Tagged: Vera Rubin Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 11:53 am on February 23, 2020 Permalink | Reply
    Tags: , , , , , , , , , , , Vera Rubin   

    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 .


    five-ways-keep-your-child-safe-school-shootings
    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 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., , , , It all adds up to 85% of the universe., It shaped entire galaxies without touching a thing., It’s built to last., Natalia Toro, , Vera Rubin   

    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 .


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

    Please help promote STEM in your local schools.


    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.


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

    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., , , , , , , , , , The astronomer missed her Nobel Prize [in my view a crime of old white men], Vera Rubin,   

    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 9:24 am on January 7, 2020 Permalink | Reply
    Tags: , , , , , , , Vera Rubin,   

    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 .


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

    Please help promote STEM in your local schools.


    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 10:17 am on December 29, 2019 Permalink | Reply
    Tags: , , , , , , , , Vera Rubin   

    From particlebites: “Dark Photons in Light Places” 

    particlebites bloc

    From particlebites

    December 29, 2019
    Amara McCune

    Title: “Searching for dark photon dark matter in LIGO O1 data”

    Author: Huai-Ke Guo, Keith Riles, Feng-Wei Yang, & Yue Zhao

    Reference: https://www.nature.com/articles/s42005-019-0255-0

    There is very little we know about dark matter save for its existence.

    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.

    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.

    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

    Its mass(es), its interactions, even the proposition that it consists of particles at all is mostly up to the creativity of the theorist. For those who don’t turn to modified theories of gravity to explain the gravitational effects on galaxy rotation and clustering that suggest a massive concentration of unseen matter in the universe (among other compelling evidence), there are a few more widely accepted explanations for what dark matter might be. These include weakly-interacting massive particles (WIMPS), primordial black holes, or new particles altogether, such as axions or dark photons.

    In particle physics, this latter category is what’s known as the “hidden sector,” a hypothetical collection of quantum fields and their corresponding particles that are utilized in theorists’ toolboxes to help explain phenomena such as dark matter. In order to test the validity of the hidden sector, several experimental techniques have been concocted to narrow down the vast parameter space of possibilities, which generally consist of three strategies:

    1.Direct detection: Detector experiments look for low-energy recoils of dark matter particle collisions with nuclei, often involving emitted light or phonons.
    2.Indirect detection: These searches focus on potential decay products of dark matter particles, which depends on the theory in question.
    3.Collider production: As the name implies, colliders seek to produce dark matter in order to study its properties. This is reliant on the other two methods for verification.

    The first detection of gravitational waves from a black hole merger in 2015 ushered in a new era of physics, in which the cosmological range of theory-testing is no longer limited to the electromagnetic spectrum.

    MIT /Caltech Advanced aLigo


    VIRGO Gravitational Wave interferometer, near Pisa, Italy

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

    Caltech/MIT Advanced aLigo detector installation Hanford, WA, USA

    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    Gravity is talking. Lisa will listen. Dialogos of Eide

    ESA/NASA eLISA space based, the future of gravitational wave research

    Bringing LIGO (the Laser Interferometer Gravitational-Wave Observatory) to the table, proposals for the indirect detection of dark matter via gravitational waves began to spring up in the literature, with implications for primordial black hole detection or dark matter ensconced in neutron stars. Yet a new proposal, in a paper by Guo et. al., [Scientific Reports-Communication Physics] suggests that direct dark matter detection with gravitational waves may be possible, specifically in the case of dark photons.

    Dark photons are hidden sector particles in the ultralight regime of dark matter candidates. Theorized as the gauge boson of a U(1) gauge group, meaning the particle is a force-carrier akin to the photon of quantum electrodynamics, dark photons either do not couple or very weakly couple to Standard Model particles in various formulations. Unlike a regular photon, dark photons can acquire a mass via the Higgs mechanism. Since dark photons need to be non-relativistic in order to meet cosmological dark matter constraints, we can model them as a coherently oscillating background field: a plane wave with amplitude determined by dark matter energy density and oscillation frequency determined by mass. In the case that dark photons weakly interact with ordinary matter, this means an oscillating force is imparted. This sets LIGO up as a means of direct detection due to the mirror displacement dark photons could induce in LIGO detectors.

