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  • richardmitnick 11:53 am on February 23, 2020 Permalink | Reply
    Tags: , , , , , , Dark Matter, , , , ,   

    From EarthSky: “What is dark matter?” 

    1

    From EarthSky

    February 23, 2020
    Andy Briggs

    Dark Matter doesn’t emit light. It can’t be directly observed with any of the existing tools of astronomers. Yet astrophysicists believe it and Dark Energy make up most of the mass of the cosmos. What dark matter is, and what it isn’t. here.

    1
    Since the 1930s, astrophysicists have been trying to explain why the visible material in galaxies can’t account for how galaxies are shaped, or how they behave. They believe a form of dark or invisible matter pervades our universe, but they still don’t know what this dark matter might be. Image via ScienceAlert.

    Dark matter is a mysterious substance thought to compose perhaps about 27% of the makeup of the universe. What is it? It’s a bit easier to say what it isn’t.

    It isn’t ordinary atoms – the building blocks of our own bodies and all we see around us – because atoms make up only somewhere around 5% of the universe, according to a cosmological model called the Lambda Cold Dark Matter Model (aka the Lambda-CDM model, or sometimes just the Standard Model).

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

    Dark Matter isn’t the same thing as Dark Energy, which makes up some 68% of the universe, according to the Standard Model.

    Dark Energy Survey


    Dark Energy Camera [DECam], built at FNAL


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

    Timeline of the Inflationary Universe WMAP

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

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

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

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

    Dark matter is invisible; it doesn’t emit, reflect or absorb light or any type of electromagnetic radiation such as X-rays or radio waves. Thus, dark matter is undetectable directly, as all of our observations of the universe, apart from the detection of gravitational waves, involve capturing electromagnetic radiation in our telescopes.

    Gravitational waves Werner Benger-ZIB-AEI-CCT-LSU

    Yet dark matter does interact with ordinary matter. It exhibits measurable gravitational effects on large structures in the universe such as galaxies and galaxy clusters. Because of this, astronomers are able to make maps of the distribution of dark matter in the universe, even though they cannot see it directly.

    They do this by measuring the effect dark matter has on ordinary matter, through gravity.

    2
    This all-sky image – released in 2013 – shows the distribution of dark matter across the entire history of the universe as seen projected on the sky. It’s based on data collected with the European Space Agency’s Planck satellite.

    ESA/Planck 2009 to 2013

    Dark blue areas represent regions that are denser than their surroundings. Bright areas represent less dense regions. The gray portions of the image correspond to patches of the sky where foreground emission, mainly from the Milky Way but also from nearby galaxies, prevents cosmologists from seeing clearly. Image via ESA.

    There is currently a huge international effort to identify the nature of dark matter. Bringing an armory of advanced technology to bear on the problem, astronomers have designed ever-more complex and sensitive detectors to tease out the identity of this mysterious substance.

    Dark Matter Research

    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

    Scientists studying the cosmic microwave background hope to learn about more than just how the universe grew—it could also offer insight into dark matter, dark energy and the mass of the neutrino.

    Dark matter cosmic web and the large-scale structure it forms The Millenium Simulation, V. Springel et al

    Dark Matter Particle Explorer China

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

    LBNL LZ Dark Matter project at SURF, Lead, SD, USA


    Inside the ADMX experiment hall at the University of Washington Credit Mark Stone U. of Washington. Axion Dark Matter Experiment

    Dark matter might consist of an as yet unidentified subatomic particle of a type completely different from what scientists call baryonic matter – that’s just ordinary matter, the stuff we see all around us – which is made of ordinary atoms built of protons and neutrons.

    The list of candidate subatomic particles breaks down into a few groups: there are the WIMPs (Weakly Interacting Massive Particles), a class of particles thought to have been produced in the early universe. Astronomers believe that WIMPs might self-annihilate when colliding with each other, so they have searched the skies for telltale traces of events such as the release of neutrinos or gamma rays. So far, they’ve found nothing. In addition, although a theory called supersymmetry predicts the existence of particles with the same properties as WIMPs, repeated searches to find the particles directly have also found nothing, and experiments at the Large Hadron Collider to detect the expected presence of supersymmetry have completely failed to find it.

    Standard Model of Supersymmetry via DESY

    CERN/LHC Map


    CERN LHC Maximilien Brice and Julien Marius Ordan


    SixTRack CERN LHC particles

    Several different types of detector have been used to detect WIMPs. The general idea is that very occasionally, a WIMP might collide with an ordinary atom and release a faint flash of light, which can be detected. The most sensitive detector built to date is XENON1T, which consists of a 10-meter cylinder containing 3.2 tons of liquid xenon, surrounded by photomultipliers to detect and amplify the incredibly faint flashes from these rare interactions. As of July 2019, when the detector was decommissioned to pave the way for a more sensitive instrument, the XENONnT, no collisions between WIMPs and the xenon atoms had been seen.

    XENON1T at Gran Sasso LABORATORI NAZIONALI del GRAN SASSO, located in the Abruzzo region of central Italy


    Gran Sasso LABORATORI NAZIONALI del GRAN SASSO, located in the Abruzzo region of central Italy

    At the moment, a hypothetical particle called the Axion is receiving much attention.

    CERN CAST Axion Solar Telescope

    As well as being a strong candidate for dark matter, the existence of axions is also thought to provide the answers to a few other persistent questions in physics such as the Strong CP Problem.

    Fritz Zwicky discovered Dark Matter in the 1930s when observing the movement of the Coma Cluster., Vera Rubin a Woman in STEM denied the Nobel, did most of the work on Dark Matter.

    Fritz Zwicky from http:// palomarskies.blogspot.com

    Coma cluster via NASA/ESA Hubble

    In modern times, it was astronomer Fritz Zwicky, in the 1930s, who made the first observations of what we now call dark matter. His 1933 observations of the Coma Cluster of galaxies seemed to indicated it has a mass 500 times more than that previously calculated by Edwin Hubble. Furthermore, this extra mass seemed to be completely invisible. Although Zwicky’s observations were initially met with much skepticism, they were later confirmed by other groups of astronomers.

    Thirty years later, astronomer Vera Rubin provided a huge piece of evidence for the existence of dark matter. She discovered that the centers of galaxies rotate at the same speed as their extremities, whereas, of course, they should rotate faster. Think of a vinyl LP on a record deck: its center rotates faster than its edge. That’s what logic dictates we should see in galaxies too. But we do not. The only way to explain this is if the whole galaxy is only the center of some much larger structure, as if it is only the label on the LP so to speak, causing the galaxy to have a consistent rotation speed from center to edge.

    Vera Rubin, following Zwicky, postulated that the missing structure in galaxies is dark matter. Her ideas were met with much resistance from the astronomical community, but her observations have been confirmed and are seen today as pivotal proof of the existence of dark matter.

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


    Vera Rubin measuring spectra, worked on Dark Matter (Emilio Segre Visual Archives AIP SPL)


    Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970. https://home.dtm.ciw.edu

    The Vera C. Rubin Observatory currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

    LSST Data Journey, Illustration by Sandbox Studio, Chicago with Ana Kova

    Some astronomers have tried to negate the need the existence of dark matter altogether by postulating something called Modified Newtonian dynamics (MOND).

    Mordehai Milgrom, MOND theorist, is an Israeli physicist and professor in the department of Condensed Matter Physics at the Weizmann Institute in Rehovot, Israel http://cosmos.nautil.us

    MOND Modified Newtonian Dynamics a Humble Introduction Marcus Nielbock

    The idea behind this is that gravity behaves differently over long distances to what it does locally, and this difference of behavior explains phenomena such as galaxy rotation curves which we attribute to dark matter. Although MOND has its supporters, while it can account for the rotation curve of an individual galaxy, current versions of MOND simply cannot account for the behavior and movement of matter in large structures such as galaxy clusters and, in its current form, is thought unable to completely account for the existence of dark matter. That is to say, gravity does behave in the same way at all scales of distance. Most versions of MOND, on the other hand, have two versions of gravity, the weaker one occurring in regions of low mass concentration such as in the outskirts of galaxies. However, it is not inconceivable that some new version of MOND in the future might yet account for dark matter.

    Although some astronomers believe we will establish the nature of dark matter in the near future, the search so far has proved fruitless, and we know that the universe often springs surprises on us so that nothing can be taken for granted.

    The approach astronomers are taking is to eliminate those particles which cannot be dark matter, in the hope we will be left with the one which is.

    It remains to be seen if this approach is the correct one.

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. “Being an EarthSky editor is like hosting a big global party for cool nature-lovers,” she says.

     
  • richardmitnick 2:58 pm on February 22, 2020 Permalink | Reply
    Tags: "Through the Lens: Milky Matter Magnifies Magellanic Motion", , , , , , Dark Matter, ,   

    From astrobites: “Through the Lens: Milky Matter Magnifies Magellanic Motion” 

    Astrobites bloc

    From astrobites

    Feb 22, 2020
    Luna Zagorac

    Title: First Results on Dark Matter Substructure from Astrometric Weak Lensing
    Authors: Cristina Mondino, Anna-Maria Taki, Ken Van Tilburg, and Neal Weiner
    First Author’s Institution: Center for Cosmology and Particle Physics, Department of Physics, New York University, New York, NY 10003, USA

    Status: pre-published on arXiv

    There is about five times more invisible Dark Matter than its luminous counterpart in the universe—but how do we go about detecting something that can’t be directly imaged?

    Fritz Zwicky discovered Dark Matter when observing the movement of the Coma Cluster., Vera Rubin a Woman in STEM denied the Nobel, did most of the work on Dark Matter.

    Fritz Zwicky from http:// palomarskies.blogspot.com

    Coma cluster via NASA/ESA Hubble

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


    Vera Rubin measuring spectra, worked on Dark Matter (Emilio Segre Visual Archives AIP SPL)


    Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970. https://home.dtm.ciw.edu

    The LSST, or Large Synoptic Survey Telescope is to be named the Vera C. Rubin Observatory by an act of the U.S. Congress.

    LSST telescope, The Vera C. Rubin Observatory currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

    LSST Data Journey, Illustration by Sandbox Studio, Chicago with Ana Kova

    Dark Matter Research

    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

    Scientists studying the cosmic microwave background [CMB]hope to learn about more than just how the universe grew—it could also offer insight into dark matter, dark energy and the mass of the neutrino.

    [caption id="attachment_73741" align="alignnone" width="632"] CMB per ESA/Planck

    Dark matter cosmic web and the large-scale structure it forms The Millenium Simulation, V. Springel et al

    Dark Matter Particle Explorer China

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

    LBNL LZ Dark Matter project at SURF, Lead, SD, USA


    Inside the ADMX experiment hall at the University of Washington Credit Mark Stone U. of Washington. Axion Dark Matter Experiment

    One way is to look for the gravitational effects of dark matter clumps on images of normal matter along the same line of sight. This type of effect is called gravitational lensing.

