Another set of monitors, staffed by SLAC Facilities, tracks water, compressed air and electricity systems that serve the lab campus.

    Ripman and his fellow operators are experts in reading these digital vital signs. But they are also some of the most knowledgeable people at the lab when it comes to the entire physical machine.

    “We know the accelerator from beginning to end,” he says. “When an operator adjusts something from the control room, they can picture that machine part and what it is doing.”

    For LCLS, they measure the amount of energy in individual X-ray pulses being fed to experimental hutches and often spend hours improving the pulses: tweaking magnets, adjusting the undulators, tuning the shape and length of the electron bunches.

    Some days the control room is quiet, and the operators focus on training and individual projects. On other, more challenging days when the machine is running in exotic modes, they work elbow to elbow with physicists.

    “We love this machine, but the accelerator was built decades ago and can be cantankerous,” Ripman explains. “When things do go wrong, it’s like a game of pickup sticks – one problem triggers another and you need to know how it all fits together.”

    An important part of the job is knowing who to call for help. “We wake up a lot of people in the middle of the night,” Ripman says with a smile.

    Control room operators also make sure everyone who goes into the accelerator tunnel stays safe.

    There are two ways to get into the accelerator. For minor repairs and inspections, people take keys from special key banks that block the accelerator from turning on until all the keys have been returned. On official maintenance days, the doors are thrown open.

    “On those days, maintenance crews, engineers and physicists descend into the tunnel and swarm the machine to resolve as many issues as possible before we have to summon them out again,” Ripman says. “We search the machine to make sure everyone is out before it’s turned back on.”

    Almost all of the displays in the control room were designed by the operators, he says. “We are known to hide ‘Easter eggs’ in them, but you have to get in our good graces to find out about them.”

    New operators take more than a year to get trained and proficient, Ripman says. “People come with a physics degree, but there is not a lot of formal coursework you can take on accelerator operations – it’s a lot of on-the-job training.”

    It was that hands-on learning that drew him to the job in 2010.

    “I was a nerd in high school,” Ripman admits proudly, “Stephen Hawking was my hero.” After studying physics and astronomy in college, Ripman worked as a contractor for NASA before joining SLAC. On his off hours, he plays board games and travels several times a year for card tournaments. He also loves hiking, skiing and snowboarding, and is a member of the Stanford University Singers.

    His favorite thing about the job? “My coworkers,” he says. “I have the privilege of working with smart, fun, quirky people. We all get along quite well, and there’s a great camaraderie.”

    Operators leave sticky notes with jokes or short messages for the next shift and share stories about their days and nights in the accelerator’s brain.

    Like the one about a ghost calling from an abandoned tunnel. But that’s a tale for another night…

    LCLS and SSRL are DOE Office of Science user facilities.

    See the full article here .

    Please help promote STEM in your local schools.

    Stem Education Coalition


    SLAC/LCLS II projected view

    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

  • richardmitnick 8:04 am on April 23, 2019 Permalink | Reply
    Tags: , , , , Basic Research, , , ESA's proposed Hera spaceraft, , NASA's Deep Impact spacecraft 2004, US Double Asteroid Redirect Test or DART spacecraft   

    From European Space Agency: “Earth vs. asteroids: humans strike back” 

    ESA Space For Europe Banner

    From European Space Agency

    22 April 2019

    Incoming asteroids have been scarring our home planet for billions of years. This month humankind left our own mark on an asteroid for the first time: Japan’s Hayabusa2 spacecraft dropped a copper projectile at very high speed in an attempt to form a crater on asteroid Ryugu. A much bigger asteroid impact is planned for the coming decade, involving an international double-spacecraft mission.

    JAXA/Hayabusa 2 Credit: JAXA/Akihiro Ikeshita

    On 5 April, Hayabusa2 released an experiment called the ‘Small Carry-on Impactor’ or SCI for short, carrying a plastic explosive charge that shot a 2.5-kg copper projectile at the surface of the 900-m diameter Ryugu asteroid at a velocity of around 2 km per second. The objective is to uncover subsurface material to be brought back to Earth for detailed analysis.

    “We are expecting it to form a distinctive crater,” comments Patrick Michel, CNRS Director of Research of France’s Côte d’Azur Observatory, serving as co-investigator and interdisciplinary scientist on the Japanese mission. “But we don’t know for sure yet, because Hayabusa2 was moved around to the other side of Ryugu, for maximum safety.

    “The asteroid’s low gravity means it has an escape velocity of a few tens of centimetres per second, so most of the material ejected by the impact would have gone straight out to space. But at the same time it is possible that lower-velocity ejecta might have gone into orbit around Ryugu and might pose a danger to the Hayabusa2 spacecraft.

    “So the plan is to wait until this Thursday, 25 April, to go back and image the crater. We expect that very small fragments will meanwhile have their orbits disrupted by solar radiation pressure – the slow but persistent push of sunlight itself. In the meantime we’ve also been downloading images from a camera called DCAM3 that accompanied the SCI payload to see if it caught a glimpse of the crater and the early ejecta evolution.”

    According to simulations, the crater is predicted to have a roughly 2 m diameter, although the modelling of impacts in such a low-gravity environment is extremely challenging. It should appear darker than the surrounding surface, based on a February touch-and-go sampling operation when Hayabusa2’s thrusters dislodged surface dust to expose blacker material underneath.

    “For us this is an exciting first data point to compare with simulations,” adds Patrick, “but we have a much larger impact to look forward to in future, as part of the forthcoming double-spacecraft Asteroid Impact & Deflection Assessment (AIDA) mission.

    “In late 2022 the US Double Asteroid Redirect Test or DART spacecraft will crash into the smaller of the two Didymos asteroids.

    NASA DART Double Impact Redirection Test vehicle depiction schematic

    As with Hayabusa2’s SCI test it should form a very distinct crater and expose subsurface material in an even lower gravity environment, but its main purpose is to actually divert the orbit of the 160 m diameter ‘Didymoon’ asteroid in a measurable way.”

    The DART spacecraft will have a mass of 550 kg, and will strike Didymoon at 6 km/s. Striking an asteroid five times smaller with a spacecraft more than 200 times larger and moving three times faster should deliver sufficient impact energy to achieve the first ever asteroid deflection experiment for planetary defence.

    DART mission profile. APL – Johns Hopkins University Applied Physics Laboratory

    A proposed ESA mission called Hera would then visit Didymos to survey the diverted asteroid, measure its mass and perform high-resolution mapping of the crater left by the DART impact.

    DLR Asteroid Framing Camera used on NASA Dawn and ESA HERA missions

    ESA’s proposed Hera spaceraft

    “The actual relation between projectile size, speed and crater size in low gravity environments is still poorly understood,” adds Patrick, also serving as Hera’s lead scientist. “Having both SCI and Hera data on crater sizes in two different impact speed regimes will offer crucial insights.

    “These scaling laws are also crucial on a practical basis, because they underpin how our calculations estimating the efficiency of asteroid deflection are made, taking account the properties of the asteroid material as well as the impact velocity involved.

    “This is why Hera is so important; not only will we have DART’s full-scale test of asteroid deflection in space, but also Hera’s detailed follow-up survey to discover Didymoon’s composition and structure. Hera will also record the precise shape of the DART crater, right down to centimetre scale.

    “So, building on this Hayabusa2 impact experiment, DART and Hera between them will go on to close the gap in asteroid deflection techniques, bringing us to a point where such a method might be used for real.”

    Didymoon will also be by far the smallest asteroid ever explored, so will offer insights into the cohesion of material in an environment whose gravity is more than a million times weaker than our own – an alien situation extremely challenging to simulate.

    In 2004, NASA’s Deep Impact spacecraft launched an impactor into comet Tempel 1. The body was subsequently revisited, but the artificial crater was hard to pinpoint – largely because the comet had flown close to the Sun in the meantime, and its heating would have modified the surface.

    NASA’s Deep Impact hitting a comet

    NASA Deep Impact spacecraft 2004

    Hera will visit Didymoon around four years after DART’s impact, but because it is an inactive asteroid in deep space, no such modification will occur. “The crater will still be ‘fresh’ for Hera,” Patrick concludes.

    See the full article here .

    Please help promote STEM in your local schools.

    Stem Education Coalition

    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

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