    3
    Figure 1: The experimental setup of the Advanced LIGO interferometer. We can see that light leaves the laser and is reflected between a few power recycling mirrors (PR), split by a beam splitter (BS), and bounced between input and end test masses (ITM and ETM). The entire system is mounted on seismically-isolated platforms to reduce noise as much as possible. Source: https://arxiv.org/pdf/1411.4547.pdf

    LIGO consists of a Michelson interferometer, in which a laser shines upon a beam splitter which in turn creates two perpendicular beams. The light from each beam then hits a mirror, is reflected back, and the two beams combine, producing an interference pattern. In the actual LIGO detectors, the beams are reflected back some 280 times (down a 4 km arm length) and are split to be initially out of phase so that the photodiode detector should not detect any light in the absence of a gravitational wave. A key feature of gravitational waves is their polarization, which stretches spacetime in one direction and compresses it in the perpendicular direction in an alternating fashion. This means that when a gravitational wave passes through the detector, the effective length of one of the interferometer arms is reduced while the other is increased, and the photodiode will detect an interference pattern as a result.

    LIGO has been able to reach an incredible sensitivity of one part in 10^{23} in its detectors over a 100 Hz bandwidth, meaning that its instruments can detect mirror displacements up to 1/10,000th the size of a proton. Taking advantage of this number, Guo et. al. demonstrated that the differential strain (the ratio of the relative displacement of the mirrors to the interferometer’s arm length, or h = \Delta L/L) is also sensitive to ultralight dark matter via the modeling process described above. The acceleration induced by the dark photon dark matter on the LIGO mirrors is ultimately proportional to the dark electric field and charge-to-mass ratio of the mirrors themselves.

    Once this signal is approximated, next comes the task of estimating the background. Since the coherence length is of order 10^9 m for a dark photon field oscillating at order 100 Hz, a distance much larger than the separation between the LIGO detectors at Hanford and Livingston (in Washington and Louisiana, respectively), the signals from dark photons at both detectors should be highly correlated. This has the effect of reducing the noise in the overall signal, since the noise in each of the detectors should be statistically independent. The signal-to-noise ratio can then be computed directly using discrete Fourier transforms from segments of data along the total observation time. However, this process of breaking up the data, known as “binning,” means that some signal power is lost and must be corrected for.

    4
    Figure 2: The end result of the Guo et. al. analysis of dark photon-induced mirror displacement in LIGO. Above we can see a plot of the coupling of dark photons to baryons as a function of the dark photon oscillation frequency. We can see that over further Advanced LIGO runs, up to O4-O5, these limits are expected to improve by several orders of magnitude. Source: https://www.nature.com/articles/s42005-019-0255-0

    In applying this analysis to the strain data from the first run of Advanced LIGO, Guo et. al. generated a plot which sets new limits for the coupling of dark photons to baryons as a function of the dark photon oscillation frequency. There are a few key subtleties in this analysis, primarily that there are many potential dark photon models which rely on different gauge groups, yet this framework allows for similar analysis of other dark photon models. With plans for future iterations of gravitational wave detectors, further improved sensitivities, and many more data runs, there seems to be great potential to apply LIGO to direct dark matter detection. It’s exciting to see these instruments in action for discoveries that were not in mind when LIGO was first designed, and I’m looking forward to seeing what we can come up with next!

    Learn More:

    An overview of gravitational waves and dark matter: https://www.symmetrymagazine.org/article/what-gravitational-waves-can-say-about-dark-matter
    A summary of dark photon experiments and results: https://physics.aps.org/articles/v7/115
    Details on the hardware of Advanced LIGO: https://arxiv.org/pdf/1411.4547.pdf
    A similar analysis done by Pierce et. al.: https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.121.061102

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    What is ParticleBites?

    ParticleBites is an online particle physics journal club written by graduate students and postdocs. Each post presents an interesting paper in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.

    The papers are accessible on the arXiv preprint server. Most of our posts are based on papers from hep-ph (high energy phenomenology) and hep-ex (high energy experiment).

    Why read ParticleBites?

    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. With each brief ParticleBite, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in particle physics.

    Who writes ParticleBites?

    ParticleBites is written and edited by graduate students and postdocs working in high energy physics. Feel free to contact us if you’re interested in applying to write for ParticleBites.

    ParticleBites was founded in 2013 by Flip Tanedo following the Communicating Science (ComSciCon) 2013 workshop.

    2
    Flip Tanedo UCI Chancellor’s ADVANCE postdoctoral scholar in theoretical physics. As of July 2016, I will be an assistant professor of physics at the University of California, Riverside

    It is now organized and directed by Flip and Julia Gonski, with ongoing guidance from Nathan Sanders.

     
  • richardmitnick 11:51 am on August 23, 2019 Permalink | Reply
    Tags: , , , , , , Vera Rubin,   

    From Scientific American: Women in STEM- “In Support of the Vera C. Rubin Observatory” 

    Scientific American

    From Scientific American

    August 23, 2019
    Megan Donahue

    The House of Representatives has taken the first step toward honoring a pioneering woman in astronomy.