    Gravitational Lensing NASA/ESA

    In today’s paper, the authors specifically look for the effects of weak lensing from low-mass structures consisting entirely of dark matter.

    Weak gravitational lensing NASA/ESA Hubble

    The foreground dark matter structure creates a lens that bends the light coming towards an observer from some background luminous source. Unlike strong lensing, weak lensing doesn’t impact a single background source, but instead serves to preferentially align several background sources along some field. For more information on different types of lensing and how they work, check out this bite.

    Why Use Weak Lensing?

    Alignments of foreground and background sources that lead to weak lensing are much more common than those leading to strong lensing. Because low-mass dark matter structures are predicted to exist in the Milky Way, they should be both common in observational data sets and detectable through microlensing signatures. Furthermore, because such structures are completely devoid of normal matter, they pose a “pristine testing ground” for probing the microphysics of dark matter without the interference of normal, luminous matter.

    How to Look For Weak Lensing?

    1
    Figure 1: Diagram of gravitational lensing of sources i by lens l. Note the blue monopole pattern of the angular displacement \Delta \theta_{il}. This is not constant in time, leading to the red dipole pattern lensing corrections \Delta \mu_{il} to the sources’ proper motions \mu_i. This dipole pattern is universal, and is what the authors look for. Figure 1 in the paper.

    The authors use a template approach, which is similar to the one used when detecting astrophysical signals with LIGO. Figure 1 shows the dipole pattern of velocity corrections of background stars which stems from weak lensing. The exact shape and size of the template depend on the angular position \mathbf{\theta}_t, angular scale \beta_t, and effective lens velocity direction \hat{\mathbf{v}}_{t} of the dark matter lens. The details of the matched filter to the lens-induced velocity vector profile also include information about the density profile of the dark matter lens. This means that finding the correct shape of velocity corrections in the data and comparing its magnitude with the theoretical template model can inform the size, position, and density profile (and subsequently, mass) of the dark matter lens.

    Where to Look For Weak Lensing?

    The researchers looked to the Milky Way to provide the dark matter lenses, and extra-galactically to the Large and Small Magellanic Clouds (LMC, SMC) to provide the luminous matter to be lensed.

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

    Large Magellanic Cloud. Adrian Pingstone December 2003

    smc

    Small Magellanic Cloud. NASA/ESA Hubble and ESO/Digitized Sky Survey 2

    They used the second data release from Gaia and chose the LMC and SMC data for their large stellar number densities and low proper motion dispersions, both intrinsic and instrumental.

    ESA/GAIA satellite

    This left the authors with a high signal-to-noise ratio, thus best equipping them to look for signatures of weak lensing.

    In order to look for the tell-tale dipole template motion, the authors cleaned the data up a bit. First, they subtracted overdense stellar clusters, as they generally move coherently and independently from the bulk stars in the Magellanic Clouds. Additionally, they subtracted the large-scale proper motion of the clouds themselves. Finally, they removed stars which are in the line of sight, but not bound to the clouds.

    3
    Figure 2: Average stellar proper motion per 0.03° pixels in the RA (left) and DEC (right) across the Large Magellanic Cloud. The top panel shows the proper motion in the original Gaia data sample after the removal of dense clusters; the bottom shows it after further background motion subtraction and removal of outlier stars. Figure 7 in the paper.

    What did the authors find?

    In performing their analysis, the authors produced exclusions on the fraction of dark matter present in lensing sources as a function of lens mass (see Figure 3). They also noted that the current analysis is statistics-limited, with their figure of merit being largest for relatively faint stars, such as the majority of those present in the Magellanic Clouds. Thus, the statistics in their analysis will improve with additional integration time, which is currently at 22 months for Gaia DR2. Furthermore, having a larger sample of stars, better resolution of binaries, and accurate modeling of telescope systematics will all lead to improvements over time, yielding promising prospects for the use of their method on future data releases from Gaia and other astrometric surveys.

    4
    Figure 3: Constraints from the Magellanic Cloud velocity template analysis on the fractional dark matter abundance f_l of compact objects with mass M_l with a given density profile. The three linewidths represent compact object radii r_{l}=10^{-3}, 0.5, \text { and } 1 \mathrm{pc}. The constraint for the smallest radius is equivalent to the one for point-like objects. Above the diagonal line at the bottom right, at least one subhalo eclipses the data sample with 90% confidence level (CL). Figure 5 in the paper.

    See the full article here .


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    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 6:05 pm on February 20, 2020 Permalink | Reply
    Tags: "Stargazing with Computers: What Machine Learning Can Teach Us about the Cosmos", , , , , , , , Dark Matter, Vera C Rubin Observatory   

    From Argonne National Laboratory: “Stargazing with Computers: What Machine Learning Can Teach Us about the Cosmos” 

    Argonne Lab
    News from From Argonne National Laboratory

    February 18, 2020
    Shannon Brescher Shea
    shannon.shea@science.doe.gov

    Gazing up at the night sky in a rural area, you’ll probably see the shining moon surrounded by stars. If you’re lucky, you might spot the furthest thing visible with the naked eye – the Andromeda galaxy.

    Andromeda Galaxy Adam Evans

    It’s the nearest neighbor to our galaxy, the Milky Way. But that’s just the tiniest fraction of what’s out there. When the Department of Energy’s (DOE) Legacy Survey of Space and Time (LSST) Camera at the National Science Foundation’s Vera Rubin Observatory turns on in 2022, it will take photos of 37 billion galaxies and stars over the course of a decade.

    Fritz Zwicky discovered Dark Matter when observing the movement of the Coma Cluster., Vera Rubin a Woman in STEM denied the Nobel, did most of the work on Dark Matter.

    Fritz Zwicky from http:// palomarskies.blogspot.com

    Coma cluster via NASA/ESA Hubble

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


    Vera Rubin measuring spectra, worked on Dark Matter (Emilio Segre Visual Archives AIP SPL)


    Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970. https://home.dtm.ciw.edu

    The Vera C. Rubin Observatory currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

    The Vera C. Rubin Observatory Data Journey, Illustration by Sandbox Studio, Chicago with Ana Kova

    Dark Matter Research

    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

    Scientists studying the cosmic microwave background [CMB]hope to learn about more than just how the universe grew—it could also offer insight into dark matter, dark energy and the mass of the neutrino.

    [caption id="attachment_73741" align="alignnone" width="632"] CMB per ESA/Planck

    Dark matter cosmic web and the large-scale structure it forms The Millenium Simulation, V. Springel et al

    Dark Matter Particle Explorer China

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

    LBNL LZ Dark Matter project at SURF, Lead, SD, USA


    Inside the ADMX experiment hall at the University of Washington Credit Mark Stone U. of Washington. Axion Dark Matter Experiment

    The output from this huge telescope will swamp researchers with data. In those 10 years, the Vera C Rubin Observatory Camera will take 2,000 photos for each patch of the Southern Sky it covers. Each image can have up to a million objects in it.

    “In terms of the scale of the data, the amount of the data, the complexity of the data, they’re well beyond any of the current data sets we have,” said Rachel Mandelbaum, a professor at Carnegie Mellon University and LSST Dark Energy Science Collaboration spokesperson. “This opens up a huge amount of discovery space.”

    Scientists aren’t building the LSST Camera to just take pretty pictures. They want to identify, categorize, and measure celestial objects that can reveal information about the very structure of the universe. Understanding dark energy and other cosmological mysteries requires data on supernovae and galaxies. Researchers may even find entirely new classes of objects.

    “There are going to be some objects that we have never seen before because that is the point of new discovery,” said Renée Hložek, an assistant professor of astrophysics at the University of Toronto, who works with the LSST Dark Energy Science Collaboration. “We will find a bunch of what we call weirdos, or anomalies.”

    The sheer volume and strangeness of the data will make it difficult to analyze. While a stargazer new to an area might go out in the field with a local expert, scientists don’t have such a guide to new pieces of the universe. So they’re making their own. More accurately, they’re making many different guides that can help them identify and categorize these objects. Astrophysicists supported by the DOE Office of Science are developing these guides in the form of computer models that rely on machine learning to examine the Vera C Rubin Observatory data. Machine learning is a process where a computer program learns over time about the relationships in a set of data.

    Computer Programs that Learn

    Processing data quickly is a must for scientists in the Dark Energy Science Collaboration.

    Dark Energy Survey


    Dark Energy Camera [DECam], built at FNAL


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

    Timeline of the Inflationary Universe WMAP

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

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

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

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

    “There are going to be some objects that we have never seen before because that is the point of new discovery,” said Renée Hložek, an assistant professor of astrophysics at the University of Toronto, who works with the LSST Dark Energy Science Collaboration. “We will find a bunch of what we call weirdos, or anomalies.”

    The sheer volume and strangeness of the data will make it difficult to analyze. While a stargazer new to an area might go out in the field with a local expert, scientists don’t have such a guide to new pieces of the universe. So they’re making their own. More accurately, they’re making many different guides that can help them identify and categorize these objects. Astrophysicists supported by the DOE Office of Science are developing these guides in the form of computer models that rely on machine learning to examine the LSST data. Machine learning is a process where a computer program learns over time about the relationships in a set of data.

    Computer Programs that Learn

    Processing data quickly is a must for scientists in the Dark Energy Science Collaboration. Scientists need to know that the camera is pointing at exactly the right place and taking data correctly each time. This quick processing also helps them know if anything has changed in that part of the sky since the last time they took photos of it. Subtracting the current photo from previous ones shows them if there’s a sign of an interesting celestial object or phenomenon.

    They also need to combine a lot of photos together in a way that’s accurate and usable. This project is looking into the depths of the universe to capture images of some of the faintest stars and galaxies. It will also be taking photos in less-than-ideal atmospheric conditions. To compensate, scientists need programs that can combine images together to improve clarity.

    Machine learning can tackle these challenges in addition to handling the sheer amount of data. As these programs analyze more data, the more accurate they become. Just like a person learning to identify a constellation, they gain better judgement over time.

    “Many scientists regard machine learning as the most promising option for classifying sources based on photometric measurements (measurements of light intensity),” said Eve Kovacs, a physicist at DOE’s Argonne National Laboratory.

    But machine learning programs need to teach themselves before they can tackle a pile of new data. There are two main ways to “train” a machine learning program: unsupervised and supervised.

    Unsupervised machine learning is like someone teaching themselves about stars from just their nightly observations. The program trains itself on unlabeled data. While unsupervised machine learning can group images and identify outliers, it can’t categorize them without a guidebook of some sort.

    Supervised machine learning is like a newbie relying on a guidebook. The researchers feed it a massive set of data that is labeled with the classes of each object. By examining the data over and over, the program learns the relationship between the observation and the labels. This technique is especially useful for classifying objects into known groups.

