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  • richardmitnick 9:29 pm on October 17, 2018 Permalink | Reply
    Tags: , Astrophysics, , , Gemini Near-Infrared Spectrograph on Gemini North, , , Hawaii USA, , Sierra Remote Observatory, The core-collapse supernova 2017eaw   

    From Gemini Observatory: “Nearby Supernova Sheds Light on Ancient Dust” 

    NOAO

    Gemini Observatory
    From Gemini Observatory

    October 16, 2018

    Thanks to two allocations of Director’s Discretionary Time and a successful Fast-Turnaround program, an international team (including Gemini Emeritus Astronomer Tom Geballe, who wrote this summary on behalf of the team) used Gemini North/GNIRS to follow the evolution of the near-infrared spectrum of the core-collapse supernova 2017eaw (ccSN 2017eaw) over three semesters.

    Gemini Near-Infrared Spectrograph on Gemini North, Mauna Kea, Hawaii USA

    The data obtained from this relatively nearby event may help us to better understand the existence of dusty galaxies in the early, much more distant Universe.

    One of the unexpected discoveries in studies of the very early Universe is that many high redshift galaxies are “dusty.” These dusty galaxies exist as recently as several hundred million to a billion years after the Big Bang. The origin of this dust is somewhat of a mystery, because stars with masses similar to the Sun, which constitute the vast majority of stars in a galaxy, would not have evolved to the dust-producing stage in such a short time. Thus, there must be another source of dust in these very distant and very young galaxies.

    __________________________________________________
    Where Does Interstellar Dust Originate?

    Interstellar dust constitutes about 1% of the mass of interstellar matter in our Milky Way and in many other galaxies. It is generally understood that the origin of most of that dust is stars with masses roughly similar to that of our Sun, that became red giants and ejected their outer layers into space. Although initially almost entirely hydrogen and helium, during the red giant phase the outer layers of those stars are polluted by heavier elements such as carbon, nitrogen, oxygen, silicon, magnesium, and many others that are produced by thermonuclear reactions deep inside the stars and then mixed into the outer layers. Once the ejecta cool to temperatures lower than about 2,000 K, dust particles inevitably start to form out of these heavy elements. However, it is billions of years after these stars formed when this happens. On the other hand, core collapse supernovae live only a few millions to a few tens of millions of years before they explode, during which time they turn most of their hydrogen-rich and helium-rich interiors into vast reservoirs of heavy elements. Thus, unlike stars like the Sun, massive stars are potential dust-producers in the early Universe.
    __________________________________________________

    One possible source is the ejecta from massive stars that explode after only a few millions to a few tens of millions of years after they form, the so-called core-collapse supernovae (ccSNe).

    1
    Figure 1. Image of spiral galaxy NGC 6946 and SN 2017eaw indicated by arrow. Photo courtesy of Damian Peach, obtained on May 28th, 2017, at 10:31 UTC from the Sierra Remote Observatory, California.

    Sierra Remote Observatory in the Sierra Nevada Mountains, a mountain range in the Western United States, between the Central Valley of California and the Great Basin

    2
    The Great Basin is the largest area of contiguous endorheic watersheds in North America. It spans nearly all of Nevada, much of Oregon and Utah, and portions of California, Idaho, and Wyoming.

    While we cannot study individual supernovae in such distant galaxies, we can find examples of them in the nearby Universe. Infrared- and millimeter-wave observations of several “local” examples have revealed that ccSNe can produce copious amounts of dust — up to one solar mass for each event. Until now, however, detailed evolution of dust production in such supernovae, which can take place over several years, has only been followed in one object: the very nearby, famous, and rather unusual ccSN 1987A in the Large Magellanic Cloud. Fortuitously, our recent observations of ccSN 2017eaw in the nearby galaxy NGC 6946 provided another rare opportunity to follow that evolution in detail over an extended period. NGC 6946 is located about 7 megaparsecs away and is popularly known as the Fireworks Galaxy, because it is a prodigious supplier of supernovae (see Figure 1 and a pre-SN 2017eaw Gemini Legacy Image of NGC 6946).

    SN 2017eaw was discovered on May 14, 2017, just as its host galaxy, NGC 6946, became observable in the eastern sky before dawn. Because of its high northerly location, we saw an opportunity to follow SN 2017eaw continuously from May until December (before it became too low in the western sky to observe from Maunakea) and proposed the idea to Gemini Observatory. Thanks to two allocations of Director’s Discretionary Time and a successful Fast-Turnaround program, the team led by Jeonghee Rho (SETI Institute) was able to follow the evolution of the supernova’s near-infrared (0.84-2.52 micron) spectrum in Semesters 2017A, 2017B, and 2018A. The team also includes Tom Geballe (Gemini Observatory), Dipankar Banerjee and Vishal Joshi (Physical Research Laboratory, Ahmedabad, India), Nye Evans (Keele University, U.K.), and Luc Dessart (Universidad de Chile).

    During 2017-18, we obtained Gemini North/GNIRS (Gemini Near-InfraRed Spectrometer) data on ten dates between 22 and 387 days after the discovery. It is believed that these data represent the highest quality and most extensive near-infrared time-sequence of spectra ever obtained for a Type II-P SN, the most common type of ccSN, whose light curve has a distinctive flat stretch (called a plateau).

    The first nine of these spectra, obtained in 2017, are shown in Figure 2. While they are a goldmine of information — revealing details on elemental abundances, nucleosynthesis, changes in ionization, and velocities of the ejecta — our major goal was to witness and model the formation of the molecule carbon monoxide (CO) and dust, which is quite hot when it forms. Information on these species is contained only at the long wavelength end of the spectra, from 2.0 to 2.5 microns.

    CO is important because it is a powerful coolant of the ejecta, which aids in making dust formation possible. Its presence is clearly detected on day 124 by the sharp increase in signal near 2.30 microns, and we think it was already marginally present at day 107. The dust signature also begins at day 124, and is the flattening slope of the continuum from 2.1 microns to longer wavelengths, compared to the steadily decreasing continuum signal at shorter wavelengths, and across the entire spectrum at earlier times.

    We have used the spectra to estimate the CO mass produced by SN 2017eaw and find that it is qualitatively matched by models in the literature of a progenitor star of mass roughly 15 times that of the Sun. Fits to the continuum indicate that the temperature of the dust emitting at 2.1-2.5 microns is ~ 1,300 K and that the dust is mainly graphitic, which, unlike amorphous carbon, can condense at higher temperatures than this. Discussion of these and other results and analysis are reported in Rho et al., The Astrophysical Journal Letters, 864: L20, 2018.

    We are continuing our monitoring of SN 2017eaw in Semester 2018B; thereafter it will be too faint. In future semesters, we hope to measure additional nearby ccSNe that occur in order to estimate the frequency of CO and dust production by such SNe, as well as the masses of CO and dust produced by each.

    See the full article here .


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    Please help promote STEM in your local schools.


    Stem Education Coalition

    Gemini/North telescope at Maunakea, Hawaii, USA,4,207 m (13,802 ft) above sea level

    Gemini South telescope, Cerro Tololo Inter-American Observatory (CTIO) campus near La Serena, Chile, at an altitude of 7200 feet

    AURA Icon

    Gemini’s mission is to advance our knowledge of the Universe by providing the international Gemini Community with forefront access to the entire sky.

    The Gemini Observatory is an international collaboration with two identical 8-meter telescopes. The Frederick C. Gillett Gemini Telescope is located on Mauna Kea, Hawai’i (Gemini North) and the other telescope on Cerro Pachón in central Chile (Gemini South); together the twin telescopes provide full coverage over both hemispheres of the sky. The telescopes incorporate technologies that allow large, relatively thin mirrors, under active control, to collect and focus both visible and infrared radiation from space.

    The Gemini Observatory provides the astronomical communities in six partner countries with state-of-the-art astronomical facilities that allocate observing time in proportion to each country’s contribution. In addition to financial support, each country also contributes significant scientific and technical resources. The national research agencies that form the Gemini partnership include: the US National Science Foundation (NSF), the Canadian National Research Council (NRC), the Chilean Comisión Nacional de Investigación Cientifica y Tecnológica (CONICYT), the Australian Research Council (ARC), the Argentinean Ministerio de Ciencia, Tecnología e Innovación Productiva, and the Brazilian Ministério da Ciência, Tecnologia e Inovação. The observatory is managed by the Association of Universities for Research in Astronomy, Inc. (AURA) under a cooperative agreement with the NSF. The NSF also serves as the executive agency for the international partnership.

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  • richardmitnick 1:27 pm on October 17, 2018 Permalink | Reply
    Tags: , Astrophysics, , , , from Euclid to LIGO, , , The Australian International Gravitational Research Centre   

    From The Australian International Gravitational Research Centre via COSMOS: “A short [?] history of spacetime from Euclid to LIGO” 

    From The Australian International Gravitational Research Centre

    via

    COSMOS

    17 October 2018
    David Blair

    A year ago today, the world learned that a huge team of scientists around the world had confirmed the existence of gravitational waves, the long history of discovery that led to breakthrough.

    1
    The discovery of gravitational waves marked an important step on a never-ending journey of discovery regarding the nature of the universe.
    sakkmesterke/Getty Images

    In 2015 we first heard the whooping sound made by a pair of colliding black holes. Two years later it was the unique chirp made by a pair of colliding neutron stars. Our newfound ability to eavesdrop on cataclysmic events at the far reaches of the universe is thanks to a new generation of gravitational wave detectors. The gravitational sound show is just beginning, and it promises to reveal the nature of spacetime as never before.