    LSST the Vera C. Rubin Observatory

    LSST Camera, built at SLAC



    LSST 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

    On July 23, the U.S. House of Representatives approved H.R. 3196, the Vera C. Rubin Observatory Designation Act, which was introduced by Representative Eddie Bernice Johnson of Texas and Representative Jenniffer González-Colón of Puerto Rico (at large). If the Senate agrees, it will name the facility housing the Large Synoptic Survey Telescope the Vera C. Rubin Observatory in honor of Carnegie Institution for Science researcher Vera Cooper Rubin, who died in 2016.

    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

    As a woman astronomer working in the field of cosmology and galaxy studies, Rubin has always been a personal hero of mine. I can’t think of a more appropriate tribute to her memory and her incredible contributions to science, astronomy and future astronomers than this honor.

    The text of the bill itself celebrates the milestones of Rubin’s scientific career. As a student and young professor, she studied how galaxies cluster and move inside such clusters. In 1970 she and astronomer W. Kent Ford, Jr., published measurements of the line-of-sight velocities and locations of individual ionized clouds of gas inside the nearby Andromeda galaxy (M31), showing that they were moving too fast to be gravitationally bound to the galaxy if the only matter binding it was the matter we can see (in the form of stars).

    We call these kinds of observations “rotation curves,” because inside spiral galaxies such as Andromeda or our own Milky Way, the orbits of stars and gas circle the center of the galaxy inside a volume of space shaped like a disk. A typical rotation curve plots the velocities of gas clouds or stars toward or away from us as a function of distance from the center of the disk. These curves can be fit to models of where the matter is inside those orbits to work out how much matter is inside the galaxy and where it sits.

    In Rubin and Ford’s paper, they did not make much of a fuss about the interpretation. By 1980 however, Rubin, Ford and the late Norbert Thonnard presented long-slit spectroscopy of a sample of 21 galaxies. They derived the rotation curves from these data, and in this, their most-cited work, and in the most cited work around this time in Rubin’s career, they boldly posited that gravity caused by something other than stars and gas must be binding the galaxies together. These observations provided some of the first direct evidence of the existence of dark matter inside of galaxies.

    Later observations of clusters of galaxies and of the cosmic microwave background confirm that dark matter exists in even larger structures, and it appears to outweigh the stars and gas in the universe by a factor of about seven. Rubin investigated questions related to the nature of spiral galaxies and dark matter for most of her life. We still don’t know exactly what dark matter is made out of, but her discoveries transformed our thinking about the universe and its contents.

    Although many of us astronomers thought Rubin should have won a Nobel Prize in Physics for her work in finding dark matter in galaxies, it’s not as if she went unrecognized during her life. She was a very highly regarded scientist, and she was recognized by her fellow researchers. In 1993, she was awarded the National Medal of Science, which is based on nomination by one’s peers, submitted to the National Science Foundation, and subsequent selection by 12 presidentially appointed scientists.

    This award was set up by John F. Kennedy in 1962. In the category of physical sciences, it was first given to a woman—Margaret Burbidge—20 years later, after more than 60 men had received that prize. After another 10 years and more than 30 male prizewinners, Rubin won it. (If you’re wondering: yes, an additional 14 years passed and 27 more men won the prize in the physical sciences category before any other women did so.)

    In 1996 Rubin was the second woman ever to receive the Gold Medal of the Royal Astronomical Society. The first woman so honored was Caroline Herschel, nearly 170 years prior. As did many women of her generation (or any of them), Rubin faced many barriers in her career simply because she was a woman. For example, as a scientific staff member of the Carnegie Institution in the 1960s, she had institutional access to the world-class Palomar Observatory in California. But she was denied access to the observatory, with the excuse that there were limited bathroom facilities.

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

    Nevertheless, she persisted, and in 1965 she was finally allowed to observe at Palomar. She was the first woman to be officially allowed to do so. (Burbidge had gained access under the name of her husband Geoffrey.) Rubin carried on as an advocate for the equal treatment of women in science and helped many other women in their careers as astronomers. The Large Synoptic Survey Telescope, funded primarily by the NSF and the Department of Energy, will carry on her legacy and her work to study the nature of dark energy and dark matter and map out the structure of the universe as traced by billions of galaxies.

