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  • richardmitnick 9:34 am on October 25, 2020 Permalink | Reply
    Tags: Andrea Ghez of University of California Los Angeles (USA), , , , , , , EHT - Event Horizon Telescope, Reinhard Genzel of the MPG Institut für extraterrestrische Physik(DE), Roger Penrose of the University of Oxford (UK),   

    From EarthSky: “How the world came to understand black holes” We cannot get enough of these stories. 

    1

    From EarthSky

    October 25, 2020
    Sayali Avachat

    1
    Roger Penrose, Reinhard Genzel and Andrea Ghez. They are joint winners of 2020’s Nobel Prize in physics for their work on black holes. Credit: Nobel Media.

    Earlier this month (October 6, 2020), the Nobel Prize in physics was announced for two groundbreaking discoveries in astrophysics, both centered on black holes. Half of 2020’s prize went to mathematician Roger Penrose of the University of Oxford (UK) “for the discovery that black hole formation is a robust prediction of the general theory of relativity.” The other half went jointly to Reinhard Genzel of the MPG Institut für extraterrestrische Physik(DE) in Germany and Andrea Ghez of University of California, Los Angeles, “for the discovery of a supermassive compact object at the center of our galaxy.”

    It was a great moment for black hole physics as well as for the astronomy and astrophysics field in general. And it’s a wonderful time to contemplate the fascinating history of black hole science.

    What are black holes?

    Black holes are exotic objects in space. The classic scenario for black hole formation centers on a massive star that runs out of the internal fuel it needs to shine. The star collapses under the pull of its own self-gravity, leaving behind a high-density, compact object with an immense gravitational pull. A black hole is a place in space containing an object so dense and so compact that it forms a region around itself from which light cannot escape. The boundary of this region is known as an event horizon. Once past a black hole’s event horizon, the gravitational pull of the hole is inexorable.

    If there is material in space near the black hole – and if this material draws too close – it’s pulled inside. But it doesn’t just drop all at once into the hole; instead, it forms a glowing disk surrounding the black hole called an accretion disk. Friction within the accretion disk can heat the disk to billions of degrees, causing it to emit radiation across the electromagnetic spectrum. Thus, although no light can escape a black hole, astronomers can observe black holes in space via their accretion disks.

    What’s more, in the process of conservation of angular momentum, black holes can cause outbursts which come out perpendicular to the accretion disk. These outbursts are called jets by astronomers, and they can propel material out into space at relativistic speeds, that is, speeds that are a significant fraction of the speed of light (186,000 miles or 300,000 km per second). Astronomers can study black hole jets, too, to learn more about black holes.

    Development of theories of black holes

    All of the above was theory, developed in the 20th century. Albert Einstein’s General Theory of Relativity, published in 1916, contained the seeds of the modern concept of black holes, although the first ever mention of a similar concept is found in 1783, when an English natural philosopher by the name of John Michell theorized the existence of massive objects from which light cannot escape.

    Einstein’s theory of relativity discusses the curvature of space-time as a result of gravity. This curvature causes an object to move along a curved path equivalent to a straight line in the absence of gravity. The theory allowed for the existence of matter packed in small and infinitely warped space. The theory was published as The Field Equations of Gravitation in 1915.

    While serving in the German Army during World War I, astronomer and director of the Astrophysical Observatory in Potsdam Karl Schwarzschild was the first to solve Einstein’s field equations. His solution successfully described how space-time is curved, not just around a planet or a star, but also around theoretical high-density masses, such as black holes. In the space around an object that’s dense enough, and massive enough, gravity is so strong that even light – the fastest-moving stuff in the universe at 186,000 miles (300,000 km) per second – cannot escape. Thus it was Schwarzschild who first conceived of the event horizon, or boundary region around a black hole. Today, physicists speak of the Schwarzschild radius, which is (basically) the radius of a black hole’s event horizon. Schwarzschild’s solution to Einstein’s field equations also elegantly explained the concept of a singularity – the central point of a black hole – a point in space where all the laws of physics break down.

    At first, this concept was considered a mathematical curiosity. Scientists, including Einstein, had no idea such objects could exist in nature.

    But 50 years later, in 1965, Roger Penrose, working with the great theoretical physicist and cosmologist Stephen Hawking, showed that the black holes can indeed exist in nature and that they can form through a stable and robust process. And in fact, for some stars, black holes are the ultimate fate, an unavoidable outcome of stellar collapse.

    The momentous work by Penrose and Hawking opened a new era in the study of black holes. Penrose’s work was also pivotal in showing how black holes emit energy through the Penrose process, in the form of jets and outbursts.

    In the meantime, it was physicist John Wheeler who, in 1967, popularized the term black hole. Wheeler summarized Einstein’s equations as:

    “Space-time tells matter how to move; matter tells space-time how to curve.”

    Observations of black holes

    Astronomers didn’t discover the first stellar-mass black hole – Cygnus X-1 – until after the middle of the 20th century.

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    Left: Image of Cygnus X-1 as observed by the Chandra X-ray observatory. Right: By now iconic artist’s concept of black hole accreting matter from its companion star. Image via (left) NASA/ CXC/ SAO; (right) NASA/ CXC/ M.Weiss.

    A 1964 rocket flight revealed Cygnus X-1 as one of the strongest sources of X-rays that had yet been seen from Earth. By the 1970s, most astronomers believed Cygnus X-1 was indeed a black hole. It’s now thought to be a black hole with a mass some 14.8 times that of our sun and an event horizon with a radius of around 27 miles (44 km). That’s in contrast to our sun’s radius of about 433,000 miles (696,000 km).

    Stellar-mass black holes are hard to find because of their quiescent nature. They might display short and unpredictable outbursts when some passing material strikes their accretion disks, after which they might go quiet for decades.

    That is why it took the discovery of supermassive black holes at the centers of most galaxies, including our own Milky Way, to give black hole science its real boost.

    Supermassive black holes

    Today, astronomers believe that most galaxies harbor supermassive black holes in their centers. Supermassive black holes have masses equivalent to millions to billions of solar masses and are believed to form in the centers of galaxies around the same time as the galaxy is forming. Over 100,000 supermassive black hole candidates have been observed to date, many more than the number of known stellar-mass black holes.

    Among the many observed black hole candidates, the one at the center of our own Milky Way galaxy is called Sagittarius A* (Sgr A*, pronounced Sagittarius A-star). Two independent studies carried out in the last 25 years, led by Andrea Ghez and Reinhard Genzel – joint winners of half of 2020’s Nobel prize in physics – mapped the stars orbiting an invisible object at the center of our Milky Way. Using the powerful telescopes at Keck Observatory in Hawaii and the Very Large Telescope in Chile, the teams focused on one star known as S0-2. S0-2 orbits closer to our galaxy’s central supermassive black hole than any other observed star.

    Keck Observatory, operated by Caltech and the University of California, Maunakea Hawaii USA, altitude 4,207 m (13,802 ft).

    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.

    Knowing the orbital period of the star S0-2, its very elongated elliptical orbit and the distance of its closest approach to our galaxy’s central black hole enabled scientists to calculate the mass of Sgr A* as the equivalent of 4 million solar masses. The teams were able to observe two full orbits of the star S0-2 around the central black hole, which further bolstered their claims and also proved, through observations, what Einstein, Schwarzchild, and Penrose had predicted in theory about black holes.

    SgrA* NASA/Chandra supermassive black hole at the center of the Milky Way, X-ray image of the center of our galaxy, where the supermassive black hole Sagittarius A* resides. Image via X-ray: NASA/UMass/D.Wang et al., IR: NASA/STScI.

    Star S0-2 Andrea Ghez Keck/UCLA Galactic Center Group at SGR A*, the supermassive black hole at the center of the Milky Way.

    Further validation of Einstein’s general theory of relativity came when, on April 10, 2019, the Event Horizon Telescope collaboration released the first-ever image of [the event horizon] of a black hole* in the relatively nearby (by cosmic standards) galaxy known as Messier 87, visible in the constellation Virgo.

    The gargantuan black hole in Messier 87’s center, Messier 87*, weighs a whopping 6.5 billion solar masses.

    Messier 87*, The first image of the event horizon of a black hole. This is the supermassive black hole at the center of the galaxy Messier 87. Image via JPL/ Event Horizon Telescope Collaboration released on 10 April 2019.

    The galaxy Messier 87 and its famous jet – an energetic outflow of high energy particles from its center – had been observed for several decades. However, this was the first ever successful attempt at direct imaging of its [event horizon]. The image shows a bright ring formed by the bending of light at the boundary of the black hole’s event horizon, caused by its extreme gravitational pull.

    *One cannot speak of the image of the black hole itself, because no light emerges from the black hole. It is, after all, black. All that can be imaged is the event horizon which is the thin area which surrounds the black hole.

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

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

     
  • richardmitnick 10:53 am on October 1, 2020 Permalink | Reply
    Tags: "Einstein's Description of Gravity Just Got Much Harder to Beat", , , , , EHT - Event Horizon Telescope, ,   

    From University of Arizona: “Einstein’s Description of Gravity Just Got Much Harder to Beat” 

    From University of Arizona

    10.1.20

    Dimitrios Psaltis
    Department of Astronomy
    dpsaltis@arizona.edu

    Feryal Özel
    Department of Astronomy
    fozel@arizona.edu

    Pierre Christian
    Department of Astronomy
    pchristian@arizona.edu

    Media contact:
    Mikayla Mace
    University Communications
    520-621-1878
    mikaylamace@arizona.edu

    Daniel Stolte
    University Communications
    520-626-4402
    stolte@email.arizona.edu

    Lee Sandberg
    Institute for Advanced Study
    609-455-4398
    lsandberg@ias.edu

    U Arizona researchers put general relativity to a new test with black hole images.