    In some cases, the researchers also feed the program a specific set of features to look for, like brightness, shape, or color. They provide guidance on how important each feature is compared to the others. In other programs, the machine learning program figures out the relevant features itself.

    However, the accuracy of supervised machine learning depends on having a good training set, with all of the diversity and variability of a real one. For photos from the LSST Camera, that variability could include streaks from satellites moving across the sky. The labeling also has to be extremely accurate.

    “We have to put as much physics as we can into the training sets,” said Mandelbaum. “It doesn’t remove from us the burden to understand the physics. It just moves it into a different part of the problem.”

    See the full article here .

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    Argonne National Laboratory seeks solutions to pressing national problems in science and technology. The nation’s first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America’s scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science. For more visit http://www.anl.gov.

    The Advanced Photon Source at Argonne National Laboratory is one of five national synchrotron radiation light sources supported by the U.S. Department of Energy’s Office of Science to carry out applied and basic research to understand, predict, and ultimately control matter and energy at the electronic, atomic, and molecular levels, provide the foundations for new energy technologies, and support DOE missions in energy, environment, and national security. To learn more about the Office of Science X-ray user facilities, visit http://science.energy.gov/user-facilities/basic-energy-sciences/.

    Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science

    Argonne Lab Campus

     
  • richardmitnick 1:54 pm on February 11, 2020 Permalink | Reply
    Tags: Although scientists have yet to find the spooky stuff they aren’t completely in the dark., , Dark Matter, , It all adds up to 85% of the universe., It shaped entire galaxies without touching a thing., It’s built to last., Natalia Toro, ,   

    From Symmetry: “What we know about dark matter” 

    Symmetry Mag
    From Symmetry<

    02/11/20
    Jim Daley

    Caterpillar Project A Milky-Way-size dark-matter halo and its subhalos circled, an enormous suite of simulations . Griffen et al. 2016

    Although scientists have yet to find the spooky stuff, they aren’t completely in the dark.

    There are a lot of things scientists don’t know about dark matter: Can we catch it in a detector? Can we make it in a lab? What kinds of particles is it made of? Is it made of more than one kind of particle? Is it even made of particles at all?

    In short, dark matter is still pretty mysterious. The term is really just the name scientists gave to an ingredient that seems to be missing from our understanding of the universe.

    But there are some things scientists can definitively say about the stuff.

    Natalia Toro is a theoretical physicist at the US Department of Energy’s SLAC National Accelerator Laboratory and a member of the Light Dark Matter Experiment (LDMX) and the Beam Dump Experiment (BDX) dark matter search. She gave a talk at the 2019 meeting of the American Physical Society’s Division of Particles and Fields about the short list of things we do know about dark matter.

    2
    Light Dark Matter Experiment (LDMX).https://www.researchgate.net/figure/The-LDMX-experiment-layout_fig4_330726206

    3
    Beam Dump Experiment. https://www.jlab.org/accel/ops/ops_liaison/BDX/BDX.html

    1. It’s built to last.

    Dark matter formed very early on in the universe’s history. The evidence of this is apparent in the cosmic microwave background, or CMB—the ethereal layer of radiation left over from the universe’s searingly hot first moments.

    The fact that so much dark matter still seems to be around some 13.7 billion years later tells us right away that it has a lifetime of at least 1017 seconds (or about 3 billion years), Toro says.

    But there is another, more obvious clue that the lifetime of dark matter is much longer than that: We don’t see any evidence of dark matter decay.

    The heaviest particles in the Standard Model of particle physics break down, releasing their energy in the form of lighter particles. Dark matter doesn’t seem to do that, Toro says. “Whatever dark matter is made of, it lasts a really long time.”

    This property isn’t unheard of—electrons, protons and neutrinos all have extremely long lifespans—but it would be unusual, especially if dark matter turns out to be heavier than those light, stable particles.

    “One possibility is that there’s some kind of charge in nature, and dark matter is the lightest thing that carries that charge,” Toro says.

    In particle physics, charge must be conserved—meaning it cannot be created or destroyed. Take the decay of a muon, a heavier version of an electron. A muon often decays into a pair of neutrinos, one positively charged and one negatively charged, and an electron, which shares the muon’s negative charge. The charges of the neutrinos cancel one another out. So even though the muon has fallen apart into three other particles, its electromagnetic charge is conserved overall in the results of the decay.

    The electron is the lightest particle with a negative electromagnetic charge. Since there’s nothing with a smaller mass for it to decay into, it remains stable.

    But the electromagnetic charge is not the only type of charge. Protons, for example, are the lightest particle to carry a charge called the baryon number, which is related to the fact that they’re made of particles called quarks (but not anti-quarks). Quarks and gluons have what physicists call color charge, which seems to be conserved in particle interactions.

    It could be that dark matter particles are the most stable particles with a new kind of charge.

    2. It shaped entire galaxies without touching a thing.

    Dark matter’s apparent stability seems to have been key to another of its qualities: its ability to influence the evolution of the universe. Astrophysicists think that most galaxies would probably not have formed as they did without the help of dark matter.

    In the 1930s Swiss astrophysicist Fritz Zwicky noted that something seemed to be causing galaxies in the Coma Cluster to behave as if they were 400 times heavier than they would if they contained only luminous material. That discrepancy has today been calculated to be smaller, but it still exists. Zwicky coined the term “dark matter” to describe whatever could be giving the galaxies their extra mass.

    In the 1970s Vera Rubin, an astronomer at the Carnegie Institution in Washington, used spectrographic evidence to determine that spiral galaxies such as our own also seemed to be acting more massive than they appeared. They were rotating far more quickly than expected, something that could happen if they were, for example, sitting in invisible halos of dark matter.

    Fritz Zwicky discovered Dark Matter when observing the movement of the Coma Cluster., Vera Rubin a Woman in STEM denied the Nobel, did most of the work on Dark Matter.

    Fritz Zwicky from http:// palomarskies.blogspot.com

    Coma cluster via NASA/ESA Hubble

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


    Vera Rubin measuring spectra, worked on Dark Matter (Emilio Segre Visual Archives AIP SPL)


    Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970. https://home.dtm.ciw.edu

    The LSST, or Large Synoptic Survey Telescope is to be named the Vera C. Rubin Observatory by an act of the U.S. Congress.

    LSST telescope, The Vera Rubin Survey Telescope currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

    LSST Data Journey, Illustration by Sandbox Studio, Chicago with Ana Kova

    Dark Matter Research

    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

    Scientists studying the cosmic microwave background [CMB]hope to learn about more than just how the universe grew—it could also offer insight into dark matter, dark energy and the mass of the neutrino.

    [caption id="attachment_73741" align="alignnone" width="632"] CMB per ESA/Planck

    Dark matter cosmic web and the large-scale structure it forms The Millenium Simulation, V. Springel et al

    Dark Matter Particle Explorer China

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

    LBNL LZ Dark Matter project at SURF, Lead, SD, USA


    Inside the ADMX experiment hall at the University of Washington Credit Mark Stone U. of Washington. Axion Dark Matter Experiment

    Scientists have seen another effect of dark matter on luminous material. Clusters of dark matter act as cosmic potholes on the path that light travels through the cosmos, bending and distorting it in a process called “gravitational lensing.” Astronomers can map the distribution of otherwise invisible dark matter by studying this lensing.

    Just like regular matter, dark matter isn’t evenly distributed across the universe. Astrophysicists think that when the galaxies first formed, areas of the universe that had slightly more dark matter (and thus more gravitational pull) attracted more matter, leading to the distribution of galaxies that we now see.

    Had there been a different pattern of dark matter throughout the universe—or slightly more or less of it—then galaxies might have formed later, formed with different densities or never formed at all, Toro says. “Galaxies become a lot denser, and you could end up in a situation where lots of black holes form, or you could end up with much more dark matter.”

    Despite being massively (forgive the pun) influential, dark matter is famously standoffish, avoiding most of the kinds of interactions that Standard Model particles commonly undergo from the very beginning. “One thing that we know concretely from looking at the CMB is that there was a component of that plasma that was not interacting with the electrons and protons,” she says. “That’s one very clear constraint—that the constituents of dark matter interacted less than electrons and protons.”

    Dark matter is so nonreactive that it may not even interact with itself; when two galaxies merge, their respective dark matter halos simply pass through one another like ghosts.

    3. It all adds up to 85%.

    Amazingly, despite being unclear on precisely what dark matter is, astrophysicists do know pretty well how much of it there is—which is why we can say that it accounts for 85% of the known matter in the universe. Physicists call that amount the “cosmological abundance” of dark matter.

    Cosmological abundance can tell us a great deal about the makeup of the universe, Toro says—particularly in its earliest days, when it was much smaller and denser. During the evolution of the early universe, “average density was very representative” of the actual dark matter present in any area of it, she says.

    Currently, Toro says, dark matter’s cosmological abundance is “the only number physicists can hang our hat on.” Scientists have proposed—and are actively searching for—a number of different possible dark matter candidates. Whether dark matter is made up of a smaller number of heavy WIMPs or a larger number of light axions, its total mass must add up to the measure of the cosmological abundance.

    Toro says it’s important to take that number as far as it can be taken and to try to extrapolate different strategies for looking for dark matter from it.

    Quantifying anything else about dark matter—its interaction strength, its scattering rate and a laundry list of other potential properties—would be “amazing,” she says. “Having any confirmation, finding one more property of dark matter that we could actually quantify, would be a huge jump.”

    See the full article here .


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    Please help promote STEM in your local schools.


    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 5:06 pm on February 6, 2020 Permalink | Reply
    Tags: , , , , Dark Energy Camera, Dark Matter, , ,   

    From University of Chicago: “Leftover Big Bang light helps calculate how massive faraway galaxies are” 

    U Chicago bloc

    From University of Chicago

    Feb 6, 2020
    Catherine N. Steffel , FNAL

    1
    The South Pole Telescope provided key data for scientists to create a new method to weigh galaxy clusters. Photo by Daniel Michalik

    Fermilab, UChicago scientists tap South Pole Telescope data to shed light on universe.

    A team of scientists have demonstrated how to “weigh” galaxy clusters using light from the earliest moments of the universe—a new method that could help shed light on dark matter, dark energy and other mysteries of the cosmos, such as how the universe formed.

    The new method calculates the bending of light around galaxy clusters using the orientation of light from shortly after the Big Bang—data taken by the South Pole Telescope and the Dark Energy Camera.

    Dark Energy Survey


    Dark Energy Camera [DECam], built at FNAL


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

    Timeline of the Inflationary Universe WMAP

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

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

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

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

    “Gravitational lensing,” a phenomenon in which light distorts as it’s affected by the gravity of big objects like galaxies, can function as a kind of magnifying glass.