    We have come a long way from the days where women weren’t allowed in the same buildings as men. But we still have a long way to travel, because it is still too easy, even in science and with our desire to avoid bias, for a man to cast doubt on the worth of a woman’s work. We also apparently have much to learn about the nature of dark matter—which may be a dark sector of dark matter particle species, for all we know so far. Because of Rubin’s pioneering work, we are all further along these journeys than we would be without her. By hearing her name and her story, along with the wonderful discoveries we all anticipate from the Vera C. Rubin Observatory, little girls everywhere can learn they, too, can contribute to our understanding of the universe.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    Scientific American, the oldest continuously published magazine in the U.S., has been bringing its readers unique insights about developments in science and technology for more than 160 years.

     
  • richardmitnick 11:41 am on April 18, 2019 Permalink | Reply
    Tags: "What gravitational waves can say about dark matter", , , , , , , , , , Vera Rubin   

    From Symmetry: “What gravitational waves can say about dark matter” 

    Symmetry Mag
    From Symmetry

    04/18/19
    Caitlyn Buongiorno

    Scientists think that, under some circumstances, dark matter could generate powerful enough gravitational waves for equipment like LIGO to detect.

    1
    Artwork by Sandbox Studio, Chicago

    In 1916, Albert Einstein published his theory of general relativity, which established the modern view of gravity as a warping of the fabric of spacetime. The theory predicted that objects that interact with gravity could disturb that fabric, sending ripples across it.

    Any object that interacts with gravity can create gravitational waves. But only the most catastrophic cosmic events make gravitational waves powerful enough for us to detect. Now that observatories have begun to record gravitational waves on a regular basis, scientists are discussing how dark matter—only known so far to interact with other matter only through gravity—might create gravitational waves strong enough to be found.

    Fritz Zwicky discovered Dark Matter when observing the movement of the Coma Cluster. But , 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 spacetime blanket

    In the universe, space and time are invariably linked as four-dimensional spacetime. For simplicity, you can think of spacetime as a blanket suspended above the ground.

    Spacetime with Gravity Probe B. NASA

    Jupiter might be a single Cheerio on top of that blanket. The sun could be a tennis ball. R136a1—the most massive known star—might be a 40-pound medicine ball.

    Each of these objects weighs down the blanket where it sits: the heavier the object, the bigger the dip in the blanket. Like objects of different weights on a blanket, objects of different masses have different effects on the fabric of spacetime. A dip in spacetime is gravitational field.

    The gravitational field of one object can affect another object. The other object might fall into the first object’s gravitational field and orbit around it, like the moon around Earth, or Earth around the sun.

    Alternatively, two bodies with gravitational fields might spiral toward each other, getting closer and closer until they collide. As this happens, they create ripples in spacetime—gravitational waves.

    On September 14, 2015, scientists used the Laser Interferometer Gravitational-Wave Observatory, or LIGO, to make the first direct observation of gravitational waves, part of the buildup to the crash between two massive black holes.

    Since that first detection, the LIGO collaboration—together with the collaboration that runs a partner gravitational-wave observatory called Virgo—has detected gravitational waves from at least 10 more mergers of black holes and, in 2017, the first merger between two neutron stars.


    VIRGO Gravitational Wave interferometer, near Pisa, Italy


    Caltech/MIT Advanced aLigo Hanford, WA, USA installation


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

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

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

    Gravity is talking. Lisa will listen. Dialogos of Eide

    ESA/eLISA the future of gravitational wave research

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


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

    Dark matter is believed to be five times as prevalent as visible matter. Its gravitational effects are seen throughout the universe. Scientists think they have yet to definitively see gravitational waves caused by dark matter, but they can think of numerous ways this might happen.

    Primordial black holes

    Scientists have seen the gravitational effects of dark matter, so they know it must be there—or at least, something must be going on to cause those effects. But so far, they’ve never directly detected a dark matter particle, so they’re not sure exactly what dark matter is like.

    One idea is that some of the dark matter could actually be primordial black holes.

    Imagine the universe as an infinitely large petri dish. In this scenario, the Big Bang is the point where matter-bacteria begins to grow. That point quickly expands, moving outward to encompass more and more of the petri dish. If that growth is slightly uneven, certain areas will become more densely inhabited by matter than others.

    These pockets of dense matter—mostly photons at this point in the universe—might have collapsed under their own gravity and formed early black holes.

    “I think it’s an interesting theory, as interesting as a new kind of particle,” says Yacine Ali-Haimoud, an assistant professor of physics at New York University. “If primordial black holes do exist, it would have profound implications on the conditions in the very early universe.”

    By using gravitational waves to learn about the properties of black holes, LIGO might be able to prove or constrain this dark matter theory.