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    Simulation of M87 black hole showing the motion of plasma as it swirls around the black hole. The bright thin ring that can be seen in blue is the edge of what we call the black hole shadow. L. Medeiros; C. Chan; D. Psaltis; F. Özel; University of Arizona; Institute for Advanced Study.

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    Visualization of the new gauge developed to test the predictions of modified gravity theories against the measurement of the size of the M87 shadow. Credit: D. Psaltis, UArizona; EHT Collaboration.

    Einstein’s theory of general relativity – the idea that gravity is matter warping spacetime – has withstood over 100 years of scrutiny and testing, including the newest test by University of Arizona astrophysicists from the Event Horizon Telescope collaboration.

    According to their findings, Einstein’s theory just got 500 times harder to beat.

    Despite its successes, Einstein’s robust theory remains mathematically irreconcilable with quantum mechanics, the scientific understanding of the subatomic world. Testing general relativity is important because the ultimate theory of the universe must encompass both gravity and quantum mechanics.

    “We expect a complete theory of gravity to be different from general relativity, but there are many ways one can modify it. We found that whatever the correct theory is, it can’t be significantly different from general relativity when it comes to black holes. We really squeezed down the space of possible modifications,” said UArizona astronomy professor Dimitrios Psaltis, who until recently was the project scientist of the Event Horizon Telescope, or EHT, collaboration.

    Psaltis is lead author of a new paper, published in Physical Review Letters, that details the researchers’ findings.

    “This is a brand new way to test general relativity using supermassive black holes,” said Keiichi Asada, an EHT science council member and an expert on radio observations of black holes for Academia Sinica Institute of Astronomy and Astrophysics.

    To perform the test, the team used the first image ever taken of the supermassive black hole at the center of nearby galaxy Messier 87 obtained with the EHT last year.

    Messier 87*, The first image of a black hole. This is the supermassive black hole at the center of the galaxy Messier 87. Image via JPL/ Event Horizon Telescope Collaboration.

    EHT map.

    The first results had shown that the size of the black-hole shadow was consistent with the size predicted by general relativity.

    “At that time, we were not able to ask the opposite question: How different can a gravity theory be from general relativity and still be consistent with the shadow size?” said UArizona Steward Theory Fellow Pierre Christian. “We wondered if there was anything we could do with these observations in order to cull some of the alternatives.”

    The team did a very broad analysis of many modifications to the theory of general relativity to identify the unique characteristic of a theory of gravity that determines the size of a black hole shadow.

    “In this way, we can now pinpoint whether any alternative to general relativity is in agreement with the Event Horizon Telescope observations, without worrying about any other details,” said Lia Medeiros, a postdoctoral fellow at the Institute for Advanced Study who has been part of the EHT collaboration since her time as a UArizona graduate student.

    The team focused on the range of alternatives that had passed all the previous tests in the solar system.

    “Using the gauge we developed, we showed that the measured size of the black hole shadow in M87 tightens the wiggle room for modifications to Einstein’s theory of general relativity by almost a factor of 500, compared to previous tests in the solar system,” said UArizona astronomy professor Feryal Özel, a senior member of the EHT collaboration. “Many ways to modify general relativity fail at this new and tighter black hole shadow test.”

    “Black hole images provide a completely new angle for testing Einstein’s theory of general relativity,” said Michael Kramer, director of the Max Planck Institute for Radio Astronomy and EHT collaboration member.

    “Together with gravitational wave observations, this marks the beginning of a new era in black hole astrophysics,” Psaltis said.

    Testing the theory of gravity is an ongoing quest: Are the general relativity predictions for various astrophysical objects good enough for astrophysicists to not worry about any potential differences or modifications to general relativity?

    “We always say general relativity passed all tests with flying colors – if I had a dime for every time I heard that,” Özel said. “But it is true, when you do certain tests, you don’t see that the results deviate from what general relativity predicts. What we’re saying is that while all of that is correct, for the first time we have a different gauge by which we can do a test that’s 500 times better, and that gauge is the shadow size of a black hole.”

    Next, the EHT team expects higher fidelity images that will be captured by the expanded array of telescopes, which includes the Greenland Telescope and the 12-meter Telescope on Kitt Peak near Tucson and the Northern Extended Millimeter Array Observatory in France.

    NSF CfA Greenland telescope, at the Summit Station research camp, located at the highest point of the Greenland ice sheet at an altitude of 3,210 meters (10,530 feet).

    NRAO 12m Radio Telescope, Kitt Peak National Observatory, In the Arizona-Sonoran Desert on the Tohono O’odham Nation Arizona USA,Altitude 1,914 m (6,280 ft).

    “When we obtain an image of the black hole at the center of our own galaxy, then we can constrain deviations from general relativity even further,” Özel said.

    Will Einstein still be right, then?

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    The University of Arizona (UA) is a place without limits-where teaching, research, service and innovation merge to improve lives in Arizona and beyond. We aren’t afraid to ask big questions, and find even better answers.

    In 1885, establishing Arizona’s first university in the middle of the Sonoran Desert was a bold move. But our founders were fearless, and we have never lost that spirit. To this day, we’re revolutionizing the fields of space sciences, optics, biosciences, medicine, arts and humanities, business, technology transfer and many others. Since it was founded, the UA has grown to cover more than 380 acres in central Tucson, a rich breeding ground for discovery.

    U Arizona mirror lab-Where else in the world can you find an astronomical observatory mirror lab under a football stadium?

    University of Arizona’s Biosphere 2, located in the Sonoran desert. An entire ecosystem under a glass dome? Visit our campus, just once, and you’ll quickly understand why the UA is a university unlike any other.

     
  • richardmitnick 8:16 am on September 24, 2020 Permalink | Reply
    Tags: "The ring around the black hole glitters", , , , , , EHT - Event Horizon Telescope,   

    From Max Planck Institute for Radio Astronomy: “The ring around the black hole glitters” 


    From Max Planck Institute for Radio Astronomy

    September 23, 2020

    Dr. Norbert Junkes
    Press and public relations
    Max Planck Institute for Radio Astronomy, Bonn
    +49 2 28525-399
    njunkes@mpifr-bonn.mpg.de

    Prof. Dr. J. Anton Zensus
    Max Planck Institute for Radio Astronomy, Bonn
    +49 228 525-378
    azensus@mpifr-bonn.mpg.de

    Astronomers of the Event Horizon Telescope conclude from archive data how the surroundings of the mass monster in the galaxy M 87 have changed.

    In the center of the giant galaxy Messier 87 lurks a giant black hole.

    Messier 87*, The first image of a black hole. This is the supermassive black hole at the center of the galaxy Messier 87. Image via JPL/ Event Horizon Telescope Collaboration.

    The image of this mass monster published last year and obtained with the Event Horizon Telescope (EHT) went around the world.

    EHT map

    Now the EHT team has analyzed archive data from 2009 to 2013, some of which are still unpublished. The researchers found that the ring-shaped shadow around the black hole is indeed always present, but changes its orientation and brightness distribution – the ring seems to be glittering. The participation of the European APEX telescope in Chile and the IRAM 30-meter telescope co-financed by the Max Planck Society on Pico Veleta in the Spanish Sierra Nevada played an important part in this discovery.

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

    IRAM 30m Radio telescope, on Pico Veleta in the Spanish Sierra Nevada,, Altitude 2,850 m (9,350 ft).

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    Snapshots of the M 87* black hole obtained through imaging / geometric modeling, and the EHT array of telescopes in 2009 – 2017. The diameter of all rings is similar, but the location of the bright side varies. The variation of the thickness of the ring is most likely not real and results from the limited number of participating observatories in earlier experiments. © M. Wielgus, D. Pesce & EHT Collaboration.

    “The results announced in April 2019 show an image of the shadow of a black hole, consisting of a bright ring formed by hot plasma swirling around the black hole in Messier 87, and a dark central part, where we expect the event horizon to be”, reminds Maciek Wielgus, astronomer at Harvard University, and lead author of the new paper.

    However, those results were based only on observations performed throughout a one-week long time window in April 2017, which is far too short to see if the ring is evolving over longer time scales. Even after careful data analysis, therefore some open questions with regard to the stationarity of the ring features over time remained. For that reason, an investigation of earlier archival data was considered.

    The 2009 – 2013 observations consist of far less data than the ones performed in 2017, making it hard to image Messier 87 without a-priori assumptions. For the available archive data, the EHT team used statistical modeling based on geometrical assumptions to look at changes in the appearance of the black hole in M 87 (M 87*) over time.

    Expanding the analysis to the 2009-2017 observations, scientists have shown that Messier 87* adheres to theoretical expectations. The black hole’s shadow diameter has remained consistent with the prediction of Einstein’s theory of general relativity for a black hole of 6.5 billion solar masses. The morphology of an asymmetric ring persists on timescales of several years, in a consistent manner which provides additional confidence about the nature of M 87* and the origin of its shadow.

    But while the diameter of the ring remained constant over time, the EHT team found that the data were hiding a surprise. Thomas Krichbaum, astronomer at the Max Planck Institute for Radio Astronomy and one of the leading authors of the publication, says: “The data analysis suggests that the orientation and fine structure of the ring varies with time. This gives a first impression on the dynamical structure of the accretion flow, which surrounds the event horizon”. He adds: “Studying this region will be crucial for a better understanding of how black holes accrete matter and launch relativistic jets.”

    The gas falling onto a black hole heats up to billions of degrees, ionizes and becomes turbulent in the presence of magnetic fields. Since the flow of matter is turbulent, the ring brightness appears to glittering with time, which challenges some theoretical models of accretion.