    The quest to understand space

    What is space? We know thinkers have pondered that question at least for as long as there are recorded texts. The clay tablets left by Ancient Babylonians show they were toying with the nature of triangles.

    But, 2300 years ago, the Greek mathematician Euclid revolutionised the science of geometry with systematic thinking that captured the descriptive work of the past and elevated it to the level of universal truths or axioms.

    His 13-volume treatise Elements uncovered the perfection of lines and shapes and put it all together in the most influential science book of all time, in print for 2000 years and published in 1000 editions. It is still taught in schools today.

    But are Euclid’s axioms truly universal?

    In the early 1800s, German mathematician and physicist Carl Gauss was the first to challenge Euclid’s laws of geometry, especially his fifth axiom, which states that parallel lines can never meet.

    Gauss observed that on curved surfaces, parallel lines – such as longitude lines at the earth’s equator – intersect at the poles. He also realised that space could have shape, and his Egregium Theorem showed that you could measure its shape if you measured distances and angles.

    Imagine you’re an ant living on a balloon; your world would seem flat. But an ant familiar with the Egregium Theorem would stretch strings and draw triangles. If the angles of the triangle added up to more than 180 degrees, the ant would know it’s living on curved space.

    Egregium, by the way, is Latin for “exceptional”.

    Gauss’ determination to put Euclid’s theorems to the test set the scene for Einstein.

    By 1905, he had already come up with his theory of Special Relativity. This was the theory that gave us E=Mc2, which means that energy has mass and mass has energy.

    In 1907 Einstein had another revelation that he later described as “the happiest thought of my life”. He realised that gravity is indistinguishable from acceleration. If you’re riding an elevator with your bathroom scales, you’ll find you’re lighter as the elevator accelerates down and heavier when it decelerates. So, Einstein realised, gravity is the force you feel when you prevent free fall.

    It took eight more years and help from his friends for him to combine this happy thought with Gauss’s thinking about the shape of space, to create his final theory of gravity: General Relativity. Published in 1915, it was based on the revolutionary idea that mass and energy deform space and time, and that deformed spacetime itself has energy. In a certain sense spacetime is an elastic material: immensely stiff but deformable – like a trampoline.

    Einstein’s publication gave rise to a succession of remarkable discoveries.

    Within months, while serving in the German army, physicist and astronomer Karl Schwarzschild solved Einstein’s equations to reveal how the curvature of space and the warping of time depends on distance from a central mass. The closer the distance and the larger the mass, the more warping there is, and at a certain distance from a central point mass space and time actually come to an end.

    He was of course imagining a ‘black hole’, but it would take 50 years before the term was coined.

    A few months later, in 1916, Einstein found a solution to his own equations. It predicted the existence of gravitational waves, ripples in spacetime that would travel at the speed of light.

    And in the following years, discoveries provided support for the notion that space was a deformable elastic medium – one that could propagate gravitational waves.

    In 1919, English physicist Sir Arthur Eddington’s observation of an eclipse from the island of Principe near West Africa proved that space is curved by the Sun. In 1922 Russian scientist Alexander Friedmann showed that Einstein’s equations predicted a dynamic universe in which space itself must either expand or contract. And in 1929 American astronomer Edwin Hubble discovered that the universe was in fact expanding.

    When Einstein predicted gravitational waves in 1916 he realised that they could be generated by pair of stars circling each other. He came up with a formula that describes how gravitational wave power depends on their masses, the speeds and the spacing – all measurable numbers.

    But there was a catch: in his formula, the wave power was divided by an enormous number, a crazy number, that I call Einstein’s number. Algebraically, Einstein’s number is c5/G – the speed of light multiplied by itself five times, divided by G, the tiny number that tells us the weakness of gravity.

    Put together, c5/G is more than 1054. If you divide anything by a number this vast, you get next to nothing. Einstein realised this. Nothing he could conceive of could possibly produce measurable gravitational waves. The waves were of academic interest only, he concluded.

    What Einstein hadn’t been aware of was that Schwarzschild, who died of an auto-immune disease in 1916, had left him a hidden treasure. The trouble was that Schwarzschild’s solution, which described a singularity where space and time cease to exist, was viewed by Einstein and others as a mathematical oddity, not a description of anything that could possibly be real.

    But 50 years on, black holes – as these singularities were later dubbed – were the best hypothesis to explain a strange x-ray emitting star called Cygnus X-1.

    A tiny object with vast gravity was needed to explain this powerful erratic x-ray emission. People began to think that black holes might be real.

    Then someone took Einstein’s 1916 equation for wave power, and substituted in Schwarzschild’s black hole formula. A school kid could have done it. The result was miraculous!

    With Schwarzschild’s formula, the division by Einstein’s number that made gravitational waves merely academic is transformed into a multiplication by the same number. Suddenly the wave power for a pair of black holes circling each other up-close becomes almost as big as Einstein’s number itself.

    This is roughly the power of all the stars in the visible universe! The catch is it lasts for only an instant. This was Schwarzschild’s hidden treasure.

    Schwarzschild’s work tells us that when black holes collide they create a pure gravitational explosion, more powerful than a supernova or a gamma ray burst. Nothing beats it except the Big Bang itself.

    However, as an explosion of rippling space, it would pass freely through you. Even if it happened as nearby to Earth as the Sun, you would feel no more than a tiniest shudder. Yet each such gravitational explosion would in principle be detectable across the entire universe.

    Harnessing inertia to build a gravitational wave detector

    I was inspired to join the quest to detect colliding black holes by the eccentric pioneer of gravitational wave astronomy, American physicist Joseph Weber. Back then, we reasoned that explosions so vast must be detectable. We thought that if we worked hard at inventing a gravitational detector, we might pick up a signal by Christmas! That was in 1973.

    Our ability to detect gravitational waves relies on the concept of inertia – the tendency of matter to continue in its state of motion unless acted on by an external force.

    Scientists have been relying on inertia to detect relative motion for nearly 2000 years. In 132 AD, Chinese scientist Zhang Heng harnessed inertia to build the first seismometer.

    Inside a big bronze urn he suspended a mass so that it could swing freely in the horizontal plane. If the ground moved, so would the urn, but the mass, anchored to space by the law of inertia, would stay in place.

    Inside, the movement dislodged a ball from the mouth of one of eight dragons that marked the cardinal directions. The ball rolled out and was caught in the mouth of a bronze toad. This way he detected an earthquake hundreds of kilometres away.

    Heng’s seismometer allowed him to detect the motion of the earth against unchanging space. But what if space suddenly stretches? You won’t feel a thing, and nor will a seismometer, just as you do not feel the universe expanding. But, you might notice that a distant object has just moved away from you. It did this because inertia caused it to follow expanding space.

    Modern day gravitational wave detectors like the Laser Interferometer Gravitational-Wave Observatory (LIGO) in the US detect the stretching and shrinking of space caused by a passing wave by suspending two 40 kilogram masses four kilometres apart.

    These masses are coated with near-perfect mirrors, so changes in the distance between them can be measured by using a beam of laser light as a ruler. The catch is the minuscule size of the change. Like ripples in a pond, gravitational waves diminish as they expand away from the source.

    Even though LIGO was aiming to measure the space distortion created by colliding black holes – the biggest dynamic distortion possible – the ripples they create reduce to half every time you double the distance.

    By the time the wave reaches the Earth from a black hole collision a billion light years away, the stretching and shrinking of space in a LIGO detector has reduced to a hundredth of a billionth of a billionth of a metre – much smaller than the size of a proton.


    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    Caltech/MIT Advanced aLigo Hanford, WA, USA installation


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

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

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

    ESA/eLISA the future of gravitational wave research

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

    A dream fulfilled

    It took more than 40 years and several generations of detectors, before, finally, the pair of advanced LIGO detectors were ready to begin listening for the sounds of gravitational waves. The new detectors were three times more sensitive than previous ones, but still three times below their ultimate design specification. We were hopeful but not optimistic.

    On September 14, 2015, a few days before the official start date, the first signal came in. Was it a hoax? Was it accidental? A short rapidly rising pitch, from two octaves below to middle-C made a brief whoop sound. It was heard in two detectors 3000 kilometres apart and had a time delay just right for a wave travelling at the speed of light. After months of investigation there was no doubt that it was real.

    All our dreams were finally fulfilled on February 11, 2016, when gravitational wave astronomers announced in a Washington press conference, that they had indeed detected a pair of black holes spiralling together and merging into a single black hole.

    And since that first detection, more whoops from other colliding black holes have followed.

    You might think that detecting the collision of a pair black holes would be a hard act to follow. Yet a year and a half after that announcement, the world was again thrilling to the news of another type of cosmic cataclysm.

    We had not been optimistic about detecting colliding black holes because we had very little idea how many pairs of black holes might exist. Instead we had placed our hopes on something we knew much more about: neutron stars.

    Neutron stars are one step away from becoming a black hole. Many exist as pulsars: rapidly spinning remnants of supernova explosions that emit powerful flickering beams of radio waves. They have a dimeter of about 20 kilometres, are composed of neutrons, and are denser than an atomic nucleus.

    Thousands of them are known in the Milky Way, and the predictions were that out in the distant universe we might be able to detect one or two of them merging every year.

    Little did we know that we were already detecting those events.

    During the 1980s astronomers were puzzling over vast bursts of gamma rays being detected by orbiting gamma ray telescopes, on average one every day.