    Unlike normal black holes, primordial black holes don’t have a minimum mass threshold they need to reach in order to form. If LIGO were to see a black hole less massive than the sun, for example, it might be a primordial black hole.

    Even if primordial black holes do exist, it’s doubtful that they account for all of the dark matter in the universe. Still, finding proof of primordial black holes would expand our fundamental understanding of dark matter and how the universe began.

    Neutron star rattles

    Dark matter seems to interact with normal matter only through gravity, but, based on the way known particles interact, theorists think it’s possible that dark matter might also interact with itself.

    If that is the case, dark matter particles might bind together to form dark objects that are as compact as a neutron star.

    We know that stars drastically “weigh down” the fabric of spacetime around them. If the universe were populated with compact dark objects, there would be a chance that at least some of them would end up trapped inside of ordinary matter stars.

    A normal star and a dark object would interact only through gravity, allowing the two to co-exist without much of a fuss. But any disruption to the star—for example, a supernova explosion—could create a rattle-like disturbance between the resulting neutron star and the trapped dark object. If such an event occurred in our galaxy, it would create detectable gravitational waves

    “We understand neutron stars quite well,” says Sanjay Reddy, University of Washington physics professor and senior fellow with the Institute for Nuclear Theory. “If something ‘odd’ happens with gravitational waves, we would know there was potentially something new going on that might involve dark matter.”

    The likelihood that any exist in our solar system is limited. Chuck Horowitz, Maria Alessandra Papa and Reddy recently analyzed LIGO’s data and found no indication of compact dark objects of a specific mass range within Earth, Jupiter or the sun.

    Further gravitational-wave studies could place further constraints on compact dark objects. “Constraints are important,” says Ann Nelson, a physics professor at the University of Washington. “They allow us to improve existing theories and even formulate new ones.”

    Axion stars

    One light dark matter candidate is the axion, named by physicist Frank Wilczek after a brand of detergent, in reference to its ability to tidy up a problem in the theory of quantum chromodynamics.

    Scientists think it could be possible for axions to bind together into axion stars, similar to neutron stars but made up of extremely compact axion matter.

    “If axions exist, there are scenarios where they can cluster together and form stellar objects, like ordinary matter,” says Tim Dietrich, a LIGO-Virgo member and physicist. “We don’t know if axion stars exist, and we won’t know for sure until we find constraints for our models.”

    If an axion star merged with a neutron star, scientists might not be able to tell the difference between the two with their current instruments. Instead, scientists would need to rely on electromagnetic signals accompanying the gravitational wave to identify the anomaly.

    It’s also possible that axions could bunch around a binary black hole or neutron star system. If those stars then merged, the changes in the axion “cloud” would be visible in the gravitational wave signal. A third possibility is that axions could be created by the merger, an action that would be reflected in the signal.

    This month, the LIGO-Virgo collaborations began their third observing run and, with new upgrades, expect to detect a merger event every week.

    Gravitational-wave detectors have already proven their worth in confirming Einstein’s century-old prediction. But there is still plenty that studying gravitational waves can teach us. “Gravitational waves are like a completely new sense for science,” Ali-Haimoud says. “A new sense means new ways to look at all the big questions in physics.”

    See the full article here .


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

    Please help promote STEM in your local schools.


    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 11:00 am on November 29, 2018 Permalink | Reply
    Tags: , , , , , , , , Vera Rubin   

    From NASA/ESA Hubble Telescope: “Hubble Uncovers Thousands of Globular Star Clusters Scattered Among Galaxies” 

    NASA Hubble Banner

    NASA/ESA Hubble Telescope

    From NASA/ESA Hubble Telescope

    Nov 29, 2018

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

    Juan Madrid
    Australian Telescope National Facility, Sydney, Australia
    jmadrid@astro.swin.edu.au

    1
    Survey will allow for mapping of dark matter in huge galaxy cluster

    Gazing across 300 million light-years into a monstrous city of galaxies, astronomers have used NASA’s Hubble Space Telescope to do a comprehensive census of some of its most diminutive members: a whopping 22,426 globular star clusters found to date.

    The survey, published in the November 9, 2018, issue of The Astrophysical Journal, will allow for astronomers to use the globular cluster field to map the distribution of matter and dark matter in the Coma galaxy cluster, which holds over 1,000 galaxies that are packed together.

    Because globular clusters are much smaller than entire galaxies – and much more abundant – they are a much better tracer of how the fabric of space is distorted by the Coma cluster’s gravity. In fact, the Coma cluster is one of the first places where observed gravitational anomalies were considered to be indicative of a lot of unseen mass in the universe – later to be called “dark matter.”

