Tagged: Cosmology Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 2:25 pm on July 25, 2017 Permalink | Reply
    Tags: , , , , , Cosmology   

    From astrobites: “Dark Matter in the Milky Way: ‘A Matter of Perspective’ “ 

    Astrobites bloc

    Astrobites

    Jul 25, 2017
    Nora Shipp

    Title: The core-cusp problem: A matter of perspective
    Authors: Anna Genina, Alejandro Benitez-Llambay, Carlos S. Frenk, Shaun Cole, Azadeh Fattahi, Julio F. Navarro, Kyle A. Oman, Till Sawala, Tom Theuns
    First Author’s Institution: Institute for Computational Cosmology,University, UK

    Status: Submitted to the Monthly Notices of the Royal Astronomical Society, Open Access

    Dark matter dominates the Universe around us, far exceeding the amount of everyday baryonic matter that makes up humans, the Earth, and the entire visible Milky Way. Our galaxy is embedded in an invisible cloud of dark matter, which contains smaller dark matter clouds that orbit around us like satellites. These satellites do not contain big spiral galaxies like the Milky Way and, although they may contain smaller galaxies, they are made up of almost entirely dark matter, which means that they are very sensitive to the precise nature of the dark matter particle.

    Today’s paper investigates whether two of the Milky Way’s largest satellite galaxies (Fornax and Sculptor, Figure 1) conflict with the leading theory of Cold Dark Matter (CDM), potentially requiring a complete reconsideration of our understanding of the evolution of the Universe.

    2
    Projected density plot of a redshift {\displaystyle z=2.5} dark matter halo from a cosmological N-body simulation. The visible part of the galaxy (not shown in the image) lies at the dense centre of the halo and has a diameter of roughly 20 kiloparsecs. There are also many satellite galaxies, each with its own subhalo which is visible as a region of high dark matter density in the image. http://en.wikipedia.org/wiki/User:Cosmo0

    Don’t get too excited, though. I will break the suspense and say that, as usual, the answer is “not yet” – we don’t know enough about these mini galaxies to throw away CDM. There is still a lot of work to be done if we want to break this paradigm.

    1
    Figure 1. The Fornax (left) and Sculptor (right) galaxies. (Source: ESO)

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

     
  • richardmitnick 2:06 pm on July 25, 2017 Permalink | Reply
    Tags: , , , , Cosmology, , , ,   

    From JPL: “Large, Distant Comets More Common Than Previously Thought” 

    NASA JPL Banner

    JPL-Caltech

    July 25, 2017
    Elizabeth Landau
    Jet Propulsion Laboratory, Pasadena, Calif.
    818-354-6425
    elizabeth.landau@jpl.nasa.gov

    1
    This illustration shows how scientists used data from NASA’s WISE spacecraft to determine the nucleus sizes of comets. They subtracted a model of how dust and gas behave in comets in order to obtain the core size. Credit: NASA/JPL-Caltech.

    2
    An animation of a comet. Credit: NASA/JPL-Caltech.

    Comets that take more than 200 years to make one revolution around the Sun are notoriously difficult to study. Because they spend most of their time far from our area of the solar system, many “long-period comets” will never approach the Sun in a person’s lifetime. In fact, those that travel inward from the Oort Cloud — a group of icy bodies beginning roughly 186 billion miles (300 billion kilometers) away from the Sun — can have periods of thousands or even millions of years.

    Oort Cloud NASA

    NASA’s WISE spacecraft, scanning the entire sky at infrared wavelengths, has delivered new insights about these distant wanderers.

    NASA/WISE Telescope

    Scientists found that there are about seven times more long-period comets measuring at least 0.6 miles (1 kilometer) across than had been predicted previously. They also found that long-period comets are on average up to twice as large as “Jupiter family comets,” whose orbits are shaped by Jupiter’s gravity and have periods of less than 20 years.

    Researchers also observed that in eight months, three to five times as many long-period comets passed by the Sun than had been predicted. The findings are published in The Astronomical Journal.

    “The number of comets speaks to the amount of material left over from the solar system’s formation,” said James Bauer, lead author of the study and now a research professor at the University of Maryland, College Park. “We now know that there are more relatively large chunks of ancient material coming from the Oort Cloud than we thought.”

    The Oort Cloud is too distant to be seen by current telescopes, but is thought to be a spherical distribution of small icy bodies at the outermost edge of the solar system. The density of comets within it is low, so the odds of comets colliding within it are rare. Long-period comets that WISE observed probably got kicked out of the Oort Cloud millions of years ago. The observations were carried out during the spacecraft’s primary mission before it was renamed NEOWISE and reactivated to target near-Earth objects (NEOs).

    “Our study is a rare look at objects perturbed out of the Oort Cloud,” said Amy Mainzer, study co-author based at NASA’s Jet Propulsion Laboratory, Pasadena, California, and principal investigator of the NEOWISE mission. “They are the most pristine examples of what the solar system was like when it formed.”