    Gravitational Lensing NASA/ESA

    It’s helped scientists discover key information about the universe—but it’s always been done by looking for the smearing of light around distant objects like stars.

    In a study published in Physical Review Letters, Fermilab and University of Chicago scientist Brad Benson and colleagues use a different method to calculate the masses of distant galaxies: the polarization, or orientation, of the light left over from the moments after the Big Bang.

    “Making this estimate is important because most of the mass of galaxy clusters isn’t even visible—it’s dark matter, which does not emit light but interacts through gravity and makes up about 85% of the matter in our universe,” said Benson, an assistant professor in the Department of Astronomy and Astrophysics. “Since photons from the cosmic microwave background have literally traveled across the entire observable universe, this method has the potential to more accurately measure the dark matter mass in the most distant galaxy clusters.”

    Fritz Zwicky discovered Dark Matter when observing the movement of the Coma Cluster., Vera Rubin a Woman in STEM denied the Nobel, did most of the work on Dark Matter.

    Fritz Zwicky from http:// palomarskies.blogspot.com

    Coma cluster via NASA/ESA Hubble

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


    Vera Rubin measuring spectra, worked on Dark Matter (Emilio Segre Visual Archives AIP SPL)


    Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970. https://home.dtm.ciw.edu

    The LSST, or Large Synoptic Survey Telescope is to be named the Vera C. Rubin Observatory by an act of the U.S. Congress.

    LSST telescope, The Vera Rubin Survey Telescope currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

    LSST Data Journey, Illustration by Sandbox Studio, Chicago with Ana Kova

    Dark Matter Research

    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

    Scientists studying the cosmic microwave background [CMB]hope to learn about more than just how the universe grew—it could also offer insight into dark matter, dark energy and the mass of the neutrino.

    [caption id="attachment_73741" align="alignnone" width="632"] CMB per ESA/Planck

    Dark matter cosmic web and the large-scale structure it forms The Millenium Simulation, V. Springel et al

    Dark Matter Particle Explorer China

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

    LBNL LZ Dark Matter project at SURF, Lead, SD, USA


    Inside the ADMX experiment hall at the University of Washington Credit Mark Stone U. of Washington. Axion Dark Matter Experiment

    Clues from the beginning of time

    In the infant universe, temperatures were so high that electrons and protons were too hot to form atoms. Everything was a hot, ionized gas, not unlike the surface of the sun.

    Over the next 400,000 years, the universe expanded and cooled to about 3,000 degrees Celsius. At these temperatures, electrons and protons combined into hydrogen atoms and released photons in the process. This light, called the cosmic microwave background, or CMB, has been traveling through space ever since—a sort of “time machine” carrying information from the early universe.

    At the Amundsen-Scott South Pole Station, support staff and scientists, nicknamed “beakers,” work around the clock to manage the South Pole Telescope.

    South Pole Telescope SPTPOL. The SPT collaboration is made up of over a dozen (mostly North American) institutions, including the University of Chicago, the University of California, Berkeley, Case Western Reserve University, Harvard/Smithsonian Astrophysical Observatory, the University of Colorado Boulder, McGill University, The University of Illinois at Urbana-Champaign, University of California, Davis, Ludwig Maximilian University of Munich, Argonne National Laboratory, and the National Institute for Standards and Technology. It is funded by the National Science Foundation.

    It’s not easy work; it is located at the southernmost place on Earth, where the average temperature is minus 47 degrees Celsius and the sun rises and sets only once a year. But the South Pole Telescope needs this harsh environment to carry out its scientific work.

    The camera on the South Pole Telescope measures minuscule fluctuations in the polarization, or orientation, of CMB light across the southern sky on the order of 1 part in 100 million on average, more sensitive than any other experiment to date.

    “These minuscule variations can be affected by large objects such as galaxy clusters, which act as lenses that create distinctive distortions in our signal,” Benson said.

    The signal Benson and other scientists were searching for was a small-scale ripple around galaxy clusters—an effect called gravitational lensing. You can see a similar effect yourself by looking through the base of a clear wine glass behind which a candle is lit.

    “If you look through the bottom of a wine glass base at a flame, you can see a ring of light. That’s like the effect we would see from a strong gravitational lens,” Benson said. “We are seeing a similar effect here, except the distortion is much weaker and the CMB light is spread out over a much larger area on the sky.”

    An assist from the Dark Energy Camera

    To find the maximum number of clusters, the scientists cross-referenced data from the Dark Energy Survey, a multi-year survey of the sky that captured the locations of more than 17,000 galaxy clusters in the universe.

    Then they could put these locations into a computer program that searched for evidence of gravitational lensing by the clusters in the polarization of the CMB. Once evidence was found, they could calculate the masses of the galaxy clusters themselves using their new mathematical estimator.

    Though the idea had been proposed, no one had yet demonstrated the method on actual data.

    The scientists found the average galaxy cluster mass to be around 100 trillion times the mass of our sun, an estimate that agrees with other methods. A substantial fraction of this mass is in the form of dark matter.

    To probe deeper, the scientists plan to perform similar experiments using an upgraded South Pole Telescope camera, SPT-3G, installed in 2017, and a next-generation CMB experiment, CMB-S4, that will offer further improvements in sensitivity and more galaxy clusters to examine.

    CMB-S4 will consist of dedicated telescopes equipped with highly sensitive superconducting cameras operating at the South Pole, the Chilean Atacama plateau and possibly northern-hemisphere sites, allowing researchers to constrain the parameters of inflation, dark energy and the number and masses of neutrinos, and even test general relativity on large scales.

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    U Chicago Campus

    An intellectual destination

    One of the world’s premier academic and research institutions, the University of Chicago has driven new ways of thinking since our 1890 founding. Today, UChicago is an intellectual destination that draws inspired scholars to our Hyde Park and international campuses, keeping UChicago at the nexus of ideas that challenge and change the world.

    The University of Chicago is an urban research university that has driven new ways of thinking since 1890. Our commitment to free and open inquiry draws inspired scholars to our global campuses, where ideas are born that challenge and change the world.

    We empower individuals to challenge conventional thinking in pursuit of original ideas. Students in the College develop critical, analytic, and writing skills in our rigorous, interdisciplinary core curriculum. Through graduate programs, students test their ideas with UChicago scholars, and become the next generation of leaders in academia, industry, nonprofits, and government.

    UChicago research has led to such breakthroughs as discovering the link between cancer and genetics, establishing revolutionary theories of economics, and developing tools to produce reliably excellent urban schooling. We generate new insights for the benefit of present and future generations with our national and affiliated laboratories: Argonne National Laboratory, Fermi National Accelerator Laboratory, and the Marine Biological Laboratory in Woods Hole, Massachusetts.

    The University of Chicago is enriched by the city we call home. In partnership with our neighbors, we invest in Chicago’s mid-South Side across such areas as health, education, economic growth, and the arts. Together with our medical center, we are the largest private employer on the South Side.

    In all we do, we are driven to dig deeper, push further, and ask bigger questions—and to leverage our knowledge to enrich all human life. Our diverse and creative students and alumni drive innovation, lead international conversations, and make masterpieces. Alumni and faculty, lecturers and postdocs go on to become Nobel laureates, CEOs, university presidents, attorneys general, literary giants, and astronauts.

     
  • richardmitnick 7:26 am on January 17, 2020 Permalink | Reply
    Tags: , , , , , Dark Matter, ,   

    From European Space Agency – United space in Europe: “XMM-Newton discovers scorching gas in Milky Way’s halo” 

    ESA Space For Europe Banner

    From European Space Agency – United space in Europe

    From United space in Europe

    16/01/2020

    Sanskriti Das
    The Ohio State University, USA
    das.244@buckeyemail.osu.edu

    Smita Mathur
    The Ohio State University, USA
    smita@astronomy.ohio-state.edu

    Fabrizio Nicastro
    Osservatorio Astronomico di Roma—INAF, Italy
    Harvard-Smithsonian Center for Astrophysics, USA
    fabrizio.nicastro@inaf.it

    Norbert Schartel
    XMM-Newton project scientist
    European Space Agency
    norbert.schartel@esa.int

    1

    ESA’s XMM-Newton has discovered that gas lurking within the Milky Way’s halo reaches far hotter temperatures than previously thought and has a different chemical make-up than predicted, challenging our understanding of our galactic home.

    ESA/XMM Newton

    A halo is a vast region of gas, stars and invisible dark matter surrounding a galaxy. It is a key component of a galaxy, connecting it to wider intergalactic space, and is thus thought to play an important role in galactic evolution.

    Until now, a galaxy’s halo was thought to contain hot gas at a single temperature, with the exact temperature of this gas dependent on the mass of the galaxy.

    However, a new study using ESA’s XMM-Newton X-ray space observatory now shows that the Milky Way’s halo contains not one but three different components of hot gas, with the hottest of these being a factor of ten hotter than previously thought. This is the first time multiple gas components structured in this way have been discovered in not only the Milky Way, but in any galaxy.

    “We thought that gas temperatures in galactic haloes ranged from around 10,000 to one million degrees – but it turns out that some of the gas in the Milky Way’s halo can hit a scorching 10 million degrees,” says Sanskriti Das, a graduate student at The Ohio State University, USA, and lead author of the new study.

    “While we think that gas gets heated to around one million degrees as a galaxy initially forms, we’re not sure how this component got so hot. It may be due to winds emanating from the disc of stars within the Milky Way.”

    The study used a combination of two instruments aboard XMM-Newton: the Reflection Grating Spectrometer (RGS) and European Photon Imaging Camera (EPIC). EPIC was used to study the light emitted by the halo, and RGS to study how the halo affects and absorbs light that passes through it.

    To probe the Milky Way’s halo in absorption, Sanskriti and colleagues observed an object known as a blazar: the very active, energetic core of a distant galaxy that is emitting intense beams of light.

    By now iconic image of a blazar. NASA Fermi Gamma ray Space Telescope. Credits M. Weiss/ CfA

    NASA/Fermi LAT


    NASA/Fermi Gamma Ray Space Telescope

    Having travelled almost five billion light-years across the cosmos, the X-ray light from this blazar also passed through our galaxy’s halo before reaching XMM-Newton’s detectors, and thus holds clues about the properties of this gaseous region.

    Caterpillar Project A Milky-Way-size dark-matter halo and its subhalos circled, an enormous suite of simulations . Griffen et al. 2016

    Unlike previous X-ray studies of the Milky Way’s halo, which normally last a day or two, the team performed observations over a period of three weeks, enabling them to detect signals that are usually too faint to see.

    “We analysed the blazar’s light and zeroed in on its individual spectral signatures: the characteristics of the light that can tell us about the material it’s passed through on its way to us,” says co-author Smita Mathur, also of The Ohio State University, and Sanskriti’s advisor.