    “The monitoring of the time variable structure of Messier 87 with the EHT is a challenge that will keep us busy over the next few years,” says Anton Zensus, Director at the Max Planck Institute for Radio Astronomy and Founding Chairman of the EHT Collaboration Board. „We are working in the analysis of the 2018 data, and preparing newer observations in 2021, with the addition of new sites such as the NOEMA Observatory in France, the most powerful radio telescope of its kind in the Northern Hemisphere and also co-financed by the Max-Plack-Gesellschaft as well as the Greenland Telescope, and Kitt Peak in Arizona,” adds Zensus.

    IRAM NOEMA in the French Alps on the wide and isolated Plateau de Bure at an elevation of 2550 meters, the telescope currently consists of ten antennas, each 15 meters in diameter.interferometer, Located in the French Alpes on the wide and isolated Plateau de Bure at an elevation of 2550 meters.

    NSF CfA Greenland telescope, at the Summit Station research camp, located at the highest point of the Greenland ice sheet at an altitude of 3,210 meters (10,530 feet).

    ARO 12m Radio Telescope, Kitt Peak National Observatory, In the Arizona-Sonoran Desert on the Tohono O’odham Nation Arizona USA, Altitude 1,914 m (6,280 ft).

    The enhanced imaging capabilities provided by this extended array will provide a more detailed view on the shadow of the black hole Messier 87* and on the innermost jet of the Messier 87 radio galaxy.

    Science paper:
    Monitoring the Morphology of M87* in 2009–2017 with the Event Horizon Telescope
    The Astrophysical Journal


    Cosmic twinkling. An animation representing one year of Messier 87* image evolution according to numerical simulations. Measured position angle is shown along with a 42 microarcsecond ring. For a part of the animation, image blurred to the EHT resolution is shown. © G. Wong, B. Prather, Ch. Gammie, M. Wielgus & EHT Collaboration.

    See the full article here .
    See also the full article from MIT Haystack here.

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    Please help promote STEM in your local schools.

    Stem Education Coalition



    MPIFR/Effelsberg Radio Telescope, Germany

    The Max Planck Institute for Radio Astronomy (German: Max-Planck-Institut für Radioastronomie) is located in Bonn, Germany. It is one of 80 institutes in the Max Planck Society.

    By combining the already existing radio astronomy faculty of the University of Bonn led by Otto Hachenberg with the new Max Planck institute the Max Planck Institute for Radio Astronomy was formed. In 1972 the 100-m radio telescope in Effelsberg was opened. The institute building was enlarged in 1983 and 2002.

    The institute was founded in 1966 by the Max-Planck-Gesellschaft as the “Max-Planck-Institut für Radioastronomie” (MPIfR).

    The foundation of the institute was closely linked to plans in the German astronomical community to construct a competitive large radio telescope in (then) West Germany. In 1964, Professors Friedrich Becker, Wolfgang Priester and Otto Hachenberg of the Astronomische Institute der Universität Bonn submitted a proposal to the Stiftung Volkswagenwerk for the construction of a large fully steerable radio telescope.

    In the same year the Stiftung Volkswagenwerk approved the funding of the telescope project but with the condition that an organization should be found, which would guarantee the operations. It was clear that the operation of such a large instrument was well beyond the possibilities of a single university institute.

    Already in 1965 the Max-Planck-Gesellschaft (MPG) decided in principle to found the Max-Planck-Institut für Radioastronomie. Eventually, after a series of discussions, the institute was officially founded in 1966.

    The Max Planck Society for the Advancement of Science (German: Max-Planck-Gesellschaft zur Förderung der Wissenschaften e. V.; abbreviated MPG) is a formally independent non-governmental and non-profit association of German research institutes founded in 1911 as the Kaiser Wilhelm Society and renamed the Max Planck Society in 1948 in honor of its former president, theoretical physicist Max Planck. The society is funded by the federal and state governments of Germany as well as other sources.

    According to its primary goal, the Max Planck Society supports fundamental research in the natural, life and social sciences, the arts and humanities in its 83 (as of January 2014)[2] Max Planck Institutes. The society has a total staff of approximately 17,000 permanent employees, including 5,470 scientists, plus around 4,600 non-tenured scientists and guests. Society budget for 2015 was about €1.7 billion.

    The Max Planck Institutes focus on excellence in research. The Max Planck Society has a world-leading reputation as a science and technology research organization, with 33 Nobel Prizes awarded to their scientists, and is generally regarded as the foremost basic research organization in Europe and the world. In 2013, the Nature Publishing Index placed the Max Planck institutes fifth worldwide in terms of research published in Nature journals (after Harvard, MIT, Stanford and the US NIH). In terms of total research volume (unweighted by citations or impact), the Max Planck Society is only outranked by the Chinese Academy of Sciences, the Russian Academy of Sciences and Harvard University. The Thomson Reuters-Science Watch website placed the Max Planck Society as the second leading research organization worldwide following Harvard University, in terms of the impact of the produced research over science fields.

     
  • richardmitnick 7:29 am on September 10, 2020 Permalink | Reply
    Tags: "Space Could Be Littered With Eerie Transparent Stars Made Entirely of Bosons", , , , , EHT - Event Horizon Telescope, , ,   

    From Science Alert: “Space Could Be Littered With Eerie Transparent Stars Made Entirely of Bosons” 

    ScienceAlert

    From Science Alert

    9 SEPTEMBER 2020
    MICHELLE STARR

    1
    L-R: A non-rotating black hole; a rotating black hole; a boson star as they’d appear to the EHT. (Olivares et al., MNRAS, 2020)

    Last year, the astronomical community achieved an absolute wonder. For the very first time, the world collectively laid eyes on an actual image of the shadow of a black hole.

    Messier 87*, The first image of a black hole. This is the supermassive black hole at the center of the galaxy Messier 87. Image via JPL/ Event Horizon Telescope Collaboration.

    It was the culmination of years of work, a magnificent achievement in both human collaboration and technical ingenuity.

    Event Horizon Telescope Array

    Arizona Radio Observatory at Kitt Peak, AZ USA, U Arizona Steward Observatory at altitude 2,096 m (6,877 ft).


    Arizona Radio Observatory.

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


    ESO APEX.

    Combined Array for Research in Millimeter-wave Astronomy (CARMA), in the Inyo Mountains to the east of the Owens Valley Radio Observatory, at a site called Cedar Flat, Altitude 1,222 m (4,009 ft), relocated to Owens Valley Radio Observatory, Altitude 1,222 m (4,009 ft).


    CARMA.

    NAOJ Atacama Submillimeter Telescope Experiment (ASTE) deployed to its site on Pampa La Bola, near Cerro Chajnantor and the Llano de Chajnantor, Observatory in northern Chile, Altitude 4,800 m (15,700 ft).


    NAOJ Atacama Submillimeter Telescope Experiment (ASTE).

    Caltech Submillimeter Observatory on Mauna Kea, Hawaii, USA, Altitude 4,205 m (13,796 ft).


    Caltech Submillimeter Observatory.

    NSF CfA Greenland telescope.


    Greenland Telescope.

    IRAM 30m Radio telescope, on Pico Veleta in the Spanish Sierra Nevada,, Altitude 2,850 m (9,350 ft).


    Institut de Radioastronomie Millimetrique (IRAM) 30m.

    IRAM NOEMA in the French Alps on the wide and isolated Plateau de Bure at an elevation of 2550 meters, the telescope currently consists of ten antennas, each 15 meters in diameter.interferometer, Located in the French Alpes on the wide and isolated Plateau de Bure at an elevation of 2550 meters.


    IRAM NOEMA, France.

    East Asia Observatory James Clerk Maxwell Telescope, Mauna Kea, Hawaii, USA,4,207 m (13,802 ft).


    James Clerk Maxwell Telescope.

    The University of Massachusetts Amherst and Mexico’s Instituto Nacional de Astrofísica, Óptica y Electrónica
    Large Millimeter Telescope Alfonso Serrano, Mexico, at an altitude of 4850 meters on top of the Sierra Negra.


    Large Millimeter Telescope Alfonso Serrano.

    CfA Submillimeter Array Mauna Kea, Hawaii, USA, Altitude 4,080 m (13,390 ft).


    Submillimeter Array Hawaii SAO.

    ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres.


    ESO/NRAO/NAOJ ALMA Array.

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


    South Pole Telescope SPTPOL.

    Future Array/Telescopes

    Caltech Owens Valley Radio Observatory, located near Big Pine, California (US) in Owens Valley, Altitude1,222 m (4,009 ft).


    Caltech Owens Valley Radio Observatory.

    And, like the best scientific breakthroughs, it opened a whole new world of enquiry. For a team led by astrophysicist Hector Olivares from Radboud University in the Netherlands and Goethe University in Germany, that enquiry was: how do we know M87* is a black hole?

    “While the image is consistent with our expectations on what a black hole would look like, it is important to be sure that what we are seeing is really what we think,” Olivares told ScienceAlert.

    “Similarly to black holes, boson stars are predicted by general relativity and are able to grow to millions of solar masses and reach a very high compactness. The fact that they share these features with supermassive black holes led some authors to propose that some of the supermassive compact objects located at the center of galaxies could actually be boson stars.”

    So, in a new paper, Olivares and his team have calculated what a boson star might look like to one of our telescopes, and how that would differ from a direct image of an accreting black hole.

    Boson stars are among the strangest theoretical objects out there. They’re not much like conventional stars, except that they’re a glob of matter. But where stars are primarily made up of particles called fermions – protons, neutrons, electrons, the stuff that forms more substantial parts of our Universe – boson stars would be made up entirely of… bosons.