    Astronomers already had broader estimates of how many long-period and Jupiter family comets are in our solar system, but had no good way of measuring the sizes of long-period comets. That is because a comet has a “coma,” a cloud of gas and dust that appears hazy in images and obscures the cometary nucleus. But by using the WISE data showing the infrared glow of this coma, scientists were able to “subtract” the coma from the overall comet and estimate the nucleus sizes of these comets. The data came from 2010 WISE observations of 95 Jupiter family comets and 56 long-period comets.

    The results reinforce the idea that comets that pass by the Sun more often tend to be smaller than those spending much more time away from the Sun. That is because Jupiter family comets get more heat exposure, which causes volatile substances like water to sublimate and drag away other material from the comet’s surface as well.

    “Our results mean there’s an evolutionary difference between Jupiter family and long-period comets,” Bauer said.

    The existence of so many more long-period comets than predicted suggests that more of them have likely impacted planets, delivering icy materials from the outer reaches of the solar system.

    Researchers also found clustering in the orbits of the long-period comets they studied, suggesting there could have been larger bodies that broke apart to form these groups.

    The results will be important for assessing the likelihood of comets impacting our solar system’s planets, including Earth.

    “Comets travel much faster than asteroids, and some of them are very big,” Mainzer said. “Studies like this will help us define what kind of hazard long-period comets may pose.”

    NASA’s Jet Propulsion Laboratory in Pasadena, California, managed and operated WISE for NASA’s Science Mission Directorate in Washington. The NEOWISE project is funded by the Near Earth Object Observation Program, now part of NASA’s Planetary Defense Coordination Office. The spacecraft was put into hibernation mode in 2011 after twice scanned the entire sky, thereby completing its main objectives. In September 2013, WISE was reactivated, renamed NEOWISE and assigned a new mission to assist NASA’s efforts to identify potentially hazardous near-Earth objects.

    For more information on WISE, visit:

    https://www.nasa.gov/wise

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    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 [1], 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 12:57 pm on July 25, 2017 Permalink | Reply
    Tags: , , , Cosmology, , ,   

    From JPL: “A Final Farewell to LISA Pathfinder” 

    NASA JPL Banner

    JPL-Caltech

    July 24, 2017
    Andrew Good
    Jet Propulsion Laboratory, Pasadena, Calif.
    818-393-2433
    andrew.c.good@jpl.nasa.gov

    1
    An artist’s concept of the European Space Agency’s LISA Pathfinder spacecraft, designed to pave the way for a mission detecting gravitational waves. NASA/JPL developed a thruster system on board.

    Official ESA/LISA Pathfinder image

    With the push of a button, final commands for the European Space Agency’s LISA Pathfinder mission were beamed to space on July 18, a final goodbye before the spacecraft was powered down.

    LISA Pathfinder had been directed into a parking orbit in April, keeping it out of Earth’s way. The final action this week switches it off completely after a successful 16 months of science measurements.

    While some spacecraft are flashy, never sitting still as they zip across the solar system, LISA Pathfinder was as steady as they come — literally.

    It housed a space-age motion detector so sensitive that it had to be protected against the force of photons from the Sun. That was made possible thanks to a system of thrusters that applied tiny reactive forces to the spacecraft, cancelling out the force of the Sun and allowing the spacecraft to stay within 10 nanometers of an ideal gravitational orbit.

    These requirements for Pathfinder were so challenging and unique that LISA Pathfinder flew two independent systems based on different designs – one provided by NASA and one by ESA – and ran tests with both during its 16-month mission.

    “We were trying to hold it as stable as the width of a DNA helix,” said John Ziemer, systems lead for the U.S. thruster system at NASA’s Jet Propulsion Laboratory in Pasadena, California. “And we went down from there to the width of part of a DNA helix.”

    JPL managed development of the thruster system, formally called the Space Technology 7 Disturbance Reduction System (ST7-DRS). The thrusters were developed by Busek Co., Inc., Natick, Massachusetts, with technical support from JPL. During the U.S. operations phase, Pathfinder was controlled using algorithims developed by ST7 team members at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. This control system took inputs from the European sensors and sent commands to the thrusters to precisely guide the spacecraft along its path.

    JPL finished primary mission experiments in the fall of 2016. In March and April of this year, they continued validating the algorithms used in stabilizing the spacecraft. They improved them through a number of tests.

    “The main goal for us was to show we can fly the spacecraft drag-free,” Ziemer said. “The main force on the spacecraft comes from the Sun, from photons with extremely tiny force that can subtly move the spacecraft.”

    So why build something this sensitive to begin with?

    LISA Pathfinder was just a starting point. The mission was led by ESA as a stepping-stone of sorts, proving the technology needed for an even more ambitious plan, the Laser Interferometer Space Antenna (LISA): a trio of spacecraft proposed to launch in 2034. With each spacecraft holding as still as possible, they would be able to detect the ripples sent out across space by the merging of black holes.

    ESA/eLISA the future of gravitational wave research

    These ripples, known as gravitational waves, have been a source of intense scientific interest in recent years. The ground-based Laser Interferometry Gravitational Wave Observatory detected gravitational waves for the first time in 2015.