    In 1989 a paper published in Nature by Hebrew University physicist Tsvi Piran proposed these bursts were created by merging neutron stars, spiralling together at 10% of light speed, and flinging some of their nearly pure neutron matter out into space. Here it would go off like an enormous nuclear fission bomb, giving off bursts of gamma rays. The process would also be a forge for heavy elements in the universe like platinum and gold.

    Since the advanced LIGO detectors started working in 2015, our 1000-strong team comprising researchers based at more than 80 universities around the world were hoping for all of this: a long slow chirp of gravitational waves as a pair of neutron stars spiralled together, a burst of gamma rays produced when they collided, and an atomic explosion where we might see the signature of gold production.

    Most of us thought the chances of all of this was very small. The gamma ray beam might miss the earth. The explosion, called a macronova or kilonova, is much weaker than a supernova and would be hard to detect.

    However, more than 100 telescopes around the world had already signed up to receive alerts from the LIGO detectors on either side of the US, and the European Virgo detector in Pisa, Italy, in the event of a gravitational wave signal.

    On August 17, 2017, all of our Christmases came at once.

    It was exactly what we had dreamed of. The gravitational wave signal was loud and clear in the two LIGO detectors in the US, but very weak in the European Virgo detector because of its orientation.

    The non-detection by Virgo told us roughly where to look in the sky. The Fermi gamma ray observatory out in space detected a burst of gamma rays 1.7 seconds later, coming from the same region of sky. A few hours later the Swope telescope in Chile detected the fading glow of a vast explosion, in that same region, at the edge of a known galaxy, 130 million light years away.

    Before long 100 telescopes across the southern hemisphere were watching it. The colours in the light indicated the presence of heavy elements like gold and platinum.

    The future

    We called this the birth of multi-messenger astronomy: the gravity wave messenger and the electromagnetic messenger worked in unison. This discovery was a stupendous example of scientific prediction. It confirmed Einstein’s 102 year-old prediction that gravity waves travel at the speed of light, and Piran’s 28 year-old prediction that gamma ray bursts were the signature of colliding neutron stars, and that gold and platinum were formed in this explosion.

    Think about this: that gold on your finger is a fossil from the collision of two neutron stars.

    From these recent discoveries we can predict what lies ahead. As sensitivity improves, we’ll exponentially increase our reach into the universe. Increase the sensitivity by two and you’re reaching into a volume 23 times larger, which means eight times as many signals.

    In the next few years the world’s existing three detectors, plus two more under construction in Japan and India, should be tuning in to the sounds of hundreds of black hole and neutron stars collisions every year.

    More detectors will help to pinpoint the source of the signals, but the biggest pay-off comes from increasing sensitivity. Just a four-fold increase in sensitivity would expand our horizon to more than half of the visible universe. A 10-fold improvement would give us the whole universe! Detectors with this capability have been suggested for Australia, China, Europe and the USA.

    The legacy of Einstein, the recent Nobel Prize winners and the huge international LIGO and Virgo team, will be the ability to listen to the symphony of the universe. It will be in a minor key because the truth is that our universe is winding down as black holes form, grow and gobble up each other.

    But I can’t end on a melancholy note. Rather I want to sing in celebration of gravitational waves as humanity’s new set of ears. We are no longer deaf to the sounds of space. And we can be pretty certain that our cosmic ears will give us deeper understanding of the nature of space.

    We are still groping to understand its microstructure and its reason for being. Is it a quantum foam inhabited by strings, or is it something else?

    Stay tuned for surprises, unforeseen revelations, and an avalanche of discoveries as our remarkable new technology develops.

    An extra treat https://sciencesprings.wordpress.com/2017/10/20/from-ucsc-neutron-stars-gravitational-waves-and-all-the-gold-in-the-universe/

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    The Australian International Gravitational Observatory (AIGO) Located at Gingin

    Welcome to the Australian International Gravitational Research Centre. The Australian International Gravitational Research Centre is based in the School of physics of the University of Western Australia (UWA) and is part of the Australian Consortium for Interferometric Gravitational Astronomy (ACIGA). It was established in 1990 to enable a cooperative research centre providing a national focus in a major frontier in physics: the detection of gravitational waves and the development of gravitational astronomy. Through strong national and international participation, the research centre concentrates on the development of advanced technologies driven by the goal of the next generation large scale gravitational observatory construction.

     
  • richardmitnick 10:47 am on October 17, 2018 Permalink | Reply
    Tags: "Largest Galaxy Proto-Supercluster Found", , Astrophysics, , , , Hyperion galaxy proto-supercluster, VIMOS instrument of ESO’s Very Large Telescope   

    From European Southern Observatory: “Largest Galaxy Proto-Supercluster Found” 

    ESO 50 Large

    From European Southern Observatory

    17 October 2018

    Olga Cucciati
    INAF Fellow – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna
    Bologna, Italy
    Email: olga.cucciati@inaf.it

    Calum Turner
    ESO Public Information Officer
    Garching bei München, Germany
    Tel: +49 89 3200 6670
    Email: pio@eso.org

    1
    An international team of astronomers using the VIMOS instrument of ESO’s Very Large Telescope have uncovered a colossal structure in the early Universe. This galaxy proto-supercluster — which they nickname Hyperion — was unveiled by new measurements and a complex examination of archive data. This is the largest and most massive structure yet found at such a remote time and distance — merely 2 billion years after the Big Bang. This visualization shows Hyperion and is based on real data. Credit: ESO/L. Calçada & Olaga Cucciati et al.

    A team of astronomers, led by Olga Cucciati of Istituto Nazionale di Astrofisica (INAF) Bologna, have used the VIMOS instrument on ESO’s Very Large Telescope (VLT) Melipal UT3 to identify a gigantic proto-supercluster of galaxies forming in the early Universe, just 2.3 billion years after the Big Bang.

    ESO VIMOS on VLT Melipal UT3

    This structure, which the researchers nicknamed Hyperion, is the largest and most massive structure to be found so early in the formation of the Universe [1]. The enormous mass of the proto-supercluster is calculated to be more than one million billion times that of the Sun. This titanic mass is similar to that of the largest structures observed in the Universe today, but finding such a massive object in the early Universe surprised astronomers.

    “This is the first time that such a large structure has been identified at such a high redshift, just over 2 billion years after the Big Bang,” explained the first author of the discovery paper, Olga Cucciati [2]. “Normally these kinds of structures are known at lower redshifts, which means when the Universe has had much more time to evolve and construct such huge things. It was a surprise to see something this evolved when the Universe was relatively young!”

    Located in the COSMOS field in the constellation of Sextans (The Sextant), Hyperion was identified by analysing the vast amount of data obtained from the VIMOS Ultra-deep Survey led by Olivier Le Fèvre (Aix-Marseille Université, CNRS, CNES). The VIMOS Ultra-Deep Survey provides an unprecedented 3D map of the distribution of over 10 000 galaxies in the distant Universe.

    The team found that Hyperion has a very complex structure, containing at least 7 high-density regions connected by filaments of galaxies, and its size is comparable to nearby superclusters, though it has a very different structure.

    “Superclusters closer to Earth tend to a much more concentrated distribution of mass with clear structural features,” explains Brian Lemaux, an astronomer from University of California, Davis and LAM, and a co-leader of the team behind this result. “But in Hyperion, the mass is distributed much more uniformly in a series of connected blobs, populated by loose associations of galaxies.”

    This contrast is most likely due to the fact that nearby superclusters have had billions of years for gravity to gather matter together into denser regions — a process that has been acting for far less time in the much younger Hyperion.

    Given its size so early in the history of the Universe, Hyperion is expected to evolve into something similar to the immense structures in the local Universe such as the superclusters making up the Sloan Great Wall or the Virgo Supercluster that contains our own galaxy, the Milky Way.

    Sloan Great Wall, SDSS

    Virgo Supercluster NASA


    Virgo Supercluster, Wikipedia

    “Understanding Hyperion and how it compares to similar recent structures can give insights into how the Universe developed in the past and will evolve into the future, and allows us the opportunity to challenge some models of supercluster formation,” concluded Cucciati. “Unearthing this cosmic titan helps uncover the history of these large-scale structures.”

    Notes

    [1] The moniker Hyperion was chosen after a Titan from Greek mythology, due to the immense size and mass of the proto-supercluster. The inspiration for this mythological nomenclature comes from a previously discovered proto-cluster found within Hyperion and named Colossus. The individual areas of high density in Hyperion have been assigned mythological names, such as Theia, Eos, Selene and Helios, the latter being depicted in the ancient statue of the Colossus of Rhodes.

    The titanic mass of Hyperion, one million billion times that of the Sun, is 1015 solar masses in scientific notation.

    [2] Light reaching Earth from extremely distant galaxies took a long time to travel, giving us a window into the past when the Universe was much younger. This wavelength of this light has been stretched by the expansion of the Universe over its journey, an effect known as cosmological redshift. More distant, older objects have a correspondingly larger redshift, leading astronomers to often use redshift and age interchangeably. Hyperion’s redshift of 2.45 means that astronomers observed the proto-supercluster as it was 2.3 billion years after the Big Bang.

