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  • richardmitnick 9:16 am on February 22, 2017 Permalink | Reply
    Tags: , , , , Dark Energy Survey, Paul Sutter,   

    From CBS: “When the lights went out in the universe” 

    CBS News

    CBS News

    February 21, 2017
    Paul Sutter

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    Astronomers think that the expansion of the universe is regulated by both the force of gravity, and a mysterious dark energy. In this artist’s conception, dark energy is represented by the purple grid above, and gravity by the green grid below.
    NASA/JPL-Caltech

    About 5 billion years ago, everything changed. The expansion of the universe, which had been gradually decelerating for billions of years, reversed course and entered into a period of unbridled acceleration. (It was sort of like a car that switches from decelerating to accelerating, but is still moving forward the whole time.) The unhurried, deliberate process of structure formation — the gradual buildup of ever-larger assemblies of matter from galaxies to groups to clusters — froze and began to undo itself.

    Map of voids and superclusters within 500 million light years from Milky Way 8/11/09 http://www.atlasoftheuniverse.com/nearsc.html  Richard Powell
    Map of voids and superclusters within 500 million light years from Milky Way 8/11/09 http://www.atlasoftheuniverse.com/nearsc.html Richard Powell

    Five billion years ago, a mysterious force overtook the universe. Hidden in the shadows, it lay dormant, buried underneath fields of matter and radiation. But once it uncovered itself, it worked quickly, bending the entire cosmos to its will.

    Five billion years ago, dark energy awoke.

    The guts of the universe

    To explain what’s going on in this overly dramatic telling of the emergence of dark energy, we need to talk about what the universe is made of and how that affects its expansion.

    Let’s start with the mantra of general relativity: mass and energy tell space-time how to bend, and the bending of space-time tells objects how to move. Usually, we think of this as a local interaction, used to explain the orbits of particular planets or the unusual properties of a black hole.

    But those same mathematics of relativity — which provide the needed accuracy for GPS satellites to tell you how close you are to your coffee fix — also serve as the foundation for understanding the growth and evolution of the entire universe. I mean, it is “general” relativity after all.

    The universe is made of all sorts of stuff, and the properties of that stuff influence the overall curvature of the entire cosmos, which impacts its expansion. It’s the mantra of relativity writ large: the mass and energy of the entire universe is bending the spacetime of the entire universe, which is telling the entire universe how to move.

    If the total density of all the stuff is greater than a very specific value — called “the critical density” and equal to about 4 hydrogen atoms per cubic meter — then the universe’s expansion will slow down, stop and reverse in a Big Crunch. If the universe’s density is less than this critical value, the universe will expand forever. And if it’s exactly equal to the critical value, then the universe will expand forever, but at an ever-diminishing rate.

    Measurements suggest that we live in a contradictory universe, where the total density exactly equals the critical density — but the universe’s expansion is still accelerating as if the density was too low.

    What in Hubble’s ghost is going on?

    An empty argument

    What’s going on is dark energy. Totaling 69.2 percent of the energy density of the universe, it simply behaves … strangely. Dark energy’s most important property is that its density is constant. Its second most important property is that it appears to be tied to the vacuum of empty space.

    Dark Energy Icon
    Dark Energy Camera. Built at FNAL
    Dark Energy Camera. Built at FNAL
    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile
    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile

    Take a box, and empty out everything, removing all the matter (regular and dark), neutrinos, radiation … everything. If you did it right, you’ll have a box of pure, unadulterated vacuum — which means you’ll have a box of pure dark energy. Double the size of the box, and you’ll have double the dark energy.

    This behavior is the total opposite of the behavior of matter and radiation. If you have a box (or, say, a universe) with a fixed amount of matter and you double that container’s volume, the density of matter is cut in half. Radiation’s energy density goes down even further: Not only does the expansion of the universe dilute radiation, it also stretches out its wavelength.

    But as the universe expands, we continually get more empty space (vacuum) in it, so we continually get more dark energy. If you’re worried that this violates some sort of principle of conservation of energy, you can rest easy tonight: The universe is a dynamic system, and the form of the conservation laws taught in Physics 101 only apply to static systems. The universe is a dynamic place, and the concept of “conservation of energy” still holds but in a more complex, noninuitive way. But that’s an article for another day.

    You may also be wondering how I can talk so confidently about the nature of dark energy, since we don’t seem to understand it at all. You’re right: We don’t understand dark energy. At all. We know it exists, because we directly observe the accelerated expansion of the universe, and a half-dozen other lines of evidence all point to its existence.

    And while we don’t know what’s creating the accelerated expansion, we do know that we can model it as a property of the vacuum of space that has a constant density, so that’s good enough for now.

    A vacuum and an empty place

    The fact that dark energy has constant density means that in the distant past, it simply didn’t matter — because of matter. All the stuff in the universe was crammed into a smaller volume, which means regular and dark matter had very high densities. This high density meant that for a long time, the expansion of the universe was slowing down.


    The day Dark Energy switched on – Ask a Spaceman! by Paul M. Sutter on YouTube

    But as expansion continued, the matter and radiation in the universe became more and more dilute, and they got less and less dense. Eventually, about 5 billion years ago, the density of matter dropped beneath that of dark energy, which had been holding constant all that time. And once dark energy took over, the game changed completely. Because of the constant nature of its density, compared to the lowering density of matter, expansion not only continued but also accelerated. And that accelerated expansion halted the process of structure formation: Galaxies would love to continue gluing onto each other to form larger structures like clusters and superclusters, but the intervening empty space is inexorably pulling them apart.

    Some chance mergers will continue to happen, of course, but the universe’s days of building larger structures are long over.

    A cosmic coincidence

    The emergence of dark energy leaves us with a little puzzle. In the distant past, when matter densities were incredibly high in a compact universe, dark energy didn’t matter at all. In the distant future, matter will be spread so thin — like too little butter over too much bread — that its density will be ridiculously, hilariously, pathetically small compared to dark energy’s.

    Dark energy depiction. Image: Volker Springle/Max Planck Institute for Astrophysics/SP)
    Dark energy depiction. Image: Volker Springle/Max Planck Institute for Astrophysics/SP


    The surprising coincidence between dark matter and dark energy – Ask a Spaceman! by Paul M. Sutter on YouTube

    Right now, we live in the in-between epoch, where dark energy is roughly three-quarters of the total mass-energy of the universe and dark matter is about one-quarter (regular matter is a negligible amount). This seems a bit … coincidental. Considering the grand history of the universe, we just happen to observe it in the tiny slice of time when matter and dark energy are trading places.

    Did we just happen to get lucky? To arise to consciousness and observe the universe where both dark matter and dark energy are of roughly equal strength? Or is the universe telling us something more? Maybe it’s not a coincidence at all. Maybe dark matter and dark energy “talk” to each other and keep in balance via additional forces of nature; forces that simply don’t manifest in Earthly laboratories. Maybe they’re connected and related.