    These particles – including photons, gluons and the famous Higgs boson – don’t follow the same physical rules as fermions.

    2

    Fermions are subject to the Pauli exclusion principle, which means you can’t have two identical particles occupying the same space. Bosons, however, can be superimposed; when they come together, they act like one big particle or matter wave. We know this, because it’s been done in a lab, producing what we call a Bose-Einstein condensate.

    In the case of boson stars, the particles can be squeezed into a space which can be described with distinct values, or points on a scale. Given the right kind of bosons in the right arrangements, this ‘scalar field’ could fall into a relatively stable arrangement.

    That’s the theory, at least. Not that anybody has seen one in action. Bosons with the mass required to form such a structure, let alone one with the mass of a supermassive black hole, are yet to be spotted.

    If we could identify a boson star, we would have effectively located this elusive particle.

    “In order to form a structure as large as the SMBH candidates, the mass of the boson needs to be extremely small (less than 10-17 electronvolts),” Olivares said.

    “Spin-0 bosons with similar or smaller masses appear in several cosmological models and string theories, and have been proposed as dark matter candidates under different names (scalar field dark matter, ultra-light axions, fuzzy dark matter, quantum wave dark matter). Such hypothetical particles would be extremely difficult to detect, but the observation of an object looking like a boson star would point to their existence.”

    Boson stars do not fuse nuclei, and they would not emit any radiation. They’d just sit there in space, being invisible. Much like black holes.

    Unlike black holes, however, boson stars would be transparent – they lack an absorbing surface that would stop photons, nor do they have an event horizon. Photons can escape boson stars, although their path may be bent a little by the gravity.

    But some boson stars may be surrounded by a rotating ring of plasma – a lot like the accretion disc that surrounds a black hole. And it would look fairly similar, like a glowing doughnut with a dark region inside.

    So, Olivares and his team performed simulations of the dynamics of these plasma rings, and compared them to what we might expect to see of a black hole.

    “The plasma configuration that we use is not set up ‘by hand’ (under reasonable assumptions), but results from a simulation of plasma dynamics. This allows the plasma to evolve in time and to form structures as it would in nature,” Olivares explained.

    “In this way we could relate the size of the dark region in the boson star images (which mimics a black hole shadow) to the radius where a plasma instability stops operating. In turn, this means that the size of the dark region is not arbitrary – it will depend on the properties of the boson star space-time – and also allows us to predict its size for other boson stars that we have not simulated.”

    They found that the boson star’s shadow would be significantly smaller than the shadow of a black hole of similar mass. Thus, the team ruled out M87* as a boson star – the object’s mass has been inferred from the rotation velocity of the gas around it, and the shadow is too big to be produced by a boson star of that mass.

    But the team also took into account the technical capabilities and limitations of the Event Horizon Telescope which delivered that first black hole image; they deliberately set about visualising their results as they thought boson stars might look as imaged by the EHT.

    This means their results can be compared to future EHT observations, to determine if what we’re looking at is indeed a supermassive black hole.

    If it were not, that would be a very big deal. It wouldn’t mean that supermassive black holes don’t exist – the range of masses for black holes is way too broad for boson stars. But it would hint that boson stars are real, and in turn that would have huge implications, for everything from the inflation of the early Universe to the search for dark matter.

    “It would mean that cosmological scalar fields exist and play an important role in the formation of structures in the Universe,” Olivares told ScienceAlert.

    “The growth of supermassive black holes is still not understood very well, and if it turns out that at least some of the candidates are actually boson stars, we would need to think of different formation mechanisms involving scalar fields.”

    The research was published in July in the MNRAS.

    See the full article here.


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  • richardmitnick 12:07 pm on August 21, 2020 Permalink | Reply
    Tags: "Spinning Black Hole Powers Jet by Magnetic Flux", , , , , EHT - Event Horizon Telescope, Julius-Maximilians-Universität Würzburg, , Quasar 3C279   

    From Julius-Maximilians-Universität Würzburg: “Spinning Black Hole Powers Jet by Magnetic Flux” 

    1

    From Julius-Maximilians-Universität Würzburg

    08/21/2020
    Prof. Dr. Karl Mannheim
    Chair of Astronomy
    University of Würzburg
    mannheim@astro.uni-wuerzburg.de

    A new letter has been found in the mysterious alphabet of black holes. Two astrophysicists share this discovery in the journal Nature Communications.

    1
    The centre of quasar 3C279 emits flickering gamma radiation, which is characteristic of the phenomenon of magnetic reconnection. (Image: Amit Shukla / Indian Institute of Technology.)

    Black holes are at the center of almost all galaxies that have been studied so far. They have an unimaginably large mass and therefore attract matter, gas and even light. But they can also emit matter in the form of plasma jets – a kind of plasma beam that is ejected from the centre of the galaxy with tremendous energy. A plasma jet can extend several hundred thousand light years far into space.

    When this intense radiation is emitted, the black hole remains hidden because the light rays near it are strongly bent leading to the appearance of a shadow. This was recently reported by researchers of the Event Horizon Telescope (EHT) collaboration for the massive black hole in the giant ellipse galaxy Messier 87.

    Event Horizon Telescope Array

    Arizona Radio Observatory
    Arizona Radio Observatory/Submillimeter-wave Astronomy (ARO/SMT)

    ESO/APEX
    Atacama Pathfinder EXperiment

    CARMA Array no longer in service
    Combined Array for Research in Millimeter-wave Astronomy (CARMA)

    Atacama Submillimeter Telescope Experiment (ASTE)
    Atacama Submillimeter Telescope Experiment (ASTE)

    Caltech Submillimeter Observatory
    Caltech Submillimeter Observatory (CSO)

    IRAM 30m Radio telescope, on Pico Veleta in the Spanish Sierra Nevada,, Altitude 2,850 m (9,350 ft)


    Institut de Radioastronomie Millimetrique (IRAM) 30m

    James Clerk Maxwell Telescope interior, Mauna Kea, Hawaii, USA
    James Clerk Maxwell Telescope interior, Mauna Kea, Hawaii, USA

    Large Millimeter Telescope Alfonso Serrano
    Large Millimeter Telescope Alfonso Serrano

    CfA Submillimeter Array Mauna Kea, Hawaii, USA, Altitude 4,080 m (13,390 ft)

    Submillimeter Array Hawaii SAO

    ESO/NRAO/NAOJ ALMA Array
    ESO/NRAO/NAOJ ALMA Array, Chile

    South Pole Telescope SPTPOL
    South Pole Telescope SPTPOL

    Future Array/Telescopes

    IRAM NOEMA in the French Alps on the wide and isolated Plateau de Bure at an elevation of 2550 meters, the telescope currently consists of ten antennas, each 15 meters in diameter.interferometer, Located in the French Alpes on the wide and isolated Plateau de Bure at an elevation of 2550 meters

    NSF CfA Greenland telescope


    Greenland Telescope

    ARO 12m Radio Telescope, Kitt Peak National Observatory, Arizona, USA, Altitude 1,914 m (6,280 ft)


    ARO 12m Radio Telescope

    Caltech Owens Valley Radio Observatory, located near Big Pine, California (US) in Owens Valley, Altitude1,222 m (4,009 ft)

    Messier 87*, The first image of a black hole. This is the supermassive black hole at the center of the galaxy Messier 87. Image via JPL/ Event Horizon Telescope Collaboration.

    In quasar 3C279 – also a black hole – the EHT team found another phenomenon: At a distance of more than a thousand times the shadow of the black hole, the core of a plasma jet suddenly lit up. How the energy for this jet could get there as if through an invisible chimney was not yet known.

    Extremely flickering gamma radiation detected

    This quasar has now been observed with the NASA space telescope Fermi-LAT by the astrophysicist Amit Shukla, who until 2018 did research at Julius-Maximilians-Universität (JMU) Würzburg in Bavaria, Germany.

    NASA/Fermi LAT


    NASA/Fermi Gamma Ray Space Telescope

    He now is working at the Indian Institute of Technology in Indore. Shukla discovered that the core of the jet, which was found in the millimeter wavelength range, also emits high-energy gamma radiation, but with an extremely flickering brightness. This brightness can double within a few minutes, as reported in the journal Nature Communications.

    The special pattern of the sequence of brightness changes is characteristic of a universal process called magnetic reconnection, which occurs in many astrophysical objects with strong magnetic fields.

    NASA Magnetic reconnection, Credit: M. Aschwanden et al. (LMSAL), TRACE, NASA

    Solar activity also has to do with the dynamics of magnetic fields and reconnection. This was recently demonstrated by observing “campfires” in the solar atmosphere with the “Solar Orbiter” mission of the European Space Agency ESA.

    ESA/NASA Solar Orbiter depiction

    Invisibly stored energy is suddenly released

    But back to the quasar 3C279: “I saw how the analysis of the data revealed the special pattern of magnetic reconnection in the light curve. It felt as if I had suddenly deciphered a hieroglyph in the black hole alphabet,” says Amit Shukla happily.

    During reconnection, energy that is initially stored invisibly in the magnetic field is suddenly released in numerous “mini-jets”. In these jets, particles are accelerated, which then produce the observed gamma radiation. Magnetic reconnection would explain how the energy reaches the jet’s core from the black hole and where it ultimately comes from.

    Energy from the spinning black hole

    Professor Karl Mannheim, head of the JMU Chair of Astronomy and co-author of the publication, explains: “Spacetime near the black hole in the quasar 3C279 is forced to swirl around in corotation. Magnetic fields anchored to the plasma around the black hole expel the jet slowing down the black hole’s rotation and converting part of its rotational energy into radiation”.

    See the full article here.