    Fritz Zwicky discovered Dark Matter when observing the movement of the Coma Cluster.

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

    Coma cluster via NASA/ESA Hubble

    But most of the real work was done by Vera Rubin a Woman in STEM

    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

    Among the earliest homesteaders of the universe, globular star clusters are snow-globe-shaped islands of several hundred thousand ancient stars. They are integral to the birth and growth of a galaxy. About 150 globular clusters zip around our Milky Way galaxy, and, because they contain the oldest known stars in the universe, were present in the early formative years of our galaxy.

    Some of the Milky Way’s globular clusters are visible to the naked eye as fuzzy-looking “stars.” But at the distance of the Coma cluster, its globulars appear as dots of light even to Hubble’s super-sharp vision. The survey found the globular clusters scattered in the space between the galaxies. They have been orphaned from their home galaxy due to galaxy near-collisions inside the traffic-jammed cluster. Hubble revealed that some globular clusters line up along bridge-like patterns. This is telltale evidence for interactions between galaxies where they gravitationally tug on each other like pulling taffy.

    Astronomer Juan Madrid of the Australian Telescope National Facility in Sydney, Australia first thought about the distribution of globular clusters in Coma when he was examining Hubble images that show the globular clusters extending all the way to the edge of any given photograph of galaxies in the Coma cluster.

    He was looking forward to more data from one of the legacy surveys of Hubble that was designed to obtain data of the entire Coma cluster, called the Coma Cluster Treasury Survey. However, halfway through the program, in 2006, Hubble’s powerful Advanced Camera for Surveys (ACS) had an electronics failure. (The ACS was later repaired by astronauts during a 2009 Hubble servicing mission.)

    NASA Hubble Advanced Camera forSurveys

    To fill in the survey gaps, Madrid and his team painstakingly pulled numerous Hubble images of the galaxy cluster taken from different Hubble observing programs. These are stored in the Space Telescope Science Institute’s Mikulski Archive for Space Telescopes in Baltimore, Maryland. He assembled a mosaic of the central region of the cluster, working with students from the National Science Foundation’s Research Experience for Undergraduates program. “This program gives an opportunity to students enrolled in universities with little or no astronomy to gain experience in the field,” Madrid said.

    The team developed algorithms to sift through the Coma mosaic images that contain at least 100,000 potential sources. The program used globular clusters’ color (dominated by the glow of aging red stars) and spherical shape to eliminate extraneous objects – mostly background galaxies unassociated with the Coma cluster.

    Though Hubble has superb detectors with unmatched sensitivity and resolution, their main drawback is that they have tiny fields of view. “One of the cool aspects of our research is that it showcases the amazing science that will be possible with NASA’s planned Wide Field Infrared Survey Telescope (WFIRST) that will have a much larger field of view than Hubble,” said Madrid.

    NASA/WFIRST

    “We will be able to image entire galaxy clusters at once.”

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

    ESA50 Logo large

    AURA Icon

     
  • richardmitnick 10:43 am on November 14, 2018 Permalink | Reply
    Tags: , , , , , The search for Dark Matter, Vera Rubin,   

    From Sanford Underground Research Facility: “Success of experiment requires testing” 

    SURF logo
    Sanford Underground levels

    From Sanford Underground Research Facility

    November 13, 2018
    Erin Broberg

    1
    Tomasz Biesiadzinski, project scientist for SLAC National Accelerator Laboratory (SLAC), works on the mock PMT [photomultiplier tubes] array. Erin Broberg

    “The LZ detector is kind of like a spacecraft,” said Tomasz Biesiadzinski, project scientist for SLAC National Accelerator Laboratory (SLAC). “Repairing it after it’s installed would be very difficult, so we do everything we can to make sure it works correctly the first time.”

    LZ Dark Matter Experiment at SURF lab

    LBNL LZ project at SURF, Lead, SD, USA

    Biesiadzinski himself is responsible for planning and carrying out tests during the assembly of time projection chamber (TPC), the main detector for LUX-ZEPLIN experiment (LZ). Currently being constructed on the 4850 Level at Sanford Underground Research Facility (Sanford Lab), this main detector consists of a large tank that will hold 7 tonnes of ultra-pure, cryogenic liquid xenon maintained at -100o C. All the pieces of this detector are designed to function with precision; it’s Biesiadzinski job to verify that each part continues to work correctly as they are integrated. That includes hundreds of photomultiplier tubes (PMT).

