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  • richardmitnick 9:52 am on October 19, 2016 Permalink | Reply
    Tags: , , Dark Matter, , No Number Of Additional Galaxies Can Prevent The Universe From Needing Dark Matter   

    From Ethan Siegel: “No Number Of Additional Galaxies Can Prevent The Universe From Needing Dark Matter” 

    Ethan Siegel

    The Hubble eXtreme Deep Field (XDF), which revealed approximately 50% more galaxies-per-square-degree than the previous Ultra-Deep Field. Image credit: NASA; ESA; G. Illingworth, D. Magee, and P. Oesch, University of California, Santa Cruz; R. Bouwens, Leiden University; and the HUDF09 Team.

    It was perhaps the biggest news in space since we detected gravitational waves: instead of “billions and billions” of galaxies, there are at least two trillion of them — that’s 2,000,000,000,000 — within our observable Universe. Previously, the best estimate was merely 170 billion, coming from galaxy counts informed by the deepest observations of the Hubble Space Telescope. You might wonder, with more than ten times the galaxies present than we’d previously thought, whether this means that dark matter might not be necessary after all. Let’s see what the science has to say.

    The different shapes, structures and morphologies of some of the galaxies in Hickson Compact Group 59 show evidence for a wide variety of stars, plus gas, plasma and dust as well. Image credit: ESA/Hubble and NASA.

    If you take a look at stars, galaxies or clusters of galaxies in the nearby Universe, you can gather all the light available over the full set of wavelengths covering the electromagnetic spectrum. Because astronomers think we know how stars work, by measuring all of that light, we can calculate how much mass is present in the form of stars. This is one form of normal matter: matter made up of protons, neutrons and electrons. But stars aren’t all of it; there are plenty of other sources as well, like gas, dust, plasma, planets and black holes.

    A multiwavelength view of the Milky Way reveals the presence of many different phases and states of normal matter, far beyond the stars we’re used to seeing in visible light. Image credit: NASA.

    Each of them leave their own signature and each has its own methods to constrain or detect its presence and abundance. You might think that adding all of these different components together is how we get an estimate for the amount of matter in the Universe, but that’s actually a horrible approach, and not how we do it at all. Instead, there are three separate, independent signatures that measure the total normal matter content of the Universe all at once.

    An illustration of clustering patterns due to Baryon Acoustic Oscillations. Image credit: Zosia Rostomian.

    One is to look at the clustering data of all the different galaxies we observe. If you put your finger on one galaxy and ask, “how likely am I to find a galaxy at a particular distance away,” you’ll find a nice, smooth distribution as you increase that distance. But thanks to normal matter, there’s an increased likelihood of finding a galaxy that’s 500 million light years away versus finding one that’s either 400 or 600 million light years. The amount of normal matter present determines this distance, and thanks to this technique, we get a very particular number for the amount of normal matter: about 5% of the critical density.

    The fluctuations in the Cosmic Microwave Background, or the Big Bang’s leftover glow, contain a plethora of information about what’s encoded in the Universe’s history. Image credit: ESA and the Planck Collaboration.

    A second is to look at the fluctuations in the cosmic microwave background. The Big Bang’s leftover glow is one of the best signals we have from the young Universe to piece together what it was like in the distant past. While this map of the slightly hotter and cooler spots might look like random fluctuations to the naked eye, the fluctuations are larger than average on a very specific scale — about 0.5º — that corresponds to a very particular density of normal matter in the Universe. That density? About 5% of the critical density, the same as from the first method.

    An ultra-distant quasar will encounter gas clouds on the light’s journey to Earth, with some of the most distant clouds containing ultra-pristine gas that has never formed stars. Image credit: Ed Janssen, ESO.

    And finally, you can look at the earliest matter you can observe: pristine clouds of gas that have never formed a single star. Stars don’t form everywhere in the Universe at once, so if you can find an ultra-bright galaxy or a quasar that emits light from when the Universe was less than one billion years old, you might get lucky enough to find an intervening cloud of gas that absorbs some of that light. Those absorption features tell you what elements are present and in what abundance, and that in turn tells you how much normal matter must be present in the Universe to form those ratios of elements like hydrogen, deuterium, helium-3, helium-4 and lithium-7. The result from all this data? A Universe with about 5% of the critical density in the form of normal matter.

    The predicted abundances of helium-4, deuterium, helium-3 and lithium-7 as predicted by Big Bang Nucleosynthesis, with observations shown in the red circles. Image credit: NASA/WMAP Science Team.

    The fact that these three wildly independent methods all give the same answer for the density of normal matter is a particularly compelling argument that we know how much normal matter is in the Universe. When you hear a story about more stars, galaxies, gas or plasma being found in the Universe, that’s good, because it helps us understand where that 5% is located and how it’s distributed. More stars might mean less gas; more plasma might mean less dust; more planets and brown dwarfs might mean fewer black holes. But it can’t encroach on the other 27% that dark matter makes up, or the other 68% that dark energy composes.

    The percentages of normal matter, dark matter and dark energy in the Universe, as measured by our best cosmic probes before (L) and after (R) the first results of the Planck mission. Image credit: ESA and the Planck Collaboration.

    Those same sources of data that tell us the normal matter density — plus many others — can all be combined to paint a single cohesive picture of the Universe: 68% dark energy, 27% dark matter and 5% normal matter, with no more than 0.1% of anything else like neutrinos, photons or gravitational waves. It’s important to remember that the “5% normal matter” doesn’t just include stars or other light-emitting forms of matter, but rather everything that’s composed of protons, neutrons and electrons in the entire Universe. More stars, more galaxies or more sources of light might be a remarkably interesting discovery, but it doesn’t mean that we don’t need dark matter. In fact, to obtain the Universe as we observe it to be, dark matter is an indispensable ingredient.

    Access mp4 video here .

    The discovery that there are more galaxies than we’d ever known before better informs us how the matter we have is distributed, but does nothing to change what the matter itself fundamentally is. We’re still on the hunt for exactly what the nature of dark matter and dark energy are, to be sure. From a cosmic perspective, not only don’t these new observations change our picture of what’s out there, but in order for dark matter and dark energy to be wrong, something would have to be off about what we’ve already seen. Nevertheless, we have no choice but to keep looking. The mysteries of nature might not yield easily, but neither does human curiosity.

    See the full article here .

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    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

  • richardmitnick 6:33 pm on October 17, 2016 Permalink | Reply
    Tags: Dark Matter, , ,   

    From SURF: “LUX: The end of an era” 

    SURF logo
    Sanford Underground levels

    Sanford Underground Research facility

    October 17, 2016
    Constance Walter

    The top of the the LUX detector can be seeen emerging from the water tank. From Left Doug Tiedt, Wei Ji, and Ken Wilson work on the removal.
    Credit: Matthew Kapust

    Five years ago, the Large Underground Xenon (LUX) experiment began its long journey to the Davis Cavern on the 4850 Level of Sanford Lab. Results published in 2013 proved LUX to be the most sensitive dark matter experiment in the world. When LUX completed its 300-live-day run in May of this year, the world learned LUX was even more sensitive than previously determined.

    Earlier this month, the LUX collaboration began decommissioning the experiment. “It’s bittersweet, the end of an era, but it was time,” said Simon Fiorruci, a LUX collaborator from Lawrence Berkeley National Laboratory.

    “The detector delivered everything we promised in sensitivity and then went even further,” said Rick Gaitskell, physics professor at Brown University and a co-spokesperson for LUX. “So there is great pride, but also sadness to see an old friend being pensioned off. Of course, the success of LUX acted as an important pathfinder for the larger LZ experiment.”

    LZ (LUX-ZEPLIN), the second-generation dark matter detector, will hold 30 times more xenon and be 100 times more sensitive than LUX.

    Lux Zeplin project at SURF
    Lux Zeplin project at SURF

    It will continue the hunt for WIMPs, or weakly interacting massive particles. The top prospects for explaining dark matter are observed only through gravitational effects on galaxies.