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  • richardmitnick 9:01 am on April 7, 2020 Permalink | Reply
    Tags: , , , , , EHT - Event Horizon Telescope, , , Quasar 3C 279, , Telescopes contributing also are the Submillimeter Telescope; and the South Pole Telescope., Telescopes contributing to this result were ALMA; APEX; the IRAM 30-meter telescope; the James Clerk Maxwell Telescope; the Large Millimeter Telescope; the Submillimeter Array., The data analysis to transform raw data to an image required specific computers (or correlators) hosted by the MPIfR in Bonn and the MIT Haystack Observatory.,   

    From ALMA: “Event Horizon Telescope Images of a Black-Hole Powered Jet” 

    ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres

    From ALMA

    Nicolás Lira
    Education and Public Outreach Coordinator
    Joint ALMA Observatory, Santiago – Chile
    Phone: +56 2 2467 6519
    Cell phone: +56 9 9445 7726
    Email: nicolas.lira@alma.cl

    Masaaki Hiramatsu
    Education and Public Outreach Officer, NAOJ Chile
    Observatory
, Tokyo – Japan
    Phone: +81 422 34 3630
    Email: hiramatsu.masaaki@nao.ac.jp

    Bárbara Ferreira
    ESO Public Information Officer
    Garching bei München, Germany
    Phone: +49 89 3200 6670
    Email: pio@eso.org

    Iris Nijman
    Public Information Officer
    National Radio Astronomy Observatory Charlottesville, Virginia – USA
    Cell phone: +1 (434) 249 3423
    Email: alma-pr@nrao.edu

    1
    2
    Illustration of multiwavelength 3C 279 jet structure in April 2017. The observing epochs, arrays, and wavelengths are noted at each panel. Credit: J.Y. Kim (MPIfR), Boston University Blazar Program (VLBA and GMVA), and Event Horizon Telescope Collaboration.

    Something is Lurking in the Heart of Quasar 3C 279. One year ago, the Event Horizon Telescope (EHT) Collaboration published the first image of a black hole in the nearby radio galaxy Messier 87.

    Mesier 87*, The first image of a black hole. This is the supermassive black hole at the center of the galaxy Messier 87. Image via JPL/ Event Horizon Telescope Collaboration.

    Now the collaboration has extracted new information from the EHT data of the far quasar 3C 279: they observed in the finest detail ever a relativistic jet that is believed to originate from the vicinity of a supermassive black hole. In their analysis, which was led by astronomer Jae-Young Kim from the Max Planck Institute for Radio Astronomy in Bonn, they studied the jet’s fine-scale morphology close to the jet base where highly variable gamma-ray emission is thought to originate. The technique used for observing the jet is called very long baseline interferometry (VLBI). The results are published in the coming issue of “Astronomy & Astrophysics, April 2020.

    The EHT collaboration continues extracting information from the groundbreaking data collected in its global campaign in April 2017. One target of the observations was the quasar 3C 279, a galaxy 5 billion light-years away, in the constellation Virgo that scientists classify as a quasar because a point of light at its center shines ultra-bright and flickers as massive amounts of gases and stars fall into the giant black hole there. The black hole is about one billion times the mass of the Sun, that is, 200 more massive than our Galactic Centre black hole. It is shredding the gas and stars that come near into an inferred accretion disk and we see it is squirting some of the gas back out in two fine fire-hose-like jets of plasma at velocities approaching the speed of light. This tells of enormous forces at play in the center.

    The EHT collaboration continues extracting information from the groundbreaking data collected in its global campaign in April 2017. One target of the observations was the quasar 3C 279, a galaxy 5 billion light-years away, in the constellation Virgo that scientists classify as a quasar because a point of light at its center shines ultra-bright and flickers as massive amounts of gases and stars fall into the giant black hole there. The black hole is about one billion times the mass of the Sun, that is, 200 more massive than our Galactic Centre black hole. It is shredding the gas and stars that come near into an inferred accretion disk and we see it is squirting some of the gas back out in two fine fire-hose-like jets of plasma at velocities approaching the speed of light. This tells of enormous forces at play in the center.

    The interpretation of the observations is challenging. Motions different than the jet direction, and apparently as fast as about 20 times the speed of light are difficult to reconcile with the early understanding of the source, this suggests traveling shocks or instabilities in a bent, possibly rotating jet, which also emits at high energies, such gamma-rays.

    The telescopes contributing to this result were ALMA, APEX, the IRAM 30-meter telescope, the James Clerk Maxwell Telescope, the Large Millimeter Telescope, the Submillimeter Array, the Submillimeter Telescope, and the South Pole Telescope.

    The telescopes work together using a technique called very long baseline interferometry (VLBI). This synchronizes facilities around the world and exploits the rotation of our planet to form one huge, Earth-size telescope. VLBI allows the EHT to achieve a resolution of 20 micro-arcseconds — equivalent to identifying an orange on Earth as seen by an astronaut from the Moon. The data analysis to transform raw data to an image required specific computers (or correlators), hosted by the MPIfR in Bonn and the MIT Haystack Observatory.

    Anton Zensus, Director at the MPIfR and Chair of the EHT Collaboration Board, stresses the achievement as a global effort: “Last year we could present the first image of the shadow of a black hole. Now we see unexpected changes in the shape of the jet in 3C 279, and we are not done yet. We are working on the analysis of data from the centre of our Galaxy in Sgr A*, and on other active galaxies such as Centaurus A, OJ 287, and NGC 1052. As we told last year: this is just the beginning.”

    Opportunities to conduct EHT observing campaigns occur once a year in early Northern springtime, but the March/April 2020 campaign had to be cancelled in response to the CoViD-19 global outbreak. In announcing the cancellation Michael Hecht, astronomer from the MIT/Haystack Observatory and EHT Deputy Project Director, concluded that: “We will now devote our full concentration to completion of scientific publications from the 2017 data and dive into the analysis of data obtained with the enhanced EHT array in 2018. We are looking forward to observations with the EHT array expanded to eleven observatories in the spring of 2021”.

    Additional Information

    The Event Horizon Telescope international collaboration announced the first-ever image of a black hole at the heart of the radio galaxy Messier 87 on April 10, 2019 by creating a virtual Earth-sized telescope. Supported by considerable international investment, the EHT links existing telescopes using novel systems — creating a new instrument with the highest angular resolving power that has yet been achieved.

    The individual telescopes involved in the EHT collaboration are: the Atacama Large Millimetre Telescope (ALMA), the Atacama Pathfinder EXplorer (APEX), the Greenland Telescope (since 2018), the IRAM 30-meter Telescope, the IRAM NOEMA Observatory (expected 2021), the Kitt Peak Telescope (expected 2021), the James Clerk Maxwell Telescope (JCMT), the Large Millimeter Telescope (LMT), the Submillimeter Array (SMA), the Submillimeter Telescope (SMT), and the South Pole Telescope (SPT).

    The EHT consortium consists of 13 stakeholder institutes; the Academia Sinica Institute of Astronomy and Astrophysics, the University of Arizona, the University of Chicago, the East Asian Observatory, Goethe-Universität Frankfurt, Institut de Radioastronomie Millimétrique, Large Millimeter Telescope, Max-Planck-Institut für Radioastronomie, MIT Haystack Observatory, National Astronomical Observatory of Japan, Perimeter Institute for Theoretical Physics, Radboud University and the Smithsonian Astrophysical Observatory.

    See the full article here .

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    The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA is funded in Europe by the European Organization for Astronomical Research in the Southern Hemisphere (ESO), in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and in East Asia by the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Academia Sinica (AS) in Taiwan.

    ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI) and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

    NRAO Small
    ESO 50 Large

     
  • richardmitnick 11:50 am on January 27, 2020 Permalink | Reply
    Tags: "This NASA Visualisation of a Black Hole Is So Beautiful We Could Cry", , , , , EHT - Event Horizon Telescope, , ,   

    From NASA via Science Alert: “This NASA Visualisation of a Black Hole Is So Beautiful, We Could Cry” 

    From NASA

    via

    ScienceAlert

    Science Alert

    26 JAN 2020
    MICHELLE STARR

    1
    NASA Visualization Shows a Black Hole’s Warped World

    The first-ever direct image of a black hole’s event horizon was a truly impressive feat of scientific ingenuity. But it was extremely difficult to achieve, and the resulting image was relatively low-resolution.

    Mesier 87*, The first image of a black hole. First-ever direct image of a black hole, Messier 87*. (EHT Collaboration).This is the supermassive black hole at the center of the galaxy Messier 87. Image via JPL/ Event Horizon Telescope Collaboration.

    EHT map

    Now iconic image of Katie Bouman-Harvard Smithsonian Astrophysical Observatory after the image of Messier 87 was achieved. Headed from Harvard to Caltech as an Assistant Professor. On the committee for the next iteration of the EHT .

    Techniques and technology will be refined, and it’s expected that future direct images of black holes will improve with time. In September 2019, a NASA visualisation – made for the agency’s Black Hole Week – showed what we might expect to see in high-resolution images of an actively accreting supermassive black hole.

    Supermassive black holes sit at the centres of most large galaxies, and how they got there is a mystery; which came first, the black hole or the galaxy, is one of the big questions in cosmology.

    What we do know is that they are really huge, as in millions or billions of times the mass of the Sun; that they can control star formation; that when they wake up and start feeding, they can become the brightest objects in the Universe. Over the decades, we have also figured out some of their strange dynamics.

    In fact, the very first simulated image of a black hole, calculated using a 1960s punch card IBM 7040 computer and plotted by hand by French astrophysicist Jean-Pierre Luminet in 1978, still looks a lot like NASA’s simulation.