    But there’s a bigger role for thrusters like the ones on LISA Pathfinder. Ziemer said the operation of super-steady thrusters could serve as an alternative to reaction wheels, the current standard for rotating and pointing spacecraft.

    “This kind of technology could be essential for space telescopes,” Ziemer said. “They could potentially hold them still enough to image exoplanets, or allow for formation flying of a series of spacecraft.”

    The thrusters are an enabling technology, opening up a magnitude of precision that simply wasn’t available before.

    The Pathfinder spacecraft was built by Airbus Defence and Space, Ltd., United Kingdom. Airbus Defence and Space, GmbH, Germany, is the payload architect for the LISA Technology Package.

    For more information about ST7-DRS, visit:

    http://www.jpl.nasa.gov/news/news.php?feature=4825

    [It was my understanding that this satellite would have a further mission in detecting NEO’s.]

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    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 [1], 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 7:40 am on July 25, 2017 Permalink | Reply
    Tags: Astron, , , , Cosmology, Lofar Ireland,   

    From Astron: “LOFAR Ireland officially launched” 

    ASTRON bloc

    Netherlands Institute for Radio Astronomy

    ASTRON LOFAR Map

    ASTRON LOFAR Radio Antenna Bank

    New antenna station further increases sensitivity of the world’s largest radio telescope

    On 27 July 2017, the newly built Low Frequency Array (LOFAR) station in Ireland will be officially opened.

    1
    Astron Lofar Ireland Section

    This extends the largest radio telescope in the world, connecting to its central core of antennas in the north of the Netherlands, now forming a network of two thousand kilometres across. Astronomers can now study the history of the universe in even more detail. The station will be opened by the Irish Minister for Training, Skills, Innovation, Research and Development, John Halligan.

    The international LOFAR telescope (ILT) is a European network of radio antennas, connected by a high-speed fibre optic network. With the data of thousands of antennas together, now including the Irish antennas, powerful computers create a virtual dish with a diameter of two thousand kilometres. The telescope thus gets has an even sharper and more sensitive vision.

    More detail

    Rene Vermeulen, Director of the ILT, is very excited about this new collaboration. “Thanks to the new LOFAR station in Ireland, we can observe the universe in even more detail. For example, we can look more closely at objects near and far, from our Sun to black holes, magnetic fields, and the emergence of galaxies in the early Universe. These are important areas of research for astronomers in the Netherlands and other ILT partner countries.”

    The Irish LOFAR team is led by Professor Peter Gallagher (Trinity College Dublin), an expert on Solar astrophysics. Vermeulen: “Studying the Sun, including solar flares, is an important branch of astronomical research. In this and other areas Irish researchers bring important reinforcement to our partnership.”

    Successful tests

    LOFAR was designed and built by ASTRON, the Netherlands Institute for Radio Astronomy. Earlier this month, a team from ASTRON conducted the final delivery tests of the Irish station on the Birr castle estate. The antennas, which conduct measurements at the lowest frequencies that can be observed from the earth, perform according to specification. The fibre optic network has already been successfully connected to the supercomputer in the computing centre in Groningen, which combines the data of the thousands of antennas.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    ASTRON-Westerbork Synthesis Radio Telescope
    Westerbork Synthesis Radio Telescope (WSRT)

    ASTRON was founded in 1949, as the Foundation for Radio radiation from the Sun and Milky Way (SRZM). Its original charge was to develop and operate radio telescopes, the first being systems using surplus wartime radar dishes. The organisation has grown from twenty employees in the early 1960’s to about 180 staff members today.

     
  • richardmitnick 1:54 pm on July 24, 2017 Permalink | Reply
    Tags: , , , Cosmology, Sgr A*, The Story of a Boring Encounter with a Black Hole   

    From AAS NOVA: “The Story of a Boring Encounter with a Black Hole” 

    AASNOVA

    American Astronomical Society

    24 July 2017
    Susanna Kohler

    1
    Many simulations from before G2’s encounter with Sgr A* (like the one shown here, from a group in Europe) predicted an exciting show! So why was the approach so uneventful? [ESO/S. Gillessen/MPE/Marc Schartmann.]

    Remember the excitement three years ago before the gas cloud G2’s encounter with the supermassive black hole at the center of our galaxy, Sgr A*?

    SGR A* NASA’s Chandra X-Ray Observatory

    Did you notice that not much was said about it after the fact? That’s because not much happened — and a new study suggests that this isn’t surprising.

    An Anticipated Approach

    G2, an object initially thought to be a gas cloud, was expected to make its closest approach to the 4.6-million-solar-mass Sgr A* in 2014. At the pericenter of its orbit, G2 was predicted to pass as close as 36 light-hours from the black hole.