    “The nature of dark matter, which comprises 85 percent of all matter in the universe, is one of the most perplexing mysteries in all of contemporary science,” said Harry Nelson, LZ spokesperson and a physics professor at University of California, Santa Barbara. “Just as science has elucidated the nature of familiar matter, LZ will lead science in testing one of the most attractive hypotheses for the nature of dark matter.”

    LZ recently received approval from the Department of Energy that set in motion the build-out of major components and the preparation of the Davis Cavern. But to make way for the new experiment, LUX must be completely uninstalled—with the exception of the water tank in which LZ will be housed.

    “Essentially, we have to do everything we did to build the LUX detector, but in reverse,” Gaitskell said.

    But decommissioning isn’t as simple as pulling the detector vessel out of the 72,000-gallon water tank in which it has resided for four years. The team first had to remove the 370 kg of xenon and prepare it for transport to SLAC National Accelerator Laboratory. Then they disabled the support system and disconnected thousands of cables. Next, the detector was removed from the water tank and readied for its trip to the surface. The vessel will be opened and the parts analyzed for possible use in LZ.

    “By March we should be removing the last table and chair and handing the space over to LZ,” Fiorruci said.

    Construction of LZ will begin in 2017. Operations are expected to begin in 2020.

    “And so, the process of build, operate, and deconstruct begins again,” Gaitskell said.

    See the full article here .

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    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.

    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

  • richardmitnick 10:47 am on October 16, 2016 Permalink | Reply
    Tags: Acceleration relation found among spiral and irregular galaxies challenges current understanding of dark matter, , , , Dark Matter, Gravitational acceleration,   

    From phys.org: “Acceleration relation found among spiral and irregular galaxies challenges current understanding of dark matter” 


    September 21, 2016 [Just found this in social media.]

    In spiral galaxies such as NGC 6946, researchers found that a 1-to-1 relationship between the distribution of stars plus gas and the acceleration caused by gravity exists.

    In the late 1970s, astronomers Vera Rubin and Albert Bosma independently found that spiral galaxies rotate at a nearly constant speed: the velocity of stars and gas inside a galaxy does not decrease with radius, as one would expect from Newton’s laws and the distribution of visible matter, but remains approximately constant. Such ‘flat rotation curves’ are generally attributed to invisible, dark matter surrounding galaxies and providing additional gravitational attraction.

    Now a team led by Case Western Reserve University researchers has found a significant new relationship in spiral and irregular galaxies: the acceleration observed in rotation curves tightly correlates with the gravitational acceleration expected from the visible mass only.

    “If you measure the distribution of star light, you know the rotation curve, and vice versa,” said Stacy McGaugh, chair of the Department of Astronomy at Case Western Reserve and lead author of the research.

    The finding is consistent among 153 spiral and irregular galaxies, ranging from giant to dwarf, those with massive central bulges or none at all. It is also consistent among those galaxies comprised of mostly stars or mostly gas.

    In a paper accepted for publication by the journal Physical Review Letters and posted on the preprint website arXiv, McGaugh and co-authors Federico Lelli, an astronomy postdoctoral scholar at Case Western Reserve, and James M. Schombert, astronomy professor at the University of Oregon, argue that the relation they’ve found is tantamount to a new natural law.

    An astrophysicist who reviewed the study said the findings may lead to a new understanding of internal dynamics of galaxies.

    “Galaxy rotation curves have traditionally been explained via an ad hoc hypothesis: that galaxies are surrounded by dark matter,” said David Merritt, professor of physics and astronomy at the Rochester Institute of Technology, who was not involved in the research. “The relation discovered by McGaugh et al. is a serious, and possibly fatal, challenge to this hypothesis, since it shows that rotation curves are precisely determined by the distribution of the normal matter alone. Nothing in the standard cosmological model predicts this, and it is almost impossible to imagine how that model could be modified to explain it, without discarding the dark matter hypothesis completely.”

    McGaugh and Schombert have been working on this research for a decade and with Lelli the last three years. Near-infrared images collected by NASA’s Spitzer Space Telescope during the last five years allowed them to establish the relation and that it persists for all 153 galaxies.

    The key is that near-infrared light emitted by stars is far more reliable than optical-light for converting light to mass, Lelli said.

    The researchers plotted the radial acceleration observed in rotation curves published by a host of astronomers over the last 30 years against the acceleration predicted from the observed distribution of ordinary matter now in the Spitzer Photometry & Accurate Rotation Curves database McGaugh’s team created. The two measurements showed a single, extremely tight correlation, even when dark matter is supposed to dominate the gravity.

    “There is no intrinsic scatter, which is how far the data differ on average from the mean when plotted on a graph,” McGaugh said. “What little scatter is found is consistent with stellar mass-to-light ratios that vary a little from galaxy to galaxy.”

    Lelli compared the relation to a long-used natural law. “It’s like Kepler’s third law for the solar system: if you measure the distance of each planet from the sun, you get the orbital period, or vice versa” he said. “Here we have something similar for galaxies, with about 3,000 data points.”

    “In our case, we find a relation between what you see in normal matter in galaxies and what you get in their gravity,” McGaugh said. “This is important because it is telling us something fundamental about how galaxies work.”

    Arthur Kosowsky, professor of physics and astronomy at the University of Pittsburgh, was not involved but reviewed the research.

    “The standard model of cosmology is remarkably successful at explaining just about everything we observe in the universe,” Kosowsky said. “But if there is a single observation which keeps me awake at night worrying that we might have something essentially wrong, this is it.”

    He said McGaugh and collaborators have steadily refined the spiral galaxy scaling relation for years and called this latest work a significant advance, reducing uncertainty in the mass in normal matter by exploiting infrared observations.

    “The result is a scaling relation in the data with no adjustable parameters,” Kosowky said. “Throughout the history of physics, unexplained regularities in data have often pointed the way towards new discoveries.”

    McGaugh and his team are not pressing any theoretical interpretation of their empirical relation at this point.

    “The natural inference is that this law stems from a universal force such as a modification of gravity like MOND, the hypothesis of Modified Newtonian Dynamics proposed by Israeli physicist Moti Milgrom. But it could also be something in the nature of dark matter like the superfluid dark matter proposed by Justin Khoury,” McGaugh said. “Most importantly, whatever theory you want to build has to reproduce this.”

    See the full article here .

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    Phys.org™ (formerly Physorg.com) is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004, Phys.org’s readership has grown steadily to include 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page. set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

  • richardmitnick 11:52 am on October 7, 2016 Permalink | Reply
    Tags: , , Correlation between galaxy rotation and visible matter puzzles astronomers, Dark Matter, ,   

    From physicsworld: “Correlation between galaxy rotation and visible matter puzzles astronomers” 


    Oct 7, 2016
    Keith Cooper

    Strange correlation: why is galaxy rotation defined by visible mass? No image credit.

    A new study of the rotational velocities of stars in galaxies has revealed a strong correlation between the motion of the stars and the amount of visible mass in the galaxies. This result comes as a surprise because it is not predicted by conventional models of dark matter.

    Stars on the outskirts of rotating galaxies orbit just as fast as those nearer the centre. This appears to be in violation of Newton’s laws, which predict that these outer stars would be flung away from their galaxies. The extra gravitational glue provided by dark matter is the conventional explanation for why these galaxies stay together. Today, our most cherished models of galaxy formation and cosmology rely entirely on the presence of dark matter, even though the substance has never been detected directly.

    These new findings, from Stacy McGaugh and Federico Lelli of Case Western Reserve University, and James Schombert of the University of Oregon, threaten to shake things up. They measured the gravitational acceleration of stars in 153 galaxies with varying sizes, rotations and brightness, and found that the measured accelerations can be expressed as a relatively simple function of the visible matter within the galaxies. Such a correlation does not emerge from conventional dark-matter models.