    This research is published in the paper “The progeny of a Cosmic Titan: a massive multi-component proto-supercluster in formation at z=2.45 in VUDS”, which will appear in the journal Astronomy & Astrophysics. https://www.eso.org/public/archives/releases/sciencepapers/eso1833/eso1833a.pdf

    The team behind this result was composed of O. Cucciati (INAF-OAS Bologna, Italy), B. C. Lemaux (University of California, Davis, USA and LAM – Aix Marseille Université, CNRS, CNES, France), G. Zamorani (INAF-OAS Bologna, Italy), O.Le Fèvre (LAM – Aix Marseille Université, CNRS, CNES, France), L. A. M. Tasca (LAM – Aix Marseille Université, CNRS, CNES, France), N. P. Hathi (Space Telescope Science Institute, Baltimore, USA), K-G. Lee (Kavli IPMU (WPI), The University of Tokyo, Japan, & Lawrence Berkeley National Laboratory, USA), S. Bardelli (INAF-OAS Bologna, Italy), P. Cassata (University of Padova, Italy), B. Garilli (INAF–IASF Milano, Italy), V. Le Brun (LAM – Aix Marseille Université, CNRS, CNES, France), D. Maccagni (INAF–IASF Milano, Italy), L. Pentericci (INAF–Osservatorio Astronomico di Roma, Italy), R. Thomas (European Southern Observatory, Vitacura, Chile), E. Vanzella (INAF-OAS Bologna, Italy), E. Zucca (INAF-OAS Bologna, Italy), L. M. Lubin (University of California, Davis, USA), R. Amorin (Kavli Institute for Cosmology & Cavendish Laboratory, University of Cambridge, UK), L. P. Cassarà (INAF–IASF Milano, Italy), A. Cimatti (University of Bologna & INAF-OAS Bologna, Italy), M. Talia (University of Bologna, Italy), D. Vergani (INAF-OAS Bologna, Italy), A. Koekemoer (Space Telescope Science Institute, Baltimore, USA), J. Pforr (ESA ESTEC, the Netherlands), and M. Salvato (Max-Planck-Institut für Extraterrestrische Physik, Garching bei München, Germany)

    See the full article here .


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    ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre EEuropean Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

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    ESO/NTT at Cerro La Silla, Chile, at an altitude of 2400 metres



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    ESO/APEX high on the Chajnantor plateau in Chile’s Atacama region, at an altitude of over 4,800 m (15,700 ft)

    Leiden MASCARA instrument, La Silla, located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    Leiden MASCARA cabinet at ESO Cerro la Silla located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    ESO Next Generation Transit Survey at Cerro Paranel, 2,635 metres (8,645 ft) above sea level

    SPECULOOS four 1m-diameter robotic telescopes 2016 in the ESO Paranal Observatory, 2,635 metres (8,645 ft) above sea level

    ESO TAROT telescope at Paranal, 2,635 metres (8,645 ft) above sea level

    ESO ExTrA telescopes at Cerro LaSilla at an altitude of 2400 metres

     
  • richardmitnick 9:04 am on October 17, 2018 Permalink | Reply
    Tags: , Astrophysics, , Collimated jets, , Cygnus A, HAWC+ camera on SOFIA, Magnetic Fields May Be the Key to Black Hole Activity, ,   

    From NASA/DLR SOFIA: “Magnetic Fields May Be the Key to Black Hole Activity” 

    From NASA/DLR SOFIA

    NASA SOFIA Banner

    NASA SOFIA

    NASA SOFIA GREAT [German Receiver for Astronomy at Terahertz Frequencies]

    NASA SOFIA High-resolution Airborne Wideband Camera-Plus HAWC+ Camera

    NASA/SOFIA Forcast

    1
    Artist’s conception of the core of Cygnus A, including the dusty donut-shaped surroundings, called a torus, and jets launching from its center. Magnetic fields are illustrated trapping the dust in the torus. These magnetic fields could be helping power the black hole hidden in the galaxy’s core by confining the dust in the torus and keeping it close enough to be gobbled up by the hungry black hole.
    Credits: NASA/SOFIA/Lynette Cook

    Collimated jets provide astronomers with some of the most powerful evidence that a supermassive black hole lurks in the heart of most galaxies. Some of these black holes appear to be active, gobbling up material from their surroundings and launching jets at ultra-high speeds, while others are quiescent, even dormant. Why are some black holes feasting and others starving? Recent observations from the Stratospheric Observatory for Infrared Astronomy, or SOFIA, are shedding light on this question.

    SOFIA data indicate that magnetic fields are trapping and confining dust near the center of the active galaxy, Cygnus A, and feeding material onto the supermassive black hole at its center.

    The unified model, which attempts to explain the different properties ­of active galaxies, states that the core is surrounded by a donut-shaped dust cloud, called a torus. How this obscuring structure is created and sustained has never been clear, but these new results from SOFIA indicate that magnetic fields may be responsible for keeping the dust close enough to be devoured by the hungry black hole. In fact, one of the fundamental differences between active galaxies like Cygnus A and their less active cousins, like our own Milky Way, may be the presence or absence of a strong magnetic field around the black hole.

    Although celestial magnetic fields are notoriously difficult to observe, astronomers have used polarized light — optical light from scattering and radio light from accelerating electrons — to study magnetic fields in galaxies. But optical wavelengths are too short and the radio wavelengths are too long to observe the torus directly. The infrared wavelengths observed by SOFIA are just right, allowing scientists, for the first time, to target and isolate the dusty torus.

    SOFIA’s new instrument, the High-resolution Airborne Wideband Camera-plus (HAWC+), is especially sensitive to the infrared emission from aligned dust grains. This has proven to be a powerful technique to study magnetic fields and test a fundamental prediction of the unified model: the role of the dusty torus in the active-galaxy phenomena.

    “It’s always exciting to discover something completely new,” noted Enrique Lopez-Rodriguez, a scientist at the SOFIA Science Center, and the lead author on the report of this new discovery. “These observations from HAWC+ are unique. They show us how infrared polarization can contribute to the study of galaxies.”

    2
    Two images of Cygnus A layered over each other to show the galaxy’s jets glowing with radio radiation (shown in red). Quiescent galaxies, like our own Milky Way, do not have jets like this, which may be related to magnetic fields. The yellow image shows background stars and the center of the galaxy shrouded in dust when observed with visible light. The area SOFIA observed is inside the small red dot in the center.
    Credits: Optical Image: NASA/STSiC Radio Image: NSF/NRAO/AUI/VLA

    NASA/ESA Hubble Telescope

    NRAO/Karl V Jansky Expanded Very Large Array, on the Plains of San Agustin fifty miles west of Socorro, NM, USA, at an elevation of 6970 ft (2124 m)

    Recent observations of the heart of Cygnus A made with HAWC+ show infrared radiation dominated by a well-aligned dusty structure. Combining these results with archival data from the Herschel Space Observatory, the Hubble Space Telescope and the Gran Telescopio Canarias, the research team found that this powerful active galaxy, with its iconic large-scale jets, is able to confine the obscuring torus that feeds the supermassive black hole using a strong magnetic field.

    ESA/Herschel spacecraft active from 2009 to 2013

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

    The results of this study were published in the July 10th issue of The Astrophysical Journal Letters.

    Cygnus A is in the perfect location to learn about the role magnetic fields play in confining the dusty torus and channeling material onto the supermassive black hole because it is the closest and most powerful active galaxy. More observations of different types of galaxies are necessary to get the full picture of how magnetic fields affect the evolution of the environment surrounding supermassive black holes. If, for example, HAWC+ reveals highly polarized infrared emission from the centers of active galaxies but not from quiescent galaxies, it would support the idea that magnetic fields regulate black hole feeding and reinforce astronomers’ confidence in the unified model of active galaxies.

    See the full article here .

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    SOFIA is a Boeing 747SP jetliner modified to carry a 100-inch diameter telescope. SOFIA is a joint project of NASA and the German Aerospace Center (DLR). The aircraft is based at and the program is managed from NASA Armstrong Flight Research Center’s facility in Palmdale, California. NASA’s Ames Research Center, manages the SOFIA science and mission operations in cooperation with the Universities Space Research Association (USRA) headquartered in Columbia, Maryland, and the German SOFIA Institute (DSI) at the University of Stuttgart.

    NASA image

    DLR Bloc

     
  • richardmitnick 8:23 am on October 17, 2018 Permalink | Reply
    Tags: , Astrophysics, , , , , Speed of Light, The CMB: the cosmic microwave background, The CNB: the cosmic neutrino background, The Universe Has A Speed Limit And It Isn’t The Speed Of Light, The WHIM: the warm-hot intergalactic medium   

    From Ethan Siegel: “The Universe Has A Speed Limit, And It Isn’t The Speed Of Light” 

    From Ethan Siegel

    Oct 16, 2018

    1
    All massless particles travel at the speed of light, including the photon, gluon and gravitational waves, which carry the electromagnetic, strong nuclear and gravitational interactions, respectively. Particles with mass must always travel at speeds below the speed of light, and there’s an even more restrictive cutoff in our Universe. (NASA/Sonoma State University/Aurore Simonnet)

    Nothing can go faster than the speed of light in a vacuum. But particles in our Universe can’t even go that fast.

    When it comes to speed limits, the ultimate one set by the laws of physics themselves is the speed of light. As Albert Einstein first realized, everyone looking at a light ray sees that it appears to move at the same speed, regardless of whether it’s moving towards you or away from you. No matter how fast you travel or in what direction, all light always moves at the same speed, and this is true for all observers at all times. Moreover, anything that’s made of matter can only approach, but never reach, the speed of light. If you don’t have mass, you must move at the speed of light; if you do have mass, you can never reach it.

    But practically, in our Universe, there’s an even more restrictive speed limit for matter, and it’s lower than the speed of light. Here’s the scientific story of the real cosmic speed limit.