    “There are specific signatures that only exist at specific temperatures, so we were able to determine how hot the halo gas must have been to affect the blazar light as it did.”

    The Milky Way’s hot halo is also significantly enhanced with elements heavier than helium, which are usually produced in the later stages of a star’s life. This indicates that the halo has received material created by certain stars during their lifetimes and final stages, and flung out into space as they die.

    3
    Elements found in the Milky Way halo – artist’s impression

    “Until now, scientists have primarily looked for oxygen, as it’s abundant and thus easier to find than other elements,” explains Sanskriti.

    “Our study was more detailed: we looked at not only oxygen but also nitrogen, neon and iron, and found some hugely interesting results.”

    Scientists expect the halo to contain elements in similar ratios to those seen in the Sun. However, Das and colleagues noticed less iron in the halo than expected, indicating that the halo has been enriched by massive dying stars, and also less oxygen, likely due to this element being taken up by dusty particles in the halo.

    “This is really exciting – it was completely unexpected, and tells us that we have much to learn about how the Milky Way has evolved into the galaxy it is today,” adds Sanskriti.

    4
    The cosmic budget of ‘ordinary’ matter

    While the mysterious dark matter and dark energy make up about 25 and 70 percent of our cosmos respectively, the ordinary matter that makes up everything we see – from stars and galaxies to planets and people – amounts to only about five percent.

    ______________________________________________________________________

    Fritz Zwicky discovered Dark Matter when observing the movement of the Coma Cluster., Vera Rubin a Woman in STEM denied the Nobel, did most of the work on Dark Matter.

    Fritz Zwicky from http:// palomarskies.blogspot.com

    Coma cluster via NASA/ESA Hubble

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


    Vera Rubin measuring spectra, worked on Dark Matter (Emilio Segre Visual Archives AIP SPL)


    Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970. https://home.dtm.ciw.edu

    The LSST, or Large Synoptic Survey Telescope is to be named the Vera C. Rubin Observatory by an act of the U.S. Congress.

    LSST telescope, The Vera Rubin Survey Telescope currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

    LSST Data Journey, Illustration by Sandbox Studio, Chicago with Ana Kova

    Dark Matter Research

    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

    Scientists studying the cosmic microwave background [CMB]hope to learn about more than just how the universe grew—it could also offer insight into dark matter, dark energy and the mass of the neutrino.

    [caption id="attachment_73741" align="alignnone" width="632"] CMB per ESA/Planck

    Dark matter cosmic web and the large-scale structure it forms The Millenium Simulation, V. Springel et al

    Dark Matter Particle Explorer China

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

    LBNL LZ Dark Matter project at SURF, Lead, SD, USA


    Inside the ADMX experiment hall at the University of Washington Credit Mark Stone U. of Washington. Axion Dark Matter Experiment

    Dark Energy Survey


    Dark Energy Camera [DECam], built at FNAL


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

    Timeline of the Inflationary Universe WMAP

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

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

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

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

    ______________________________________________________________________

    However, stars in galaxies across the Universe only make up about seven percent of all ordinary matter. The cold interstellar gas that permeates galaxies – the raw material to create stars – amounts to about 1.8 percent of total, while the hot, diffuse gas in the haloes that encompass galaxies makes up roughly five percent, and the even hotter gas that fills galaxy clusters – the largest cosmic structures held together by gravity – accounts for four percent.

    This is not surprising: stars, galaxies and galaxy clusters form in the densest knots of the cosmic web, the filamentary distribution of both dark and ordinary matter that extends throughout the Universe. While these sites are dense, they are also rare, so not the best spots to look for the majority of cosmic matter.

    Most of the Universe’s ordinary matter, or baryons, must be lurking in the ubiquitous filaments of this cosmic web, where matter is however less dense and therefore more challenging to observe. Using different techniques over the years, they were able to locate a good chunk of this intergalactic material – mainly its cool component (also known as Lyman-alpha forest, which makes up about 28 percent of all baryons) and its warm component (about 15 percent).

    After two decades of observations, astronomers using ESA’s XMM-Newton space observatory have detected the hot component of this intergalactic material along the line of sight to a distant quasar. The amount of hot intergalactic gas detected in these observations amounts up to 40 percent of all baryons in the Universe, closing the gap in the overall budget of ordinary matter in the cosmos.

    The newly discovered hot gas component also has wider implications that affect our overall understanding of the cosmos. Our galaxy contains far less mass than we expect: this is known as the ‘missing matter problem’, in that what we observe does not match up with theoretical predictions.

    From its long-term mapping of the cosmos, ESA’s Planck spacecraft predicted that just under 5% of the mass in the Universe should exist in the form of ‘normal’ matter – the kind making up stars, galaxies, planets, and so on.

    ESA/Planck 2009 to 2013

    “However, when we add up everything we see, our figure is nowhere by S. Das, S. Mathur, F. Nicastro, and Y. Krongold near this prediction,” adds co-author Fabrizio Nicastro of Osservatorio Astronomico di Roma—INAF, Italy, and the Harvard-Smithsonian Center for Astrophysics, USA.

    “So where’s the rest? Some suggest that it may be hiding in the extended and massive halos surrounding galaxies, making our finding really exciting.”

    As this hot component of the Milky Way’s halo has never been seen before, it may have been overlooked in previous analyses – and may thus contain a large amount of this ‘missing’ matter.

    “These observations provide new insights into the thermal and chemical history of the Milky Way and its halo, and challenge our knowledge of how galaxies form and evolve,” concludes ESA XMM project scientist Norbert Schartel.

    “The study looked at the halo along one sightline – that towards the blazar – so it will be hugely exciting to see future research expand on this.”

    Science papers:
    https://iopscience.iop.org/article/10.3847/2041-8213/ab3b09 , by S. Das, S. Mathur, F. Nicastro, and Y. Krongold

    https://iopscience.iop.org/article/10.3847/1538-4357/ab5846 , S. Das, S. Mathur, A, Gupta, F. Nicastro, and Y. Krongold

    See the full article here .


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    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.

    ESA50 Logo large

     
  • richardmitnick 2:24 pm on January 16, 2020 Permalink | Reply
    Tags: , , , , Dark Matter, , , The LSST Vera C. Rubin Observatory,   

    From The Kavli Foundation: “Behold the Whole Sky” The LSST Vera C. Rubin Observatory 

    KavliFoundation

    From The Kavli Foundation

    01/02/2020
    Adam Hadhazy

    Fritz Zwicky discovered Dark Matter when observing the movement of the Coma Cluster., Vera Rubin a Woman in STEM denied the Nobel, did most of the work on Dark Matter.

    Fritz Zwicky from http:// palomarskies.blogspot.com

    Coma cluster via NASA/ESA Hubble

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

    Vera Rubin measuring spectra, worked on Dark Matter (Emilio Segre Visual Archives AIP SPL)

    Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970.

    The LSST Vera C. Rubin Observatory

    LSST Camera, built at SLAC



    LSST telescope, Vera C. Rubin Observatory, currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.


    LSST Data Journey, Illustration by Sandbox Studio, Chicago with Ana Kova

    When construction is complete, the LSST, Vera C. Rubin Observatory, will be “the widest, fastest, deepest eye of the new digital age.”

    There’s about to be a new telescope in town—in the figurative sense, that is, unless you happen to literally live more than a mile-and-a-half up on the summit of a mountain named Cerro Pachón in the foothills of the Chilean Andes.

    There, construction is humming along for the Large Synoptic Survey Telescope, or LSST. Slated to start science operations early next decade, LSST in all likelihood will be a gamechanger for astronomy and astrophysics.

    What makes LSST so special is how big and fast it will be compared to other telescopes. “Big” in this case refers to the telescope’s field of view, which captures a chunk of sky 40 times the size of the full Moon. “Big” also refers to LSST’s mirror size, a very respectable 8.4 meters in diameter, which means it can collect ample amounts of cosmic light. Thirdly, “big” applies to LSST’s 3.2 billion-pixel camera, the biggest digital camera ever built. Put all those bits together, and LSST will be able to record images of significantly fainter and farther-away objects than other ground-based optical telescopes.

    And finally, as for “fast,” LSST will soak up more than 800 panoramas each night, cumulatively scanning the entire sky twice per week. That means the telescope will catch sight of fleeting astrophysical events, known as transients, that are often missed because telescopes—even today’s state-of-the-art, automated networks of ‘scopes—are not gobbling up so much of the sky so quickly. Transients that last days, weeks, and months—for instance, cataclysmic stellar explosions called supernovae—are routinely spotted. But the shortest events, lasting mere hours or even minutes, are another, untold story.

    “Unfortunately, we still know relatively little about the transient optical sky because we have never before had a survey that can make observations of a very large fraction of the sky repeatedly every few nights,” says Steven Kahn, Director of the LSST project. “LSST will meet this need.”

    Kahn, the Cassius Lamb Kirk Professor in the Natural Sciences and Professor of Particle Physics and Astrophysics at Stanford University, is also a member of the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC). He stepped into the director role back in 2013 when LSST was on the drawing board. Now the huge instrument is nearing the completion of its construction. Kahn and his colleagues are dearly looking forward to all that LSST will bring to the table, building on the pioneering work into gauging the transient sky underway with other, precursor projects worldwide.

    “LSST will go significantly deeper and cover the sky more rapidly,” says Kahn. “By covering more sky per unit time, we are more sensitive to very rare events, which are often the most interesting.”

    In this way, LSST is going to open up a major discovery space, for phenomena both (poorly) known and (entirely) unknown.

    “The Universe is far from static,” says Kahn. “There are stellar explosions of many different kinds that allow stars to brighten dramatically and then fade away on different timescales.” Some of these transient flashes of light are expected from the vicinities of neutron stars and black holes as they interact with matter that strays too close. Researchers hope to gain new insights into these dense objects’ properties, whose extreme physics challenge our best-supported theories.

    Another primary goal for LSST is to advance our understanding of the “dark universe” of dark matter and dark energy. Together, these entities compose 95 percent of the cosmos, with the “normal” matter that makes up stars, planets, and people registering as the remaining rounding error. Yet scientists have only stabs in the dark, as it were, on what exactly dark matter and dark energy really are. LSST will help by acquiring images of billions of galaxies, stretching back to some of the earliest epochs in the universe. Analyzing the shapes and distributions of these galaxies in space as well as time (recall that the farther away you see something in the universe, the farther you’re seeing back in time) will better show dark matter’s role in building up cosmic structure. The signature of dark energy, a force that is seemingly accelerating the universe’s expansion, will also be writ across the observed eons of galactic loci.

    Closer to home, LSST will vastly expand our knowledge of our own Solar System. It will take a census of small bodies, such as asteroids and comets, that fly by overhead, too faint for us humans to notice but there all the same—and in rare instances, potentially dangerously so; just ask the dinosaurs.