    2
    Log-scale column density plots from one of the authors’ simulations, showing the cloud at a time relative to periapsis (t=0) of −5, −1, 0, 1, 5, and 10 yr (left to right, top to bottom). [Morsony et al. 2017]

    This close brush with such a massive black hole was predicted to tear G2 apart, causing much of its material to accrete onto Sgr A*. It was thought that this process would temporarily increase the accretion rate onto the black hole relative to its normal background accretion rate, causing Sgr A*’s luminosity to increase for a time.

    Instead, Sgr A* showed a distinct lack of fireworks, with very minimal change to its brightness after G2’s closest approach. This “cosmic fizzle” has raised questions about the nature of G2: was it really a gas cloud? What else might it have been instead? Now, a team of scientists led by Brian Morsony (University of Maryland and University of Wisconsin-Madison) have run a series of simulations of the encounter to try to address these questions.

    No Fireworks

    Morsony and collaborators ran three-dimensional hydrodynamics simulations using the FLASH code. They used a range of different simulation parameters, like cloud structure, background structure, background density, grid resolution, and accretion radius, in order to better understand how these factors might have affected the accretion rate and corresponding luminosity of Sgr A*.

    3
    Accretion rate vs. time for two of the simulations, one with a wind background and one with no wind background. The accretion rate in both cases displays no significant increase when G2 reaches periapsis. [Morsony et al. 2017]

    Based on their simulations, the authors showed that we actually shouldn’t expect G2’s encounter to have caused a significant change in Sgr A*’s accretion rate relative to its normal rate from background accretion: with the majority of the simulation parameters used, only 3–21% of the material Sgr A* accreted from 0–5 years after periapsis is from the cloud, and only 0.03–10% of the total cloud mass is accreted.

    Not Just a Cloud?

    By comparing their simulations to observations of G2 after its closest approach, Morsony and collaborators find that to fit the observations, G2 cannot be solely a gas cloud. Instead, two components are likely needed: an extended, cold, low-mass gas cloud responsible for most of the emission before G2 approached pericenter, and a very compact component such as a dusty stellar object that dominates the emission observed since pericenter.

    The authors argue that any future emission detected should no longer be from the cloud, but only from the compact core or dusty stellar object. Future observations should help us to confirm this model — but in the meantime these simulations give us a better sense of why G2’s encounter with Sgr A* was such a fizzle.

    Citation

    Brian J. Morsony et al 2017 ApJ 843 29. doi:10.3847/1538-4357/aa773d

    Related Journal Articles
    See the full article for further references with links.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    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 7:57 am on July 24, 2017 Permalink | Reply
    Tags: , , , Cosmology, , Gamma ray telescopes, How non-optical telescopes see the universe, Infrared telescopes, , Optical telescopes, Pair production telescope, , Ultraviolet telescopes, X-ray telescopes   

    From COSMOS: “How non-optical telescopes see the universe” 

    Cosmos Magazine bloc

    COSMOS Magazine

    24 July 2017
    Jake Port

    The human eye can only see a tiny band of the electromagnetic spectrum. That tiny band is enough for most day-to-day things you might want to do on Earth, but stars and other celestial objects radiate energy at wavelengths from the shortest (high-energy, high-frequency gamma rays) to the longest (low-energy, low-frequency radio waves).

    1
    The electromagnetic spectrum is made up of radiation of all frequencies and wavelengths. Only a tiny range is visible to the human eye. NASA.

    Beyond the visible spectrum

    To see what’s happening in the distant reaches of the spectrum, astronomers use non-optical telescopes. There are several varieties, each specialised to catch radiation of particular wavelengths.

    Non-optical telescopes utilise many of the techniques found in regular telescopes, but also employ a variety of techniques to convert invisible light into spectacular imagery. In all cases, a detector is used to capture the image rather than an eyepiece, with a computer then processing the data and constructing the final image.

    There are also more exotic ways of looking at the universe that don’t use electromagnetic radiation at all, like neutrino telescopes and the cutting-edge gravitational wave telescopes, but they’re a separate subject of their own.

    To start off, let’s go straight to the top with the highest-energy radiation, gamma rays.

    Gamma ray telescopes

    Gamma radiation is generally defined as radiation of wavelengths less than 10−11 m, or a hundredth of a nanometre.

    Gamma-ray telescopes focus on the highest-energy phenomena in the universe, such as black holes and exploding stars. A high-energy gamma ray may contain a billion times as much energy as a photon of visible light, which can make them difficult to study.

    Unlike photons of visible light, that can be redirected using mirrors and reflectors, gamma rays simply pass through most materials. This means that gamma-ray telescopes must use sophisticated techniques that track the movement of individual gamma rays to construct an image.

    One technology that does this, in use in the Fermi Gamma-ray Space Telescope among other places, is called a pair production telescope.

    NASA/Fermi Telescope

    It uses a multi-layer sandwich of converter and detector materials. When a gamma ray enters the front of the detector it hits a converter layer, made of dense material such as lead, which causes the gamma-ray to produce an electron and a positron (known as a particle-antiparticle pair).