    When scientists talk about the speed of light — 299,792,458 m/s — we implicitly mean “the speed of light in a vacuum.” Only in the absence of particles, fields, or a medium to travel through can we achieve this ultimate cosmic speed. Even at that, it’s only the truly massless particles and waves that can achieve this speed. This includes photons, gluons, and gravitational waves, but not anything else we know of.

    Quarks, leptons, neutrinos, and even the hypothesized dark matter all have masses as a property inherent to them. Objects made out of these particles, like protons, atoms, and human beings all have mass, too. As a result, they can approach, but never reach, the speed of light in a vacuum. No matter how much energy you put into them, the speed of light, even in a vacuum, will forever be unattainable.

    But there’s no such thing, practically, as a perfect vacuum. Even in the deepest abyss of intergalactic space, there are three things you absolutely cannot get rid of.

    The WHIM: the warm-hot intergalactic medium. This tenuous, sparse plasma are the leftovers from the cosmic web. While matter clumps into stars, galaxies, and larger groupings, a fraction of that matter remains in the great voids of the Universe. Starlight ionizes it, creating a plasma that may make up about 50% of the total normal matter in the Universe.

    WHIM-Warm-Hot Intergalactic Medium Trevor Ponman U Birmingham


    The CMB: the cosmic microwave background. This leftover bath of photons originates from the Big Bang, where it was at extremely high energies. Even today, at temperatures just 2.7 degrees above absolute zero, there are over 400 CMB photons per cubic centimeter of space.

    CMB per ESA/Planck


    ESA/Planck 2009 to 2013

    The CNB: the cosmic neutrino background. The Big Bang, in addition to photons, creates a bath of neutrinos. Outnumbering protons by perhaps a billion to one, many of these now-slow-moving particles fall into galaxies and clusters, but many remain in intergalactic space as well.

    CNB- the cosmic neutrino background-Amand Faessler U Tuebingen

    3
    A multiwavelength view of the galactic center shows stars, gas, radiation and black holes, among other sources. But the light coming from all of these sources, from gamma rays to visible to radio light, can only indicate what our instruments are sensitive enough to detect from 25,000+ light years away. (NASA/ESA/SSC/CXC/STScI)

    Any particle traveling through the Universe will encounter particles from the WHIM, neutrinos from the CNB, and photons from the CMB. Even though they’re the lowest-energy things, the CMB photons are the most numerous and evenly-distributed particles of all. No matter how you’re generated or how much energy you have, it’s not really possible to avoid interacting with this 13.8 billion year old radiation.

    When we think about the highest-energy particles in the Universe — i.e., the ones that will be moving the fastest — we fully expect they’ll be generated under the most extreme conditions the Universe has to offer. That means we think we’ll find them where energies are highest and fields are strongest: in the vicinity of collapsed objects like neutron stars and black holes.

    4
    In this artistic rendering, a blazar is accelerating protons that produce pions, which produce neutrinos and gamma rays. (IceCube/NASA)

    U Wisconsin IceCube experiment at the South Pole



    Neutron stars and black hole are where you can not only find the strongest gravitational fields in the Universe, but — in theory — the strongest electromagnetic fields, too. The extremely strong fields are generated by charged particles, either on the surface of a neutron star or in the accretion disk around a black hole, that move close to the speed of light. Moving charged particles generate magnetic fields, and as particles move through these fields, they accelerate.

    This acceleration causes not only the emission of light of a myriad of wavelengths, from X-rays down to radio waves, but also the fastest, highest-energy particles ever seen: cosmic rays.

    Cosmic rays produced by high-energy astrophysics sources (ASPERA collaboration – AStroParticle ERAnet)

    Artist’s impression of the active galactic nucleus (DESY, Science Communication Lab)

    Whereas the Large Hadron Collider accelerates particles here on Earth up to a maximum velocity of 299,792,455 m/s, or 99.999999% the speed of light, cosmic rays can smash that barrier. The highest-energy cosmic rays have approximately 36 million times the energy of the fastest protons ever created at the Large Hadron Collider. Assuming that these cosmic rays are also made of protons gives a speed of 299,792,457.99999999999992 m/s, which is extremely close to, but still below, the speed of light in a vacuum.

    There’s a very good reason that, by time we receive them, these cosmic rays aren’t more energetic than this.

    The problem is that space isn’t a vacuum. In particular, the CMB will have its photons collide and interact with these particles as they travel through the Universe. No matter how high the energy is of the particle you made, it has to pass through the radiation bath that’s left over from the Big Bang in order to reach you.

    Even though this radiation is incredibly cold, at an average temperature of some 2.725 Kelvin, the mean energy of each photon in there isn’t negligible; it’s around 0.00023 electron-Volts. Even though that’s a tiny number, the cosmic rays hitting it can be incredibly energetic. Every time a high-energy charged particle interacts with a photon, it has the same possibility that all interacting particles have: if it’s energetically allowed, by E=mc², then there’s a chance it can create a new particle!

    5
    Whenever two particles collide at high enough energies, they have the opportunity to produce additional particle-antiparticle pairs, or new particles as the laws of quantum physics allow. Einstein’s E = mc² is indiscriminate this way. (E. Siegel / Beyond The Galaxy)

    If you ever create a particle with energies in excess of 5 × 10¹⁹ eV, they can only travel a few million light years — max — before one of these photons, left over from the Big Bang, interacts with it. When that interaction occurs, there will be enough energy to produce a neutral pion, which steals energy away from the original cosmic ray.

    The more energetic your particle is, the more likely you are to produce pions, which you’ll continue to do until you fall below this theoretical cosmic energy limit, known as the GZK cutoff. (Named for three physicists: Greisen, Zatsepin, and Kuzmin.) There’s even more braking (Bremsstrahlung) radiation that arises from interactions with any particles in the interstellar/intergalactic medium. Even lower-energy particles are subject to it, and radiate energy away in droves as electron/positron pairs (and other particles) are produced.

    We believe that every charged particle in the cosmos — every cosmic ray, every proton, every atomic nucleus — should limited by this speed. Not just the speed of light, but a little bit lower, thanks to the leftover glow from the Big Bang and the particles in the intergalactic medium. If we see anything that’s at a higher energy, then it either means:

    1.particles at high energies might be playing by different rules than the ones we presently think they do,
    2.they are being produced much closer than we think they are: within our own Local Group or Milky Way, rather than these distant, extragalactic black holes,
    3.or they’re not protons at all, but composite nuclei.

    The few particles we’ve seen that break the GZK barrier are indeed in excess of 5 × 10¹⁹ eV, in terms of energy, but do not exceed 3 × 10²¹ eV, which would be the corresponding energy value for an iron nucleus. Since many of the highest-energy cosmic rays have been confirmed to be heavy nuclei, rather than individual protons, this reigns as the most likely explanation for the extreme ultra-high-energy cosmic rays.

    6
    The spectrum of cosmic rays. As we go to higher and higher energies, we find fewer and fewer cosmic rays. We expected a complete cutoff at 5 x 10¹⁹ eV, but see particles coming in with up to 10 times that energy. (Hillas 2006 / University of Hamburg)

    There is a speed limit to the particles that travel through the Universe, and it isn’t the speed of light. Instead, it’s a value that’s very slightly lower, dictated by the amount of energy in the leftover glow from the Big Bang. As the Universe continues to expand and cool, that speed limit will slowly rise over cosmic timescales, getting ever-closer to the speed of light. But remember, as you travel through the Universe, if you go too fast, even the radiation left over from the Big Bang can fry you. So long as you’re made of matter, there’s a cosmic speed limit that you simply cannot overcome.

    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 10:34 pm on October 16, 2018 Permalink | Reply
    Tags: An Alternative Technique for Detecting Forming Exoplanets Around Young Stars, , Astrophysics, , ,   

    From Isaac Newton Group of Telescopes: “An Alternative Technique for Detecting Forming Exoplanets Around Young Stars” 

    Isaac Newton Group of Telescopes Logo
    From Isaac Newton Group of Telescopes

    16 October, 2018

    The large number of detected exoplanets around evolved stars sharply contrasts with the lack of detections of forming planets in protoplanetary disks around young stars, mainly because of the observational difficulties.

    One example of the latter is the young, almost solar-mass star LkCa 15, which is located at around 520 light years in the Taurus-Auriga star-forming region.

    On the one hand, a team of astronomers reported that LkCa 15 hosts 3 infrared bright planets in its protoplanetary disk. One of them, LkCa 15 b, was also detected in bright H-alpha emission and it is claimed to be the first exoplanet caught in the process of formation. This discovery was made using a technique called “near-IR non-redundant masking” using the Large Binocular Telescope, and from simultaneous differential imaging using the Magellan Adaptive Optics System on the Clay telescope.

    U Arizona Large Binocular Telescope, Large Binocular Telescope Interferometer, or LBTI, is a ground-based instrument connecting two 8-meter class telescopes on Mount Graham, Arizona, USA, Altitude 3,221 m (10,568 ft.) to form the largest single-mount telescope in the world. The interferometer is designed to detect and study stars and planets outside our solar system. Image credit: NASA/JPL-Caltech.

    Las Campanas Clay Magellan telescope, located at Carnegie’s Las Campanas Observatory, Chile, approximately 100 kilometres (62 mi) northeast of the city of La Serena, over 2,500 m (8,200 ft) high

    On the other hand, a more recent work using SPHERE on the Very Large Telescope suggests that the infrared bright planets are not such, but instead persistent structures of the inner protoplanetary disk that surrounds LkCa 15. However, the bright H-alpha emission of LkCa 15 b remains unexplained.