    “LSST will measure everything that moves in the sky,” says Kahn. “Of particular interest, we will provide the most complete catalogue of potentially hazardous asteroids, those objects whose orbits might allow them to impact the Earth.”

    Not done yet, LSST will also extend our catalogue of stars in the galaxy, aiding in charting the history and evolution of our own Milky Way galaxy. Furthermore, LSST will be a premier instrument for discovering the sources of gravitational waves, the ripples in spacetime first predicted by Albert Einstein in 1915 and finally directly detected in 2015 by the LIGO experiment. It can be a tough business today, even with the rich array of telescopes in operation, to rapidly pinpoint the visible light that gravitational wave-spawning neutron star collisions give off. LSST should aid in that regard admirably.

    The wait is nearly over. The LSST building is nearly complete, the large mirrors are on site, and the camera is being integrated at the at SLAC National Accelerator Laboratory in California, which co-hosts KIPAC along with Stanford.

    “Basically, everything that needed to be fabricated for the LSST telescope and camera has been fabricated,” says Kahn. “The remaining work largely involves putting the system together and getting it working.”

    Kahn has been to the telescope site recently, in both September and October. He likes what he sees.

    “Visiting the site in Chile is a remarkable experience,” Kahn says. “It is a beautiful site, and the LSST facility sits prominently atop the edge of a cliff on Cerro Pachón. The sheer size of the building and its complexity is striking.”

    Before long, the impressiveness of the building will recede into the background as the profundity of the science LSST generates takes center stage.

    See the full article here .


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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    The Kavli Foundation, based in Oxnard, California, is dedicated to the goals of advancing science for the benefit of humanity and promoting increased public understanding and support for scientists and their work.

    The Foundation’s mission is implemented through an international program of research institutes, professorships, and symposia in the fields of astrophysics, nanoscience, neuroscience, and theoretical physics as well as prizes in the fields of astrophysics, nanoscience, and neuroscience.

     
  • richardmitnick 1:07 pm on January 14, 2020 Permalink | Reply
    Tags: A pursuit that stretches from underground particle colliders to orbiting telescopes with all manner of ground-based observatories in between., , , , , , Dark Matter, , , , The astronomer missed her Nobel Prize [in my view a crime of old white men], ,   

    From The New York Times: Women in STEM-“Vera Rubin Gets a Telescope of Her Own” 

    From The New York Times

    Jan. 11, 2020
    Dennis Overbye

    The astronomer missed her Nobel Prize [in my view a crime of old white men]. But she now has a whole new observatory to her name.

    1
    The astronomer Vera Rubin at the Lowell Observatory in Flagstaff, Ariz., in 1965.Credit: via Carnegie Institution of Science

    Vera Rubin measuring spectra, worked on Dark Matter (Emilio Segre Visual Archives AIP SPL)

    Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970.

    Vera Rubin, a young astronomer at the Carnegie Institution in Washington, was on the run in the 1970s when she overturned the universe.

    Seeking refuge from the controversies and ego-bashing of cosmology, she decided to immerse herself in the pearly swirlings of spiral galaxies, only to find that there was more to them than she and almost everybody else had thought.

    For millenniums, humans had presumed that when we gaze out at the universe, what we see is a fair representation of reality. Dr. Rubin, with her colleague Kent Ford, discovered that was not true. The universe — all those galaxies and the vast spaces between — was awash with dark matter, an invisible something with sufficient gravity to mold the large scale structures of the universe.

    Fritz Zwicky discovered Dark Matter when observing the movement of the Coma Cluster., Vera Rubin a Woman in STEM denied the Nobel, did most of the work on Dark Matter.

    Coma cluster via NASA/ESA Hubble, the original example of Dark Matter discovered during observations by Fritz Zwicky and confirmed by Vera Rubin

    Esteemed astronomers dismissed her findings at first. But half a century later, the still futile quest to identify this “dark matter” is a burning question for both particle physics and astronomy. It’s a pursuit that stretches from underground particle colliders to orbiting telescopes, with all manner of ground-based observatories in between.

    Last week the National Science Foundation announced that the newest observatory joining this cause will be named the Vera C. Rubin Observatory. The name replaces the mouthful by which the project was previously known: the Large Synoptic Survey Telescope, or L.S.S.T.

    2
    The Vera C. Rubin Observatory, formerly the Large Synoptic Survey Telescope, under construction in Cerro Pachon, Chile. Credit: LSST Project/NSF/AURA

    The Rubin Observatory joins a handful of smaller astronomical facilities that have been named for women. The Maria Mitchell Observatories in Nantucket, Mass., is named after the first American woman to discover a comet. The Swope telescope, at Carnegie’s Las Campanas Observatory in Chile, is named after Henrietta Swope, who worked at the Harvard College Observatory in the early 20th century. She used a relationship between the luminosities and periodicities of variable stars to measure distances to galaxies.

    And finally there is the new Annie Maunder Astrographic Telescope at the venerable Royal Greenwich Observatory, just outside London. It is named after Annie Maunder, who with her husband Walter made pioneering observations of the sun and solar cycle of sunspots in the late 1800s.

    Heros of science, all of them.

    In a field known for grandiloquent statements and frightening intellectual ambitions, Dr. Rubin was known for simple statements about how stupid we are. In an interview in 2000 posted on the American Museum of Natural History website, Dr. Rubin said:

    “In a spiral galaxy, the ratio of dark-to-light matter is about a factor of 10. That’s probably a good number for the ratio of our ignorance to knowledge. We’re out of kindergarten, but only in about third grade.”

    Once upon a time cosmologists thought there might be enough dark matter in the universe for its gravity to stop the expansion of the cosmos and pull everything back together in a Big Crunch. Then astronomers discovered an even more exotic feature of the universe, now called dark energy, which is pushing the galaxies apart and speeding up the cosmic expansion.

    Dark Energy Survey


    Dark Energy Camera [DECam], built at FNAL


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

    Timeline of the Inflationary Universe WMAP

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

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

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

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

    These discoveries have transformed cosmology still further, into a kind of Marvel Comics super-struggle between invisible, titanic forces. One, dark matter, pulls everything together toward its final doom; the other, dark energy, pushes everything apart toward the ultimate dispersal, some times termed the Big Rip. The rest of us, the terrified populace looking up at this cosmic war, are bystanders, made of atoms, which are definitely a minority population of the universe. Which force will ultimately prevail? Which side should we root for?

    Until recently the money was on dark energy and eventual dissolution of the cosmos. But lately cracks have appeared in the data, suggesting that additional forces may be at work beneath the surface of our present knowledge.

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

     
  • richardmitnick 8:36 pm on January 13, 2020 Permalink | Reply
    Tags: , , , Calculate the masses of enormous galaxy clusters using a new mathematical estimator., , , , Dark Matter, Destination: Antarctica-the South Pole Telescope., Destination: Chile-Cerro Tololo Inter-American Observatory-The Dark Energy Camera of the Dark Energy Survey, Destination: Unspoiled places-, , Most of the mass of galaxy clusters isn’t even visible – it’s dark matter.   

    From Fermi National Accelerator Lab: “Data from antipodal places: First use of CMB polarization to detect gravitational lensing from galaxy clusters” 

    FNAL Art Image
    FNAL Art Image by Angela Gonzales

    From Fermi National Accelerator Lab , an enduring source of strength for the US contribution to scientific research world wide.

    January 13, 2020
    Catherine N. Steffel

    Galaxies. Amalgamations of stars, interstellar gas, dust, stellar debris and dark matter. They waltz through the cold universe, gravity nurturing their embrace. Occasionally, galaxies snowball into enormous galaxy clusters with masses averaging 100 trillion times that of our sun.

    But this wasn’t always the case.

    In the infant universe, temperatures were so high that electrons and protons were too hot to form atoms. Everything was a hot, ionized gas, not unlike the surface of the sun.

    Over the next 400,000 years, the universe expanded and cooled to around 3,000 degrees Celsius, about the temperature of an industrial furnace. At these temperatures, electrons and protons combined into hydrogen atoms and released photons in the process. This light, called the cosmic microwave background radiation, has been traveling through space ever since, a watermark of space and time.

    Now, scientists have found new ways to tease information out of this inexhaustible time machine.

    Constraining cosmology with CMB polarization

    In a study published in Physical Review Letters, Fermilab and University of Chicago scientist Brad Benson and colleagues use the polarization, or orientation, of the cosmic microwave background [CMB] to calculate the masses of enormous galaxy clusters using a new mathematical estimator.

    CMB per ESA/Planck

    This is the first time that scientists have measured these masses using the polarization of the CMB and the novel estimation method.

    “Making this estimate is important because most of the mass of galaxy clusters isn’t even visible – it’s dark matter, which does not emit light but interacts through gravity and makes up about 85% of the matter in our universe,” Benson said.

    The scientists’ work may eventually shed light on dark matter, dark energy and cosmological parameters that reveal more about structure formation in the universe.

    1
    The camera on the South Pole Telescope measures minuscule fluctuations in the polarization of cosmic-microwave-background light across the southern sky. Photo: Jason Gallicchio, University of Chicago

    Destination: Antarctica

    At Amundsen-Scott South Pole Station, support staff and scientists, nicknamed “beakers,” work around the clock to manage the South Pole Telescope. It’s not easy work. Amundsen-Scott South Pole Station is located at the southernmost place on Earth, where the average temperature is minus 47 degrees Celsius and the sun rises and sets only once a year. But the South Pole Telescope, a 10-meter telescope charged with observing the cosmic microwave background, known as the CMB, is more than capable of achieving its scientific goals in this harsh environment.

    The camera on the South Pole Telescope measures minuscule fluctuations in the polarization of CMB light across the southern sky on the order of 1 part in 100 million on average, more sensitive than any other experiment to date.

    “These minuscule variations can be affected by large objects such as galaxy clusters, which act as lenses that create distinctive distortions in our signal,” Benson said.

    The signal Benson and other scientists were looking for was a small-scale ripple around galaxy clusters — an effect called gravitational lensing. You can see a similar effect yourself by looking through the base of a clear wine glass behind which a candle is lit.

    “If you look through the bottom of a wine glass base at a flame, you can see a ring of light. That’s like the effect we would see from a strong gravitational lens,” Benson said.

    2
    Scientists look for small-scale ripple around galaxy clusters — an effect called gravitational lensing. The lensing is similar to the effect you would see looking through the base of a clear wine glass behind which a candle is lit — a ring of light. Image: Sandbox Studio

    Gravitational Lensing NASA/ESA

    “We are seeing a similar effect here, except the distortion is much weaker and the CMB light is spread out over a much larger area on the sky.”

    There was a problem, however. Scientists estimated they would need to look at around 17,000 galaxy clusters to measure the gravitational lensing effect from the CMB and estimate galaxy cluster masses with any certainty, even using their new mathematical estimator. While the South Pole Telescope provided deeper and more sensitive measurements of the CMB’s polarization than ever before, its library of galaxy locations contained only about 1,000 galaxy clusters.