    Test run

    The most recent test was piecing together an intricate mock array for the PMTs, which will detect light signals created by the collision of a dark matter particle and a xenon atom, inside the main detector. In a soft-wall cleanroom in the Surface Laboratory at Sanford Lab, Biesiadzinski and his team carefully practiced placing instruments like thermometers, sensors and reflective covering. They practiced installing routing cabling, including PMT high voltage power cables, PMT signal cables and thermometer cables.

    “Essentially, we wanted to gain experience so we could be faster during the actual assembly. The faster we work, the more we limit dust exposure and therefore potential backgrounds,” said Biesiadzinski. “It was also an opportunity to test fit real components. We did find that there were some very tight places that motivated us to slightly redesign some small parts to make assembly easier.”

    These tests will make the installment of the actual LZ arrays much smoother.

    “LZ’s main detector will have two PMT arrays, one on the top of the tank and one on the bottom,” Biesiadzinski explained. “The bottom array will hold 241 PMTs pointing up into the liquid Xenon volume of the main detector. The top array will hold PMTs 253 pointing down on the liquid Xenon and the gas layer above it in the main detector.”

    In total, there will be 494 PMTs lining the main detector. If a WIMP streaks through the tank and strikes a xenon nucleus, two things will happen. First, the xenon will emit a flash of light. Then, it will release electrons, which drift in an electric field to the top of the tank, where they will produce a second flash of light. Hundreds of PMTs will be waiting to detect a characteristic combination of flashes from inside the tank—a WIMPs’ telltale signature.

    “Both arrays—top and bottom—record the light from particle interactions inside the detector, including, hopefully, dark matter,” said Biesiadzinski. “This data allows us to estimate both the energy created and 3D location of the interaction.”

    Catching light

    The PMTs used for LZ are extremely sensitive. Not only can they distinguish individual photons of light arriving just a few tens of nanoseconds apart, they can also see the UV light produced by xenon that is far outside the human vision range. The X-Y location of events in the detector can be measured using the top PMT array to within a few millimeters for sufficiently energetic events.

    To insure every bit of light makes its way to a PMT, the inside surfaces of the arrays are covered with Polytetrafluoroethylene (PTFE or teflon), a material highly reflective to xenon scintillation light, in between the PMT faces.

    “This way, photons that don’t enter the PMTs right away—and are therefore not recorded—are reflected and will get a second, third, and so on, chance of being detected as they bounce around the detector,” said Biesiadzinski.

    Researchers will also cover the outside of the bottom array, including all of the cables, with PTFE to maximize light collection there. Light recorded there by additional PMTs that are not part of the array, allow us to measure radioactive backgrounds that can contaminate the main detector.

    Keeping it “clean”

    In addition to being very specific, these PMTs are also ultra-clean.

    “By clean, we mean radio-pure,” said Briana Mount, director of the BHUC, where 338 of LZ’s PMTs have already been tested for radio-purity.

    The tiniest amounts of radioactive elements in the very materials used to construct LZ can also overwhelm the rare-event signal. Radioactive elements can be found in rocks, titanium—even human sweat. As these elements decay, they emit signals that quickly light up ultra-sensitive detectors. To lessen these misleading signatures, researchers assay, or test, their materials for radio-purity using low-background counters (LBCs).

    “Our PMTs are special made to have very low radioactivity so as to not overwhelm a very sensitive detector like LZ with background signal,” said Biesiadzinski.

    Testing the PMTs at the BHUC allows researchers to understand exactly how much of a remaining background they can expect to see from these materials during the experiment. Mount explained that most of the samples currently being assayed at the BHUC are LZ samples, including cable ties, wires, nuts and bolts.

    “We have assayed every component that will make up LZ,” said Kevin Lesko, senior physicist at Lawrence Berkeley National Lab (Berkeley Lab) and a spokesperson for LZ. “At this point we have performed over 1300 assays with another 800 assays planned. These have kept BHUC and the UK’s Boulby LBCs fully occupied for approximately 4 years. These assays permit us ensure no component contributes a major background to the detector and also allows us to assemble a model of the backgrounds for the entire detector before we turn on a single PMT.”

    For a visual description and breakdown of LZ’s design, watch this video created by SLAC.

    Fritz Zwicky discovered Dark Matter when observing the movement of the Coma Cluster.

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

    Coma cluster via NASA/ESA Hubble

    But most of the real work was done by Vera Rubin a Woman in STEM

    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

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    About us.
    The Sanford Underground Research Facility in Lead, South Dakota, advances our understanding of the universe by providing laboratory space deep underground, where sensitive physics experiments can be shielded from cosmic radiation. Researchers at the Sanford Lab explore some of the most challenging questions facing 21st century physics, such as the origin of matter, the nature of dark matter and the properties of neutrinos. The facility also hosts experiments in other disciplines—including geology, biology and engineering.