    The electron and the positron then continue to traverse the telescope, passing through layers of detector material. These layers track the movement of each particle by recording slight bursts of electrical charge along the layer. This trail of bursts allows astronomers to reconstruct the energy and direction of the original gamma ray. Tracing back along that path points to the source of the ray out in space. This data can then be used to create an image.

    The video below shows how this works in the space-based Fermi Large Area Telescope.

    NASA/Fermi LAT

    X-ray telescopes

    X-rays are radiation with wavelengths between 10 nanometres and 0.01 nanometres. They are used every day to image broken bones and scan suitcases in airports and can also be used to image hot gases floating in space. Celestial gas clouds and remnants of the explosive deaths of large stars, known as supernovas, are the focus of X-ray telescopes.

    Like gamma rays, X-rays are a high-energy form of radiation that can pass straight through most materials. To catch X-rays you need to use materials that are very dense.

    X-ray telescopes often use highly reflective mirrors that are coated with dense metals such as gold, nickel or iridium. Unlike optical mirrors, which can bounce light in any direction, these mirrors can only slightly deflect the path of the X-ray. The mirror is orientated almost parallel to the direction of the incoming X-rays. The X-rays lightly graze the mirror before moving on, a little like a stone skipping on a pond. By using lots of mirrors, each changing the direction of the radiation by a small amount, enough X-rays can be collected at the detector to produce an image.

    To maximise image quality the mirrors are loosely stacked, creating an internal structure resembling the layers of an onion.

    2
    Diagram showing how ‘grazing incidence’ mirrors are used in X-ray telescopes. NASA.

    NASA/Chandra X-ray Telescope

    ESA/XMM Newton X-ray telescope

    NASA NuSTAR X-ray telescope


    Ultraviolet telescopes

    Ultraviolet light is radiation with wavelengths just too short to be visible to human eyes, between 400 nanometres and 0.01 nanometres. It has less energy than X-rays and gamma rays, and ultraviolet telescopes are more like optical ones.

    Mirrors coated in materials that reflect UV radiation, such as silicon carbide, can be used to redirect and focus incoming light. The Hopkins Ultraviolet Telescope, which flew two short missions aboard the space shuttle in the 1990s, used a parabolic mirror coated with this material.

    3
    A schematic of the Hopkins Ultraviolet Telescope. NASA.

    NASA Hopkins Ultraviolet Telescope which flew on the ISS

    As redirected light reaches the focal point, a central point where all light beams converge, they are detected using a spectrogram. This specialised device can separate the UV light into individual wavelength bands in a way akin to splitting visible light into a rainbow.

    Analysis of this spectrogram can indicate what the observation target is made of. This allows astronomers to analyse the composition of interstellar gas clouds, galactic centres and planets in our solar system. This can be particularly useful when looking for elements essential to carbon-based life such as oxygen and carbon.

    Optical telescopes

    Optical telescopes are used to view the visible spectrum: wavelengths roughly between 400 and 700 nanometres. See separate article here.


    Keck Observatory, Maunakea, Hawaii, USA

    ESO/VLT at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level

    Gran Telescopio Canarias at the Roque de los Muchachos Observatory on the island of La Palma, in the Canaries, Spain, sited on a volcanic peak 2,267 metres (7,438 ft) above sea level

    Gemini/North telescope at Maunakea, Hawaii, USA

    Gemini South telescope, Cerro Tololo Inter-American Observatory (CTIO) campus near La Serena, Chile

    Infrared telescopes

    Sitting just below visible light on the electromagnetic spectrum is infrared light, with wavelengths between 700 nanometres and 1 millimetre.

    It’s used in night vision goggles, heaters and tracking devices as found in heat-seeking missiles. Any object or material that is hotter than absolute zero will emit some amount of infrared radiation, so the infrared band is a useful window to look at the universe through.

    Much infrared radiation is absorbed by water vapour in the atmosphere, so infrared telescopes are usually at high altitudes in dry places or even in space, like the Spitzer Space Telescope.

    Infrared telescopes are often very similar to optical ones. Mirrors and reflectors are used to direct the infrared light to a detector at the focal point. The detector registers the incoming radiation, which a computer then converts into a digital image.

    NASA/Spitzer Infrared Telescope

    Radio telescopes

    At the far end of the electromagnetic spectrum we find the radio waves, with frequencies less than 1000 megahertz and wavelengths of a metre and more. Radio waves penetrate the atmosphere easily, unlike higher-frequency radiation, so ground-based observatories can catch them.

    Radio telescopes feature three main components that each play an important role in capturing and processing incoming radio signals.

    The first is the massive antenna or ‘dish’ that faces the sky. The Parkes radio telescope in New South Wales, Australia, for instance, has a dish with a diameter of 64 metres, while the Aperture Spherical Telescope in southwest China is has a whopping 500-metre diameter.

    The great size allows for the collection of long wavelengths and very quiet signals. The dish is parabolic, directing radio waves collected over a large area to be focused to a receiver sitting in front of the dish. The larger the antenna, the weaker the radio source that can be detected, allowing larger telescopes to see more distant and faint objects billions of light years away.