    Destination: Chile

    To identify more galaxy cluster locations from which to examine the gravitational lensing of CMB light around galaxy clusters, the scientists needed to travel roughly 6,000 kilometers north of the South Pole to the Atacama region of Chile, home to the Cerro Tololo Inter-American Observatory.

    Cerro Tololo Inter-American Observatory on Cerro Tololo in the Coquimbo Region of northern Chile Altitude 2,207 m (7,241 ft)

    The Dark Energy Camera, mounted 2,200 meters above sea level on the 4-meter Blanco telescope at Cerro Tololo, is one of the largest digital cameras in the world. Its 520 megapixels see light from objects originating billions of light-years away and capture them in unprecedented quality. Most importantly, the camera captures the light and locations of the 17,000 galaxy clusters scientists needed to observe gravitational lensing of CMB light by galaxy clusters.

    Dark Energy Survey


    Dark Energy Camera [DECam], built at FNAL


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

    Timeline of the Inflationary Universe WMAP

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

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

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

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

    The scientists identified the locations of these clusters using three years’ worth of data from the Fermilab-led Dark Energy Survey and then put these locations into a computer program that searched for evidence of gravitational lensing by the clusters in the polarization of the CMB. Once evidence was found, they could calculate the masses of the galaxy clusters themselves using their new mathematical estimator.

    Destination: Unspoiled places

    In the current study, the scientists found the average galaxy cluster mass to be around 100 trillion times the mass of our sun, an estimate that agrees with other methods. A substantial fraction of this mass is in the form of dark matter.

    To probe deeper, the scientists plan to perform similar experiments using an upgraded South Pole Telescope camera, SPT-3G, installed in 2017, and a next-generation CMB experiment, CMB-S4, that will offer further improvements in sensitivity and more galaxy clusters to examine.

    CMB-S4 will consist of dedicated telescopes equipped with highly sensitive superconducting cameras operating at the South Pole, the Chilean Atacama plateau and possibly northern-hemisphere sites, allowing researchers to constrain the parameters of inflation, dark energy and the number and masses of neutrinos, and even test general relativity on large scales.

    Anthony Bourdain, a gifted storyteller and food writer, once called Antarctica “the last unspoiled place on Earth … where people come together to explore the art of pure science, looking for something called facts.”

    Scientists go far beyond Antarctica to another unspoiled place, the farthest reaches of our universe, to grapple with fundamental cosmological parameters and the behavior of structure in our universe.

    See the full here.


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    FNAL Icon

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics. Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. Thousands of scientists from universities and laboratories around the world
    collaborate at Fermilab on experiments at the frontiers of discovery.

     
  • richardmitnick 9:24 am on January 7, 2020 Permalink | Reply
    Tags: , , , , Dark Matter, , , ,   

    From Symmetry: Women in STEM -“Vera Rubin, giant of astronomy” 

    Symmetry Mag
    From Symmetry<

    01/07/20
    Kathryn Jepsen

    1
    Illustration by Sandbox Studio, Chicago with Ana Kova

    The Large Synoptic Survey Telescope will be named for an influential astronomer who left the field better than she found it.

    The LSST Vera C. Rubin Observatory

    LSST telescope, Vera C. Rubin Observatory Telescope currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.


    LSST Data Journey, Illustration by Sandbox Studio, Chicago with Ana Kova

    The Large Synoptic Survey Telescope, a flagship astronomy and astrophysics project currently under construction on a mountaintop in Chile, will be named for astronomer Vera Rubin, a key figure in the history of the search for dark matter.

    Fritz Zwicky discovered Dark Matter when observing the movement of the Coma Cluster., Vera Rubin a Woman in STEM denied the Nobel, did most of the work on Dark Matter.

    Fritz Zwicky from http:// palomarskies.blogspot.com

    Coma cluster via NASA/ESA Hubble

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


    Vera Rubin measuring spectra, worked on Dark Matter (Emilio Segre Visual Archives AIP SPL)


    Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970. https://home.dtm.ciw.edu

    The LSST, or Large Synoptic Survey Telescope is to be named the Vera C. Rubin Observatory by an act of the U.S. Congress.

    Dark Matter Research

    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

    Scientists studying the cosmic microwave background hope to learn about more than just how the universe grew—it could also offer insight into dark matter, dark energy and the mass of the neutrino.

    Dark matter cosmic web and the large-scale structure it forms The Millenium Simulation, V. Springel et al

    Dark Matter Particle Explorer China

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

    LBNL LZ Dark Matter project at SURF, Lead, SD, USA


    Inside the ADMX experiment hall at the University of Washington Credit Mark Stone U. of Washington. Axion Dark Matter Experiment

    The LSST collaboration announced the new name at the 235th American Astronomical Society meeting in Honolulu on Monday evening, in conjunction with US funding agencies the Department of Energy and the National Science Foundation.

    Scheduled to begin operation in late 2022, the Vera C. Rubin Observatory will undertake a decade-long survey of the sky using an 8.4-meter telescope and a 3200-megapixel camera to study, among other things, the invisible material Rubin is best known for bringing into the realm of accepted theory.

    Rubin was a role model, a mentor, and a boundary-breaker fueled by a true love of science and the stars. “For me, doing astronomy is incredibly great fun,” she said in a 1989 interview with physicist and writer Alan Lightman. “It’s just an incredible joy to get up every morning and come to work and, in some much larger framework, not even really quite know what it is I’m going to be doing.”

    Between the Lightman interview and An Interesting Voyage, a biography she wrote in 2010 for the Annual Review of Astronomy and Astrophysics, among other things, she left behind a detailed record of the story of her life.

    A curious child

    Rubin’s father, Pesach Kobchefski (later known as Philip Cooper), was born in Lithuania. Her mother, Rose Applebaum, was a second-generation American born to Bessarabian parents in Philadelphia. Rubin’s parents met at work at the Bell Telephone Company. They married and raised two children, Vera and her older sister, Ruth.

    Rubin was born in 1928. She wrote that she remembered growing up “amid a cheery scatter of grandparents, aunts, uncles and cousins… largely shielded from the financial difficulties” of the Great Depression. Ruth and Vera shared a room, with Vera’s bed against a window with a clear view of the north sky. “Soon it was more interesting to watch the stars than to sleep,” Rubin wrote.

    Her parents encouraged her curiosity. Her mother gave her written permission at an early age to check out books from the “12 and over” section of the library, and her father helped her build a (rather so-so) homemade telescope. “My parents were very, very supportive,” Rubin said in the interview with Lightman, “except that they didn’t like me to stay up all night.”

    Rubin’s teachers were not universally as encouraging. Her high school physics teacher, she wrote, “did not know how to include the few young girls in the class, so he chose to ignore us.” Still, Rubin knew she wanted to go into astronomy. “I didn’t know a single astronomer,” she said, “but I just knew that was what I wanted to do.”

    She did know about at least one female astronomer: Maria Mitchell, the first female professional astronomer in the United States. From 1865 to 1888, Mitchell taught at Vassar College in New York and served as director of Vassar College Observatory.

    Looking to follow in her footsteps, Rubin applied to Vassar. She was accepted with a necessary scholarship. Rubin said that when she told the high school physics teacher about it, he replied, “‘As long as you stay away from science, you should be okay.’”

    She graduated in three years as the only astronomy major in her class.

    A family effort

    Rubin spent summers in Washington, DC, working at the Naval Research Laboratory. The summer of 1947, her parents introduced her to Robert (Bob) Rubin. He was training to be an officer in the US Navy and studying chemistry at Cornell University.

    The two married in 1948. She was 19 and he was 21. Vera had been accepted to Harvard University, which was well known for its astronomy department, but she decided to join her husband at Cornell instead.

    Rubin completed her master’s thesis just before giving birth to her first child, and she gave a talk on her research at the 1950 meeting of the American Astronomical Society just after. Her adviser had said it made more sense for him to give the talk, as he was already a member of AAS and she would be a new mother, but Rubin insisted she would do it.

    “We had no car,” Rubin wrote. “My parents drove from Washington, DC, to Ithaca, then crossed the snowy New York hills with Bob, me and their first grandchild, ‘thereby aging 20 years,’ my father later insisted.”

    She gave a 10-minute talk on her study of the velocity distribution of the galaxies that at that time had published velocities. It solicited replies from several “angry-sounding men,” along with pioneering astronomer Martin Schwarzschild, who, Rubin wrote, kindly “said what you say to a young student: ‘This is very interesting, and when there are more data, we will know more.’”

    For a few months after the experience, Rubin stayed home with her newborn son. But she couldn’t keep away from the science. “I would push David to the playground, sit him in the sandbox, and read The Astrophysical Journal,” Rubin wrote.

    With her husband’s encouragement, she enrolled in the astronomy PhD program at Georgetown University. Her classes took place at night, twice per week. Those nights, between 1952 and 1954, Rubin’s mother babysat David (and, not long after, also her daughter, Judy) while Bob drove her to the observatory and waited to take her back home, eating his dinner in the car. In astronomy, “women generally required more luck and perseverance than men did,” Rubin wrote. “It helped to have supportive parents and a supportive husband.”

    PhD and beyond

    Theoretical physicist and cosmologist George Gamow—known for his contributions to developing the Big Bang theory, among other foundational work—heard about Rubin’s AAS talk and began asking her questions, Rubin wrote. One question—“Is there a scale length in the distribution of galaxies?”—so intrigued her that she decided to take it on for her thesis. Gamow served as her advisor.

    Rubin wrote that when she sent her research to The Astrophysical Journal in 1954, then-editor and later Nobel Laureate Subrahmanyan Chandrasekhar rejected it, saying he wanted her to wait until his student finished his work on the same subject. She did not wait, publishing in the Proceedings of the National Academy of Sciences instead. (A later editor of Astrophysical Journal asked her to send him Chandrasekhar’s letter as proof, and she wrote, “I refused, telling him to look it up in his files.”)

    In 1955, Georgetown offered Rubin a research position, which soon became a teaching position as well. She stayed there for 10 years.

    In 1962, Rubin taught a graduate course in statistical astronomy with six students, five who worked for the US Naval Observatory and one who worked for NASA. “Due to their jobs, the students were experts in star catalogs,” Rubin wrote, “so I gave the students (plus me as a student) a research problem: Can we use cataloged stars to determine a rotation curve for stars distant from the center of our [g]alaxy?”

    The group completed the paper, “some of it finished by seven of us working around my large kitchen table, long into the night,” Rubin wrote, and they submitted it to The Astrophysical Journal.

    The editor called to say he would accept the paper but that he would not take the then-unusual step of publishing the names of the students, Rubin wrote. When Rubin replied that she would then withdraw the paper, however, he changed his mind.