    In both simulations (the one above, and Luminet’s work below), you see a black circle in the centre. That’s the event horizon, the point at which electromagnetic radiation – light, radio waves, X-rays and so forth – are no longer fast enough to achieve escape velocity from the black hole’s gravitational pull.

    4
    (Jean-Pierre Luminet)

    Across the middle of the black hole is the front of the disc of material that is swirling around the black hole, like water into a drain. It generates such intense radiation through friction that we can detect this part with our telescopes – that’s what you are seeing in the picture of Messier 87*.

    You can see the photon ring, a perfect ring of light around the event horizon. And you can see a broad sweep of light around the black hole. That light is actually coming from the part of the accretion disc behind the black hole; but the gravity is so intense, even outside the event horizon, that it warps spacetime and bends the path of light around the black hole.

    You can also see that one side of the accretion disc is brighter than the other. This effect is called relativistic beaming, and it’s caused by the rotation of the disc. The part of the disc that is moving towards us is brighter because it is moving close to light-speed. This motion produces a change in frequency in the wavelength of the light. It’s called the Doppler effect.

    The side that’s moving away from us, therefore, is dimmer, because that motion has the opposite effect.

    “It is precisely this strong asymmetry of apparent luminosity,” Luminet wrote in a paper last year, “that is the main signature of a black hole, the only celestial object able to give the internal regions of an accretion disk a speed of rotation close to the speed of light and to induce a very strong Doppler effect.”

    Simulations such as these can help us understand the extreme physics around supermassive black holes – and that helps us understand what we are seeing when we look at the picture of Messier 87*.

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    The National Aeronautics and Space Administration (NASA) is the agency of the United States government that is responsible for the nation’s civilian space program and for aeronautics and aerospace research.

    President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA’s predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

    Since that time, most U.S. space exploration efforts have been led by NASA, including the Apollo moon-landing missions, the Skylab space station, and later the Space Shuttle. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle and Commercial Crew vehicles. The agency is also responsible for the Launch Services Program (LSP) which provides oversight of launch operations and countdown management for unmanned NASA launches. Most recently, NASA announced a new Space Launch System that it said would take the agency’s astronauts farther into space than ever before and lay the cornerstone for future human space exploration efforts by the U.S.

    NASA science is focused on better understanding Earth through the Earth Observing System, advancing heliophysics through the efforts of the Science Mission Directorate’s Heliophysics Research Program, exploring bodies throughout the Solar System with advanced robotic missions such as New Horizons, and researching astrophysics topics, such as the Big Bang, through the Great Observatories [Hubble, Chandra, Spitzer, and associated programs. NASA shares data with various national and international organizations such as from the [JAXA]Greenhouse Gases Observing Satellite.

     
  • richardmitnick 6:50 am on January 21, 2020 Permalink | Reply
    Tags: "The dynamic behaviour of a black hole corona", "XMM-Newton maps black hole surroundings", , , , Black hole IRAS 13224–3809, , EHT - Event Horizon Telescope, ,   

    From European Space Agency – United space in Europe (2): “The dynamic behaviour of a black hole corona” and “XMM-Newton maps black hole surroundings” 

    ESA Space For Europe Banner

    From European Space Agency – United space in Europe

    1. The dynamic behaviour of a black hole corona

    20/01/2020

    United space in Europe

    1
    XMM-Newton maps black hole surroundings. ESA

    The dynamic behaviour of a black hole corona

    These illustrations show the surroundings of a black hole feeding on ambient gas as mapped using ESA’s XMM-Newton X-ray observatory.

    ESA/XMM Newton

    As the material falls into the black hole, it spirals around to form a flattened disc, as shown here, heating up as it does so. At the very centre of the disc, close to the black hole, a region of very hot electrons – with temperatures of around a billion degrees – known as the corona produced high-energy X-rays that stream out into space.

    A new study has used the reverberating echoes of this radiation, as observed by XMM-Newton, to map the surroundings of a black hole. The study focussed on the black hole at the core of an active galaxy named IRAS 13224–3809, which is one of the most variable X-ray sources in the sky, undergoing very large and rapid fluctuations in brightness of a factor of 50 in mere hours.

    By tracking the X-ray echoes, it was possible to track the dynamic behaviour of the corona itself, where the intense X-ray emission originates from. The corona is shown here as the bright region hovering over the black hole, changing in size and brightness. The study found that the corona of the black hole within IRAS 13224–3809 changed in size incredibly quickly, over a matter of days.

    The Full Story

    2. XMM-Newton maps black hole surroundings

    20/01/2020

    William Alston
    Institute of Astronomy
    University of Cambridge, UK
    Email: wna@ast.cam.ac.uk

    Michael Parker
    European Space Agency
    European Space Astronomy Centre
    Villanueva de la Cañada, Madrid, Spain
    Email: Michael.Parker@esa.int

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

    Material falling into a black hole casts X-rays out into space – and now, for the first time, ESA’s XMM-Newton X-ray observatory [above] has used the reverberating echoes of this radiation to map the dynamic behaviour and surroundings of a black hole itself.

    Most black holes are too small on the sky for us to resolve their immediate environment, but we can still explore these mysterious objects by watching how matter behaves as it nears, and falls into, them.

    As material spirals towards a black hole, it is heated up and emits X-rays that, in turn, echo and reverberate as they interact with nearby gas. These regions of space are highly distorted and warped due to the extreme nature and crushingly strong gravity of the black hole.

    For the first time, researchers have used XMM-Newton to track these light echoes and map the surroundings of the black hole at the core of an active galaxy. Named IRAS 13224–3809, the black hole’s host galaxy is one of the most variable X-ray sources in the sky, undergoing very large and rapid fluctuations in brightness of a factor of 50 in mere hours.

    “Everyone is familiar with how the echo of their voice sounds different when speaking in a classroom compared to a cathedral – this is simply due to the geometry and materials of the rooms, which causes sound to behave and bounce around differently,” explains William Alston of the University of Cambridge, UK, lead author of the new study.

    “In a similar manner, we can watch how echoes of X-ray radiation propagate in the vicinity of a black hole in order to map out the geometry of a region and the state of a clump of matter before it disappears into the singularity. It’s a bit like cosmic echo-location.”

    As the dynamics of infalling gas are strongly linked to the properties of the consuming black hole, William and colleagues were also able to determine the mass and spin of the galaxy’s central black hole by observing the properties of matter as it spiralled inwards.

    The inspiralling material forms a disc as it falls into the black hole. Above this disc lies a region of very hot electrons – with temperatures of around a billion degrees – called the corona. While the scientists expected to see the reverberation echoes they used to map the region’s geometry, they also spotted something unexpected: the corona itself changed in size incredibly quickly, over a matter of days.

    “As the corona’s size changes, so does the light echo – a bit like if the cathedral ceiling is moving up and down, changing how the echo of your voice sounds,” adds William.

    “By tracking the light echoes, we were able to track this changing corona, and – what’s even more exciting – get much better values for the black hole’s mass and spin than we could have determined if the corona was not changing in size. We know the black hole’s mass cannot be fluctuating, so any changes in the echo must be down to the gaseous environment.”

    The study used the longest observation of an accreting black hole ever taken with XMM-Newton, collected over 16 spacecraft orbits in 2011 and 2016 and totalling 2 million seconds – just over 23 days.

    This, combined with the strong and short-term variability of the black hole itself, allowed William and collaborators to model the echoes comprehensively over day-long timescales.

    The region explored in this study is not accessible to observatories such as the Event Horizon Telescope [EHT], which managed to take the first ever picture of gas in the immediate vicinity of a black hole – the one sitting at the centre of the nearby massive galaxy Messier 87.

    EHT map

    The result, based on observations performed with radio telescopes across the world in 2017 and published last year, immediately became a global sensation.

    M87*, The first image of a black hole. This is the supermassive black hole at the center of the galaxy Messier 87. Image via JPL/ Event Horizon Telescope Collaboration.

    Now iconic image of Katie Bouman-Harvard Smithsonian Astrophysical Observatory after the image of Messier 87 was achieved. Headed from Harvard to Caltech as an Assistant Professional. On the committee for the next iteration of the EHT .

    “The Event Horizon Telescope image was obtained using a method known as interferometry – a wonderful technique that can only work on the very few nearest supermassive black holes to Earth, such as those in Messier 87 and in our home galaxy, the Milky Way, because their apparent size on the sky is large enough for this method to work,” says co-author Michael Parker, who is an ESA research fellow at the European Space Astronomy Centre near Madrid, Spain.

    “By contrast, our approach is able to probe the nearest few hundred supermassive black holes that are actively consuming matter – and this number will increase significantly with the launch of ESA’s Athena satellite.”

    ESA/Athena spacecraft depiction

    Characterising the environments closely surrounding black holes is a core science goal for ESA’s Athena mission, which is scheduled for launch in the early 2030s and will unveil the secrets of the hot and energetic Universe.

    Measuring the mass, spin and accretion rates of a large sample of black holes is key to understanding gravity throughout the cosmos.

    Additionally, since supermassive black holes are strongly linked to their host galaxy’s properties, these studies are also key to furthering our knowledge of how galaxies form and evolve over time.

    “The large dataset provided by XMM-Newton was essential for this result,” says Norbert Schartel, ESA XMM-Newton Project Scientist.

    “Reverberation mapping is an exciting technique that promises to reveal much about both black holes and the wider Universe in coming years. I hope that XMM-Newton will perform similar observing campaigns for several more active galaxies in coming years, so that the method is fully established when Athena launches.”

    Science paper:
    A dynamic black hole corona in an active galaxy through X-ray reverberation mapping by W. N. Alston et al.
    Nature Astronomy.