    The receiver works with an amplifier to boost the very weak radio signal to make it strong enough for measurement. Receivers today are so sensitive that they use powerful coolers to minimise thermal noise generated by the movement of atoms in the metal of the structure.

    Finally, a recorder stores the radio signal for later processing and analysis.

    Radio telescopes are used to observe a wide array of subjects, including energetic pulsar and quasar systems, galaxies, nebulae, and of course to listen out for potential alien signals.

    CSIRO/Parkes Observatory, located 20 kilometres north of the town of Parkes, New South Wales, Australia



    GBO radio telescope, Green Bank, West Virginia, USA

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
  • richardmitnick 11:35 am on July 23, 2017 Permalink | Reply
    Tags: , , , Cosmology, Hot gas in the center of the milky way, , Universo Magico   

    From Universo Magico: “Hot gas in the center of the milky way” 

    Universo Magico

    July 23, 2017
    Juan Carlos

    1

    This image was produced by combining 12 observations of the X Chandra x-ray Observatory of a region 130 light-years from the center of the Milky way .

    NASA/Chandra Telescope

    The colors represent low-energy red X rays, average energy in green and high power in azul. Thanks to the unique power of resolution of Chandra, astronomers have been able to identify thousands of x-ray sources, as well as neutron stars, black holes, white dwarfs, stars in the foreground and the background galaxies. What remains is a diffuse glow of x-rays that extends from the upper left to the lower right, along the direction of the Galactic disk. The spectrum of the diffuse glow is consistent with a cloud of hot gas that contains two components, 10 million degrees Celsius and gas to 100 million degrees. Diffuse x-rays seem to be the brightest part of a crest of x-ray emission measuring thousands of years light across the disk of the Galaxy. The extension of this Crest implies that the diffuse hot gas in this image, probably not is being warmed by the supermassive black hole at the center of the milky way, known by astronomers as Sagittarius A.

    The shockwaves from explosions of supernovae are the most likely explanation to heat the gas up to 10 million degrees, but it is not known how heats the gas of 100 million degrees. Ordinary shock waves from supernova would not warm by very high energy particles that produces the wrong spectrum of x-rays. Moreover, the observed Galactic magnetic field appears to discard the heating and confinement by magnetic turbulence. It is possible that the high energy of the hot gas x-ray component seem only diffuse and, indeed, is due to the combined glow of a yet undetected population of point sources, as well as diffuse lights of a city seen at a great distance. The difficulty with this explanation is that 200,000 radioactive sources in the observed region would be necessary. A population so large sources undetected, would produce a glow of x-rays much softer than is observed. In addition, there is a known class of objects that can account for such a large number of high energy x-ray sources in the center of the milky way.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
  • richardmitnick 10:22 am on July 23, 2017 Permalink | Reply
    Tags: , , , , , , Cosmology, , FDM-Fuzzy Dark Matter, Lyman-alpha forest   

    From Astro Watch: “Flashes of Light on the Dark Matter” 

    Astro Watch bloc

    Astro Watch

    July 23, 2017
    No writer credit found

    1

    A web that passes through infinite intergalactic spaces, a dense cosmic forest illuminated by very distant lights and a huge enigma to solve. These are the picturesque ingredients of a scientific research – carried out by an international team composed of researchers from the International School for Adavnced Studies (SISSA) and the Abdus Salam International Center for Theoretical Physics (ICTP) in Trieste, the Institute of Astronomy of Cambridge and the University of Washington – that adds an important element for understanding one of the fundamental components of our Universe: the dark matter.

    In order to study its properties, scientists analyzed the interaction of the “cosmic web” – a network of filaments made up of gas and dark matter present in the whole Universe – with the light coming from very distant quasars and galaxies. Photons interacting with the hydrogen of the cosmic filaments create many absorption lines defined “Lyman-alpha forest”. This microscopic interaction succeeds in revealing several important properties of the dark matter at cosmological distances. The results further support the theory of Cold Dark Matter, which is composed of particles that move very slowly. Moreover, for the first time, they highlight the incompatibility with another model, i.e. the Fuzzy Dark Matter, for which dark matter particles have larger velocities. The research was carried out through simulations performed on international parallel supercomputers and has recently been published in Physical Review Letters.

    Although constituting an important part of our cosmos, the dark matter is not directly observable, it does not emit electromagnetic radiation and it is visible only through gravitational effects. Besides, its nature remains a deep mystery. The theories that try to explore this aspect are various. In this research, scientists investigated two of them: the so-called Cold Dark Matter, considered a paradigm of modern cosmology, and an alternative model called Fuzzy Dark Matter (FDM), in which the dark matter is deemed composed of ultralight bosons provided with a non-negligible pressure at small scales. To carry out their investigations, scientists examined the cosmic web by analyzing the so-called Lyman-alpha forest. The Lyman-alpha forest consists of a series of absorption lines produced by the light coming from very distant and extremely luminous sources, that passes through the intergalactic space along its way toward the earth’s telescopes. The atomic interaction of photons with the hydrogen present in the cosmic filaments is used to study the properties of the cosmos and of the dark matter at enormous distances.