    Rubin wrote that she received many negative “and some very unpleasant” responses to the paper, but that it continued to be referenced every few years, even as she was writing in 2010. As she pointed out in her article, “[t]his was my first flat rotation curve”—a result she would see repeated in what would become her most famous publication.

    During the 1963-1964 school year, Bob took a sabbatical so Vera could move the family to San Diego and work with married couple Margaret and Geoffrey Burbidge. With two other scientists, they had in 1957 published the seminal paper explaining how thermonuclear reactions in stars could transform a universe originally made up only of hydrogen, helium and lithium into one that could support life. With the Burbidges, Rubin traveled to both Kitt Peak National Observatory in Arizona and McDonald Observatory in Texas.

    More than three decades later, in letter to Margaret Burbidge on her 80th birthday, Rubin described what the scientist had meant to her: “Did the words ‘role model’ and ‘mentor’ exist then? I think they did not. But for most of the women that followed you into astronomical careers, these were the roles you filled for us.”

    What Rubin best remembers from when she first arrived in San Diego, she wrote, “was my elation because you took me seriously and were interested in what I had to say…

    “From you we have learned that a woman too can rise to great heights as an astronomer, and that it’s all right to be charming, gracious, brilliant, and to be concerned for others as we make our way in the world of science.”

    The view from Palomar

    Caltech Palomar Hale Telescope, located in San Diego County, California, US, at 1,712 m (5,617 ft)

    In 1964, Rubin and her family (which now included four children, between ages 4 and 13) returned home. Shortly thereafter, Vera and Bob took off again for the meeting of the International Astronomical Union in Hamburg. (“Fortunately, my parents enjoyed being with their grandchildren,” Rubin wrote.)

    On the last evening of the conference, influential astronomer Allan Sandage, who in 1958 had published the first good estimate of the Hubble constant, asked Rubin if she were interested in observing on Palomar Mountain at the Carnegie Institution’s 200-inch telescope. It was a telescope, located on a mountain northeast of San Diego, that women had officially been prohibited from using (though it was a “known secret” that both Margaret and Geoffrey Burbidge had observed there together as postgraduate students). “Of course, I said yes,” Rubin wrote.

    Rubin would be observing on the same mountain where, in 1933, astronomer Fritz Zwicky [above] made a startling discovery. He noticed that the galaxies in the Coma Cluster were moving too quickly—so quickly that they should have broken apart. Judging by the mass of their visible matter, they should not have had the gravitational pull to hold together.

    He concluded that the cluster must be more massive than it appeared, and that most of this mass must come from matter that could not be seen. The Swiss astronomer called the source of the missing mass dunkle Materie, or dark matter. He presented this idea to the Swiss Physical Society, but it did not catch on. (He made several other big splashes in astronomy, though.)

    On Rubin’s first night at Palomar in December 1965, clouds prevented anyone from observing, so another observer took her on an unofficial tour of the facilities. The tour included the single available toilet, labeled “MEN.”

    On Rubin’s next visit, “I drew a skirted woman and pasted her up on the door,” she wrote. The third time she came to observe, heating had been added to the observing room, along with a gender-neutral bathroom.

    The world’s best spectrograph

    In 1965, Rubin decided to prioritize observing over teaching. She asked her colleague Bernie Burke—famous for co-discovering the first detection of radio noise from another planet, Jupiter—for a job at the Carnegie Institution’s Department of Terrestrial Magnetism. Burke invited her to the DTM’s community lunch. And that’s where she met astronomer Kent Ford.

    Working over the previous decade, Ford had pioneered the use of highly sensitive light detectors called photomultiplier tubes for astronomical observation. “Kent Ford had built a very exceptional spectrograph,” Rubin said. “He probably had the best spectrograph anywhere. He had a spectrograph that could do things that no other spectrographs could do.”

    Rubin got the job at DTM, becoming the first female scientist on its staff. Using Ford’s spectrograph on the telescope at Lowell Observatory in Arizona [above], Ford and Rubin could observe objects that were not otherwise detectable. Among the astronomers who noticed was Jim Peebles, winner of the 2019 Nobel Prize for Physics.

    By 1968, Rubin and Ford had published nine papers. “It was an exciting time,” Rubin wrote, “but I was not comfortable with the very rapid pace of the competition. Even very polite phone calls asking me which galaxies I was studying (so as not to overlap) made me uncomfortable.”

    So she decided to go back to a subject she had previously dabbled in: the velocity of stars and regions of ionized hydrogen in Messier 31, the Andromeda galaxy. “I decided to pick a problem that I could go observing and make headway on, hopefully a problem that people would be interested in, but not so interested [in] that anyone would bother me before I was done,” Rubin said.

    Astronomers had been studying the spectra of light from Andromeda since at least January 1899, but no one had taken a look with an instrument as advanced as Ford’s.

    One astronomer had gotten a better look than most, though. In the 1940s, astronomer Walter Baade had taken advantage of wartime blackout rules—meant to make it difficult for enemy planes to hit targets during World War II—to observe Andromeda from Mount Wilson Observatory northeast of Los Angeles.


    Mt Wilson 100 inch Hooker Telescope, perched atop the San Gabriel Mountains outside Los Angeles, CA, USA, Mount Wilson, California, US, Altitude 1,742 m (5,715 ft)

    He resolved the stars at the center of the galaxy for the first time and identified 688 emission regions worthy of study.

    Not knowing this, Rubin and Ford set out to do the same for themselves. They spent a frustrating night taking turns at the US Naval Observatory telescope in Arizona, huddled next to a small heater in negative 20 degree cold, before deciding they needed a new tactic.

    2
    US Naval Observatory telescope in Arizona

    On their way out in the morning, they ran into Naval Observatory Director Gerald Kron. “He took us into his warm office, opened a large cabinet and showed us copies of Baade’s many plates of stars in Messier 31!” Rubin wrote. Rubin and Ford obtained copies of the images from the Carnegie Institute and went to work.

    A rotation curveball

    Rubin and Ford made their observations at Lowell Observatory[above] and Kitt Peak.

    Kitt Peak National Observatory of the Quinlan Mountains in the Arizona-Sonoran Desert on the Tohono O’odham Nation, 88 kilometers 55 mi west-southwest of Tucson, Arizona, Altitude 2,096 m (6,877 ft)

    “On a typical clear night we would obtain four to five spectra,” Rubin wrote. “The surprises came very quickly.”

    In our solar system, planets closest to the center are the fastest-moving, as they are most affected by the gravitational pull of the sun. Mercury, the closest, moves about 1.6 times as rapidly as Earth, whereas Neptune, the farthest, moves at less than 0.2 times Earth’s speed.

    “The expectation was that galaxies behaved the same way, in that stars farthest from the massive center would be moving most slowly,” Rubin wrote.

    But that’s not what they found. The rotation curves were flat, meaning that objects closer to the center of Andromeda were moving at the same speed as objects closer to the outskirts. “This was discovered over the course of about 4 ice cream cones that first night,” Rubin wrote, “as I alternated between developing the plates and eating (Kent would be starting the next observation).”

    This time, Rubin said, people believed the data. “It just piled up too fast. Soon there were 20, then 40, then 60 rotation curves, and they were all flat… And it was just a joy to have that kind of a program, after a program where you had to go through deep analysis and everybody doubted the answer.”

    But what did the flat rotation curves mean? The popularly accepted answer is that the way the galaxies in Andromeda move is influenced by dark matter.

    If a galaxy is formed in the center of a disk of invisible dark matter, the gravitational pull of the dark matter will affect how quickly each of its parts moves, flattening the rotation curves.

    Theorists Peebles, Jeremiah P. Ostriker, Amos Yahil and others had predicted the existence of dark matter independent of Rubin and Ford’s findings, Rubin said. “The ideas had been around for a while… But the observations fit in so well, [since] there was already a framework, so some people embraced the observations very enthusiastically.”

    Rubin was agnostic about the idea of dark matter and wrote that she would be delighted if the explanation actually came in the form of a new understanding of how gravity works on the cosmic scale. “One needs to keep an open mind in seeking solutions,” she wrote.

    A scientific legacy

    Rubin continued her work, receiving recognition for her contributions in various ways.

    From 1972 to 1977 she served as associate editor of The Astronomical Journal, and from 1977 to 1982 she served as associate editor of Astrophysical Journal Letters. In 1993, she received the National Medal of Science from President Bill Clinton. In 1994 she received the Dickson Prize in Science from Carnegie-Mellon University and the Henry Norris Russell Lectureship from the American Astronomical Society. In 1996 she became the second woman to receive the Gold Medal of the Royal Astronomical Society in London (168 years after the first, Caroline Herschel in 1828). In 1996 President Clinton nominated her to provide input to Congress as a member of the National Science Board for a term of six years.

    In 1997 she and a few other members of the board were invited to visit the McMurdo research station at the South Pole. Rubin wrote that she was asked if she would spend her time at McMurdo with the astronomers. “With a little embarrassment, I asked if that meant that I would miss everything else, the penguins, the mountains and all the other events,” she wrote. “Without much difficulty, I voted for the penguins.”

    In 2004 the National Academy of Sciences awarded Rubin the James Craig Watson Medal for “her seminal observations of dark matter in galaxies… and for generous mentoring of young astronomers, men and women.”

    Rubin made it a priority to listen to and encourage students and up-and-coming astronomers, and she was especially interested in improving the chances for women in science.

    Asked by Lightman, “Do you think that your experience in science has been different because you are a woman rather than a man?” she replied, “Of course. Yes, of course. But I’m the wrong person to ask that question. The tragedy in that question is all the women who would have liked to have become astronomers and didn’t.”

    Rubin shared her love of astronomy far and wide. “We are fortunate to live in an era when it is possible to learn so much about the [u]niverse,” she wrote. “But I envy our children, our grandchildren, and their children. They will know more than any of us do now, and they may even be able to travel there!”

    All four of the Rubin children have gone into science.

    Her son Allan, quoted in the 2010 article, remembered his parents often spent evenings “with their work spread out along the very long dining room table, which wasn’t used for eating unless a lot of company was expected,” he said. “At some point I grew old enough to realize that if what they really wanted to do after dinner was the same thing they did all day at work, then they must have pretty good jobs.”

    Rubin’s daughter followed Vera into the field of astronomy, initially hooked by a lesson her mother taught on black holes. Over several decades, Judy has collaborated on numerous publications and attended meetings around the world with her mom.

    Rubin died in 2016 at the age of 88. Her name lives on in the AAS Vera Rubin Early Career Prize, Vera Rubin Ridge on the planet Mars, Asteroid 5726 Rubin and, now, the Vera C. Rubin Observatory on Cerro Pachón

    See the full article here .


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    Please help promote STEM in your local schools.


    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.


     
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