    Or maybe not. We simply don’t know. It’s a little too dark out there to tell.

    Paul Sutter is an astrophysicist at The Ohio State University and the chief scientist at COSI Science Center. Sutter is also host of Ask a Spaceman, RealSpace and COSI Science Now.

    See the full article here .

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  • richardmitnick 4:07 pm on February 8, 2017 Permalink | Reply
    Tags: , Dark Energy Survey, DECam - built at FNAL, Lambda-The Cosmological Constant, What is Dark Energy?   

    From the Dark Energy Survey: “Science” A Monster of an Article and a Must Read 

    Dark Energy Icon

    The Dark Energy Survey

    2.8.17
    No writer credit

    Today marks the 100th anniversary of Einstein’s cosmological constant! Read more about how his “biggest blunder” may actually explain dark energy in the following article.

    The accelerated expansion of the universe is thought to be caused by a new phenomenon, dark energy, or perhaps requires a modification in our theory of gravity. We know little about the fundamental nature of dark energy: is it constant, or does it change in time? DES will observe thousands of supernovae and hundreds of millions of galaxies to measure or constrain changes in dark energy over cosmic time.

    The Universe is getting away from us

    For over 13 billion years, the universe has been expanding. The earliest evidence for expansion came from the work of Edwin Hubble, Vesto Slipher, and others in the 1920’s, who studied the distances to and the motions of galaxies a few million light-years distant. They found that the farther away galaxies are, the faster they recede from us, with recession speed proportional to distance. This Hubble Law of recession is universal: all galaxies across the universe are speeding away from each other with speed proportional to distance; that is, the universe is expanding.

    The expansion can be visualized by imagining a rubber sheet with a square grid imprinted on it, with galaxies occupying points on the grid. As the sheet stretches with the expansion, the size of the grid squares grows. As a result, any two points fixed on the grid move away from each other with a relative speed that’s proportional to the distance between them. With time, there is more and more space between the galaxies.

    Another visualization is presented in Figure 1, which shows the entire history of the universe, from the moment of the Big Bang (left) to today (right): when we look out at the universe, we look (leftward) into its past. The vertical size of the cone provides a scale for relative size of the observable universe from our vantage point on the right.

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    Figure 1: Timeline of the cosmos; Photo credit: NASA/WMAP Science Team

    While cosmic expansion increases the distances between galaxies, they and their constituents still feel gravitational attraction: they are pulled toward each other whilst the expansion takes place. Galaxies and groups of galaxies can therefore remain gravitationally bound objects despite the overall expansion. Figure 1 also shows how stars, gas, dust, and dark matter eventually agglomerated into galaxies and galaxies into larger structures of the cosmic web (see Figure 3, which should be renamed Fig. 4).

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    Figure 2: The fabric of space-time is warped by any object with mass; the greater the mass, the larger the resulting curvature of space-time. No image credit.

    In the early 20th century, Albert Einstein set the stage for modern cosmology by formulating his theory of gravity, General Relativity: curved space-time tells mass and energy (including light and particles of matter) how to move, while mass and energy tell space-time how to curve. This means that any thing that has mass (or energy) will warp space-time, even if slightly; and, in turn, that warped space-time will change the trajectories of particles traveling through it.

    Applied to the universe as a whole, Einstein’s theory relates the rate of cosmic expansion to the mass-energy of all the stuff in the universe. Since galaxies feel the gravitational tug of their neighbors, we would expect them to slow down over time: the expansion should be decelerating. If there were enough matter in the universe, the curvature of space-time would be strong enough to eventually reverse the expansion, leading to a big crunch in which everything collapses to an infinitely dense point. Throughout the 20th century, cosmologists attempted to measure the density of matter in the universe and the rate of slowing of the expansion, in order to answer the question of whether the universe would expand forever or recollapse.

    This picture changed in 1998, with the discovery by two teams of astronomers studying distant supernovae–exploding stars–that the expansion is not slowing down but speeding up. A particular kind of supernova, called a type Ia, reaches its maximum brightness (comparable to the brightness of an entire galaxy) two to three weeks after exploding and then fades over a few months. Type Ia supernovae have the remarkable property that, after accounting for differences in their colors and the rates at which they fade, they all have nearly the same intrinsic maximum brightness. For such “standardizable candles”, measuring how bright they appear to us tells us how far away they are and thus roughly how long it has taken their light to reach us. The two teams of astronomers found that supernovae that exploded when the universe was about two-thirds its present size appeared about 25% fainter than would be expected if the expansion were decelerating (see Fig. 4). This discovery of cosmic acceleration was awarded the Nobel Prize in physics in 2011.

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    Figure 3: Supernova Hubble Diagram shows brightnesses of supernovae (vertical axis) vs. the size of the universe (horizontal axis). The blue region shows universes that accelerate, and the pink region shows universes in which the expansion slows down. The supernovae measured in the late 1990’s were fainter (and thus farther away) than expected for a universe that is decelerating, i.e., without dark energy. No image credit.

    Since ordinary matter would cause the expansion to slow down, cosmic acceleration requires us to posit a new, unseen form of energy in the universe–now called dark energy–that would have the strange property of giving rise to gravitational repulsion instead of attraction. Our picture is that, for much of cosmic history, matter dominated over dark energy and the expansion indeed slowed, enabling galaxies and large-scale structures to form as indicated above in Fig. 1. But several billion years ago, matter became sufficiently dilute due to expansion that dark energy became the dominant component of the universe, and the expansion hit the gas pedal.

    Around the turn of the millennium, this picture was bolstered by maps of the large-scale spatial distribution of galaxies, as shown in Fig. 4, and observations of the Cosmic Microwave Background (CMB) radiation.

    CMB per ESA/Planck
    CMB per ESA/Planck

    The CMB measurements showed that the spatial geometry of the universe is flat or Euclidean–two light rays emitted in parallel will always remain parallel, which is not the case if the geometry is curved–and this determines the total energy density of the universe. By contrast, the galaxy maps indicated that the density of matter in the universe is only about 30% of this total, so there must be another, unseen component that makes up the remaining 70%. That deficit fits perfectly with how much dark energy should be there according to the supernova observations.

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    Figure 4: Two-dimensional map of the large-scale galaxy distribution observed by the Sloan Digital Sky Survey (SDSS). The Milky Way (our galaxy) is at the center. Regions with redder color have a higher density of galaxies; regions of a greener color have lower galaxy densities, and black regions have no galaxies. The filamentary structure evident in the map is known as the “cosmic web.” Image Credit: Sloan Digital Sky Survey

    SDSS Telescope at Apache Point Observatory, NM, USA
    SDSS Telescope at Apache Point Observatory, NM, USA

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    Figure 5: Cosmic Energy Budget; Image Credit: Wikipedia

    Most of the mass in the universe comes from “dark matter,” which does not interact directly with light; dark matter interacts through gravity and at most weakly with other particles. The total cosmic energy budget is made up of about 25% dark matter, 5% “baryonic” or “ordinary” matter that is made of atoms, and about 70% dark energy (see Figure 5).