    The study uses data gathered by XMM-Newton’s European Photon Imaging Camera (EPIC).

    See the “dynamic behaviour”full article here .

    See the “Full Story” article here .


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

    Stem Education Coalition

    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

    ESA50 Logo large

     
  • richardmitnick 2:21 pm on December 28, 2019 Permalink | Reply
    Tags: , , , , , EHT - Event Horizon Telescope, , Event Horizon, ,   

    From Ethan Siegel: “Ask Ethan: Can Black Holes Ever Spit Anything Back Out?” 

    From Ethan Siegel
    Dec 28, 2019

    A black hole’s event horizon is thought of as the point of no return. But perhaps there are ways back out, after all.

    Black holes just might be the most extreme objects that exist in the entire Universe. While every quantum of matter or energy is affected by the gravitational force, there are other forces capable of overcoming gravity everywhere you go, except inside a black hole. The most important feature of a black hole is the existence of an event horizon; no other class of object has them. Although black holes have this region where gravity is so strong that nothing can escape, not even if they move at the speed of light, perhaps there are loopholes to the inescapability of a black hole’s gravity, after all. That’s the subject of this week’s question, which comes from Noah, who asks,

    Do black holes ever spit things out at any time?

    And if they do, do they ever spit out light?

    The answer must be yes. After all, the most surprising thing about black holes — both predicted theoretically and observed directly — is that they aren’t black at all.

    1
    The second-largest black hole as seen from Earth, the one at the center of the galaxy Messier 87, is shown in three views here. At the top is optical from Hubble, at the lower-left is radio from NRAO, and at the lower-right is X-ray from Chandra. These differing views have different resolutions dependent on the optical sensitivity, wavelength of light used, and size of the telescope mirrors used to observe them. These are all examples of radiation emitted from the regions around black holes, demonstrating that black holes aren’t so black, after all. (TOP, OPTICAL, HUBBLE SPACE TELESCOPE / NASA / WIKISKY; LOWER LEFT, RADIO, NRAO / VERY LARGE ARRAY (VLA); LOWER RIGHT, X-RAY, NASA / CHANDRA X-RAY TELESCOPE)

    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)

    NASA/Chandra X-ray Telescope

    If black holes were entirely dark, there would be no way to detect them at all, save for the gravitational influence that they might have on the other objects around them. If we had a black hole and a star in orbit around one another, we’d be able to infer the existence (and the mass) of the black hole simply by watching how the star appeared to move over time.

    As it wobbled back-and-forth in its orbit, we could determine the parameters of the other object present, including the mass, orbital separation distance, and if our measurements were good enough, even its angle-of-inclination relative to our line of sight. Based on the light that comes from it, we could know whether it was a star, a white dwarf, a neutron star, or — if there were no light at all — even a black hole.

    2
    When a black hole and a companion star orbit one another, the star’s motion will change over time owing to the gravitational influence of the black hole, while matter from the star can accrete onto the black hole, resulting in X-ray and radio emissions. (JINGCHUAN YU/BEIJING PLANETARIUM/2019)

    But in our practical, realistic Universe, the black holes that orbit other stars are actually detectable through radiation.

    “Hang on,” you might object, “if black holes are regions of space from which nothing can escape, not even light, then how are we seeing radiation coming from the black hole itself?”

    That’s a valid point, but what you have to understand is that the space outside of a black hole’s event horizon doesn’t have to be devoid of matter. In fact, if there’s another star nearby, that star can serve as a rich source of matter, capable of being siphoned onto the black hole, particularly if the nearby star is giant and diffuse. This sort of system, in particular, creates what we observe as an X-ray binary, and it’s how the first black hole we ever found was detected.

    3
    Black holes are not isolated objects in space, but exist amidst the matter and energy in the Universe, galaxy, and star systems where they reside. They grow by accreting and devouring matter and energy, and when they actively feed they emit X-rays. Binary black hole systems that emit X-rays are how the majority of our known non-supermassive black holes were discovered. (NASA/ESA HUBBLE SPACE TELESCOPE COLLABORATION)

    Matter, if you break it down to a subatomic level, is made of charged particles. Put this matter in the vicinity of a black hole, and it will:

    move rapidly,
    collide with other matter particles,
    heat up,
    create electric currents and magnetic fields,
    accelerate,
    and emit radiation.

    Some of the matter will lose momentum and fall into the black hole, passing through the event horizon and adding to the black hole’s mass. However, the majority of the matter won’t fall in at all, but rather will get funneled into an accretion disk (or more generally, an accretion flow) that experiences the electromagnetic forces from all the accelerating matter. As a result, we see two jets that get expelled in opposite directions emanating from black holes.

    4
    While distant host galaxies for quasars and active galactic nuclei can often be imaged in visible/infrared light, the jets themselves and the surrounding emission is best viewed in both the X-ray and the radio, as illustrated here for the galaxy Hercules A. The gaseous outflows are highlighted in the radio, and if X-ray emissions follow the same path into the gas, they can be responsible for creating hot spots owing to the acceleration of electrons. (NASA, ESA, S. BAUM AND C. O’DEA (RIT), R. PERLEY AND W. COTTON (NRAO/AUI/NSF), AND THE HUBBLE HERITAGE TEAM (STSCI/AURA))

    These relativistic jets are made of particles aAn illustration of an active black hole, one that accretes matter and accelerates a portion of it outwards in two perpendicular jets. The normal matter undergoing an acceleration like this describes how quasars work extremely well, while the accretion flows are ultimately responsible for the emitted particles and radiation we observe. (MARK A. GARLICK)nd emit enormous amounts of light from their dynamical interactions with the particles in the interstellar medium. In fact, the same physics is at play in the supermassive black holes found at the centers of galaxies: matter that falls in towards the black hole largely gets ripped apart, funneled into accretion flows, accelerated, and ejected in jet-like structures.

    If you were a real particle outside of the black hole’s event horizon, but were gravitationally bound to the black hole, you’d be compelled to move in an elliptical orbit around it. At your point of closest approach — the periapsis of your orbit — you’ll be moving at your fastest speed, which gives you the greatest likelihood of interacting with other particles. If they’re present, you’ll experience inelastic collisions, friction, electromagnetic forces, etc. In other words, all the forces that cause charged particles to emit radiation.

    5
    An illustration of an active black hole, one that accretes matter and accelerates a portion of it outwards in two perpendicular jets. The normal matter undergoing an acceleration like this describes how quasars work extremely well, while the accretion flows are ultimately responsible for the emitted particles and radiation we observe. (MARK A. GARLICK)

    Radiation, although it covers the entire electromagnetic spectrum from low-energy radio waves all the way up to X-rays and gamma rays, is just the general term for all forms of light. So long as you have particles that exist outside of the black hole’s event horizon, they will create this form of radiation, and in the cases where relatively nearby black holes are feeding at fast enough rates, we’ll actually observe that characteristic X-ray radiation.

    In fact, we can even look at the supermassive black holes from outside our own galaxy, and find those same features, only scaled up in both power and extent. The same physics is at play — charged object in motion create magnetic fields, and those fields accelerate particles along one particular axis — which is what creates the relativistic jets we observe from a distance. Those jets produce showers of both particles and radiation, and we can catch them even from Earth, sometimes even in visible light.

    6
    The galaxy Centaurus A, shown in a composite of visible light, infrared (submillimeter) light and in the X-ray. This is the nearest active galaxy to the Milky Way, and its bipolar jets are thought to arise from the active, feeding black hole inside. (ESO/WFI (OPTICAL); MPIFR/ESO/APEX/A.WEISS ET AL. (SUBMILLIMETRE); NASA/CXC/CFA/R.KRAFT ET AL. (X-RAY))

    Wide Field Imager on the 2.2 meter MPG/ESO telescope at Cerro LaSilla

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

    In some cases, where black holes are active and feeding, we can even observe a spectacular phenomenon known as a photon sphere. Around black holes, the fabric of space is so severely curved that it isn’t just particles that make circular-and-elliptical orbits around that central mass, but even photons: light itself.

    The photon sphere is a little bit larger than the event horizon, and for realistic (rotating) black holes, the physics is more complicated than a simple, non-rotating case. However, the extreme curvature of space means that these photons will create a ring-like structure visible from any faraway perspective. The ring itself is larger than the event horizon, and the curvature of space makes the angular size of the ring appear even larger than that, but this is one of the things we need to calculate in order to understand why our first image of a black hole’s event horizon appears with the famous donut-like shape we observe.

    The first image of a black hole. This is the supermassive black hole at the center of the galaxy Messier 87. Image via JPL/ Event Horizon Telescope Collaboration.