    The Sanford Lab is located at the former Homestake gold mine, which was a physics landmark long before being converted into a dedicated science facility. Nuclear chemist Ray Davis earned a share of the Nobel Prize for Physics in 2002 for a solar neutrino experiment he installed 4,850 feet underground in the mine.

    Homestake closed in 2003, but the company donated the property to South Dakota in 2006 for use as an underground laboratory. That same year, philanthropist T. Denny Sanford donated $70 million to the project. The South Dakota Legislature also created the South Dakota Science and Technology Authority to operate the lab. The state Legislature has committed more than $40 million in state funds to the project, and South Dakota also obtained a $10 million Community Development Block Grant to help rehabilitate the facility.

    In 2007, after the National Science Foundation named Homestake as the preferred site for a proposed national Deep Underground Science and Engineering Laboratory (DUSEL), the South Dakota Science and Technology Authority (SDSTA) began reopening the former gold mine.

    In December 2010, the National Science Board decided not to fund further design of DUSEL. However, in 2011 the Department of Energy, through the Lawrence Berkeley National Laboratory, agreed to support ongoing science operations at Sanford Lab, while investigating how to use the underground research facility for other longer-term experiments. The SDSTA, which owns Sanford Lab, continues to operate the facility under that agreement with Berkeley Lab.

    The first two major physics experiments at the Sanford Lab are 4,850 feet underground in an area called the Davis Campus, named for the late Ray Davis. The Large Underground Xenon (LUX) experiment is housed in the same cavern excavated for Ray Davis’s experiment in the 1960s.
    LUX/Dark matter experiment at SURFLUX/Dark matter experiment at SURF

    In October 2013, after an initial run of 80 days, LUX was determined to be the most sensitive detector yet to search for dark matter—a mysterious, yet-to-be-detected substance thought to be the most prevalent matter in the universe. The Majorana Demonstrator experiment, also on the 4850 Level, is searching for a rare phenomenon called “neutrinoless double-beta decay” that could reveal whether subatomic particles called neutrinos can be their own antiparticle. Detection of neutrinoless double-beta decay could help determine why matter prevailed over antimatter. The Majorana Demonstrator experiment is adjacent to the original Davis cavern.

    LUX’s mission was to scour the universe for WIMPs, vetoing all other signatures. It would continue to do just that for another three years before it was decommissioned in 2016.

    In the midst of the excitement over first results, the LUX collaboration was already casting its gaze forward. Planning for a next-generation dark matter experiment at Sanford Lab was already under way. Named LUX-ZEPLIN (LZ), the next-generation experiment would increase the sensitivity of LUX 100 times.

    SLAC physicist Tom Shutt, a previous co-spokesperson for LUX, said one goal of the experiment was to figure out how to build an even larger detector.
    “LZ will be a thousand times more sensitive than the LUX detector,” Shutt said. “It will just begin to see an irreducible background of neutrinos that may ultimately set the limit to our ability to measure dark matter.”
    We celebrate five years of LUX, and look into the steps being taken toward the much larger and far more sensitive experiment.

    Another major experiment, the Long Baseline Neutrino Experiment (LBNE)—a collaboration with Fermi National Accelerator Laboratory (Fermilab) and Sanford Lab, is in the preliminary design stages. The project got a major boost last year when Congress approved and the president signed an Omnibus Appropriations bill that will fund LBNE operations through FY 2014. Called the “next frontier of particle physics,” LBNE will follow neutrinos as they travel 800 miles through the earth, from FermiLab in Batavia, Ill., to Sanford Lab.

    Fermilab LBNE
    LBNE

    U Washington Majorana Demonstrator Experiment at SURF

    The MAJORANA DEMONSTRATOR will contain 40 kg of germanium; up to 30 kg will be enriched to 86% in 76Ge. The DEMONSTRATOR will be deployed deep underground in an ultra-low-background shielded environment in the Sanford Underground Research Facility (SURF) in Lead, SD. The goal of the DEMONSTRATOR is to determine whether a future 1-tonne experiment can achieve a background goal of one count per tonne-year in a 4-keV region of interest around the 76Ge 0νββ Q-value at 2039 keV. MAJORANA plans to collaborate with GERDA for a future tonne-scale 76Ge 0νββ search.

    LBNL LZ project at SURF, Lead, SD, USA

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