    We don’t yet know what makes up most of the energy in the universe. This makes dark energy one of the greatest mysteries in cosmology (perhaps all of science) as well as the focus of many experiments and surveys, possibly for years to come.

    lambda
    Figure 6: The cosmological constant, “lambda.”

    What might dark energy be?

    One explanation is that dark energy is the intrinsic energy of empty space or of the vacuum. Scientists often refer to this as the “cosmological constant” — represented by the Greek letter, Λ (“lambda”), which is the same constant proposed by Einstein a century ago! In this theory, the vacuum energy behaves as a source of negative pressure that accelerates cosmic expansion. The vacuum energy would be constant throughout space and time.

    However, what if the density of dark energy changes over time? This is the question that many modern cosmology experiments and surveys, such as DES, are working to answer.

    One possibility for dark energy that changes in time is a new field that permeates the universe and that is in essence a much, much lighter cousin of the Higgs boson discovered in 2012 (this idea is sometimes dubbed “quintessence”). In these models, the density of dark energy would be slowly decreasing with time. A more exotic possibility would be if the density of dark energy grows over time; this would eventually result in a “Big Rip,” in which the gravitational repulsion of dark energy would grow so strong as to rip apart galaxies, stars and even atoms (see Figure 7).

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    Figure 7: The consequences of different dark energy models. Where does this come from? Image credit: NASA

    How is DES suited for this study, and the probes?

    Dark Energy Camera [DECam],  built at FNAL
    Dark Energy Camera [DECam], built at FNAL

    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile
    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile

    The Dark Energy Survey is using four probes, all observed with a single instrument, to study cosmic acceleration with unprecedented accuracy and precision.

    The late 20th century gave us the era of ‘precision’ cosmology, in which we sought larger numbers of celestial objects (stars, galaxies, supernovae, etc.) for our measurements and analysis. The 21st century is now bringing the era of ‘accurate’ cosmology, in which our measurements are becoming increasingly exact. That is, we are performing our observations and analyses with greater and greater specificity, reducing the effect of systematic (measurement) uncertainties on our measurements.

    To learn that dark energy existed, we measured the structures within the universe (e.g., galaxies and galaxy clusters), the geometry of the universe (e.g., the Cosmic Microwave Background) and the expansion rate of the universe (with supernovae). In the Dark Energy Survey, we measure different versions of all of these phenomena.

    DES will use four probes of these phenomena to measure the effects of dark energy on the expansion history of the universe and on the growth of structure. We will observe thousands of supernovae, more than any other single survey in history: this reveals the expansion history of the universe. Using weak gravitational lensing and galaxy clusters, we will learn about the formation of structure and the amount of matter in the universe. Finally, we measure the distribution of galaxies across the cosmos through a technique called Baryon Acoustic Oscillations (BAO): this is similar to the measurements made of cosmic geometry with the CMB, but DES will use galaxies.

    © 2017 The Dark Energy Survey

    See the full article here .

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    The Dark Energy Survey (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 120 scientists from 23 institutions in the United States, Spain, the United Kingdom, Brazil, and Germany are working on the project. Started in Sept. 2012 and continuing for five years, DES will survey a large swath of the southern sky out to vast distances in order to provide new clues to this most fundamental of questions.

     
  • richardmitnick 4:39 pm on January 18, 2017 Permalink | Reply
    Tags: , , , , Dark Energy Survey, ,   

    From Dark Energy Survey via Inside Science: “Computer Science Technique Helps Astronomers Explore the Universe” 

    Dark Energy Icon

    The Dark Energy Survey

    1

    Inside Science

    “Deep learning” finds telltale arcs of light that indicate massive objects.

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    Image credits: Abigail Malate, Staff Illustrator

    January 13, 2017
    Ramin Skibba

    Google uses “deep learning” to generate captions for images, Facebook uses it to recognize faces and Tesla uses it to train self-driving cars. Now astronomers have caught on to deep learning, a form of machine learning in which a computer can be trained to identify or classify particular objects in images.

    The newest telescopes, such as the Dark Energy Survey, which uses a 4-meter telescope in northern Chile and covers about one quarter of the southern sky, take millions of images of a variety of celestial objects. These often include visual distortions, cosmic rays and satellite trails that make them difficult to interpret. Deep learning could help process this deluge of data quickly.

    “Astronomy is the next frontier to take it on,” said Brian Nord, an astrophysicist at Fermilab [FNAL] in Batavia, Illinois.

    Nord is one of a group of astrophysicists who search for rare gravitational lenses with signs of curved slivers of light or duplicated images that indicate the presence of massive objects skewing light rays.

    Gravitational Lensing NASA/ESA
    Gravitational Lensing NASA/ESA
    Gravitational microlensing, S. Liebes, Physical Review B, 133 (1964): 835
    Gravitational microlensing, S. Liebes, Physical Review B, 133 (1964): 835

    The scientists often have to sift through numerous images by eye, one at a time. But now they have a potentially game-changing technique at their disposal.

    Massive objects in space — like clusters of galaxies combined with dark matter hidden from view — distort the light we see from faraway galaxies and quasars, deflecting and warping the light rays around them. Distant galaxies look like magnified arcs, as if seen through the edge of a cosmic magnifying glass.

    Scientists have found hundreds of such lenses so far, confirming predictions of general relativity theory by Albert Einstein and others in the 1930s. With newly developed deep learning tools, astronomers expect to find at least 2,000 more with the Dark Energy Survey, according to research presented by Nord at the American Astronomical Society meeting in Grapevine, Texas on Jan. 4. A big catalog of gravitational lenses would help astronomers learn more about the nature of dark matter and how it holds galaxies together.

    Finding gravitational lenses is like finding needles in haystacks far away, when no two needles or haystacks are alike. “Deep learning is a way for us to create a model of a complicated system,” Nord said.

    To make complex classifications, astronomers have long used statistical machine learning techniques like neural networks, which are programmed systems with layered nodes connected in a web, much like neurons in the human brain. Deep learning just involves more interconnected layers or steps in the computation, including “hidden” ones of increasing complexity as the algorithm proceeds from input to output.

    For example, with facial recognition software, someone feeds in an image, and the system first detects edges, lines and curves. Intermediate layers then put together higher-level features, like eyes or a mouth, and eventually a face. For gravitational lenses, the software would gradually recognize a big galaxy surrounded by arcs, indicating lensed background objects.

    After it’s been trained with many lens images, such an algorithm can then find new lenses in images it has never encountered before. The current state-of-the-art algorithms can correctly identify these lenses all but a few percent of the time, when they mistake a particularly messy image for the real thing.

    “If it works but is 97 percent accurate, you could be vastly swamped by false positives,” said Colin Jacobs, who along with Karl Glazebrook at Swinburne University of Technology in Melbourne, Australia, is also working on the problem. “Ideally, it should be more accurate than what you’d need for computer vision or facial recognition,” he added.

    To address this challenge, Nord and Jacobs and their colleagues could design the algorithm to be strict, ensuring that it finds the cream of the crop, the clearest lenses in a survey. But this risks missing many lenses. Alternatively, they are trying to be more lenient in their search criteria, knowing it would mean later weeding out by hand some images that happen to look a bit like lenses.

    Over the past couple years, astronomers have begun to apply deep learning in other areas as well, mostly for deciphering images in other ways. They have used the techniques to distinguish between distant galaxies and stars in the Milky Way, to estimate the distance to faraway objects and to categorize the structures of galaxies, which can take on a variety of spiral and elliptical shapes.

    Others have utilized citizen science, recruiting people around the world to help sort through images. A project called Galaxy Zoo, for example, has classified the structures of hundreds of thousands of galaxies, while another, called Space Warps, has discovered dozens of candidate gravitational lenses missed by others.

    Nord applauds these efforts, but if his software works as well as advertised, “deep learning has the potential to be much faster,” he said.

    See the full article here .

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    DECam, built at FNAL
    DECam, built at FNAL
    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    CTIO Victor M Blanco Telescope at Cerro Tololo which houses the DECAm

    The Dark Energy Survey (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 120 scientists from 23 institutions in the United States, Spain, the United Kingdom, Brazil, and Germany are working on the project. This collaboration [has built] an extremely sensitive 570-Megapixel digital camera, DECam, and [has mounted] it on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory high in the Chilean Andes. Started in Sept. 2012 and continuing for five years, DES will survey a large swath of the southern sky out to vast distances in order to provide new clues to this most fundamental of questions.

     
  • richardmitnick 10:19 pm on December 12, 2016 Permalink | Reply
    Tags: , , Dark Energy Survey, , , TNO 2014 UZ224 a.k.a. DeeDee   

    From FNAL: “Dark Energy Survey discovers potential new dwarf planet” 

    FNAL II photo

    FNAL Art Image
    FNAL Art Image by Angela Gonzales

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    December 12, 2016
    Ricarda Laasch

    Thanks to scientists on the Dark Energy Survey (DES), the solar system just got another member.

    Dark Energy Icon

    DES scientists recently reported the discovery of a potential dwarf planet located 92 times farther from the sun than the Earth is, more than twice as distant as Pluto. The new dwarf planet was discovered using the Dark Energy Camera [DECam], a scientific instrument built at Fermilab to probe the mystery of dark energy.

    Dark Energy Camera [DECam],  built at FNAL
    Dark Energy Camera [DECam], built at FNAL

    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile
    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile

    But as scientists on the DES collaboration can attest, DECam turns out to be a powerful tool for astronomy as well as cosmology.

    The newly discovered object, which the team has nicknamed DeeDee (for “distant dwarf”), is for now known as 2014 UZ224. DeeDee takes more than 1,100 years to complete one orbit around our sun and is currently the second-most distant known object in the solar system. Light from DeeDee takes 12-and-a-half hours to reach us.

    DeeDee is one of many small icy worlds that lie beyond the most distant planet in the solar system, Neptune. Such celestial bodies are called trans-Neptunian objects, or TNOs, the most famous of which is the dwarf planet Pluto. TNOs are “cosmic leftovers” from the formation 4 billion years ago of the giant planets, such as Jupiter and Neptune, and scientists study them to learn more about the history of our solar system.

    David Gerdes and his students at the University of Michigan first spotted DeeDee as a moving spot of light that appeared in just 14 of the tens of thousands of pictures taken by the Dark Energy Survey.

    The DES collaboration uses the state-of-the-art Dark Energy Camera on a telescope in Chile to map distant galaxies, to find supernovae and to search for patterns in the cosmic structure. DES began observing the sky in 2013 with the goal of shining light on dark energy, the mysterious substance that is accelerating the expansion of the universe, and collaboration scientists are primarily engaged in that task. Trans-Neptunian objects are not part of DES’ main science interests since they don’t tell us about the universe’s expansion.

    The DES supernova search, which takes pictures of the same part of the sky every week, sparked a bright idea in Gerdes: Instead of searching for spots that change their brightness over time, his students would search for spots whose positions change over time. Although DES looks at faraway galaxies, the backyard that is our own solar system is part of every picture the telescope takes. A dwarf planet could be captured in the DES data — one just had to look for it in the right way.

    “I wanted a self-contained project for my summer students that would be fun and achievable in 10 weeks,” Gerdes said. “Most topics using DES data are parts of long and complex analyses that are not manageable in such a short time frame.”

    Gerdes and his collaborators Masao Sako and Gary Bernstein at the University of Pennsylvania employed a technique developed for DES supernova searches and adjusted it to find slow-moving objects.

    “So far we’ve discovered over 50 new TNOs in our data,” Gerdes said. “DeeDee is the largest and most distant one.”

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    David Gerdes and his students at the University of Michigan discovered DeeDee, a potential dwarf planet at the edge of our solar system, in the Dark Energy Survey data. Photo courtesy of David Gerdes

    For DeeDee to be a dwarf planet, it has to fulfill four criteria: First, it must orbit the sun. Second, it cannot be a planet’s satellite, such as our moon. Third, it can’t have attracted other objects along its orbit to become its satellites, nor can it have forced their orbits out of its way. This is the major difference between a dwarf planet and a full-fledged planet. Since Pluto’s orbit is tied to Neptune’s, by this criterion Pluto was demoted to dwarf planet status.

    And last but not least, it has to have enough mass so that its own gravitational force compacts it into a spherical shape. DeeDee easily checks the first three qualifications, but its shape is not yet confirmed.

    The team speculates that DeeDee is round because it has a diameter of about 350 miles, which means that it likely has enough mass, and therefore enough gravitational force, to be spherical. Gerdes and his team are currently analyzing additional data from a radio telescope to determine its size.

    So far DeeDee’s chances of joining the elite group of dwarf planets are good. It might even earn its own mythological name, such as the dwarf planets Eris and Haumea, named after the ancient Greek goddess of discord and strife and the Hawaiian goddess of childbirth and fertility, respectively.

    Scouting for more

    DES uses the Dark Energy Camera to take its awe-inspiring pictures of the cosmos. The camera is mounted on the Victor M. Blanco 4-meter Telescope at the Cerro Tololo Inter-American Observatory in the Chilean Andes mountains. Fermilab, with the support of DOE’s Office of Science, led its construction and plays a major role in the DES data analysis, with a focus on illuminating the dark universe.

    “The DES data set is a very rich astronomical data set, and one critical step toward its discoveries is the calibration of the data,” said William Wester, Fermilab scientist involved in DES analysis. “The calibration helps determine the brightness of an object. In DeeDee’s case, this hints to its size.”

    Not every bright dot is actually a star or a galaxy, or even a TNO. It could also be an artifact or a reflection of light created by the camera.

    “You need to know what you are searching for, then you can formulate your question correctly for the data at hand and pull out from the multitude a sensible and manageable number of candidates,” said Jim Annis, Fermilab senior scientist.

    The number of possible objects in the DES data set easily approaches a billion, so thorough and reliable data sorting is critical to find promising candidates. Wester and Annis are well-practiced in similar exercises, having been involved in many different searches across the DES collaboration.

    DeeDee’s discovery is more than just that — it is another step on the way to a greater possible discovery: Planet 9. Planet 9 is a hypothetical ninth planet at the edge of our solar system with 10 times the mass of Earth. Otherwise unexplained patterns in the orbits of the largest-orbit TNOs hint at its existence. This opens the possibility that Planet 9 itself could be captured in the DES data, as in DeeDee’s case.

    The scientists of the DES collaboration, both at Fermilab and at its other 24 partner institutions, continue to mine the three years’ worth of data they’ve already collected and will gather more data through its conclusion in 2018. DeeDee is just one more of many discoveries to come.

    See the full article here .

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    Fermilab Campus

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

     
  • richardmitnick 11:32 am on October 12, 2016 Permalink | Reply
    Tags: , , Dark Energy Survey, , New Object Vies for Kuiper Belt Record, Object 2014 UZ224,   

    From Sky & Telescope: “New Object Vies for Kuiper Belt Record” 

    SKY&Telescope bloc

    Sky & Telescope

    October 11, 2016
    Kelly Beatty

    1
    Based on observations over the past three years, astronomers know that the Kuiper Belt object known as 2014 UZ224 has a highly elliptical, 1,140-year-long orbit that stretches nearly four times farther from the Sun than Pluto can ever be. NASA / JPL / Horizons

    Kuiper Belt. Minor Planet Center
    Kuiper Belt. Minor Planet Center

    Right now 2014 UZ224 lies nearly 14 billion kilometers away, ranking it third among the most distant objects known in the Kuiper Belt.

    Early today the IAU’s Minor Planet Center announced that astronomers in Chile have discovered a Kuiper Belt object, designated 2014 UZ224, that’s currently 91.6 astronomical units from the Sun. This corresponds to 13.7 billion kilometers (8.5 billion miles), nearly three times farther out than Pluto is at the moment. Only two other known KBOs are more distant: Eris (96.2 a.u.) and V774104 (103 a.u.) to…[?]

    In fact, 2014 UZ224 is closer to the Sun than average right now and headed inbound. Its 1,140-year-long orbit is quite eccentric, swinging as close as 38 a.u. (think “Pluto’s orbit”) and as far away as 179.8 a.u. Technically, astronomers don’t consider it part of the classical Kuiper Belt but instead a “scattered disk object” whose orbits have been perturbed outward due to encounters with Neptune.

    A team led by David Gerdes (University of Michigan) first spotted this object in August 2014, and then several times again in 2015 and 2016, using the 4-m Victor Blanco reflector at Cerro Tololo Inter-American Observatory in Chile. Thanks to CTIO’s Dark Energy Camera, which Gerdes helped develop for the Dark Energy Survey (DES), 2014 UZ224 stood out clearly in images despite its apparent magnitude of only 23½.

    Dark Energy Icon
    Dark Energy Camera. Built at FNAL
    Dark Energy Camera. Built at FNAL
    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile
    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile

    “The same combination of survey area and depth that makes DES a state-of-the-art cosmological survey also makes it a great tool for making discoveries in our own cosmic backyard,” Gerdes explains. “Our search for trans-Neptunian objects is a serendipitous by-product of the survey data.” The effort has yielded dozens of Kuiper Belt objects so far, even though the team has examined only a fraction of the amassed observations. “I hope 2014 UZ224 is not the most interesting thing we eventually find!” Gerdes adds.

    For now, his team knows little more about their distant discovery other than its orbit and apparent brightness. Given its distance, however, the object should be sizable — anywhere from 400 km across (if its surface is bright and 50% reflective) to 1,200 km (if very dark and 5% reflective). If its true size edges toward the larger end of this range, then 2014 UZ224 would likely qualify for dwarf-planet status.

    Fortunately, we should have a much better estimate of the object’s size very soon. Gerdes has used the ALMA radio-telescope array to measure the heat radiating from 2014 UZ224, which can be combined with the optical measurements to yield its size and albedo.

    “The Blanco telescope is decades old, but DECam is a state-of-the-art instrument that has revitalized it in several ways,” Gerdes explains. “First, the focal plane is huge, so the telescope now has a 3°-square field of view. And second, the DECam’s CCDs are extremely sensitive in the red and near-infrared light, which makes it particularly good at detecting high-redshift objects.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

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

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

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

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

     
  • richardmitnick 3:34 pm on August 30, 2016 Permalink | Reply
    Tags: , , Dark Energy Survey, , ,   

    From Symmetry: “Our galactic neighborhood” 

    Symmetry Mag

    Symmetry

    08/30/16
    Molly Olmstead

    What can our cosmic neighbors tell us about dark matter and the early universe?

    Milky Way NASA/JPL-Caltech /ESO R. Hurt
    Milky Way NASA/JPL-Caltech /ESO R. Hurt

    Imagine a mansion.

    Now picture that mansion at the heart of a neighborhood that stretches irregularly around it, featuring other houses of different sizes—but all considerably smaller. Cloak the neighborhood in darkness, and the houses appear as clusters of lights. Many of the clusters are bright and easy to see from the mansion, but some can just barely be distinguished from the darkness.

    This is our galactic neighborhood. The mansion is the Milky Way, our 100,000-light-years-across home in the universe. Stretching roughly a million light years from the center of the Milky Way, our galactic neighborhood is composed of galaxies, star clusters and large roving gas clouds that are gravitationally bound to us.

    The largest satellite galaxy, the Large Magellanic Cloud [LMC], is also one of the closest.

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    LMC

    It is visible to the naked eye from areas clear of light pollution in the Southern Hemisphere. If the Large Magellanic Cloud were around the size of the average American home—about 2,500 square feet—then by a conservative estimate the Milky Way mansion would occupy more than a full city block. On that scale, our most diminutive neighbors would occupy the same amount of space as a toaster.

    Our cosmic neighbors promise answers to questions about hidden matter and the ancient universe. Scientists are setting out to find them.

    What makes a neighbor

    If we are the mansion, the neighboring houses are dwarf galaxies. Scientists have identified about 50 possible galaxies orbiting the Milky Way and have confirmed the identities of roughly 30 of them. These galaxies range in size from several billion stars to only a few hundred. For perspective, the Milky Way contains somewhere between 100 billion to a trillion stars.

    Dwarf galaxies are the most dark-matter-dense objects known in the universe. In fact, they have far more dark matter than regular matter. Segue 1, our smallest confirmed neighbor, is made of 99.97 percent dark matter.

    Dark matter is key to galaxy formation. A galaxy forms when enough regular matter is attracted to a single area by the gravitational pull of a clump of dark matter.

    Dark matter halo  Image credit: Virgo consortium / A. Amblard / ESA
    Dark matter halo Image credit: Virgo consortium / A. Amblard / ESA

    Projects such as the Dark Energy Survey, or DES, find these galaxies by snapping images of a segment of the sky with a powerful telescope camera. Scientists analyze the resulting images, looking for the pattern of color and brightness characteristic of galaxies.

    Dark Energy Icon
    Dark Energy Camera,  built at FNAL
    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile
    Dark Energy Camera, built at FNAL; NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile

    Scientists can find dark matter clumps by measuring the motion and chemical composition of stars. If a smaller galaxy seems to be behaving like a more massive galaxy, observers can conclude a considerable amount of dark matter must anchor the galaxy.

    “Essentially, they are nearby clouds of dark matter with just enough stars to detect them,” says Keith Bechtol, a postdoctoral researcher at the University of Wisconsin-Madison and a member of the Dark Energy Survey.

    Through these methods of identification (and thanks to the new capabilities of digital cameras), the Sloan Digital Sky Survey kicked off the modern hunt for dwarf galaxies in the early 2000s.

    SDSS Telescope at Apache Point, NM, USA
    SDSS Telescope at Apache Point, NM, USA

    The survey, which looked at the northern part of the sky, more than doubled the number of known satellite dwarf galaxies from 11 to 26 galaxies between 2005 and 2010.

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

    Now DES, along with some other surveys, is leading the search. In the last few years DES and its Dark Energy Camera, which maps the southern part of the sky, brought the total to 50 probable galaxies.

    Dark matter mysteries

    Dwarf galaxies serve as ideal tools for studying dark matter. While scientists haven’t yet directly discovered dark matter, in studying dwarf galaxies they’ve been able to draw more and more conclusions about how it behaves and, therefore, what it could be.

    “Dwarf galaxies tell us about the small-scale structure of how dark matter clumps,” says Alex Drlica-Wagner of Fermi National Accelerator Laboratory, one of the leaders of the DES analysis. “They are excellent probes for cosmology at the smallest scales.”

    Dwarf galaxies also present useful targets for gamma-ray telescopes, which could tell us more about how dark matter particles behave.

    NASA/Fermi Telescope
    NASA/Fermi Gamma-ray Telescope

    ESA/Integral
    ESA/Integral Gamma-ray telescope

    Some models posit that dark matter is its own antiparticle. If that were so, it could annihilate when it meets other dark matter particles, releasing gamma rays. Scientists are looking for those gamma rays.

    But while studying these neighbors provides clues about the nature of dark matter, they also raise more and more questions. The prevailing cosmological theory of dark matter has accurately described much of what scientists observe in the universe. But when scientists looked to our neighbors, some of the predictions didn’t hold up.

    The number of galaxies appears to be lower than expected from calculations, for example, and those that are around seem to be too small. While some of the solutions to these problems may lie in the capabilities of the telescopes or the simulations themselves, we may also need to reconsider the way we think dark matter interacts.

    The elements of the neighborhood

    Dwarf galaxies don’t just tell us about dark matter: They also present a window into the ancient past. Most dwarf galaxies’ stars formed more than 10 billion years ago, not long after the Big Bang. Our current understanding of galaxy formation, according to Bechtol, is that after small galaxies formed, some of them merged over billions of years into larger galaxies.

    If we didn’t have these ancient neighbors, we’d have to peer all the way across the universe to see far enough back in time to glimpse galaxies that formed soon after the big bang. While the Milky Way and other large galaxies bustle with activity and new star formation, the satellite galaxies remain mostly static—snapshots of galaxies soon after their birth.

    “They’ve mostly been sitting there, waiting for us to study them,” says Josh Simon, an astronomer at the Carnegie Institution for Science.

    The abundance of certain elements in stars in dwarf galaxies can tell scientists about the conditions and mechanisms that produce them. Scientists can also look to the elements to learn about even older stars.

    The first generation of stars are thought to have looked very different than those formed afterward. When they exploded as supernovae, they released new elements that would later appear in stars of the next generation, some of which are found in our neighboring galaxies.

    “They do give us the most direct fingerprint we can get as to what those first stars might have been like,” Simon says.

    Scientists have learned a lot about our satellites in just the past few years, but there’s always more to learn. DES will begin its fourth year of data collection in August. Several other surveys are also underway. And the Large Synoptic Survey Telescope, an ambitious international project currently under construction in Chile, will begin operating fully in 2022.

    LSST/Camera, built at SLAC
    LSST Interior
    LSST telescope, currently under construction at Cerro Pachón Chile
    LSST/Camera, built at SLAC; SST telescope, currently under construction at Cerro Pachón Chile

    LSST will create a more detailed map than any of the previous surveys’ combined.

    From NatGeo, Inside the Milky Way, possibly the best science video ever made.

    See the full article here .

    Please help promote STEM in your local schools.

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    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 3:20 pm on June 3, 2016 Permalink | Reply
    Tags: , , Dark Energy Survey, ,   

    From Dark Energy Survey via Universe Today: “New ‘Einstein Ring’ Discovered By Dark Energy Camera” 

    Dark Energy Icon
    The Dark Energy Survey

    1
    2

    2 Jun , 2016
    Evan Gough, Universe Today

    A rare object called an Einstein Ring has been discovered by a team in the Stellar Populations group at the Instituto de Astrofísica de Canarias (IAC) in Spain. An Einstein Ring is a specific type of gravitational lensing.

    IAC

    Einstein’s Theory of General Relativity predicted the phenomena of gravitational lensing. Gravitational lensing tells us that instead of travelling in a straight line, light from a source can be bent by a massive object, like a black hole or a galaxy, which itself bends space time.

    Einstein’s General Relativity was published in 1915, but a few years before that, in 1912, Einstein predicted the bending of light. Russian physicist Orest Chwolson was the first to mention the ring effect in scientific literature in 1924, which is why the rings are also called Einstein-Chwolson rings.

    Gravitational lensing is fairly well-known, and many gravitational lenses have been observed. Einstein rings are rarer, because the observer, source, and lens all have to be aligned. Einstein himself thought that one would never be observed at all. “Of course, there is no hope of observing this phenomenon directly,” Einstein wrote in 1936.

    The team behind the recent discovery was led by PhD student Margherita Bettinelli at the University of La Laguna, and Antonio Aparicio and Sebastian Hidalgo of the Stellar Populations group at the Instituto de Astrofísica de Canarias (IAC) in Spain. Because of the rarity of these objects, and the strong scientific interest in them, this one was given a name: The Canarias Einstein Ring.

    5
    The “Canarias Einstein Ring.” The green-blue ring is the source galaxy, the red one in the middle is the lens galaxy. The lens galaxy has such strong gravity, that it distorts the light from the source galaxy into a ring. Because the two galaxies are aligned, the source galaxy appears almost circular. Image: This composite image is made up from several images taken with the DECam camera on the Blanco 4m telescope at the Cerro Tololo Observatory in Chile.

    There are three components to an Einstein Ring. The first is the observer, which in this case means telescopes here on Earth. The second is the lens galaxy, a massive galaxy with enormous gravity. This gravity warps space-time so that not only are objects drawn to it, but light itself is forced to travel along a curved path. The lens lies between Earth and the third component, the source galaxy. The light from the source galaxy is bent into a ring form by the power of the lens galaxy.

    When all three components are aligned precisely, which is very rare, the light from the source galaxy is formed into a circle with the lens galaxy right in the centre. The circle won’t be perfect; it will have irregularities that reflect irregularities in the gravitational force of the lens galaxy.

    4
    Another Einstein Ring. This one is named LRG 3-757. This one was discovered by the Sloan Digital Sky Survey, but this image was captured by Hubble’s Wide Field Camera 3. Image: NASA/Hubble/ESA

    The objects are more than just pretty artifacts of nature. They can tell scientists things about the nature of the lens galaxy. Antonio Aparicio, one of the IAC astrophysicists involved in the research said, “Studying these phenomena gives us especially relevant information about the composition of the source galaxy, and also about the structure of the gravitational field and of the dark matter in the lens galaxy.”

    Looking at these objects is like looking back in time, too. The source galaxy is 10 billion light years from Earth. Expansion of the Universe means that the light has taken 8.5 billion light years to reach us. That’s why the ring is blue; that long ago, the source galaxy was young, full of hot blue stars.

    The lens itself is much closer to us, but still very distant. It’s 6 billion light years away. Star formation in that galaxy likely came to a halt, and its stellar population is now old.

    The discovery of the Canarias Einstein Ring was a happy accident. Bettinelli was pouring over data from what’s known as the Dark Energy Camera (DECam) of the 4m Blanco Telescope at the Cerro Tololo Observatory, in Chile. She was studying the stellar population of the Sculptor dwarf galaxy for her PhD when the Einstein Ring caught her attention. Other members of the Stellar Population Group then used OSIRIS spectrograph on the Gran Telescopio CANARIAS (GTC) to observe and analyze it further.

    Gran Telescopio de Canarias exterior

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    DECam, built at FNAL
    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile
    DECam, built at FNAL; NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile

    The Dark Energy Survey (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 120 scientists from 23 institutions in the United States, Spain, the United Kingdom, Brazil, and Germany are working on the project. This collaboration [has built] an extremely sensitive 570-Megapixel digital camera, DECam, and [has mounted] it on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory high in the Chilean Andes. Started in Sept. 2012 and continuing for five years, DES will survey a large swath of the southern sky out to vast distances in order to provide new clues to this most fundamental of questions.

     
  • richardmitnick 9:00 pm on April 29, 2016 Permalink | Reply
    Tags: , , Dark Energy Survey, DEScientist of the Week: Ting Li   

    From DES: “DEScientist of the Week: Ting Li” 

    Dark Energy Icon

    The Dark Energy Survey

    April 29, 2016

    Meet Ting Li, Graduate Student at Texas A&M University!

    1

    Ting’s main research interest is to study the stellar substructure in our own Milky Way — dwarf galaxies and stellar streams. These features in the Milky Way can help us understand the nature of dark matter. She helps the team discover these stellar associations using DES data, and also follows them spectroscopically using the world’s largest optical telescopes, including Magellan Telescopes, the Vary Large Telescope, etc.

    6.5 meter Magellan Telescopes located at Carnegie’s Las Campanas Observatory, Chile.
    6.5 meter Magellan Telescopes located at Carnegie’s Las Campanas Observatory, Chile

    ESO/VLT at Cerro Paranal
    ESO/VLT at Cerro Paranal, Chile

    Apart from the scientific research, Ting also works on the DES infrastructures. Specifically, she works on the atmospheric transmission monitoring camera and the spectrophotometric calibration system for DECam. These two auxiliary systems will help DES to achieve high precision photometry, which is crucial for DES scientist to understand the nature of dark energy.

    We asked Ting a few more questions — here’s what she had to say:

    If you weren’t a scientist, what would your dream job be?

    I would want to be an astronaut, or more specifically, a job that can take me to space. Even if I could not go to space, I still hope that an instrument I build could go to space sometime in the future. I’m probably not physically strong enough to be qualified as a astronaut, but I’m good at astrophysics and instrumentation. I also speak many languages (English, Chinese, Japanese, little French and poor Spanish…). I still hope one day the dream would come true 🙂

    What is your secret talent?

    Ting-quisition: my graduate peers made this word for me, it means that Ting asks someone questions until that person “dies”. I’m not sure if that’s a talent or not, but I do like to ask questions and I learn a lot from asking.

    What do you think has been the most exciting advance in physics / astronomy in the last 10 years?

    Sky survey with CCDs, starting from SDSS.

    SDSS Telescope at Apache Point, NM, USA
    SDSS Telescope at Apache Point, NM, USA

    Astronomy has been significantly changed since the birth of CCDs and sky surveys. The progress is huge and revolutionary in the past 10 years. That’s why I joined DES and I think it will be the next revolution (before LSST starts).

    Thinking back to when you were an undergrad in physics (if applicable), was there anything you were taught then that is not taught now?

    I wish I had learned more about python and more about statistics.

    Any advice for aspiring scientists?

    This is the advice I would give to the students who might be considering going to graduate school and pursuing a career in scientific research.
    I would say that graduate school is tough, so make sure that’s what you want before you decide to go that route. If you decide to take it, then enjoy it. Graduate school is much more independent, compared to the undergraduate program. Instead of professors telling you what to do in your undergraduate study, you are the one who needs to make the decisions about yourself most of the time. You also have to learn a lot of new things by yourself and solve the problems by yourself. So make sure you pick a field that you like and you are interested in.
    The difficulties can sometimes be incredibly frustrating. However, part of getting closer to becoming a qualified Ph.D. is dealing with setbacks and experiencing failure. Maybe you don’t feel that you are gaining new knowledge every day, or maybe you feel that you are standing still after many days of hard work. But after several months or even years, you will know that you have already made a huge improvement in your research ability. You won’t see the changes every day, but be patient and persistent, and you will succeed.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition
    DECam, built at FNAL
    DECam, built at FNAL
    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    CTIO Victor M Blanco Telescope at Cerro Tololo which houses the DECAm

    The Dark Energy Survey (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 120 scientists from 23 institutions in the United States, Spain, the United Kingdom, Brazil, and Germany are working on the project. This collaboration [has built] an extremely sensitive 570-Megapixel digital camera, DECam, and [has mounted] it on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory high in the Chilean Andes. Started in Sept. 2012 and continuing for five years, DES will survey a large swath of the southern sky out to vast distances in order to provide new clues to this most fundamental of questions.

     
  • richardmitnick 3:01 pm on April 29, 2016 Permalink | Reply
    Tags: , , Dark Energy Survey, Superluminous Supernova   

    From DES- “From the DArchive: A Newly Discovered Superluminous Supernova” 

    Dark Energy Icon

    The Dark Energy Survey

    April 29, 2016
    Mathew Smith
    Edited by R.C. Wolf & R. Cawthon

    Science paper:
    DES14X3taz: A Type I Superluminous Supernova Showing a Luminous, Rapidly Cooling Initial Pre-Peak Bump

    In this paper we present DES14X3taz, a newly discovered superluminous supernova (SLSN). This particular SLSN is very unusual – if you look at the evolution of its brightness over time, or its light curve, there are two peaks (most only have one)! In our analysis, we attempt to explain what physical process might cause such an occurrence and determine if this is truly a unique event or common to all SLSNe.

    Although the initial DECam data was fairly indicative that this was a particularly interesting object, we had to use additional information to confirm our discovery. By combining optical light-curve data from DES and its sister survey, the Survey Using Decam for Superluminous Supernovae (SUDSS), we were able to plot the evolution of brightness over time (light-curve) of DES14X3taz and find its brightest point. We then used spectra obtained on the Gran Telescopino Canarias (GTC) in La Palma, Spain to estimate the distance to this event, and thus its peak brightness, and unambiguously confirmed that it is a SLSNe.

    Gran Telescopino Canarias exterior
    Gran Telescopino de Canaries interior
    Gran Telescopino de Canaries

    What really distinguishes DES14X3taz from previously discovered SLSNe is the presence of an early “bump” in the light curve prior to the main light-curve. The figure below shows these features for DES14X3taz.

    1

    In addition to detecting this bump, we were lucky to have observed this SLSN before explosion and to have observed it at many points during its lifetime; most other observed SLSNe have been discovered post-explosion or do not have such a large a sample of measurements.

    Our observations with DECam allowed us to obtain colour information, from observations in several filters, of the bump. This enabled us to probe the physical processes driving these super-luminous events by comparing our data to pre-existing theoretical models. In the figure below, the colored-circle points are real data, and the dashed lines represent theoretical observations for different physical processes that we think might be motivating this behavior.

    2

    Fitting models to the main curve show that the physical mechanism driving the explosion is consistent with a magnetar, a rapidly rotating neutron star (as seen in the match to the Extended Material Around the Star). In the figure, this is consistent with the solid lines. Fitting black-body curves to the DES data of DES14X3taz, we show that the initial peak cools rapidly, before a period of reheating, which drives the main part of the light-curve. Using chi-squared statistics, we compare photometric data of the initial peak with various models of shock-cooling and find that shock from material at an extended radius is consistent with observations. We also find a sample of previously discovered SLSNe that also exhibit this early bump in their light curves; therefore, we believe our findings suggest a unified physical interpretation for all SLSNe.

    SLSNe are a new class of transient event, with potentially exciting consequences for cosmology. Recent work (Inserra & Smartt 2014) has suggested that these events may even be “standardisable candles”, and thus useful to measure distances to the high redshift Universe. As these events are more luminous than traditional Type Ia supernovae they have the potential to extend SN cosmology to larger distances than currently possible. However, little is well-understood about the explosion mechanism driving these events and we will need to understand more about the origin of SLSNe as we explore utilizing them as cosmological probes.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition
    DECam, built at FNAL
    DECam, built at FNAL
    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    CTIO Victor M Blanco Telescope at Cerro Tololo which houses the DECAm

    The Dark Energy Survey (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 120 scientists from 23 institutions in the United States, Spain, the United Kingdom, Brazil, and Germany are working on the project. This collaboration [has built] an extremely sensitive 570-Megapixel digital camera, DECam, and [has mounted] it on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory high in the Chilean Andes. Started in Sept. 2012 and continuing for five years, DES will survey a large swath of the southern sky out to vast distances in order to provide new clues to this most fundamental of questions.

     
  • richardmitnick 7:46 pm on April 22, 2016 Permalink | Reply
    Tags: , , Dark Energy Survey, DEScientist of the Week: Boris Leistedt   

    From DES: “DEScientist of the Week: Boris Leistedt” 

    Dark Energy Icon

    The Dark Energy Survey

    April 22, 2016
    The Dark Energy Survey

    1

    Meet Boris Leistedt, Postdoc at New York University!

    Boris’ primary research interest is data analysis.

    We asked Boris a few more questions — here’s what he had to say:

    What is your favorite part about being a scientist?

    The people. Physics and astronomy are fascinating topics, but the job wouldn’t be the same without all the amazing people working in universities, research labs and institutes around the world. I feel lucky to know and collaborate with so many exceptional scientists who come from an incredible variety of backgrounds. Sharing a passion like physics with so many colleages (who sometimes become good friends!) is very precious and this is clearly what I enjoy the most in my job.

    When did you know you wanted to be a scientist?

    I’ve always been into sciences, maths and physics in particular, but I clearly remember the day I realized all my favourite topics converged in astronomy. I first studied electrical engineering at university but I eventually returned to physics by the end of my undergraduate curriculum, and it is a research internship that crystalized my interest in observational cosmology and pushed me to pursue a PhD.

    What motivates / inspires you?

    What motivates me most is to work on hard problems involving complicated data sets and interesting physics. In that respect cosmology is perfect because it currently has a unique position at the intersection of physics, mathematics, and computer science. To answer profound questions about the Universe, for example to know its age or dynamics, cosmologists analyse very large data sets gathered by telescope and satellites, and confront them to mathematical predictions. We typically use very advanced methods from other fields such as statistics and computer science. Knowing that pretty much any topic trending in these fields might be relevant to my work is very exciting.

    Any advice for aspiring scientists?

    Follow your dreams and never give up. You are clever enough to do whatever you want in life. The world is full of great people who will give you advice and support you. You just need to be vocal about your goals and to be ready to gather all the help you can. Don’t worry, you will have tons of opportunities to give it back and support others too in due course!

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

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    DECam, built at FNAL
    DECam, built at FNAL
    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    CTIO Victor M Blanco Telescope at Cerro Tololo which houses the DECAm

    The Dark Energy Survey (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 120 scientists from 23 institutions in the United States, Spain, the United Kingdom, Brazil, and Germany are working on the project. This collaboration [has built] an extremely sensitive 570-Megapixel digital camera, DECam, and [has mounted] it on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory high in the Chilean Andes. Started in Sept. 2012 and continuing for five years, DES will survey a large swath of the southern sky out to vast distances in order to provide new clues to this most fundamental of questions.

     
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