    Event Horizon Telescope Array

    Arizona Radio Observatory
    Arizona Radio Observatory/Submillimeter-wave Astronomy (ARO/SMT)

    ESO/APEX
    Atacama Pathfinder EXperiment

    CARMA Array no longer in service
    Combined Array for Research in Millimeter-wave Astronomy (CARMA)

    Atacama Submillimeter Telescope Experiment (ASTE)
    Atacama Submillimeter Telescope Experiment (ASTE)

    Caltech Submillimeter Observatory
    Caltech Submillimeter Observatory (CSO)

    IRAM 30m Radio telescope, on Pico Veleta in the Spanish Sierra Nevada,, Altitude 2,850 m (9,350 ft)


    Institut de Radioastronomie Millimetrique (IRAM) 30m

    James Clerk Maxwell Telescope interior, Mauna Kea, Hawaii, USA
    James Clerk Maxwell Telescope interior, Mauna Kea, Hawaii, USA

    Large Millimeter Telescope Alfonso Serrano
    Large Millimeter Telescope Alfonso Serrano

    CfA Submillimeter Array Mauna Kea, Hawaii, USA, Altitude 4,080 m (13,390 ft)

    Submillimeter Array Hawaii SAO

    ESO/NRAO/NAOJ ALMA Array
    ESO/NRAO/NAOJ ALMA Array, Chile

    South Pole Telescope SPTPOL
    South Pole Telescope SPTPOL

    Future Array/Telescopes

    IRAM NOEMA in the French Alps on the wide and isolated Plateau de Bure at an elevation of 2550 meters, the telescope currently consists of ten antennas, each 15 meters in diameter.interferometer, Located in the French Alpes on the wide and isolated Plateau de Bure at an elevation of 2550 meters

    NSF CfA Greenland telescope


    Greenland Telescope

    ARO 12m Radio Telescope, Kitt Peak National Observatory, Arizona, USA, Altitude 1,914 m (6,280 ft)


    ARO 12m Radio Telescope

    Caltech Owens Valley Radio Observatory, located near Big Pine, California (US) in Owens Valley, Altitude1,222 m (4,009 ft)

    All of that, however, as interesting and light-emitting as it may be, only arises from material that hasn’t yet fallen through that critical region of space around the black hole: it’s all for things that remain outside the event horizon. Nothing can be seen arising from any material that actually goes inside the event horizon and winds up physically over that critical boundary.

    However, if you could create a black hole that was completely isolated from everything else in the Universe — isolated from particles, radiation, neutrinos, dark matter, other sources of mass, etc. — all you’d have was the curved space resulting from the black hole’s presence itself. Unlike the static picture of curved space that you typically see, any particle at rest would feel as though the space it occupies is being dragged around and into the black hole; it’s as though the space beneath a particle’s proverbial “feet” is in motion, as though it’s fundamentally on a moving walkway.

    8
    In the vicinity of a black hole, space flows like either a moving walkway or a waterfall, depending on how you want to visualize it. At the event horizon, even if you ran (or swam) at the speed of light, there would be no overcoming the flow of spacetime, which drags you into the singularity at the center. Outside the event horizon, though, other forces (like electromagnetism) can frequently overcome the pull of gravity, causing even infalling matter to escape. (ANDREW HAMILTON / JILA / UNIVERSITY OF COLORADO)

    You’d have that curved space, an event horizon, and the laws of physics. And one of the things that the laws of physics teaches us is that the quantum fields that govern the Universe, even in the absence of any particles, are still present, constantly fluctuating as they inevitably must.

    In flat space, this wouldn’t be a big deal. Energy fluctuations occur in the quantum vacuum, and in flat space, the quantum vacuum has equivalent properties everywhere. But when you have curved space — and in particular, space that’s more severely curved in one direction (towards the black hole) than the other (away from the black hole) — observers at different locations will disagree as to what the correct description of the lowest-energy state of the vacuum is.

    9
    Visualization of a quantum field theory calculation showing virtual particles in the quantum vacuum. (Specifically, for the strong interactions.) Even in empty space, this vacuum energy is non-zero, and what appears to be the ‘ground state’ in one region of curved space will look different from the perspective of an observer where the spatial curvature differs. (DEREK LEINWEBER)

    For someone far away from the event horizon, where space appears flat, they’ll observe some low-energy radiation coming from the more severely curved regions of space, even in the absence of any particles. This radiation carries real energy, and is a consequence of how quantum fields behave in curved space. The greater the curvature of space, the greater the rate that this radiation — known as Hawking radiation — gets emitted.

    The energy for the radiation only has one possible source: it has to be stolen from the mass of the black hole. Fortunately, Einstein’s most famous equation, E = mc², describes this balance exactly. The smaller in mass the black hole is, the smaller the event horizon and the greater the curvature is near it. When you put this together, you wind up with a fascinating discovery: the less massive your black hole is, the more quickly it loses mass, emits Hawking radiation, and decays away.

    Cosmic microwave background radiation. Stephen Hawking Center for Theoretical Cosmology U Cambridge

    9
    The event horizon of a black hole is a spherical or spheroidal region from which nothing, not even light, can escape. But outside the event horizon, the black hole is predicted to emit radiation. Hawking’s 1974 work was the first to demonstrate this, and it was arguably his greatest scientific achievement. (NASA; DANA BERRY, SKYWORKS DIGITAL, INC.)

    The rate at which an isolated black hole radiates its mass away, through Hawking radiation, is incredibly slow for any realistic black hole in our Universe. A black hole of our Sun’s mass would take 10⁶⁷ years to evaporate, while the one at the Milky Way’s center needs 10⁸⁷ years and the most massive ones known take up to 10¹⁰⁰ years!

    Still, this is the only case where we can say that some form of energy from inside the black hole’s event horizon affects what we observe outside of it. The things that fall in through a black hole’s event horizon don’t come out again, not under any circumstances. The only things that a black hole can spit out come from outside the event horizon, from particles to conventional photons to even the Hawking radiation that get their energy from the black hole’s mass itself. There may be plenty of light that arises from black holes, but none of it can ever come from inside the event horizon.

    SGR A* , the supermassive black hole at the center of the Milky Way. NASA’s Chandra X-Ray Observatory

    SgrA* NASA/Chandra supermassive black hole at the center of the Milky Way, X-ray image of the center of our galaxy, where the supermassive black hole Sagittarius A* resides. Image via X-ray: NASA/UMass/D.Wang et al., IR: NASA/STScI.

    Star S0-2 Andrea Ghez Keck/UCLA Galactic Center Group at SGR A*, the supermassive black hole at the center of the milky way

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

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

     
  • richardmitnick 9:58 am on December 25, 2019 Permalink | Reply
    Tags: , , , , , EHT - Event Horizon Telescope, , ,   

    From ALMA: “In the Shadow of a Black Hole” 

    ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres

    From ALMA

    10 April, 2019

    Nicolás Lira
    Education and Public Outreach Coordinator
    Joint ALMA Observatory, Santiago – Chile
    Phone: +56 2 2467 6519
    Cell phone: +56 9 9445 7726
    Email: nicolas.lira@alma.cl

    Masaaki Hiramatsu
    Education and Public Outreach Officer, NAOJ Chile
    Observatory
, Tokyo – Japan
    Phone: +81 422 34 3630
    Email: hiramatsu.masaaki@nao.ac.jp

    Bárbara Ferreira
    ESO Public Information Officer
    Garching bei München, Germany
    Phone: +49 89 3200 6670
    Email: pio@eso.org

    Iris Nijman
    Public Information Officer
    National Radio Astronomy Observatory Charlottesville, Virginia – USA
    Cell phone: +1 (434) 249 3423
    Email: alma-pr@nrao.edu

    The Event Horizon Telescope (EHT) — a planet-scale array of eight ground-based radio telescopes forged through international collaboration — was designed to capture images of a black hole. In coordinated press conferences across the globe, EHT researchers revealed that they succeeded, unveiling the first direct visual evidence of a supermassive black hole and its shadow.
    This 17-minute film explores the efforts that led to this historic image, from the science of Einstein and Schwarzschild to the struggles and successes of the EHT collaboration. Credit:ESO

    Event Horizon Telescope Array

    Arizona Radio Observatory
    Arizona Radio Observatory/Submillimeter-wave Astronomy (ARO/SMT)

    ESO/APEX
    Atacama Pathfinder EXperiment

    CARMA Array no longer in service
    Combined Array for Research in Millimeter-wave Astronomy (CARMA)

    Atacama Submillimeter Telescope Experiment (ASTE)
    Atacama Submillimeter Telescope Experiment (ASTE)

    Caltech Submillimeter Observatory
    Caltech Submillimeter Observatory (CSO)

    IRAM 30m Radio telescope, on Pico Veleta in the Spanish Sierra Nevada,, Altitude 2,850 m (9,350 ft)


    Institut de Radioastronomie Millimetrique (IRAM) 30m

    James Clerk Maxwell Telescope interior, Mauna Kea, Hawaii, USA
    James Clerk Maxwell Telescope interior, Mauna Kea, Hawaii, USA

    Large Millimeter Telescope Alfonso Serrano
    Large Millimeter Telescope Alfonso Serrano

    CfA Submillimeter Array Mauna Kea, Hawaii, USA, Altitude 4,080 m (13,390 ft)

    Submillimeter Array Hawaii SAO

    ESO/NRAO/NAOJ ALMA Array
    ESO/NRAO/NAOJ ALMA Array, Chile

    South Pole Telescope SPTPOL
    South Pole Telescope SPTPOL

    Future Array/Telescopes

    IRAM NOEMA in the French Alps on the wide and isolated Plateau de Bure at an elevation of 2550 meters, the telescope currently consists of ten antennas, each 15 meters in diameter.interferometer, Located in the French Alpes on the wide and isolated Plateau de Bure at an elevation of 2550 meters

    NSF CfA Greenland telescope


    Greenland Telescope

    ARO 12m Radio Telescope, Kitt Peak National Observatory, Arizona, USA, Altitude 1,914 m (6,280 ft)


    ARO 12m Radio Telescope

    Caltech Owens Valley Radio Observatory, located near Big Pine, California (US) in Owens Valley, Altitude1,222 m (4,009 ft)

    The first image of a black hole. This is the supermassive black hole at the center of the galaxy Messier 87. Image via JPL/ Event Horizon Telescope Collaboration.

    Katie Bouman-Harvard Smithsonian Astrophysical Observatory. Headed to Caltech.

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA is funded in Europe by the European Organization for Astronomical Research in the Southern Hemisphere (ESO), in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and in East Asia by the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Academia Sinica (AS) in Taiwan.

    ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI) and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

    NRAO Small
    ESO 50 Large

     
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