    ESO SPHERE extreme adaptive optics system and coronagraphic facility on the extreme adaptive optics system and coronagraphic facility on the VLT UT3 MELIPAL, on Cerro Paranal, Chile, with an elevation of 2,635 metres (8,645 ft) above sea level

    ESO VLT at Cerro Paranal in the Atacama Desert, •ANTU (UT1; The Sun ),
    •KUEYEN (UT2; The Moon ),
    •MELIPAL (UT3; The Southern Cross ), and
    •YEPUN (UT4; Venus – as evening star).
    elevation 2,635 m (8,645 ft) from above Credit J.L. Dauvergne & G. Hüdepohl atacama photo

    Earlier this year, an international team of astronomers led by Ignacio Mendigutía (Centro de Astrobiología, Spain), decided to use the ISIS spectrograph on the William Herschel Telescope (WHT) to study the nature of LkCa15 b, by means of a technique called spectro-astrometry.

    ISIS Spectrograph on the ING William Herschel Telescope

    This allowed them to derive not only the intensity spectrum around the H-alpha emission, but also the so called photocentre spectrum and the full width half maximum (FWHM) spectrum.

    The photocentre spectrum tells us about the position in the sky where the brightness (as a function of wavelength) comes from. If an H-alpha-bright planet is surrounding LkCa 15, the bulk of the H-alpha emission should come from a specific point in between the star and the planet, whereas the brightness at other wavelengths, where the planet is faint, should only come from the star.

    Therefore the photocentre spectrum should reveal a displacement precisely at the H-alpha wavelength when the spectrograph is oriented in the direction of the planet, and no displacement at all when the spectrograph is oriented in the perpendicular direction.

    The FWHM spectrum is a measurement of the size of the emitting source. If a planet is surrounding LkCa 15, the FWHM should also increase a bit when the spectrograph is oriented in the direction of the planet, although such signature is so weak that we would not be able to detect it with the instrumentation used. If the spectrograph is oriented in the direction perpendicular to the position of the planet, then no FWHM displacement should be observed at all.

    Surprisingly, the new observations revealed no photocentre signature at either orientation of the spectrograph, but a FWHM signature at both orientations (see the accompanying figure). These observations can be explained by the existence of a roughly symmetric H-alpha emitting source, that is larger that the central star, and may be related to an outflow or a disk wind, usually observed in young stars. Interestingly, the size of the H-alpha extended region inferred from the observations and models is similar to the orbit size initially attributed to a forming planet.

    1
    Spectro-astrometric results of LkCa 15 taken with ISIS on the WHT. From top to bottom, H-alpha intensity, photocentre, and FWHM spectra. The left panels refer to data taken when the spectrograph was oriented towards the reported position of the planet, and the right panels to the perpendicular orientation. The dotted lines show the original data and the solid lines after cleaning them to better observe possible signatures. The accuracy obtained is indicated with the horizontal dashed lines: less than one milli-arcsecond! The lack of photocentre signature at any spectrograph orientation and the similar FWHM signatures at both orientations is not compatible with the presence of a forming planet but with extended and roughly symmetric emission. The red lines show the result of the model for such extended source, reasonably fitting the observations. Credit: Ignacio Mendigutía. Large format: [ PNG ].

    Although the new observations cannot be explained by a forming planet, optical spectro-astrometry using ISIS has proven to be an efficient tool to test the presence of such planets, opening a new window to survey planet formation in protoplanetary disks.

    Spectro-astrometry of the pre-transitional star LkCa 15 does not reveal an accreting planet but extended Halpha emission“,

    See the full article here .

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    Isaac Newton Group telescopes
    Isaac Newton Group telescopes


    ING 4 meter William Herschel Telescope at Roque de los Muchachos Observatory on La Palma in the Canary Islands, 2,396 m (7,861 ft)


    ING Isaac Newton 2.5m telescope at Roque de los Muchachos Observatory on La Palma in the Canary Islands, Spain, Altitude 2,344 m (7,690 ft)

     
  • richardmitnick 9:21 pm on October 16, 2018 Permalink | Reply
    Tags: "We have a case of cosmic look-alikes " said co-author Geoffrey Ryan of UMCP-so the simplest explanation is that they are from the same family of objects.", , , Astrophysics, , , , GW170817 and GRB 150101B, ,   

    From NASA Chandra: All in the Family: Kin of Gravitational-Wave Source Discovered 

    NASA Chandra Banner

    NASA/Chandra Telescope

    From NASA Chandra

    October 16, 2018
    Media contacts:
    Megan Watzke
    Chandra X-ray Center, Cambridge, Mass.
    617-496-7998
    mwatzke@cfa.harvard.edu

    1
    Credit: X-ray: NASA/CXC/GSFC/UMC/E. Troja et al.; Optical and infrared: NASA/STScI

    NASA/ESA Hubble Telescope

    A source with remarkable similarities to GW170817, the first source identified to emit gravitational waves and light, has been discovered.

    This new object, called GRB 150101B, was first seen as a gamma-ray burst in January 2015.

    Follow-up observations with Chandra and several other telescopes at different wavelengths uncovered common traits between the two objects.

    Chandra images showed how GRB 150101B faded with time, a key piece of information.

    About a year ago, astronomers excitedly reported the first detection of electromagnetic waves, or light, from a gravitational wave source. Now, a year later, researchers are announcing the existence of a cosmic relative to that historic event.

    The discovery was made using data from telescopes including NASA’s Chandra X-ray Observatory, Fermi Gamma-ray Space Telescope, Neil Gehrels Swift Observatory, the NASA Hubble Space Telescope (HST), and the Discovery Channel Telescope (DCT).

    NASA/Fermi LAT


    NASA/Fermi Gamma Ray Space Telescope

    NASA Neil Gehrels Swift Observatory


    Discovery Channel Telescope at Lowell Observatory, Happy Jack AZ, USA, Altitude 2,360 m (7,740 ft)

    The object of the new study, called GRB 150101B, was first reported as a gamma-ray burst detected by Fermi in January 2015. This detection and follow-up observations at other wavelengths show GRB 150101B shares remarkable similarities to the neutron star merger and gravitational wave source discovered by Advanced Laser Interferometer Gravitational Wave Observatory (LIGO) and its European counterpart Virgo in 2017 known as GW170817. The latest study concludes that these two separate objects may, in fact, be related.


    “It’s a big step to go from one detected object to two,” said Eleonora Troja, lead author of the study from NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and the University of Maryland at College Park (UMCP). “Our discovery tells us that events like GW170817 and GRB 150101B could represent a whole new class of erupting objects that turn on and off in X-rays and might actually be relatively common.”

    Troja and her colleagues think both GRB 150101B and GW170817 were most likely produced by the same type of event: the merger of two neutron stars, a catastrophic coalescence that generated a narrow jet, or beam, of high-energy particles. The jet produced a short, intense burst of gamma rays (known as a short GRB), a high-energy flash that can last only seconds. GW170817 proved that these events may also create ripples in space-time itself called gravitational waves.

    The apparent match between GRB 150101B and GW170817 is striking: both produced an unusually faint and short-lived gamma ray burst, and both were a source of bright, blue optical light lasting a few days, and X-ray emission lasted much longer. The host galaxies are also remarkably similar, based on Hubble Space Telescope and DCT observations. Both are bright elliptical galaxies with a population of stars a few billion years old and displaying no evidence for new stars forming.

    “We have a case of cosmic look-alikes,” said co-author Geoffrey Ryan of UMCP. “They look the same, act the same and come from similar neighborhoods, so the simplest explanation is that they are from the same family of objects.”

    In the cases of both GRB 150101B and GW170817, the slow rise in the X-ray emission compared to most GRBs implies that the explosion was likely viewed “off-axis,” that is, with the jet not pointing directly towards the Earth. The discovery of GRB150101 represents only the second time astronomers have ever detected an off-axis short GRB.

    While there are many commonalities between GRB 150101B and GW170817, there are two very important differences. One is their location. GW170817 is about 130 million light years from Earth, while GRB 150101B lies about 1.7 billion light years away. Even if Advanced LIGO had been operating in early 2015, it would very likely not have detected gravitational waves from GRB 150101B because of its greater distance.

    “The beauty of GW170817 is that it gave us a set of characteristics, kind of like genetic markers, to identify new family members of explosive objects at even greater distances than LIGO can currently reach,” said co-author Luigi Piro of National Institute for Astrophysics in Rome.

    The optical emission from GB150101B is largely in the blue portion of the spectrum, providing an important clue that this event involved a so-called kilonova, as seen in GW170817. A kilonova is an extremely powerful explosion that not only releases a large amount energy, but may also produce important elements like gold, platinum, and uranium that other stellar explosions do not.

    It is possible that a few mergers like the ones seen in GW170817 and GRB 150101B had been detected as short GRBs before but had not been identified with other telescopes. Without detections at longer wavelengths like X-rays or optical light, GRB positions are not accurate enough to determine what galaxy they are located in.

    In the case of GRB 150101B, astronomers thought at first that the counterpart was an X-ray source detected by Swift in the center of the galaxy, likely from material falling into a supermassive black hole. However, follow-up observations with Chandra detected the true counterpart away from the center of the host galaxy.

    The other important difference between GW170817 and GRB 150101B is that without gravitational wave detection, the team does not know the masses of the two objects that merged. It is possible that the merger was between a black hole and a neutron star, rather than two neutron stars.