    Through simulations carried out with supercomputers, researchers reproduced the interaction of the light with the cosmic web. Thus they were able to infer some of the characteristics of the particles that compose the dark matter. More in particular, evidence showed for the first time that the mass of the particles, which allegedly compose the dark matter according to the FDM model, is not consistent with the Lyman-alpha Forest observed by the Keck telescope (Hawaii, US) and the Very Large Telescope (European Southern Observatory, Chile).


    Keck Observatory, Maunakea, Hawaii, USA

    ESO/VLT at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level

    Basically, the study seems not to confirm the theory of the Fuzzy Dark Matter. The data, instead, support the scenario envisaged by the model of the Cold Dark Matter.

    The results obtained – scientists say – are important as they allow to build new theoretical models for describing the dark matter and new hypotheses on the characteristics of the cosmos. Moreover, these results can provide useful indications for the realization of experiments in laboratories and can guide observational efforts aimed at making progress on this fascinating scientific theme.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
  • richardmitnick 9:57 am on July 23, 2017 Permalink | Reply
    Tags: , , , Cosmology, Hunting Molecules with the MWA, , , The mercapto radical (SH) and nitric oxide (NO)   

    From ICRAR: “Hunting Molecules with the MWA” 

    ICRAR Logo
    International Centre for Radio Astronomy Research

    July 21, 2017

    Astronomers have used an Australian radio telescope to observe molecular signatures from stars, gas and dust in our galaxy, which could lead to the detection of complex molecules that are precursors to life.

    Using the Murchison Widefield Array (MWA), a radio telescope located in the Murchison region of Western Australia, the team successfully detected two molecules called the mercapto radical (SH) and nitric oxide (NO).

    1
    This image shows the centre of the Milky Way as seen by the Galactic Centre Molecular Line Survey. Credit: Chenoa Tremblay (ICRAR-Curtin)

    “The molecular transitions we saw are from slow variable stars—stars at the end of their lives that are becoming unstable,” said Chenoa Tremblay from the International Centre for Radio Astronomy Research (ICRAR) and Curtin University.

    “One of the unique aspects of this survey is that until now, no one has ever reported detections of molecules within the 70-300MHz frequency range of the MWA and this is the widest field-of-view molecular survey of the Milky Way ever published.”

    Since the 1980s, frequencies greater than 80GHz have been used for this type of work due to the freedom from radio frequency interference emitted by our mobile phones, televisions and orbiting satellites. But the extreme “radio quietness” of the Murchison Radio-astronomy Observatory, where the telescope is located, allows astronomers to study molecular signatures from stars and star-forming regions at lower frequencies.

    “Before this study, the mercapto radical had only been seen twice before at infrared wavelengths, in a different part of the electromagnetic spectrum,” said Dr Maria Cunningham from the University of New South Wales.

    “This shows that molecules are emitting photons detectable around 100MHz and we can detect these molecular signatures using the MWA—it’s very exciting for us,” she said.

    Following on from the pilot study, a survey of the Orion region is now in progress, again using the MWA, in the frequency range of 99-270MHz. The Orion nebula is a chemical-rich environment and one of the closest star-forming regions to Earth. The aim is to detect more chemical tracers in stars, compare these regions to the observations from the Galactic Centre pilot region and to better understand the emission mechanisms of these molecules.

    “This new technique paves the way for deeper surveys that can probe the Milky Way and other galaxies in search of molecular precursors to life,” said Tremblay.

    PUBLICATION DETAILS

    A First Look for Molecules between 103 and 133MHz using the Murchison Wideeld Array, published in the Monthly Notices of the Royal Astronomical Society on July 21, 2017.

    See the full article here .

    Please help promote STEM in your local schools.
    STEM Icon

    Stem Education Coalition

    ICRAR is an equal joint venture between Curtin University and The University of Western Australia with funding support from the State Government of Western Australia. The Centre’s headquarters are located at UWA, with research nodes at both UWA and the Curtin Institute for Radio Astronomy (CIRA).
    ICRAR has strong support from the government of Australia and is working closely with industry and the astronomy community, including CSIRO and the Australian Telescope National Facility, iVEC, and the international SKA Project Office (SPO), based in the UK.

    ICRAR is:

    Playing a key role in the international Square Kilometre Array (SKA) project, the world’s biggest ground-based telescope array.


    Attracting some of the world’s leading researchers in radio astronomy, who will also contribute to national and international scientific and technical programs for SKA and ASKAP.
    Creating a collaborative environment for scientists and engineers to engage and work with industry to produce studies, prototypes and systems linked to the overall scientific success of the SKA, MWA and ASKAP.