    Mass and light

    This correlation relies strongly on the calculation of the mass-to-light ratio of the galaxies, from which the distribution of their visible mass and gravity is then determined. McGaugh attempted this measurement in 2002 using visible light data. However, these results were skewed by hot, massive stars that are millions of times more luminous than the Sun. This latest study is based on near-infrared data from the Spitzer Space Telescope.

    NASA/Spitzer Telescope
    NASA/Spitzer Telescope

    Since near-infrared light is emitted by the more common low-mass stars and red giants, it is a more accurate tracer for the overall stellar mass of a galaxy. Meanwhile, the mass of neutral hydrogen gas in the galaxies was provided by 21 cm radio-wavelength observations.

    McGaugh told physicsworld.com that the team was “amazed by what we saw when Federico Lelli plotted the data.”

    The result is confounding because galaxies are supposedly ensconced within dense haloes of dark matter.

    Spherical halo of dark matter. cerncourier.com

    Furthermore, the team found a systematic deviation from Newtonian predictions, implying that there is some other force is at work beyond simple Newtonian gravity.

    “It’s an impressive demonstration of something, but I don’t know what that something is,” admits James Binney, a theoretical physicist at the University of Oxford, who was not involved in the study.

    This systematic deviation from Newtonian mechanics was predicted more than 30 years ago by an alternate theory of gravity known as modified Newtonian dynamics (MOND). According to MOND’s inventor, Mordehai Milgrom of the Weizmann Institute in Israel, dark matter does not exist, and instead its effects can be explained by modifying how Newton’s laws of gravity operate over large distances.

    “This was predicted in the very first MOND paper of 1983,” says Milgrom. “The MOND prediction is exactly what McGaugh has found, to a tee.”

    However, Milgrom is unhappy that McGaugh hasn’t outright attributed his results to MOND, and suggests that there’s nothing intrinsically new in this latest study. “The data here are much better, which is very important, but this is really the only conceptual novelty in the paper,” says Milgrom.

    No tweaking required

    McGaugh disagrees with Milgrom’s assessment, saying that previous results had incorporated assumptions that tweak the data to get the desired result for MOND, whereas this time the mass-to-light ratio is accurate enough that no tweaking is required.

    Furthermore, McGaugh says he is “trying to be open-minded”, by pointing out that exotic forms of dark matter like superfluid dark matter or even complex galactic dynamics could be consistent with the data. However, he also feels that there is implicit bias against MOND among members of the astronomical community.

    “I have experienced time and again people dismissing the data because they think MOND is wrong, so I am very consciously drawing a red line between the theory and the data.”

    Much of our current understanding of cosmology relies on cold dark matter, so could the result threaten our models of galaxy formation and large-scale structure in the universe? McGaugh thinks it could, but not everyone agrees.

    Way too complex

    Binney points out that dark-matter simulations struggle on the scale of individual galaxies because “the physics of galaxy formation is way too complex to compute properly,” he says, the implication being that it is currently impossible to say whether dark matter can explain these results or not. “It’s unfortunately beyond the powers of humankind at the moment to know.”

    That leaves the battle between dark matter and alternate models of gravitation at an impasse. However, Binney points out that dark matter has an advantage because it can also be studied through observations of galaxy mergers and collisions between galaxy clusters. Also, there are many experiments that are currently searching for evidence of dark-matter particles.

    McGaugh’s next step is to extend the study to elliptical and dwarf spheroidal galaxies, as well as to galaxies at greater distances from the Milky Way.

    The research is to be published in Physical Review Letters and a preprint is available on arXiv.

    See the full article here .

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  • richardmitnick 11:15 am on October 4, 2016 Permalink | Reply
    Tags: , , , Dark Matter, ,   

    From Astronomy: Women in STEM – “How Vera Rubin discovered dark matter” 

    Astronomy magazine


    October 04, 2016
    Sarah Scoles

    A young Vera Rubin was already observing the stars when she was an undergraduate at Vassar College, where she earned her bachelor’s degree in astronomy in 1948. Archives & Special Collections, Vassar College Library

    In the late 1970s, Vera Rubin and Kent Ford of the Carnegie Institution of Washington stared, confused, at the punch-card readouts from their observations of the Andromeda Galaxy.

    Andromeda Galaxy Adam Evans
    Andromeda Galaxy, Adam Evans”

    The vast spiral seemed to be rotating all wrong. The stuff at the edges was moving just as fast as the stuff near the center, apparently violating Newton’s Laws of Motion (which also govern how the planets move around our Sun). While the explanation for that strange behavior didn’t become clear to Rubin until two years later, these printouts represented the first direct evidence of dark matter.

    Scientists now know that dark matter comprises some 84 percent of the universe’s material. Its invisible particles swarm and stream and slam through the whole cosmos. It affects how stars move within galaxies, how galaxies tug on each other, and how all that matter clumped together in the first place. It is to the cosmos like air is to humans: ubiquitous, necessary, unseen but felt. The discovery of this strange substance deserves a Nobel Prize. But, for Rubin, none has come, although she has long been a “people’s choice” and predicted winner.

    In the past few years, scientists have gotten that free trip to Sweden for demonstrating that neutrinos have mass, for inventing blue LEDs, for isolating graphene’s single carbon layer, and for discovering dark energy. All of these experiments and ideas are worthy of praise, and some, like dark energy, even tilted the axis of our understanding of the universe. But the graphene work began in 2004; dark energy observations happened in the late ’90s; scientists weighed neutrinos around the same time; and blue LEDs burst onto the scene a few years before that. Rubin’s work on dark matter, on the other hand, took place in the 1970s. It’s like the committee cannot see her, although nearly all of astrophysics feels her influence.

    Rubin is now 87. She is too infirm for interviews. And because the Nobel can only be awarded to the living, time is running out for her.

    Emily Levesque, an astronomer at the University of Washington in Seattle who has spoken out about Rubin’s notable lack of a Nobel, says, “The existence of dark matter has utterly revolutionized our concept of the universe and our entire field; the ongoing effort to understand the role of dark matter has basically spawned entire subfields within astrophysics and particle physics at this point. Alfred Nobel’s will describes the physics prize as recognizing ‘the most important discovery’ within the field of physics. If dark matter doesn’t fit that description, I don’t know what does.”

    There’s no way to prove why Rubin remains prize-less. But a webpage showing images of past winners looks like a 50th-reunion publication from a boys’ prep school. No woman has received the Nobel Prize in physics since 1963, when Maria Goeppert Mayer shared it with Eugene Wigner and J. Hans Jensen for their work on atomic structure and theory. And the only woman other than Mayer ever to win was Marie Curie. With statistics like that, it’s hard to believe gender has nothing to do with the decision.

    Some, like Chanda Prescod-Weinstein of the Massachusetts Institute of Technology, have called for no men to accept the prize until Rubin receives it. But given the human ego and nearly million-dollar prize amount, that’s likely to remain an Internet-only call to action.

    No room for women

    Rubin isn’t unfamiliar with discrimination more outright than the Nobel committee’s. Former colleague Neta Bahcall of Princeton University tells a story about a trip Rubin took to Palomar Observatory outside of San Diego early in her career. For many years, the observatory was a researcher’s man cave. Rubin was one of the first women to gain access to its gilt-edged, carved-pillar grandeur. But while she was allowed to be present, the building had no women’s restroom, just urinal-studded water closets.

    “She went to her room, she cut up paper into a skirt image, and she stuck it on the little person image on the door of the bathroom,” says Bahcall. “She said, ‘There you go; now you have a ladies’ room.’ That’s the type of person Vera is.”

    Rubin has continued to champion women’s rights to — and rights within — astronomy. “She frequently would see the list of speakers [at a conference],” says Bahcall, “and if there were very few or no women speakers, she would contact [the organizers] and tell them they have a problem and need to fix it.”

    But, as Rubin told science writer Ann Finkbeiner for Astronomy in 2000, she is “getting fed up. . . . What’s wrong with this story is that nothing’s changing, or it’s changing so slowly.”

    An early start

    Rubin, born in 1928, first found her interest in astronomy when her family moved to Washington, D.C. Windows lined the wall next to her bed. She watched the stars move, distant and unreachable. “What fascinated me was that if I opened my eyes during the night, they had all rotated around the pole,” she told David DeVorkin in 1995 as part of the American Institute of Physics oral history interview series. “And I found that inconceivable. I just was captured.”

    She started watching meteor showers and drew maps of the streaks, which striped the sky for a second and then were gone. She built a telescope and chose astronomical topics for English papers, using every subject as an opportunity to peer deeper into the universe. “How could you possibly live on this Earth and not want to study these things?” she wondered, retelling the story to DeVorkin.

    While her parents supported her, it was a different story at school. When she told her physics teacher, for instance, that she had received a scholarship to Vassar College, he said, “As long as you stay away from science, you should do OK.”

    She didn’t.

    Rubin and Kent for (white hat) check on their equipment at Lowell Observatory in 1965 during one of their first observing runs together. Carnegie Institution, Department of Terrestrial Magnetism

    Rotation of the universe

    After receiving her bachelor’s degree from Vassar, Rubin enrolled in graduate school in astronomy at Cornell University in Ithaca, New York. Ensconced in Ithaca’s gorges and working with astronomer Martha Stahr Carpenter, Rubin began to hunt around for a master’s thesis idea. Carpenter was obsessed with galaxies and how their innards moved. “Her course in galaxy dynamics really set me off on a direction that I followed almost my entire career,” said Rubin.

    One day, her new husband, Robert Rubin, brought her a journal article by astronomer George Gamow. In it, Gamow wondered, “What if we took the way solar systems rotate and applied it to how galaxies move in the universe?”

    Rubin wondered, “What if, indeed?” and took that wonder a step further. She began to measure how galaxies moved. Did some cluster together in their travel through space — perhaps rotating around a pole, like the planets rotate around the common Sun? Was it random?

    While gathering data, she found a plane that was denser with galaxies than other regions. She didn’t know it at the time, and no one else would discover it for years, but she had identified the “supergalactic plane,” the equator of our home supercluster of galaxies.

    When she presented her thesis, William Shaw, one of her advisers, told her just two things: One, the word data is plural. Two, her work was sloppy. But, he continued, she should consider presenting it at the American Astronomical Society (AAS) meeting. Or, rather, she should consider having it presented for her. Because she was pregnant with her first child — due just a month before the meeting — and not a member of the society, he graciously volunteered to give a talk on her results. “In his name,” she clarified to DeVorkin. “Not in my name. I said to him, ‘Oh, I can go.’ ”

    She called her talk “Rotation of the Universe,” ascribing the ambitious title to “the enthusiasm of youth,” as she recalled. At the AAS meeting, she didn’t know anyone, and she thought of herself as a different category of human. “I put these people in a very special class. They were professional astronomers, and I was not,” she said, showcasing a classic case of impostor syndrome, a psychological phenomenon in which people don’t feel they deserve their accomplishments and status and will inevitably be exposed as frauds. “One of the biggest problems in my life [during] those years was really attempting to answer the question to myself, ‘Will I ever really be an astronomer?’ ”

    The “real astronomers” pounced on her result (except, notably, Martin Schwarzschild, who defined how big black holes are). “My paper was followed by a rather acrimonious discussion,” she told DeVorkin. “I didn’t know anyone, so I didn’t know who these people were that were getting up and saying the things they said. As I recall, all the comments were negative.”

    Her paper was never published.

    Back into the field

    For six months after her first child was born, Rubin stayed home. But while she loved having a child, staying at home emptied her. She cried every time The Astrophysical Journal arrived at the house. “I realized that as much as we both adored this child, there was nothing in my background that had led me to expect that [my husband] would go off to work each day doing what he loved to do, and I would stay home with this lovely child,” she said to DeVorkin. “I really found it very, very hard. And it was he who insisted that I go back to school.”

    She was accepted into a Ph.D. program at Georgetown University in Washington, D.C., and she discovered that galaxies did clump together, like iron filings, and weren’t randomly strewn. The work, though now part of mainstream astronomy, was largely ignored for decades; that lack of reinforcement perhaps contributed to her lingering, false feeling that she wasn’t a real astronomer. As she described it, “My husband heard my question often, ‘Will I ever really be an astronomer?’ First I thought when I’d have a Ph.D., I would. Then even after I had my Ph.D., I wondered if I would.”

    Rubin operates the 2.1-meter telescope at Kitt Peak National Observatory. Kent Ford’s spectograph is attached so they can measure the speed of matter at different distances from galaxies’ centers. NOAO/AURA/NSF

    Mysteriously flat

    In 1965, after a stint as a professor at Georgetown, Rubin began her work at the Carnegie Institution’s Department of Terrestrial Magnetism in Washington, D.C., where she met astronomer Kent Ford and his spectacular spectrometer, which was more sensitive than any other at the time.

    A spectrometer takes light and splits it up into its constituent wavelengths. Instead of just showing that a fluorescent bulb glows white, for instance, it would show how much of that light is blue and how much yellow, and which specific wavelengths of blue and yellow. Ford’s spectrometer stood out from others at the time because it employed state-of-the-art photomultipliers that let researchers study small regions of galaxies, and not simply the entire objects.

    With this device, Ford and Rubin decided to look at quasars — distant galaxies with dynamic, supermassive black holes at their centers. But this was competitive work: Quasars had just been discovered in 1963, and their identity was in those days a mystery that everyone wanted to solve. Rubin and Ford didn’t have their own telescope and had to request time on the world-class instruments that astronomers who worked directly for the observatories could access all the time. Rubin didn’t like the competition.

    “After about a year or two, it was very, very clear to me that that was not the way I wanted to work,” she told Alan Lightman in another American Institute of Physics oral history interview. “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 and Ford chose to focus on the nearby Andromeda Galaxy (M31). It represented a return to Rubin’s interest in galaxy dynamics. “People had inferred what galaxy rotations must be like,” said Rubin, “but no one had really made a detailed study to show that that was so.” Now, because of Ford’s out-of-this-world spectrograph, they could turn the inferences into observations.

    When they pointed the telescope at M31, they expected to see it rotate like the solar system does: Objects closer to the center move faster than ones toward the edge. Mass causes gravity, which determines the speed of rotation. Since most of the stars, dust, and gas — and therefore gravity — is clustered in the middle of galaxies, the stuff on the periphery shouldn’t feel much pull. They concentrated their observations on Hydrogen-II (HII) regions — areas of ionized hydrogen gas where stars have recently formed — at different distances from the galaxy’s center. But no matter how far out they looked, the HII regions seemed to be moving at the same speed. They weren’t slowing down.

    “We kept going farther and farther out and had some disappointment that we never saw anything,” says Ford. “I do remember my puzzling at the end of the first couple of nights that the spectra were all so straight,” said Rubin, referring to the unchanging speed of the various HII regions.

    They didn’t know what, if anything, it meant yet.

    The project took years and involved treks westward to telescopes. Ford recalls flying to Flagstaff, Arizona, dragging the spectrograph from the closet, working for a few nights at Lowell, and then throwing the instrument into a Suburban so they could drive it to Kitt Peak. “We both thought we were better at guiding the telescope,” he says. They raced each other to be first to the eyepiece.

    The data came out on punch cards, which Rubin spent hours analyzing in a cubbyhole beneath a set of stairs. They all showed the same thing.

    Rubin and Ford moved on from M31 to test other galaxies and their rotation curves. Like an obsessive artist, each painted the same picture. Although the result contradicted theory, and although they didn’t understand what it meant, no one doubted their data. “All you had to do was show them a picture of the spectrum,” Rubin told Lightman. “It just piled up too fast. Soon there were 20, then 40, then 60 rotation curves, and they were all flat.”

    A dark answer

    Dark matter existed as a concept, first proposed by astronomers like Jan Oort in 1932 and Fritz Zwicky in 1933, who also noticed discrepancies in how much mass astronomers could see and how much physics implied should be present. But few paid their work any attention, writing their research off as little more than cosmological oddities. And no one had bagged such solid evidence of it before. And because no one had predicted what dark matter’s existence might mean for galaxy dynamics, Rubin and Ford initially didn’t recognize the meaning of their flat rotation curves.

    “Months were taken up in trying to understand what I was looking at,” Rubin told journalist Maria Popova. “One day I just decided that I had to understand what this complexity was that I was looking at, and I made sketches on a piece of paper, and suddenly I understood it all.”

    If a halo of dark matter graced each galaxy, she realized, the mass would be spread throughout the galaxy, rather than concentrating in the center. The gravitational force — and the orbital speed — would be similar throughout.

    Rubin and Ford had discovered the unseeable stuff that influences not only how galaxies move, but how the universe came to be and what it will become. “My entire education highlighted how fundamental dark matter is to our current understanding of astrophysics,” says Levesque, “and it’s hard for me to imagine the field or the universe without it.”

    Within a few years of the M31 observations, physicists like Jeremiah Ostriker and James Peebles provided the theoretical framework to support what Rubin and Ford had already shown, and dark matter settled firmly into its celebrated place in the universe.

    In more recent years, the Planck satellite measured the dark matter content of the universe by looking at the cosmic microwave background, the radiation left over from the Big Bang. The clumps of matter in this baby picture of the universe evolved into the galaxy superclusters we see today, and it was dark matter that clumped first and drew the regular matter together.

    Data from galaxy clusters now also confirms dark matter and helps scientists measure how much of it exists within a given group — a modern echo of Zwicky’s almost forgotten work. When light from more distant sources passes near a cluster, the gravity — from the cluster’s huge mass — bends the light like a lens.

    The amount of bending can reveal the amount of dark matter.

    No matter which way or where scientists measure Rubin’s discovery, it’s huge.

    And while no one knows what all the dark matter is, scientists have discovered that some small fraction of it is made of neutrinos — tiny, fast-moving particles that don’t really interact with normal matter. Measurements from the cosmic microwave background, like those being taken by experiments called POLARBEAR in Chile and BICEP2 and BICEP3 in Antarctica, will help pin down how many neutrinos are streaming through the universe and how much of the dark matter they make up.

    Some setups, like the Gran Sasso National Laboratory in Italy and the Deep Underground Science and Engineering Laboratory in South Dakota, are trying to detect dark matter particles directly, when they crash into atoms in cryogenically cooled tanks filled with liquefied noble gases. So far, they haven’t managed to capture a dark matter particle in action. But researchers are taking dark matter — whatever it is — into account when they think about how the universe evolves.

    The Nobel committee may overlook Rubin, passing by her as if they can’t see what all of astrophysics feels. But that won’t hurt her legacy, says Levesque: It will hurt the legacy of the Nobel itself. “It would then permanently lack any recognition of such groundbreaking work,” Levesque says.

    Rubin herself has never spoken about how she deserves a Nobel Prize. She simply continued her scientific work until recently, all the while influencing the origins, evolutions, and fates of other scientists. “If they didn’t get a job or they didn’t get a paper published, she would cheer people up,” says Bahcall. “She kept telling her story about how there are ups and downs and you stick with it and keep doing what you love doing.”

    Rubin, herself, loves trying to understand the universe, and in doing so, she has changed everyone’s understanding of it. That carries more weight than some medal from Sweden. But let Sweden recognize that for what it is: worthy of a prize.

    See the full article here .

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  • richardmitnick 10:32 am on September 29, 2016 Permalink | Reply
    Tags: , AU, , Dark Matter, Stawell gold mine in western Victoria, Stawell Underground Physics Laboratory (SUPL)   

    From ARC Center of Excellence for Particle Physics at the Terascale: “Digging for Dark Matter” 


    ARC Centre of Excellence for Particle Physics at the Terascale

    Digging for Dark Matter

    A tiny Australian mining town might hold the key to solving one of the universe’s biggest mysteries – and to a local economic boom. What do scientists hope to find in a cave 1km underground?

    Lisa Clausen

    The public lookout point for the Stawell gold mine in western Victoria is an unremarkable spot; a few faded information boards and pieces of old equipment, rusting among crooked gums beside the mine’s high perimeter fence.

    Beyond the wire, near the slurry-coloured mine machinery which roars into the chill air, a dirt road descends steadily, through a rocky cutting, into the mine’s black mouth. It’s noisy, muddy and industrious – much like any number of working mines on a weekday – but not the sort of place where you’d imagine science might finally answer one of the great questions of our universe.

    And yet it could be. For more than 40 years, the mystery of dark matter has defied the world’s best physicists. These invisible particles are thought to be everywhere – constantly passing through each of us and our planet. In fact, we can only observe five per cent of the whole universe; the rest is dark matter and dark energy.

    Scientists have found compelling indirect evidence of dark matter’s existence, called gravitational lensing – where dark matter bends the visible light we see coming from distant galaxies. Yet this “stuff”, thought to shape galaxies and be the universe’s missing mass, remains frustratingly elusive. Directly detecting dark matter will be one of the greatest prizes of modern physics.

    “Dark matter holds galaxies together,” says University of Melbourne particle physicist, Professor Elisabetta Barberio. “If we understand it, we will understand how the universe evolved from the Big Bang to now, and how it might continue to evolve.”

    University of Melbourne particle physicist, Professor Elisabetta Barberio. Photo: Peter Casamento

    Barberio is the project leader of an ambitious experiment set to happen in Australia. Until now, efforts to find dark matter have all taken place in the northern hemisphere, with plenty of funding and facilities. Now, thanks to the Stawell Underground Physics Laboratory (SUPL), the southern hemisphere will join the global hunt.

    Underground Physics

    Its SABRE dark matter experiment will happen 1km underground in a country town of just over 6,000 people, best known for gold, farming, and a famous annual footrace – the Stawell Gift.


    Stawell’s 160 years of gold mining history have left a network of tunnels under its streets, and disused shafts which occasionally open up in people’s gardens. It’s very much a mining town, but faced disastrous news when, in late 2012, the mine’s then-owners came to town council warning of the mine’s potential closure. After all, at its peak the mine employed about 400 people, while hundreds of others in local businesses benefited from its success.

    A panel of councillors, council staff, locals and mine management was convened to brainstorm ideas for what might come next. The list of community proposals quickly grew: should they start growing mushrooms? Or open a subterranean hotel?

    That same year, three hours down the highway in Melbourne, a group of physicists was wondering where they could stage a dark matter detection experiment. Swinburne University of Technology astrophysicist Jeremy Mould wrote to several mines across the country, outlining the group’s unusual request for a spare underground cavern. One of those letters went to Stawell’s council.

    Probing the nature of the universe hadn’t been on Stawell’s short list – yet. But what physicists needed was an underground site deep enough and in the right sort of landscape to block out the highly radioactive cosmic rays which relentlessly pelt the Earth’s surface. To the experiment’s incredibly sensitive detector, these rays are like a raucous radio station. The best way to turn down the volume is to head underground.

    Stawell’s mine, in places dug almost 2km deep through dense volcanic basalt, looked promising. Because it’s a mine with ramp access, rather than a vertical shaft, people and equipment could be driven in. And because it was in operation, power, ventilation and internet access were already in place.

    Most importantly, initial background radiation readings inside the mine were encouragingly low. Talks with council began and, in 2014, 60 scientists from around the world arrived to inspect the proposed site of the southern hemisphere’s first underground physics lab.

    “The penny dropped then that there was really something in this,” says Northern Grampians Shire Mayor Murray Emerson.

    Now, with $3.5m from the Victorian and federal governments, construction is due to begin later this year. The rock above SUPL will be a radiation shield equivalent to 3km of water. Even so, maintaining the lowest radiation levels possible means a complex build.

    It means everything from concrete to rock bolts must be tested before it can be used. By May this year, 26 component samples from sources as widespread as Adelaide to Gladstone had been tested, but only two found suitable. Quarry materials such as sand and aggregate must travel by road or train for analysis at the Australian Nuclear Science and Technology Organisation in Sydney – air travel gives off too much radiation. Materials such as the special concrete spray coating for the rock walls will have to be mixed on-site in specific containers, and stored away from mine materials.

    “It’s certainly an unusual challenge,” says site project engineer Allan Ralph. “Things that you would do on the surface without thinking about them have a significant difficulty to them when they’re underground and forming part of a world-class physics laboratory.”

    See the full article here .

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    The objectives for the ARC Centres of Excellence are to:

    undertake highly innovative and potentially transformational research that aims to achieve international standing in the fields of research envisaged and leads to a significant advancement of capabilities and knowledge
    link existing Australian research strengths and build critical mass with new capacity for interdisciplinary, collaborative approaches to address the most challenging and significant research problems
    develop relationships and build new networks with major national and international centres and research programs to help strengthen research, achieve global competitiveness and gain recognition for Australian research
    build Australia’s human capacity in a range of research areas by attracting and retaining, from within Australia and abroad, researchers of high international standing as well as the most promising research students
    provide high-quality postgraduate and postdoctoral training environments for the next generation of researchers
    offer Australian researchers opportunities to work on large-scale problems over long periods of time
    establish Centres that have an impact on the wider community through interaction with higher education institutes, governments, industry and the private and non-profit sector.

  • richardmitnick 1:09 pm on September 9, 2016 Permalink | Reply
    Tags: , , , , Dark Matter, ,   

    From Symmetry: “A tale of two black holes” 

    Symmetry Mag


    Liz Kruesi


    The historic detection of gravitational waves announced earlier this year breathed new life into a theory that’s been around for decades: that black holes created in the first second of the universe might make up dark matter. It also inspired a new idea: that those so-called primordial black holes could be contributing to a diffuse background light.

    The connection between these perhaps seemingly disparate areas of astronomy were tied together neatly in a theory from Alexander Kashlinsky, an astrophysicist at NASA’s Goddard Spaceflight Center. And while it’s an unusual idea, as he says, it could be proven true in only a few years.

    Mapping the glow

    Kashlinsky’s focus has been on a residual infrared glow in the universe, the accumulated light of the earliest stars. Unfortunately, all the stars, galaxies and other bright objects in the sky—the known sources of light—oversaturate this diffuse glow. That means that Kashlinsky and his colleagues have to subtract them out of infrared images to find the light that’s left behind.

    They’ve been doing precisely that since 2005, using data from the Spitzer space telescope to arrive at the residual infrared glow: the cosmic infrared background (CIB).

    NASA/Spitzer Telescope
    “NASA/Spitzer Telescope

    Cosmic Infrared Background, Credit: Michael Hauser (Space Telescope Science Institute), the COBE/DIRBE Science Team, and NASA)
    Cosmic Infrared Background, Credit: Michael Hauser (Space Telescope Science Institute), the COBE/DIRBE Science Team, and NASA

    Other astronomers followed a similar process using Chandra X-ray Observatory data to map the cosmic X-ray background (CXB), the diffuse glow of hotter cosmic material and more energetic sources.

    NASA/Chandra Telescope
    NASA/Chandra Telescope

    Cosmic X-ray Background, imagine.gsfc.nasa.gov
    Cosmic X-ray Background, imagine.gsfc.nasa.gov

    In 2013, Kashlinsky and colleagues compared the CIB and CXB and found correlations between the patchy patterns in the two datasets, indicating that something is contributing to both types of background light. So what might be the culprit for both types of light?

    “The only sources that could be coherent across this wide range of wavelengths are black holes,” he says.

    To explain the correlation they found, roughly 1 in 5 of the sources had to be black holes that lived in the first few hundred million years of our universe. But that ratio is oddly large.

    “For comparison,” Kashlinsky says, “in the present populations, we have 1 in 1000 of the emitting sources that are black holes. At the peak of star formation, it’s 1 in 100.”

    He wasn’t sure how the universe could have ever had enough black holes to produce the patterns his team saw in the CIB and CXB. Then the Laser Interferometric Gravitational-wave Observatory (LIGO) discovered a pair of strange beasts: two roughly-30-solar-mass black holes merging and emitting gravitational waves.

    LSC LIGO Scientific Collaboration
    Caltech/MIT Advanced aLigo Hanford, WA, USA installation
    Caltech/MIT Advanced aLigo Hanford, WA, USA installation
    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA
    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA
    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project
    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

    A few months later, Kashlinsky saw a study led by Simeon Bird analyzing the possibility that the black holes LIGO had detected were primordial—formed in the universe’s first second. “And it just all came together,” Kashlinsky says.

    Gravitational secrets

    The crucial ripples in space-time picked up by the LIGO detector on September 14, 2015, came from the last dance of two black holes orbiting each other and colliding. One black hole was 36 times the sun’s mass, the other 29 times. Those black-hole weights aren’t easy to make.

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

    The majority of the universe’s black holes are less than about 15 solar masses and form as massive stars collapse at the end of their lives. A black hole weighing 30 solar masses would have to start from a star closer to 100 times our sun’s mass—and nature seems to have a hard time making stars that enormous. To compound the strangeness of the situation, the LIGO detection is from a pair of those black holes. Scientists weren’t expecting such a system, but the universe has a tendency to surprise us.

    Bird and his colleagues from Johns Hopkins University next looked at the possibility that those black holes formed not from massive stars but instead during the universe’s first fractions of a second. Astronomers haven’t yet seen what the cosmos looked like at that time, so they have to rely on theoretical models.

    In all of these models, the early universe exists with density variations. If there were regions of very high-contrasting density, those could have collapsed into black holes in the universe’s first second. If those black holes were at least as heavy as mountains when they formed, they’d stick around until today, dark and seemingly invisible and acting through the gravitational force. And because these primordial black holes formed from density perturbations, they wouldn’t be comprised of protons and neutrons, the particles that make up you, me, stars and, thus, the material that leads to normal black holes.

    All of those characteristics make primordial black holes a tempting candidate for the universe’s mysterious dark matter, which we believe makes up some 25 percent of the universe and reveals itself only through the gravitational force. This possible connection has been around since the 1970s, and astronomers have looked for hints of primordial black holes since. Even though they’ve slowly narrowed down the possibilities, there are a few remaining hiding spots—including the region where the black holes that LIGO detected fall, between about 20 and 1000 solar masses.

    Astronomers have been looking for explanations of what dark matter is for decades. The leading theory is that it’s a new type of particle, but searches keep coming up empty. On the other hand, we know black holes exist; they stem naturally from the theory of gravity.

    “They’re an aesthetically pleasing candidate because they don’t need any new physics,” Bird says.

    A glowing contribution

    Kashlinsky’s newest analysis took the idea of primordial black holes the size that LIGO detected and looked at what that population would do to the diffuse infrared light of the universe. He evolved a model of the early universe, looking at how the first black holes would congregate and grow into clumps. These black holes matched the residual glow of the CIB and, he found, “would be just right to explain the patchiness of infrared background by sources that we measured in the first couple hundred million years of the universe.”

    This theory fits nicely together, but it’s just one analysis of one possible model that came out of an observation of one astrophysical system. Researchers need several more pieces of evidence to say whether primordial black holes are in fact the dark matter. The good news is LIGO will soon begin another observing run that will be able to see black hole collisions even farther away from Earth and thus further back in time. The European gravitational wave observatory VIRGO will also come online in January, providing more data and working in tandem with LIGO.

    VIRGO Collaboration bloc
    VIRGO interferometer EGO Campus
    VIRGO interferometer EGO Campus, in Cascina, Italy

    More cases of gravitational waves from black holes around this 30-solar-masses range could add evidence that there is a population of primordial black holes. Bird and his colleague Ilias Cholis suggest looking for a more unique signal, though, in future gravitational-wave data. For two primordial black holes to become locked in a binary system and merge, they would likely be gravitationally captured during a glancing interaction, which could result in a signal with multiple frequencies or tones at any one moment.

    “This is a rare event, but it would be very characteristic of our scenario,” Cholis says. “In the next 5 to 10 years, we might see one.”

    This smoking-gun signature, as they call it, would be a strong piece of evidence that primordial black holes exist. And if such objects are floating around our universe, it might not be such a stretch to connect them to dark matter.

    See the full article here .

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    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 10:02 am on September 8, 2016 Permalink | Reply
    Tags: , Dark Matter, , ,   

    From Don Lincoln for CNN: “Something is wrong with dark matter” 


    September 7, 2016

    FNAL Don Lincoln
    Don Lincoln

    Dr. Don Lincoln is a senior physicist at Fermilab and does research using the Large Hadron Collider. He has written numerous books and produces a series of science education videos. He is the author of The Large Hadron Collider: The Extraordinary Story of the Higgs Boson and Other Things That Will Blow Your Mind. Follow him on Facebook. The opinions expressed in this commentary are solely those of the author.

    Nearly a mile under the Black Hills of South Dakota sits a canister of the atomic element xenon, chilled cold enough to turn it to liquid. The canister is the Large Underground Xenon, or LUX, detector — the most sensitive dark matter detector in the world.

    SURF logo
    Sanford Underground levels
    Sanford Underground Research Facility
    LUX Dark matter Experiment at SURF
    LUX Dark matter Experiment at SURF

    But the results of a new analysis by the LUX Collaboration has left scientists perplexed about a substance that has guided the formation of the stars and galaxies since the cosmos began: dark matter.

    Since the 1930s, scientists have known that there was something unexplained about the heavens. Swiss astronomer Fritz Zwicky studied the Coma Cluster, a group of about a thousand galaxies, held together by their mutual gravitational interactions.

    A map of the Coma cluster. http://www.atlasoftheuniverse.com

    There was only one problem: The galaxies were moving so fast that gravity shouldn’t have been able to hold them together. The cluster should have been ripped apart. In the 1970s, astronomers Vera Rubin and her collaborator Kenneth Ford studied the rotation rates of individual galaxies and came to the same conclusion. There appeared to be no way the observed matter contained in galaxies would generate enough gravity to keep the stars locked in their stately orbits.

    These observations, combined with many other independent lines of evidence, led scientists to consider several possible explanations. These explanations included the possibility that Newton’s familiar laws of motion might be wrong, or that our understanding of gravity needed to be modified. Both these proposals, though, have been largely ruled out.

    Another idea was that there was somehow invisible matter that was generating more gravity. Initial ideas centered on the possibility of black holes, brown dwarf stars or rogue planets roaming the cosmos, but those explanations have also been dismissed. Using a ruthless process of elimination worthy of Sherlock Holmes, astronomers have come to believe the explanation for all of the gravitational anomalies is that there must be some sort of new and undiscovered type of matter in the universe, which Zwicky in 1933 named “dunkle materie,” or dark matter.

    For decades, scientists have tried to work out the properties of dark matter and, while we don’t know everything, we know a lot. From astronomical observations, we know there is five times more dark matter in the universe than all the “billions and billions” of stars and galaxies mentioned in Carl Sagan’s oft-quoted phrase. We also know that dark matter cannot have electrical charge, otherwise it would interact with light and we would have seen it. In fact, by a process of elimination, we know that dark matter is not any known form of matter. It is something new. Of this, scientists are sure.

    However, scientists are less sure about the details.

    For decades now, the most popular theoretical idea was that dark matter was a WIMP, short for weakly interacting massive particle. A WIMP would have a mass in the range of 10 to perhaps 100 times heavier than the familiar proton. It was a particle like a heavy neutron (but definitely not a neutron), massive, electrically neutral, and stable on time scales long compared to the lifetime of the universe.
    The WIMP was popular for two main reasons.

    First, when cosmologists modeled the Big Bang and included WIMPs in the calculation, the WIMPs actively participated in the earliest phases of the birth of the universe but, as the universe expanded and cooled, the space between them grew large enough that they stopped interacting with one another. When scientists calculated how much mass should be tied up in the relic WIMPs, they found it was five times as much mass as ordinary matter, exactly the amount of dark matter seen by astronomers.

    The second reason for the popularity of the WIMP idea is that it explained a mystery in particle physics. The recently discovered Higgs boson has a mass of about 130 times that of the proton. Theoretical considerations predicted a much larger mass, but if a WIMP exists, it is easy to reconcile the prediction and measurement. These two reasons account for the popularity of the WIMP idea and are called “the WIMP miracle.”

    The LUX measurement is simply the most recent and most powerful of a long line of searches for dark matter. They found no evidence for the existence of dark matter and were able to rule out a significant range of possible WIMP properties and masses.

    Now this doesn’t mean the WIMP idea is dead or that dark matter has been disproven. There remain WIMP masses that haven’t been ruled out, and there exist other possible dark matter candidates, including objects called sterile neutrinos, which are possible cousins of the well-known neutrinos generated in nuclear reactors and in the sun. Another recurring proposed dark matter particle is the axion, suggested in the 1970s to explain mysteries in the asymmetry of subatomic processes. (Although neither sterile neutrinos, nor axions, have been observed).

    Nobody knows what the final answer will be. That’s why we do research. But there is no question that there is a mystery in the cosmos. Galaxies don’t act as we expect. The LUX measurement is a powerful new bit of information for astronomers to consider and has added to the general confusion, forcing scientists to take another look at ideas other than WIMPs.

    All this reminds me of the old Buffalo Springfield song: “There’s something happening here. What it is ain’t exactly clear …”

    See the full article here .

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  • richardmitnick 10:58 am on September 7, 2016 Permalink | Reply
    Tags: , , Dark Matter,   

    From U Cambridge: “Massive holes ‘punched’ through a trail of stars likely caused by dark matter” 

    U Cambridge bloc

    Cambridge University

    07 Sep 2016
    Sarah Collins

    Artist’s impression of dark matter clumps around a Milky Way-like galaxy. Credit: V. Belokurov, D. Erkal, S.E. Koposov (IoA, Cambridge). Photo: Colour image of M31 from Adam Evans.

    The discovery of two massive holes punched through a stream of stars could help answer questions about the nature of dark matter, the mysterious substance holding galaxies together.

    Researchers have detected two massive holes which have been ‘punched’ through a stream of stars just outside the Milky Way, and found that they were likely caused by clumps of dark matter, the invisible substance which holds galaxies together and makes up a quarter of all matter and energy in the universe.

    The scientists, from the University of Cambridge, found the holes by studying the distribution of stars in the Milky Way. While the clumps of dark matter that likely made the holes are gigantic in comparison to our Solar System – with a mass between one million and 100 million times that of the Sun – they are actually the tiniest clumps of dark matter detected to date.

    The results, which have been submitted to the Monthly Notices of the Royal Astronomical Society, could help researchers understand the properties of dark matter, by inferring what type of particle this mysterious substance could be made of. According to their calculations and simulations, dark matter is likely made up of particles more massive and more sluggish than previously thought, although such a particle has yet to be discovered.

    “While we do not yet understand what dark matter is formed of, we know that it is everywhere,” said Dr Denis Erkal from Cambridge’s Institute of Astronomy, the paper’s lead author. “It permeates the universe and acts as scaffolding around which astrophysical objects made of ordinary matter – such as galaxies – are assembled.”

    Current theory on how the universe was formed predicts that many of these dark matter building blocks have been left unused, and there are possibly tens of thousands of small clumps of dark matter swarming in and around the Milky Way. These small clumps, known as dark matter sub-haloes, are completely dark, and don’t contain any stars, gas or dust.

    Dark matter cannot be directly measured, and so its existence is usually inferred by the gravitational pull it exerts on other objects, such as by observing the movement of stars in a galaxy. But since sub-haloes don’t contain any ordinary matter, researchers need to develop alternative techniques in order to observe them.

    The technique the Cambridge researchers developed was to essentially look for giant holes punched through a stream of stars. These streams are the remnants of small satellites, either dwarf galaxies or globular clusters, which were once in orbit around our own galaxy, but the strong tidal forces of the Milky Way have torn them apart. The remnants of these former satellites are often stretched out into long and narrow tails of stars, known as stellar streams.

    “Stellar streams are actually simple and fragile structures,” said co-author Dr Sergey Koposov. “The stars in a stellar stream closely follow one another since their orbits all started from the same place. But they don’t actually feel each other’s presence, and so the apparent coherence of the stream can be fractured if a massive body passes nearby. If a dark matter sub-halo passes through a stellar stream, the result will be a gap in the stream which is proportional to the mass of the body that created it.”

    The researchers used data from the stellar streams in the Palomar 5 globular cluster to look for evidence of a sub-halo fly-by. Using a new modelling technique, they were able to observe the stream with greater precision than ever before. What they found was a pair of wrinkled tidal tails, with two gaps of different widths.

    By running thousands of computer simulations, the researchers determined that the gaps were consistent with a fly-by of a dark matter sub-halo. If confirmed, these would be the smallest dark matter clumps detected to date.

    “If dark matter can exist in clumps smaller than the smallest dwarf galaxy, then it also tells us something about the nature of the particles which dark matter is made of – namely that it must be made of very massive particles,” said co-author Dr Vasily Belokurov. “This would be a breakthrough in our understanding of dark matter.”

    The reason that researchers can make this connection is that the mass of the smallest clump of dark matter is closely linked to the mass of the yet unknown particle that dark matter is composed of. More precisely, the smaller the clumps of dark matter, the higher the mass of the particle.

    Since we do not yet know what dark matter is made of, the simplest way to characterise the particles is to assign them a particular energy or mass. If the particles are very light, then they can move and disperse into very large clumps. But if the particles are very massive, then they can’t move very fast, causing them to condense – in the first instance – into very small clumps.

    “Mass is related to how fast these particles can move, and how fast they can move tells you about their size,” said Belokurov. “So that’s why it’s so interesting to detect very small clumps of dark matter, because it tells you that the dark matter particle itself must be very massive.”

    “If our technique works as predicted, in the near future we will be able to use it to discover even smaller clumps of dark matter,” said Erkal. “It’s like putting dark matter goggles on and seeing thousands of dark clumps each more massive than a million suns whizzing around.”

    See the full article here .

    Please help promote STEM in your local schools.

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    U Cambridge Campus

    The University of Cambridge (abbreviated as Cantab in post-nominal letters) is a collegiate public research university in Cambridge, England. Founded in 1209, Cambridge is the second-oldest university in the English-speaking world and the world’s fourth-oldest surviving university. It grew out of an association of scholars who left the University of Oxford after a dispute with townsfolk. The two ancient universities share many common features and are often jointly referred to as “Oxbridge”.

    Cambridge is formed from a variety of institutions which include 31 constituent colleges and over 100 academic departments organised into six schools. The university occupies buildings throughout the town, many of which are of historical importance. The colleges are self-governing institutions founded as integral parts of the university. In the year ended 31 July 2014, the university had a total income of £1.51 billion, of which £371 million was from research grants and contracts. The central university and colleges have a combined endowment of around £4.9 billion, the largest of any university outside the United States. Cambridge is a member of many associations and forms part of the “golden triangle” of leading English universities and Cambridge University Health Partners, an academic health science centre. The university is closely linked with the development of the high-tech business cluster known as “Silicon Fen”.

  • richardmitnick 8:08 am on September 6, 2016 Permalink | Reply
    Tags: , , Dark Matter,   

    From Ethan Siegel: “Dark matter riches?” 

    From Ethan Siegel

    An image of galaxy Dragonfly 44, recently discovered to have the largest offset between normal matter and dark matter of any known, large galaxy. Image credit: Pieter van Dokkum, Roberto Abraham, Gemini Observatory/AURA.

    Dragonfly 44 It was discovered just last year when the Dragonfly Telephoto Array observed a region of the sky in the constellation Coma.

    U Toronto Dunlap Dragonfly telescope Array
    U Toronto Dunlap Dragonfly telescope Array

    How we know some galaxies have more than others.

    “Motions of the stars tell you how much matter there is. They don’t care what form the matter is, they just tell you that it’s there.” -Pieter van Dokkum

    One of the biggest surprises about galaxies in our Universe is that stars only make up a tiny fraction of their mass.

    Traceable stars, neutral gas, and (even farther out) globular clusters all point to the existence of dark matter, which has mass but exists in a large, diffuse halo well beyond the normal matter’s location. Image credit: Wikimedia Commons user Stefania.deluca.

    Looking to gas, dust, plasma, black holes and other non-luminous forms fails to account for what’s missing.

    From simulations and inferred maps, dark matter (blue) may form some clumps, but overall exists in a massive, diffuse halo around the luminous, disk-like part of galaxies we’re familiar with. Image credit: NASA, ESA, and T. Brown and J. Tumlinson (STScI).

    For that, you need dark matter, which has mass but is completely invisible to all non-gravitational interactions.

    Dark matter, in a 5:1 ratio to normal matter, accounts for everything from the formation of the largest cosmic structures to galaxies’ internal motions to the fluctuation patterns in the cosmic microwave background.

    The fluctuations across the entire sky in the cosmic microwave background, the Big Bang’s leftover glow. Image credit: ESA and the Planck collaboration.

    Present in a large, diffuse halo surrounding galaxies and clusters, its gravity is observable even when collisions separate out the normal matter.

    Four colliding galaxy clusters, showing the separation between X-rays (pink) and gravitation (blue), indicative of dark matter. Images credit: X-ray: NASA/CXC/UVic./A.Mahdavi et al. Optical/Lensing: CFHT/UVic./A. Mahdavi et al. (top left); X-ray: NASA/CXC/UCDavis/W.Dawson et al.; Optical: NASA/ STScI/UCDavis/ W.Dawson et al. (top right); ESA/XMM-Newton/F. Gastaldello (INAF/ IASF, Milano, Italy)/CFHTLS (bottom left); X-ray: NASA, ESA, CXC, M. Bradac (University of California, Santa Barbara), and S. Allen (Stanford University) (bottom right).

    NASA/Chandra Telescope
    NASA/Chandra Telescope

    CFHT Telescope, Mauna Kea, Hawaii, USA
    CFHT Interior
    CFHT Telescope, Mauna Kea, Hawaii, USA

    NASA/ESA Hubble Telescope
    NASA/ESA Hubble Telescope

    ESA/XMM Newton
    ESA/XMM Newton

    The smallest galaxies are richer in dark matter, as episodes of star formation expel the normal matter.

    Galaxies undergoing massive bursts of star formation expel large quantities of matter at great speeds. In low-mass galaxies, this material easily escapes the galaxy’s gravitational pull. Image credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA), of the Cigar Galaxy, Messier 82.

    What’s left behind is mostly dark.

    The lowest-mass galaxy known, Segue 3, has 600 times more dark matter than normal matter.

    Only approximately 1000 stars are present in the entirety of dwarf galaxy Segue 3, which has a gravitational mass of 600,000 Suns. Image credit: Marla Geha and Keck Observatories, of the stars making up the dwarf satellite Segue 1.

    Keck Observatory, Mauna Kea, Hawaii, USA
    Keck Observatory Interior
    Keck Observatory, Mauna Kea, Hawaii, USA

    But large galaxies can lose their normal matter too, by speeding through the intergalactic medium.

    A Hubble (visible light) and Chandra (X-ray) composite of galaxy ESO 137–001 as it speeds through the intergalactic medium, becoming stripped of stars and gas, while its dark matter remains intact. Image credit: NASA, ESA, CXC.

    Recently, the galaxy Dragonfly 44 has surprised astronomers with its dark matter richness.

    If their normal matter was stripped away, perhaps these “dark galaxies” weren’t always so dark.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

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