    “We need more cases like GW170817 that combine gravitational wave and electromagnetic data to find an example between a neutron star and black hole. Such a detection would be the first of its kind,” said co-author Hendrik Van Eerten of the University of Bath in the United Kingdom. “Our results are encouraging for finding more mergers and making such a detection.”

    A paper describing these results appears in the journal Nature Communications today.

    See the full article here .


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    Please help promote STEM in your local schools.

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    NASA’s Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra’s science and flight operations from Cambridge, Mass.

     
  • richardmitnick 7:21 pm on October 16, 2018 Permalink | Reply
    Tags: Astrophysics, , , , MIT Plasma Science and Fusion Center, Nuno Loureiro, Physicist explores the behavior of the universe’s most abundant form of matter, Physics of plasmas, Plasma is a sort of fourth phase of matter, The solar wind is the best plasma turbulence laboratory we have, Turbulence-a major stumbling block so far to practical fusion power   

    From MIT News-“Nuno Loureiro: Probing the world of plasmas” 

    MIT News
    MIT Widget

    From MIT News

    October 15, 2018
    David L. Chandler

    1
    A major motivation for moving to MIT from his research position, Nuno Loureiro says, was working with students. Image: Jared Charney

    Physicist explores the behavior of the universe’s most abundant form of matter.

    Growing up in the small city of Viseu in central Portugal, Nuno Loureiro knew he wanted to be a scientist, even in the early years of primary school when “everyone else wanted to be a policeman or a fireman,” he recalls. He can’t quite place the origin of that interest in science: He was 17 the first time he met a scientist, he says with an amused look.

    By the time Loureiro finished high school, his interest in science had crystallized, and “I realized that physics was what I liked best,” he says. During his undergraduate studies at the IST Lisbon, he began to focus on fusion, which “seemed like a very appealing field,” where major developments were likely during his lifetime, he says.

    Fusion, and specifically the physics of plasmas, has remained his primary research focus ever since, through graduate school, postdoc stints, and now in his research and teaching at MIT. He explains that plasma research “lives in two different worlds.” On the one hand, it involves astrophysics, dealing with the processes that happen in and around stars; on the other, it’s part of the quest to generate electricity that’s clean and virtually inexhaustible, through fusion reactors.

    Plasma is a sort of fourth phase of matter, similar to a gas but with the atoms stripped apart into a kind of soup of electrons and ions. It forms about 99 percent of the visible matter in the universe, including stars and the wispy tendrils of material spread between them. Among the trickiest challenges to understanding the behavior of plasmas is their turbulence, which can dissipate away energy from a reactor, and which proceeds in very complex and hard-to-predict ways — a major stumbling block so far to practical fusion power.

    While everyone is familiar with turbulence in fluids, from breaking waves to cream stirred into coffee, plasma turbulence can be quite different, Loureiro explains, because plasmas are riddled with magnetic and electric fields that push and pull them in dynamic ways. “A very noteworthy example is the solar wind,” he says, referring to the ongoing but highly variable stream of particles ejected by the sun and sweeping past Earth, sometimes producing auroras and affecting the electronics of communications satellites. Predicting the dynamics of such flows is a major goal of plasma research.

    “The solar wind is the best plasma turbulence laboratory we have,” Loureiro says. “It’s increasingly well-diagnosed, because we have these satellites up there. So we can use it to benchmark our theoretical understanding.”

    Loureiro began concentrating on plasma physics in graduate school at Imperial College London and continued this work as a postdoc at the Princeton Plasma Physics Laboratory and later the Culham Centre for Fusion Energy, the U.K.’s national fusion lab. Then, after a few years as a principal researcher at the University of Portugal, he joined the MIT faculty at the Plasma Science and Fusion Center in 2016 and earned tenure in 2017. A major motivation for moving to MIT from his research position, he says, was working with students. “I like to teach,” he says. Another was the “peerless intellectual caliber of the Plasma Science and Fusion Center at MIT.”

    Loureiro, who holds a joint appointment in MIT’s Department of Physics, is an expert on a fundamental plasma process called magnetic reconnection. One example of this process occurs in the sun’s corona, a glowing irregular ring that surrounds the disk of the sun and becomes visible from Earth during solar eclipses. The corona is populated by vast loops of magnetic fields, which buoyantly rise from the solar interior and protrude through the solar surface. Sometimes these magnetic fields become unstable and explosively reconfigure, unleashing a burst of energy as a solar flare. “That’s magnetic reconnection in action,” he says.

    Over the last couple of years at MIT, Loureiro published a series of papers with physicist Stanislav Boldyrev at the University of Wisconsin, in which they proposed a new analytical model to reconcile critical disparities between models of plasma turbulence and models of magnetic reconnection. It’s too early to say if the new model is correct, he says, but “our work prompted a reanalysis of solar wind data and also new numerical simulations. The results from these look very encouraging.”

    Their new model, if proven, shows that magnetic reconnection must play a crucial role in the dynamics of plasma turbulence over a significant range of spatial scales – an insight that Loureiro and Boldyrev claim would have profound implications.

    Loureiro says that a deep, detailed understanding of turbulence and reconnection in plasmas is essential for solving a variety of thorny problems in physics, including the way the sun’s corona gets heated, the properties of accretion disks around black holes, nuclear fusion, and more. And so he plugs away, to continue trying to unravel the complexities of plasma behavior. “These problems present beautiful intellectual challenges,” he muses. “That, in itself, makes the challenge worthwhile. But let’s also keep in mind that the practical implications of understanding plasma behavior are enormous.”

    See the full article here .


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    Please help promote STEM in your local schools.


    Stem Education Coalition

    MIT Seal

    The mission of MIT is to advance knowledge and educate students in science, technology, and other areas of scholarship that will best serve the nation and the world in the twenty-first century. We seek to develop in each member of the MIT community the ability and passion to work wisely, creatively, and effectively for the betterment of humankind.

    MIT Campus

     
  • richardmitnick 2:49 pm on October 16, 2018 Permalink | Reply
    Tags: , , Astrophysics, , , Deep Skies Lab, Galaxy Zoo-Citizen Science, Gravitational lenses, , , ,   

    From Symmetry: “Studying the stars with machine learning” 

    Symmetry Mag
    From Symmetry

    10/16/18
    Evelyn Lamb

    1
    Illustration by Sandbox Studio, Chicago with Corinne Mucha

    To keep up with an impending astronomical increase in data about our universe, astrophysicists turn to machine learning.

    Kevin Schawinski had a problem.

    In 2007 he was an astrophysicist at Oxford University and hard at work reviewing seven years’ worth of photographs from the Sloan Digital Sky Survey—images of more than 900,000 galaxies. He spent his days looking at image after image, noting whether a galaxy looked spiral or elliptical, or logging which way it seemed to be spinning.

    Technological advancements had sped up scientists’ ability to collect information, but scientists were still processing information at the same rate. After working on the task full time and barely making a dent, Schawinski and colleague Chris Lintott decided there had to be a better way to do this.

    There was: a citizen science project called Galaxy Zoo. Schawinski and Lintott recruited volunteers from the public to help out by classifying images online. Showing the same images to multiple volunteers allowed them to check one another’s work. More than 100,000 people chipped in and condensed a task that would have taken years into just under six months.

    Citizen scientists continue to contribute to image-classification tasks. But technology also continues to advance.

    The Dark Energy Spectroscopic Instrument, scheduled to begin in 2019, will measure the velocities of about 30 million galaxies and quasars over five years.

    LBNL/DESI Dark Energy Spectroscopic Instrument for the Nicholas U. Mayall 4-meter telescope at Kitt Peak National Observatory near Tucson, Ariz, USA

    The Large Synoptic Survey Telescope, scheduled to begin in the early 2020s, will collect more than 30 terabytes of data each night—for a decade.

    LSST


    LSST Camera, built at SLAC



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

    “The volume of datasets [from those surveys] will be at least an order of magnitude larger,” says Camille Avestruz, a postdoctoral researcher at the University of Chicago.

    To keep up, astrophysicists like Schawinski and Avestruz have recruited a new class of non-scientist scientists: machines.

    Researchers are using artificial intelligence to help with a variety of tasks in astronomy and cosmology, from image analysis to telescope scheduling.

    Superhuman scheduling, computerized calibration

    Artificial intelligence is an umbrella term for ways in which computers can seem to reason, make decisions, learn, and perform other tasks that we associate with human intelligence. Machine learning is a subfield of artificial intelligence that uses statistical techniques and pattern recognition to train computers to make decisions, rather than programming more direct algorithms.

    In 2017, a research group from Stanford University used machine learning to study images of strong gravitational lensing, a phenomenon in which an accumulation of matter in space is dense enough that it bends light waves as they travel around it.

    Gravitational Lensing NASA/ESA

    Because many gravitational lenses can’t be accounted for by luminous matter alone, a better understanding of gravitational lenses can help astronomers gain insight into dark matter.

    In the past, scientists have conducted this research by comparing actual images of gravitational lenses with large numbers of computer simulations of mathematical lensing models, a process that can take weeks or even months for a single image. The Stanford team showed that machine learning algorithms can speed up this process by a factor of millions.

    3
    Greg Stewart, SLAC National Accelerator Laboratory

    Schawinski, who is now an astrophysicist at ETH Zürich, uses machine learning in his current work. His group has used tools called generative adversarial networks, or GAN, to recover clean versions of images that have been degraded by random noise. They recently published a paper [Astronomy and Astrophysics]about using AI to generate and test new hypotheses in astrophysics and other areas of research.

    Another application of machine learning in astrophysics involves solving logistical challenges such as scheduling. There are only so many hours in a night that a given high-powered telescope can be used, and it can only point in one direction at a time. “It costs millions of dollars to use a telescope for on the order of weeks,” says Brian Nord, a physicist at the University of Chicago and part of Fermilab’s Machine Intelligence Group, which is tasked with helping researchers in all areas of high-energy physics deploy AI in their work.

    Machine learning can help observatories schedule telescopes so they can collect data as efficiently as possible. Both Schawinski’s lab and Fermilab are using a technique called reinforcement learning to train algorithms to solve problems like this one. In reinforcement learning, an algorithm isn’t trained on “right” and “wrong” answers but through differing rewards that depend on its outputs. The algorithms must strike a balance between the safe, predictable payoffs of understood options and the potential for a big win with an unexpected solution.

    4
    Illustration by Sandbox Studio, Chicago with Corinne Mucha

    A growing field

    When computer science graduate student Shubhendu Trivedi of the Toyota Technological Institute at University of Chicago started teaching a graduate course on deep learning with one of his mentors, Risi Kondor, he was pleased with how many researchers from the physical sciences signed up for it. They didn’t know much about how to use AI in their research, and Trivedi realized there was an unmet need for machine learning experts to help scientists in different fields find ways of exploiting these new techniques.

    The conversations he had with researchers in his class evolved into collaborations, including participation in the Deep Skies Lab, an astronomy and artificial intelligence research group co-founded by Avestruz, Nord and astronomer Joshua Peek of the Space Telescope Science Institute. Earlier this month, they submitted their first peer-reviewed paper demonstrating the efficiency of an AI-based method to measure gravitational lensing in the Cosmic Microwave Background [CMB].

    Similar groups are popping up across the world, from Schawinski’s group in Switzerland to the Centre for Astrophysics and Supercomputing in Australia. And adoption of machine learning techniques in astronomy is increasing rapidly. In an arXiv search of astronomy papers, the terms “deep learning” and “machine learning” appear more in the titles of papers from the first seven months of 2018 than from all of 2017, which in turn had more than 2016.

    “Five years ago, [machine learning algorithms in astronomy] were esoteric tools that performed worse than humans in most circumstances,” Nord says. Today, more and more algorithms are consistently outperforming humans. “You’d be surprised at how much low-hanging fruit there is.”

    But there are obstacles to introducing machine learning into astrophysics research. One of the biggest is the fact that machine learning is a black box. “We don’t have a fundamental theory of how neural networks work and make sense of things,” Schawinski says. Scientists are understandably nervous about using tools without fully understanding how they work.

    Another related stumbling block is uncertainty. Machine learning often depends on inputs that all have some amount of noise or error, and the models themselves make assumptions that introduce uncertainty. Researchers using machine learning techniques in their work need to understand these uncertainties and communicate those accurately to each other and the broader public.

    The state of the art in machine learning is changing so rapidly that researchers are reluctant to make predictions about what will be coming even in the next five years. “I would be really excited if as soon as data comes off the telescopes, a machine could look at it and find unexpected patterns,” Nord says.

    No matter exactly the form future advances take, the data keeps coming faster and faster, and researchers are increasingly convinced that artificial intelligence is going to be necessary to help them keep up.

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 4:58 pm on October 15, 2018 Permalink | Reply
    Tags: , Astrophysics, , , , , , KIPAC- Kavli Institute for Particle Astrophysics and Cosmology,   

    From SLAC National Accelerator Lab: “Missing gamma-ray blobs shed new light on dark matter, cosmic magnetism” 

    From SLAC National Accelerator Lab

    October 15, 2018
    Manuel Gnida

    Astrophysicists use a catalog of extended gamma-ray sources spotted by Fermi spacecraft to home in on mysterious properties of deep space.

    1
    Extended gamma-ray sources (circled areas) identified in data taken with the Large Area Telescope on NASA’s Fermi spacecraft. (Matthew Wood/Fermi-LAT collaboration)

    NASA/Fermi LAT


    NASA/Fermi Gamma Ray Space Telescope

    When astrophysicists look at the gamma-ray glow from a galaxy outside our own, all they typically see is a small spot because the galaxy is extremely far away. So, when a galaxy appears as an extended blob, something extraordinary must be going on that could help researchers better understand the properties of deep space.

    Now, scientists, including researchers from the Department of Energy’s SLAC National Accelerator Laboratory, have compiled the most detailed catalog of such blobs using eight years of data collected with the Large Area Telescope (LAT) on NASA’s Fermi Gamma-Ray Space Telescope. The blobs, including 19 gamma-ray sources that weren’t known to be extended before, provide crucial information on how stars are born, how they die, and how galaxies spew out matter trillions of miles into space.

    Intriguingly, though, it was the cosmic regions where they didn’t find blobs that shed new light on two particularly mysterious ingredients of the universe: dark matter – an invisible form of matter six times more prevalent than regular matter – and the magnetic field that pervades the space between galaxies and whose origin is unknown.

    “These data are very exciting because they allow us to study some of the most fundamental processes in the universe, and they could potentially lead us to discover completely new physics,” says NASA scientist Regina Caputo, one of the leaders of the recent study by the international Fermi-LAT collaboration, which was published in The Astrophysical Journal.

    One of the things the researchers looked for were gamma-ray blobs associated with companion galaxies orbiting our Milky Way.

    2
    Researchers have discovered a set of possible dwarf satellite galaxies orbiting the Milky Way. The new objects (red dots) were detected in the new sky area (gray transparent area) covered by the Dark Energy Survey. Scientists have seen about two dozen dwarf galaxies (blue dots) before. They are the smallest known galaxy structures and may hold the key to understanding unseen dark matter, which accounts for about 85 percent of all matter in the universe but whose nature is unknown. The zoom-in region shows an image of the stars that likely belong to one of the dwarf galaxy candidates. (Kavli Institute for Particle Astrophysics and Cosmology/SLAC National Accelerator Laboratory/Fermi National Accelerator Laboratory/Dark Energy Survey/Infrared Processing and Analysis Center/California Institute of Technology/University of Massachusetts)

    Since the faintest of these satellites contain very few stars, they are thought to be held together by dark matter.

    Scientists believe dark matter could be made of particles called WIMPs, which would emit gamma rays when they collide and destroy each other. A gamma-ray blob signal coming from an ultrafaint satellite galaxy would be a strong hint that WIMPS exist.

    “Our simulations of galaxy formation predict that there should be more satellite galaxies than those we’ve been able to detect in optical surveys,” Caputo says. “Some of them could be so faint that we might only be able to see them if they produced gamma rays due to dark matter annihilation.”

    In the new study, the Fermi-LAT researchers searched for gamma-ray blobs associated with those predicted satellite galaxies. They didn’t find any. But even the fact that they came up empty-handed is an important result: It will allow them, in future studies, to define the distribution of dark matter in Milky Way satellites and the likelihood that WIMPs produce gamma rays. It also provides new input for models of galaxy evolution.

    3
    The Small Magellanic Cloud (SMC) is the second-largest satellite galaxy orbiting our Milky Way. The image superimposes a photograph of the SMC with one-half of a model of its dark matter. Lighter colors indicate greater density and show a strong concentration of dark matter toward the SMC’s center. (Regina Caputo/NASA; Axel Mellinger/Central Michigan University)

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

    Faint cosmic magnetism

    The researchers also used their data to obtain more information on the strength of the magnetic field between galaxies, which they hope will be an important puzzle piece in determining the origin of the field.

    For this part of the study, the team looked at blazars – active galaxies that spit high-speed jets of plasma far into space. The Fermi spacecraft can detect gamma rays associated with jets that point in the direction of the Earth.

    Blazars appear as point-like sources, but a mechanism involving the intergalactic magnetic field could potentially make them look like extended sources, says Manuel Meyer, a Humboldt fellow at the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) and another lead author of the study.


    Manuel Meyer, Humboldt fellow at the Kavli Institute for Particle Astrophysics and Cosmology, explains a process involving the intergalactic magnetic field that could potentially make active galaxies known as blazars appear as extended gamma-ray sources in data taken with the Large Area Telescope onboard NASA’s Fermi mission. (Manuel Meyer/Kavli Institute for Particle Astrophysics and Cosmology)

    The researchers didn’t find any blobs associated with blazars. Again, this no-show was valuable information: It allowed the team to calculate that the magnetic field is at least a tenth of a millionth billionth as strong as Earth’s magnetic field. The magnetic field’s upper limit – a billion times weaker than Earth’s field – was already known.

    The intergalactic field is stronger than the researchers had expected, Meyer says, and this new information might help them find out whether it stems from material spilled into space in recent times or whether it was created in processes that occurred in earlier cosmic history.

    The cosmic magnetism could also have ties to dark matter. In an alternative to the WIMP model, dark matter is proposed to be made of lighter particles called axions that could emerge from gamma rays (and convert back into them) in the presence of a magnetic field. “For that to occur, the field strength would need to be closer to its upper limit, though,” Meyer says. “It’s definitely interesting to take this mechanism into account in our dark matter studies, and we’re doing this right now within the Fermi-LAT collaboration.”

    NASA’s Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy Office of Science and with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States. The Fermi mission recently celebrated its 10th anniversary. A number of SLAC researchers are members of the international Fermi-LAT collaboration. SLAC assembled the LAT and hosts the operations center that processes LAT data. The new analysis benefitted from a data analysis package, initially developed by KIPAC researcher Matthew Wood, that automates common analysis tasks. KIPAC is a joint institute of SLAC and Stanford University.

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    SLAC Campus
    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

     
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