    Murchison Widefield Array,SKA Murchison Widefield Array, Boolardy station in outback Western Australia, at the Murchison Radio-astronomy Observatory (MRO)


    A Small part of the Murchison Widefield Array

    Enhancing Australia’s position in the international SKA program by contributing to the development process for the SKA in scientific, technological and operational areas.
    Promoting scientific, technical, commercial and educational opportunities through public outreach, educational material, training students and collaborative developments with national and international educational organisations.
    Establishing and maintaining a pool of emerging and top-level scientists and technologists in the disciplines related to radio astronomy through appointments and training.
    Making world-class contributions to SKA science, with emphasis on the signature science themes associated with surveys for neutral hydrogen and variable (transient) radio sources.
    Making world-class contributions to SKA capability with respect to developments in the areas of Data Intensive Science and support for the Murchison Radio-astronomy Observatory.

     
  • richardmitnick 6:23 am on July 22, 2017 Permalink | Reply
    Tags: , , , , Cosmology, Dragonfly 44 an extremely faint galaxy, Globular Clusters for Faint Galaxies   

    From AAS NOVA: ” Globular Clusters for Faint Galaxies” 

    AASNOVA

    American Astronomical Society

    21 July 2017
    Susanna Kohler

    1
    This Hubble image of Dragonfly 44, an extremely faint galaxy, reveals that it is surrounded by dozens of compact objects that are likely globular clusters. [van Dokkum et al. 2017]

    The origin of ultra-diffuse galaxies (UDGs) has posed a long-standing mystery for astronomers. New observations of several of these faint giants with the Hubble Space Telescope are now lending support to one theory.

    NASA/ESA Hubble Telescope

    2
    Hubble images of Dragonfly 44 (top) and DFX1 (bottom). The right panels show the data with greater contrast and extended objects masked. [van Dokkum et al. 2017]

    Faint-Galaxy Mystery

    UDGs — large, extremely faint spheroidal objects — were first discovered in the Virgo galaxy cluster roughly three decades ago. Modern telescope capabilities have resulted in many more discoveries of similar faint galaxies in recent years, suggesting that they are a much more common phenomenon than we originally thought.

    Despite the many observations, UDGs still pose a number of unanswered questions. Chief among them: what are UDGs? Why are these objects the size of normal galaxies, yet so dim? There are two primary models that explain UDGs:

    1. UDGs were originally small galaxies, hence their low luminosity. Tidal interactions then puffed them up to the large size we observe today.
    2. UDGs are effectively “failed” galaxies. They formed the same way as normal galaxies of their large size, but something truncated their star formation early, preventing them from gaining the brightness that we would expect for galaxies of their size.

    Now a team of scientists led by Pieter van Dokkum (Yale University) has made some intriguing observations with Hubble that lend weight to one of these models.

    3
    Globulars observed in 16 Coma-cluster UDGs by Hubble. The top right panel shows the galaxy identifications. The top left panel shows the derived number of globular clusters in each galaxy. [van Dokkum et al. 2017]

    Globulars Galore

    Van Dokkum and collaborators imaged two UDGs with Hubble: Dragonfly 44 and DFX1, both located in the Coma galaxy cluster. These faint galaxies are both smooth and elongated, with no obvious irregular features, spiral arms, star-forming regions, or other indications of tidal interactions.

    The most striking feature of these galaxies, however, is that they are surrounded by a large number of compact objects that appear to be globular clusters. From the observations, Van Dokkum and collaborators estimate that Dragonfly 44 and DFX1 have approximately 74 and 62 globulars, respectively — significantly more than the low numbers expected for galaxies of this luminosity.

    Armed with this knowledge, the authors went back and looked at archival observations of 14 other UDGs also located in the Coma cluster. They found that these smaller and fainter galaxies don’t host quite as many globular clusters as Dragonfly 44 and DFX1, but more than half also show significant overdensities of globulars.

    4
    Main panel: relation between the number of globular clusters and total absolute magnitude for Coma UDGs (solid symbols) compared to normal galaxies (open symbols). Top panel: relation between effective radius and absolute magnitude. The UDGs are significantly larger and have more globular clusters than normal galaxies of the same luminosity. [van Dokkum et al. 2017]

    Evidence of Failure

    In general, UDGs appear to have more globular clusters than other galaxies of the same total luminosity, by a factor of nearly 7. These results are consistent with the scenario in which UDGs are failed galaxies: they likely have the halo mass to have formed a large number of globular clusters, but they were quenched before they formed a disk and bulge. Because star formation never got going in UDGs, they are now much dimmer than other galaxies of the same size.

    The authors suggest that the next step is to obtain dynamical measurements of the UDGs to determine whether these faint galaxies really do have the halo mass suggested by their large numbers of globulars. Future observations will continue to help us pin down the origin of these dim giants.

    Citation

    Pieter van Dokkum et al 2017 ApJL 844 L11. doi:10.3847/2041-8213/aa7ca2

    Related Journal Articles
    See the full article for further references with links.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    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

     
c
Compose new post
j
Next post/Next comment
k
Previous post/Previous comment
r
Reply
e
Edit
o
Show/Hide comments
t
Go to top
l
Go to login
h
Show/Hide help
shift + esc
Cancel
%d bloggers like this: