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  • richardmitnick 11:40 am on May 29, 2022 Permalink | Reply
    Tags: "A New Quantum Technique Could Change How We Study The Universe", , , , , Event Horizon Telescope, , , , , , , Quantum information, , , , Stimulated Raman Adiabatic Passage (STIRAP),   

    From Macquarie University (AU) and The National University of Singapore [新加坡国立大学](SG) via Science Alert : “A New Quantum Technique Could Change How We Study The Universe” “ 

    From Macquarie University (AU)

    and

    The National University of Singapore [新加坡国立大学](SG)

    via

    ScienceAlert

    Science Alert

    29 MAY 2022
    MATT WILLIAMS | UNIVERSE TODAY

    1
    (sakkmesterke/iStock/Getty Images)

    There’s a revolution underway in astronomy. In fact, you might say there are several. In the past ten years, exoplanet studies have advanced considerably, gravitational wave astronomy has emerged as a new field, and the first images of supermassive black holes (SMBHs) have been captured.

    A related field, interferometry, has also advanced incredibly thanks to highly-sensitive instruments and the ability to share and combine data from observatories worldwide. In particular, the science of very-long baseline interferometry (VLBI) is opening entirely new realms of possibility.

    According to a recent study by researchers from Australia and Singapore, a new quantum technique could enhance optical VLBI. It’s known as Stimulated Raman Adiabatic Passage (STIRAP), which allows quantum information to be transferred without losses.

    When imprinted into a quantum error correction code, this technique could allow for VLBI observations into previously inaccessible wavelengths. Once integrated with next-generation instruments, this technique could allow for more detailed studies of black holes, exoplanets, the Solar System, and the surfaces of distant stars.

    The research was led by Zixin Huang, a postdoctoral research fellow with the Centre for Engineered Quantum Systems (EQuS) at Macquarie University in Sydney, Australia. She was joined by Gavin Brennan, a professor of theoretical physics with the Department of Electrical and Computer Engineering and the Centre of Quantum Technologies at the National University of Singapore (NUS), and Yingkai Ouyang, a senior research fellow with the Centre of Quantum Technologies at NUS.


    Animated sequence of the VLTI images of stars around the Milky Way’s central black hole. Credit: The European Southern Observatory [La Observatorio Europeo Austral] [Observatoire européen austral][Europaiche Sûdsternwarte] (EU)(CL).

    To put it plainly, the interferometry technique consists of combining light from various telescopes to create images of an object that would otherwise be too difficult to resolve.

    Very-long baseline interferometry refers to a specific technique used in radio astronomy where signals from an astronomical radio source (black holes, quasars, pulsars, star-forming nebulae, etc.) are combined to create detailed images of their structure and activity.

    In recent years, VLBI has yielded the most detailed images of the stars that orbit Sagitarrius A* (Sgr A*), the SMBH at the center of our galaxy. It also allowed astronomers with the Event Horizon Telescope (EHT) Collaboration to capture the first image of a black hole (M87*)[above] and Sgr A*[above] itself!

    _________________________________________
    Event Horizon Telescope Array

    EHT map.
    The locations of the radio dishes that will be part of the Event Horizon Telescope array. Image credit: Event Horizon Telescope sites, via University of Arizona at https://www.as.arizona.edu/event-horizon-telescope.

    About the Event Horizon Telescope (EHT)

    The EHT consortium consists of 13 stakeholder institutes; The Academia Sinica Institute of Astronomy & Astrophysics [中央研究院天文及天文物理研究所](TW) , The University of Arizona, The University of Chicago, The East Asian Observatory, Goethe University Frankfurt [Goethe-Universität](DE), Institut de Radioastronomie Millimétrique, Large Millimeter Telescope, The MPG Institute for Radio Astronomy[MPG Institut für Radioastronomie](DE), MIT Haystack Observatory, The National Astronomical Observatory of Japan[[国立天文台](JP), The Perimeter Institute for Theoretical Physics (CA), Radboud University [Radboud Universiteit](NL) and The Center for Astrophysics | Harvard & Smithsonian.
    _________________________________________

    But as they indicated in their study, classical interferometry is still hindered by several physical limitations, including information loss, noise, and the fact that the light obtained is generally quantum in nature (where photons are entangled). By addressing these limitations, VLBI could be used for much finer astronomical surveys.

    Said Dr. Huang to Universe Today via email: “Current state-of-the-art large baseline imaging systems operate in the microwave band of the electromagnetic spectrum. To realize optical interferometry, you need all parts of the interferometer to be stable to within a fraction of a wavelength of light, so the light can interfere.

    This is very hard to do over large distances: sources of noise can come from the instrument itself, thermal expansion and contraction, vibration and etc.; and on top of that, there are losses associated with the optical elements.

    “The idea of this line of research is to allow us to move into the optical frequencies from microwaves; these techniques equally apply to infrared. We can already do large-baseline interferometry in the microwave. However, this task becomes very difficult in optical frequencies, because even the fastest electronics cannot directly measure the oscillations of the electric field at these frequencies.”

    The key to overcoming these limitations, says Dr. Huang and her colleagues, is to employ quantum communication techniques like Stimulated Raman Adiabatic Passage. STIRAP consists of using two coherent light pulses to transfer optical information between two applicable quantum states.

    When applied to VLBI, said Huang, it will allow for efficient and selective population transfers between quantum states without suffering from the usual issues of noise or loss.

    As they describe in their paper [above], the process they envision would involve coherently coupling the starlight into “dark” atomic states that do not radiate.

    The next step, said Huang, is to couple the light with quantum error correction (QEC), a technique used in quantum computing to protect quantum information from errors due to decoherence and other “quantum noise.”

    But as Huang indicates, this same technique could allow for more detailed and accurate interferometry:

    “To mimic a large optical interferometer, the light must be collected and processed coherently, and we propose to use quantum error correction to mitigate errors due to loss and noise in this process.

    “Quantum error correction is a rapidly developing area mainly focused on enabling scalable quantum computing in the presence of errors. In combination with pre-distributed entanglement, we can perform the operations that extract the information we need from starlight while suppressing noise.”

    To test their theory, the team considered a scenario where two facilities (Alice and Bob) separated by long distances collect astronomical light.

    Each share pre-distributed entanglement and contain “quantum memories” into which the light is captured, and each prepare its own set of quantum data (qubits) into some QEC code. The received quantum states are then imprinted onto a shared QEC code by a decoder, which protects the data from subsequent noisy operations.

    In the “encoder” stage, the signal is captured into the quantum memories via the STIRAP technique, which allows the incoming light to be coherently coupled into a non-radiative state of an atom.

    The ability to capture light from astronomical sources that account for quantum states (and eliminates quantum noise and information loss) would be a game-changer for interferometry. Moreover, these improvements would have significant implications for other fields of astronomy that are also being revolutionized today.

    “By moving into optical frequencies, such a quantum imaging network will improve imaging resolution by three to five orders of magnitude,” said Huang.

    “It would be powerful enough to image small planets around nearby stars, details of solar systems, kinematics of stellar surfaces, accretion disks, and potentially details around the event horizons of black holes – none of which currently planned projects can resolve.”

    In the near future, the James Webb Space Telescope (JWST) will use its advanced suite of infrared imaging instruments to characterize exoplanet atmospheres like never before. The same is true of ground-based observatories like the Extremely Large Telescope (ELT), Giant Magellan Telescope (GMT), and Thirty Meter Telescope (TMT).

    Between their large primary mirrors, adaptive optics, coronagraphs, and spectrometers, these observatories will enable direct imaging studies of exoplanets, yielding valuable information about their surfaces and atmospheres.

    By taking advantage of new quantum techniques and integrating them with VLBI, observatories will have another way to capture images of some of the most inaccessible and hard-to-see objects in our Universe.

    See the full article here .

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    Please help promote STEM in your local schools.

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    The National University of Singapore (NUS) is the national research university of Singapore. Founded in 1905 as the Straits Settlements and Federated Malay States Government Medical School, NUS is the oldest higher education institution in Singapore. According to a number of surveys, it is consistently ranked within the top 20 universities in the world and is considered to be the best university in the Asia-Pacific by the QS ranking. NUS is a comprehensive research university, offering a wide range of disciplines, including the sciences, medicine and dentistry, design and environment, law, arts and social sciences, engineering, business, computing and music at both the undergraduate and postgraduate levels.

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    Established in 1964, Macquarie University (AU)began as a bold experiment in higher education. Built to break from traditions: to be distinctive, progressive, and to be transformational. Today our pioneering history continues to be a source of inspiration as we celebrate our place among the best and brightest minds.

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    Discover our story.

     
  • richardmitnick 12:44 pm on May 15, 2022 Permalink | Reply
    Tags: "Spot the difference- Imaging Sagittarius A* and M87*", , , Event Horizon Telescope,   

    From ESOblog (EU): “Spot the difference- Imaging Sagittarius A* and Messier 87*” 

    From ESOblog (EU)

    At

    ESO 50 Large

    The European Southern Observatory [La Observatorio Europeo Austral] [Observatoire européen austral][Europäische Südsternwarte](EU)(CL)

    12 May 2022
    Science@ESO

    1

    Biography Anita Chandran
    Anita Chandran is a science journalism intern at ESO. She recently completed her PhD in laser physics at Imperial College London (UK), where she also worked with the science communication department on the ethics of artificial intelligence. She is a writer and editor, having co-founding Tamarind, a literary magazine focusing on the intersections between the arts and sciences.

    For decades, scientists have gotten closer and closer to the dark heart at the centre of our Milky Way galaxy, the supermassive black hole known as Sagittarius A* (Sgr A*). Now, as a result of the incredible work of the Event Horizon Telescope (EHT) Collaboration, we finally have a long-awaited image of Sagittarius A*, providing the first visual confirmation of the black hole at our galactic centre.

    Sagittarius A* is the second black hole to be imaged by the EHT, with the first being Messier 87*, located at the centre of the Messier 87 galaxy, first imaged in 2019.

    But how did we arrive at these images, and what can we learn from their similarities and differences?

    Imaging a black hole is no easy task. Black holes are completely dark, meaning that taking a direct image of them is impossible. Instead, scientists must look at the glowing gas and dust that surround them. Even though supermassive black holes are intrinsically large, they’re so far away from us that their apparent size on the sky is extremely small, so small that no conventional telescope can discern their shape. To solve this problem, the EHT combines several radio telescopes located world-wide to form one huge, Earth-sized telescope, using a technique called Very Long Baseline interferometry.

    _________________________________________
    Event Horizon Telescope Array

    EHT map.
    The locations of the radio dishes that will be part of the Event Horizon Telescope array. Image credit: Event Horizon Telescope sites, via University of Arizona at https://www.as.arizona.edu/event-horizon-telescope.

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

    ESO/APEX
    Atacama Pathfinder EXperiment (APEX)

    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 NOEMA interferometer
    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


    Submillimeter Array Hawaii SAO

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

    Plateau de Bure interferometer
    Plateau de Bure interferometer

    About the Event Horizon Telescope (EHT)

    The EHT consortium consists of 13 stakeholder institutes; The Academia Sinica Institute of Astronomy & Astrophysics [中央研究院天文及天文物理研究所](TW) , The University of Arizona, The University of Chicago, The East Asian Observatory, Goethe University Frankfurt [Goethe-Universität](DE), Institut de Radioastronomie Millimétrique, Large Millimeter Telescope, The MPG Institute for Radio Astronomy[MPG Institut für Radioastronomie](DE), MIT Haystack Observatory, The National Astronomical Observatory of Japan[[国立天文台](JP), The Perimeter Institute for Theoretical Physics (CA), Radboud University [Radboud Universiteit](NL) and The Center for Astrophysics | Harvard & Smithsonian.
    _________________________________________

    Imaging Sagittarius A* proved challenging for scientists. In this blog, we spoke to three of the scientists in the EHT Collaboration to understand some of the similarities and differences between the images of Sagittarius A* and Messier 87*, as well as getting to the bottom of why imaging our galaxy’s central black hole was so difficult.

    Why do the images of Sagittarius A* and Messier 87* look so similar, when we know the black holes are very different?

    “There are two important things to note,” says Kazu Akiyama, an astrophysicist at MIT Haystack Observatory in the US. “Firstly, both images have a circular ring. Secondly, the rings are broadly speaking symmetric: they appear closed, without gaps.”

    “The circularity is a beautiful result of the extremely strong gravity at the edge of a black hole. The size and shape of the black hole’s silhouette is governed simply by how its strong gravity bends the surrounding space-time. Einstein’s theory of relativity predicts that the shape of the silhouette is pretty circular no matter how fast the black hole is rotating or from where we are looking at it.”

    You may think that the circular shadow that we see in the EHT images corresponds to the event horizon –– the surface beyond which not even light can escape. But that’s not the case. As the video below shows, the black hole bends the trajectory of light around it, casting a shadow that is about 2.5 times larger than the event horizon itself.


    This artist’s impression zooms into a black hole and depicts the paths of photons in its vicinity. The gravitational bending and capture of light by the event horizon is the cause of the shadow captured by the Event Horizon Telescope.
    Credit: Nicolle R. Fuller/The National Science Foundation.

    Hot matter orbits the black hole in a disc, and the orientation of this disc will determine whether the bright ring looks symmetric or not. “If the rotational axis of the matter around the black hole is tilted relative to our line of sight,” Kazu says, “the bright ring enclosing the shadow of the black hole will be asymmetric: the side where matter is approaching us will be brighter while the receding side will be dimmer. If the tilt is very pronounced we would see an unclosed ring where only a single side is visible, like a waxing crescent moon.”

    “I was indeed surprised and didn’t even expect to see such a closed ring for Sgr A*,” says Kazu. “There was no guarantee that it should be. This second ring was basically a gift from nature.”

    Black holes can also emit strong jets of material perpendicularly to the disc, which give astronomers a clue as to the orientation of the disc. Unfortunately, Sgr A* has been relatively quiet on this front.

    “In contrast with Messier 87*, which has a prominent jet indicating the orientation of the system, Sagittarius A* has never shown us a clearly visible jet,” says Katie Bouman, an assistant professor at The California Institute of Technology (Caltech). “For this reason, Sagittarius A* has been hiding its orientation from us for nearly 50 years until it was finally imaged with the EHT. As a symmetric ring appears in our image, we found that the theoretical models can explain EHT data only when the rotational axis is tilted within 30 degrees from our line of sight.”
    ===
    So, what made imaging Sagittarius A* so difficult compared with Messier 87*?

    “There were two primary challenges in imaging Sagittarius A*, arising from its unique properties,” says José L. Gómez, a Research Scientist at The Institute of Astrophysics of Andalusia [Instituto de Astrofísica de Andalucía] – CSIC (ES). “Firstly, Sagittarius A* is about 1600 times lighter and smaller than Messier 87*. Material takes days or weeks to travel around Messier 87* but just minutes or hours to get around Sagittarius A*. The EHT fills up a gigantic, planet-sized virtual mirror using the Earth’s rotation. Each individual EHT telescope is like a segment of this mirror, gradually obtaining data over a night. M87* was easier to image, as it was steady when we were observing: the data obtained by all individual telescopes came from the same stable image.”

    “However, Sagittarius A* is like a toddler who can’t stay standing still while we are taking its photo over the course of a night,” continues Katie. “The glowing gas around Sagittarius A* was dancing while we were taking the data. We needed to reconstruct how Sagittarius A* appears in the sky from a series of sparse information obtained while the gas was quickly moving around.”

    José L. continues: “The second challenge is that radio signals from Sagittarius A* become somewhat distorted and blurred by turbulent gas located between Earth and the Galactic centre. The image of Sagittarius A* ripples like a distant mountain seen from a window of an airplane through its hot jet exhaust fumes. To see a true image of Sagittarius A*, we need to reconstruct the image as it was before such turbulent gas scattered the radio waves.”

    “This was not the case for Messier 87*,” adds Kazu, “which is located far away from the plane of the Milky Way, and therefore we did not have to image it through the dense material in our galaxy.”


    Meet Sagittarius A*: Zooming into the black hole at the centre of our galaxy.
    Watch as this video sequence zooms into the black hole (Sgr A*) at the centre of our galaxy.
    Credit: L. Calçada, N. Risinger (skysurvey.org)/ESO, DSS, VISTA, VVV Survey/D. Minniti DSS, Nogueras-Lara et al., Schoedel, NACO, GRAVITY Collaboration, EHT Collaboration (Music: Azul Cobalto)

    How did you address these problems?

    “For the scattering effects, we carefully examined the optics of propagation of radio waves from Sagittarius A* through the turbulent plasma that scatters them,” says Kazu. “Over the last several years, EHT scientists have built up a sophisticated model of the scattering for Sagittarius A* with an extensive series of observations at different wavelengths, and used it to assess how the distortion and blurring of Sagittarius A* appears in the EHT data. This allows us to reconstruct the image of Sagittarius A*.”

    “As for the rapid motion of the gas around Sagittarius A*,” says José L., “we indeed saw in the EHT data that the glowing gas around Sagittarius A* is moving and dancing around during our observations. It is truly stunning that the EHT could see such complicated dynamics of the gas around a black hole, giving us a very important clue about how black holes interact with their surrounding environment.”

    “We did a careful statistical analysis of the data to see how the appearance of Sagittarius A* changes from night to night,” explains Katie, “providing a statistical model of the dynamical structure in Sagittarius A*. This allows us to image the common structure of Sagittarius A* seen across the nights.”

    As evidenced from the above answers, it is clear that a huge amount of analysis was undertaken to obtain an image of Sagittarius A*. And some very well developed algorithms were required for this analysis.

    Could you describe how the different algorithms that you used work?

    “The EHT creates the sharpest eye on the universe by computationally forming a planet-sized virtual telescope with radio telescopes spread across the Earth,” says Katie. “But we have only eight telescopes on six geographic sites, which provide a sparse coverage of telescopes that can fill up only a tiny fraction of this gigantic virtual mirror. It’s like having a fraction of the pieces of a jigsaw puzzle, from which we need to reconstruct what the entire picture of the puzzle looks like. Or like listening to a song from a piano where many of the keys are missing.”

    “Because we have such limited information, you can imagine that there are an infinite number of ways to fill up the missing pieces of the puzzle,” continues Kazu, “though most of them wouldn’t make any sense, just like randomly adding a piece to a puzzle or a note to a song results in something awkward and very unlikely.”

    “Imaging algorithms are mathematical detectives that we use to find the most reasonable images among the many possibilities that can explain the EHT’s measurements,” Katie explains. “Each algorithm has its own method for determining which image is most likely. It is a bit like hiring Sherlock Holmes, Hercule Poirot, Jane Marple, and Jules Maigret simultaneously to see what they commonly conclude and what they don’t.”

    How accurately can the algorithms recover the true shape of Sagittarius A* or any other source?

    “We vetted and evaluated each way of imaging EHT data according to whether it can distinguish and recover different shapes,” says Kazu. “including non-ring structures that may provide data similar to EHT data. Thousands of Sagittarius A* images were made from well-vetted methods that can distinguish different structures, and the vast majority show a ring shape.“

    “The rapidly varying emission from Sagittarius A* and the limited amount of data introduced some uncertainty in where the brightest parts of the ring were,” continues José L. “The ongoing expansion of the EHT network and significant technological upgrades will allow us to better constrain the emission around the ring, and even obtain the first movies of black holes.”

    4
    The Event Horizon Telescope (EHT) Collaboration has created a single image (top frame) of the supermassive black hole at the centre of our galaxy, called Sagittarius A*, or Sgr A* for short, by combining images extracted from the EHT observations.
    The main image was produced by averaging together thousands of images created using different computational methods — all of which accurately fit the EHT data. This averaged image retains features more commonly seen in the varied images, and suppresses features that appear infrequently.
    The images can also be clustered into four groups based on similar features. An averaged, representative image for each of the four clusters is shown in the bottom row. Three of the clusters show a ring structure but, with differently distributed brightness around the ring. The fourth cluster contains images that also fit the data but do not appear ring-like.
    The bar graphs show the relative number of images belonging to each cluster. Thousands of images fell into each of the first three clusters, while the fourth and smallest cluster contains only hundreds of images. The heights of the bars indicate the relative “weights,” or contributions, of each cluster to the averaged image at top.
    In addition to other facilities, the EHT network of radio observatories that made this image possible includes the Atacama Large Millimeter/submillimeter Array (ALMA) and the Atacama Pathfinder EXperiment (APEX) in the Atacama Desert in Chile, co-owned and co-operated by ESO is a partner on behalf of its member states in Europe. Credit: EHT Collaboration.

    I can’t help but ask, how confident are you that the image is a ring? What could lead to a non-ring image?

    “We have spent years developing sophisticated new tools to account for the challenges in imaging Sagittarius A*,” José L. told us. “Tens of millions of images from test data (created to best resemble Sagittarius A*) have been produced in supercomputers around the world to refine our algorithms, much like searching for the best lens and filter in a camera to obtain the sharpest snapshot.”

    “We found that our different algorithms can reliably distinguish between ring and non-ring images,” Katie adds. “Most importantly, as we found when imaging Sagittarius A*, only a very small fraction of non-ring images appear. Based on this detailed study we conclude that the non-ring images are caused by the limited amount of data and rapidly varying emission from Sagittarius A*, rather than being intrinsic to the black hole itself.”

    “The image of Sagittarius A* now holds the record (previously set by Messier 87*) of the most thoroughly vetted interferometric image that has ever been made,” José L. concludes.

    Now that we have imaged Sagittarius A*, what’s next for the EHT?

    “This is just the dawn of the exciting era opened by the EHT,” José L. tells us. “The EHT has been getting more powerful since 2017 when we obtained data providing these first images of black holes. Now, the EHT has a more sensitive and sharper eye, with new additional telescopes and upgraded instruments. We will work on new data from the upgraded EHT in the coming years, which will provide a sharper and more dynamic view of black holes.”

    “Of course challenges lie ahead too,” Kazu explains. “As the EHT becomes more powerful, we will have much richer data. The sheer volume of EHT data, which already totaled 5 petabytes in 2017, has grown even more since then. How we handle this and hunt for treasures hiding in such enormous datasets will be our next exciting challenge—with accordingly enormous rewards.”

    “The EHT is also looking at other supermassive black holes, investigating the hot plasma in their vicinity. This could one day lead to an eventual third image of a black hole — but only if we have underestimated the sizes of these black holes; if they are too small, we won’t be able to discern their shadows.”

    Of course, just the story behind the image of Sagittarius A* is one for the history books, and we asked our three interviewees what advice they’d give to future astronomers.

    “Dream big, stay curious, and don’t let anyone tell you that you can’t succeed,” says Katie. “If you set your mind to it, and work hard, oftentimes you can achieve what originally sounded impossible. Remember that you can be your own worst enemy –– once you start doubting yourself then the game is over. It’s normal to feel unsure of yourself, but just put those blinders on and plow ahead!”

    José L. agrees: “Follow your dreams! It is your imagination, and the fascination to understand how the Universe works. These are the only things you need to make every day of your life a journey of discovery.”

    “Don’t be afraid of the risk of failure,” Kazu adds. “With the last ten years of my life at the EHT, I learned that whatever happens and however it ends up, the entire experience you will get will be a very fruitful element of your life.”

    About the EHT scientists

    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 .

    Katherine L. (Katie) Bouman is an assistant professor in the Computing and Mathematical Sciences, Electrical Engineering, and Astronomy Departments at the California Institute of Technology (Caltech). Before joining Caltech, she was a postdoctoral fellow in the Harvard-Smithsonian Center for Astrophysics. She received her Ph.D. in The Computer Science and Artificial Intelligence Laboratory (CSAIL) at MIT in EECS, and her bachelor’s degree in Electrical Engineering from The University of Michigan. She is a Rosenberg Scholar, Heritage Medical Research Institute Investigator, recipient of the Royal Photographic Society Progress Medal and IST Electronic Imaging Scientist of the Year Award. As part of the Event Horizon Telescope Collaboration, she is co-organizer of the Imaging Working Group and acted as coordinator for papers concerning the first imaging of the M87* and Sagittarius A* black holes. She is also co-organizer of the Algorithms and Inference Working Group for the next-generation Event Horizon Telescope (ngEHT) effort.

    5
    Kazu Akiyama

    Kazu Akiyama is a research scientist at MIT Haystack Observatory. He joined the team of the Event Horizon Telescope (EHT) in 2010, and has worked on various aspects of EHT observations, from the development of new imaging algorithms to the calibration, imaging, and scientific interpretation of EHT data. He co-founded the Imaging Working Group of the EHT Collaboration in 2017, and has been a co-leader of the group since its establishment. As a lead of the EHT’s imaging team, he has coordinated the first imaging of two primary targets: M87* and Sgr A*. He also served as a coordinator of the EHT Sgr A* data calibration team. He developed one of the imaging software package, SMILI, used to create the first images of M87* and Sgr A*.

    6

    José L. Gómez is a Research Scientist, and head of the EHT group at the Instituto de Astrofísica de Andalucía (CSIC), in Granada, Spain. His research career has been focused on the study of relativistic jets often seen emanating as a byproduct of black hole accretion. He is a member of the EHT Science Council, and one of the coordinators of the EHT Imaging Working Group. He developed the scripts based on the classical CLEAN method for imaging interferometric data used for imaging M87* and Sgr A*, being one of the coordinators of the imaging papers for these two EHT primary targets. He also participates actively in other EHT scientific activities, in particular in the Polarisation, AGN, and Multi-wavelength Working Groups.

    See the full article here.


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

    European Southern Observatory(EU) La Silla HELIOS (HARPS Experiment for Light Integrated Over the Sun).

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    MPG Institute for Astronomy [Max-Planck-Institut für Astronomie](DE) 2.2 meter telescope at/European Southern Observatory(EU) Cerro La Silla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres.

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    European Southern Observatory(EU) , Very Large Telescope 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.

    European Southern Observatory(EU)VLTI Interferometer image, Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level, •ANTU (UT1; The Sun ),•KUEYEN (UT2; The Moon ),•MELIPAL (UT3; The Southern Cross ), and •YEPUN (UT4; Venus – as evening.

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    Part of ESO’s Paranal Observatory, the VLT Survey Telescope (VISTA) observes the brilliantly clear skies above the Atacama Desert of Chile. It is the largest survey telescope in the world in visible light, with an elevation of 2,635 metres (8,645 ft) above sea level.

    European Southern Observatory/National Radio Astronomy Observatory(US)/National Astronomical Observatory of Japan(JP) ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres.

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    ESO Speculoos telescopes four 1 meter robotic telescopes at ESO Paranal Observatory 2635 metres 8645 ft above sea level.

    TAROT telescope at Cerro LaSilla, 2,635 metres (8,645 ft) above sea level.

    European Southern Observatory (EU) ExTrA telescopes at Cerro LaSilla at an altitude of 2400 metres.

    A novel gamma ray telescope under construction on Mount Hopkins, Arizona. A large project known as the Čerenkov Telescope Array composed of hundreds of similar telescopes to be situated in the Canary Islands and Chile at, ESO Cerro Paranal site The telescope on Mount Hopkins will be fitted with a prototype high-speed camera, assembled at the. University of Wisconsin–Madison and capable of taking pictures at a billion frames per second. Credit: Vladimir Vassiliev.

    European Space Agency [La Agencia Espacial Europea] [Agence spatiale européenne][Europäische Weltraumorganisation](EU), The new Test-Bed Telescope 2 is housed inside the shiny white dome shown in this picture, at ESO’s LaSilla Facility in Chile. The telescope has now started operations and will assist its northern-hemisphere twin in protecting us from potentially hazardous, near-Earth objects.The domes of ESO’s 0.5 m and the Danish 0.5 m telescopes are visible in the background of this image.

    Part of the world-wide effort to scan and identify near-Earth objects, the European Space Agency’s Test-Bed Telescope 2 (TBT2), a technology demonstrator hosted at ESO’s La Silla Observatory in Chile, has now started operating. Working alongside its northern-hemisphere partner telescope, TBT2 will keep a close eye on the sky for asteroids that could pose a risk to Earth, testing hardware and software for a future telescope network.

    European Space Agency [La Agencia Espacial Europea] [Agence spatiale européenne][Europäische Weltraumorganisation](EU) The open dome of The black telescope structure of the‘s Test-Bed Telescope 2 peers out of its open dome in front of the rolling desert landscape. The telescope is located at ESO’s La Silla Observatory, which sits at a 2400 metre altitude in the Chilean Atacama desert.

     
  • richardmitnick 10:01 am on May 14, 2022 Permalink | Reply
    Tags: "New black hole image- 4 things we know", , , Event Horizon Telescope,   

    From EarthSky: “New black hole image- 4 things we know” 

    1

    From EarthSky

    May 13, 2022
    Dave Adalian

    1
    The inset in the upper right shows the newly revealed donut shape of Sagittarius A*, or Sgr A*, the giant black hole at the heart of our Milky Way galaxy. Image via The National Aeronautics and Space Administration.

    On Thursday, May 12, 2022, the Event Horizon Telescope (EHT) team of astronomers presented the 1st direct image taken of the Milky Way galaxy’s supermassive central black hole, Sagittarius A*, aka Sgr A* (pronounced Sajj-a-star).

    The image shows a glowing, lumpy donut. In fact, it’s a black hole with a mass some 4 million times that of our sun. EarthSky.org reporters covered the virtual event, and the EHT panel of experts specifically answered one of our questions. EarthSky.org’s full coverage of announcement details is here. A video of the entire press conference and follow-up events is available on ESO’s YouTube channel. Below are 4 things the new image confirms.

    1. The black hole is face-on to Earth.

    During the conference, Dr. Christian Fromm, EHT’s Sgr A* Theory Working Group Coordinator, described the black hole as being face-on to Earth. EarthSky.org’s question sought elaboration on that statement. Following is a transcript of the question and the answer.

    Bárbara Ferreira, Media Manager, The European Southern Observatory [La Observatorio Europeo Austral] [Observatoire européen austral][Europaiche Sûdsternwarte] (EU)(CL) Department of Communications: OK, we have one from Dave Adalian reporting for EarthSky.org. I think Christian will be able to answer that one. When the orientation of Sagittarius A* is said to be “face-on,” does that mean one of the poles is directed towards Earth? Do we know how fast Sagittarius A* precesses? And, what is the nature of the particles ejected?

    Fromm: OK, so let me start first, so we found that it’s face-on, so this is correct that one of the spin axes is pointing more or less towards us.

    The other part was about the material or the emission actually that we see, and what we model is synchrotron radiation, so you have particles, mainly electrons, gyrating magnetic fields, and while they gyrate, the magnetic fields, they emit emission, and this emission is synchrotron, and this is what we actually see.

    And there was a third part. Could you please repeat it?

    Ferreira: Ah, so it was the precesses (sic).

    Fromm: Ah, the, uh, it was– Ah, yes, so the precession. I think what you mean is spin. So what we have actually is, we have some kind of best-bet models. So we have not found an exact model which would explain everything, so we have best-bet models and best-bet regions. And there we could say that it’s spinning, and it’s in the same direction as the gas orbiting it, but the precise number of the spin has to be obtained in upcoming observations.

    2. The black hole’s direct influence on Milky Way now is small.

    Later, during a live question-and-answer session featuring other researchers who joined the EHT Collaboration, the topic of black hole emission jets was covered in more detail. Emission jets from black holes originate along their spin axes, revealing why the orientation of Sgr A* may be important to understand galactic development. Following is a partial transcript of that Q&A session.

    Juan Carlos Muñoz, host, reading a question from a viewer: Would it be possible to observe jets at this distance and in the specific case of this particular black hole (Sgr A*)?

    Dr. Sera Markoff, co-chair of the EHT Science Council and a professor of theoretical astrophysics at The University of Amsterdam [Universiteit van Amsterdam](NL): I would love to take that one, because I’ve been trying to find jets at Sgr A* for a long time. The point is, even if Sagittarius A* was launching very small jets … and we think there’s a pretty good chance, I mean at least the models we use predict there should be jets. But we have to remember that Sgr A* is basically 10s or 100,000 times less powerful than Messier 87. So if you just turn the crank down, its ability to make powerful jets is hampered. And then you have this complicated mess in the galactic center, and trying to pick out some weak feature. We have known for quite a while that it would be quite difficult to see. So the question is whether when we have our upcoming data sets from the coming years, when we have more telescopes, we also fill in some of the baselines, will we be able to maybe connect this, you know, fuzzy sort of donut thing to maybe some kind of extended emission. It’s the same issue we’d like to do with Messier 87.

    3. The black hole might still help create stars.

    The Q&A session then turned to the importance of Sgr A*’s gravitational influence on the rest of the Milky Way, and specifically what would happen if Sgr A* was suddenly removed. It is a myth, the experts explained, that supermassive central black holes play a role in holding their galaxies together. From the discussion:

    Dr. Violette Impellizzeri, Leiden Observatory [Sterrewacht Leiden](NL), The National Radio Astronomy Observatory: The short answer is, if you were to remove it now, probably nothing. That’s what would happen. The question is what role it had in the formation of our galaxy, and in the fact it looks like it does now. But the sphere of influence of the black hole itself on its surrounding is not very large. It’s very small. If you removed that, it wouldn’t impact us directly, but maybe the evolution would change again.

    The panel explained, however, that jets emitted by other supermassive central black holes might have an important indirect role to play in star formation that would be lost if Sgr A* suddenly disappeared:

    Michael Janssen, The MPG Institute for Radio Astronomy[MPG Institut für Radioastronomie](DE): Maybe more indirect effect. The jets have been mentioned before, right? Sera liked them very much in Sgr A*. Unfortunately we haven’t seen that yet, but we see it in other galaxies. In M87, there’s very, very clear indication of a jet. Another galaxy, for example, is Centaurus A, where we also imaged a jet.

    And when these jets, when they plow through the galaxy, they actually impact the gas that is in the galaxy itself and maybe compress it, maybe heat it, and that might trigger – or actually hamper, it’s a critically active field of research – trigger or hamper star formation. So we may actually have the influence of the jet or other outflows from the central black hole – it’s not only accreting; it’s also putting stuff out there – and that might influence the whole evolution of the galaxy.

    4. Our Milky Way had a violent youth

    While the potential influence of the hypothetical jets perhaps produced by Sgr A* today is relatively mild, that wasn’t so in the Milky Way’s distant past. At one point, an emission jet from Sgr A* may have erupted with extreme violence, leaving remnants we still see today surrounding our home galaxy. From the transcript:

    Ziri Younsi, UKRI Stephen Hawking Fellow, University College London: I just wanted quickly to add to that about the jet stuff, because I think it’s really interesting. We see evidence of a very violent past for Sagittarius A*. Throughout the galaxy we have these things called Fermi bubbles, which are these enormous radio lobe-like structures that extend above and below the plane of our galaxy.

    So they speak to some very violent cataclysmic event that happened a very long time ago. And it’s curious that we’re in a period right now where everything is very quiet, and probably in some way a jet of some description, some enormous eruptive event, is responsible for that. And so I think what’s really cool about these observations is we don’t see a large-scale jet, as Sera and Michael have said, but the question is really: Why don’t we see one? And yet in the past we seem to have indications that there may have been something like that, and I think we’re having this rare opportunity to finally have a look at the very heart and maybe start to answer the questions in time.

    Younsi’s comment brought a nervous moment of reflection from the other panelists:

    Impellizzeri: A thought that occurred to my mind, and I wondered what would happen if Sgr A* had a jet like M87, right? What would that mean for us?

    Markoff: Luckily, it’s pretty far away, so…

    Muñoz: … We should be safe from it. Right? (laughs)

    See the full article here .


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    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 4:35 pm on November 16, 2021 Permalink | Reply
    Tags: , "The first black hole image-A gravitomagnetic monopole as an alternative explanation", A gravitomagnetic monopole — or an NUT parameter., A Kerr spacetime a special case of the Kerr-Taub-NUT spacetime with vanishing gravitomagnetic monopole., Event Horizon Telescope, In the paper the authors propose that M87* may contain a gravitomagnetic monopole and therefore could be described as a more general Kerr-Taub-NUT spacetime., Scientists found that a non-zero gravitomagnetic monopole is still compatible with the current EHT observations., Springer, The next question is: does gravitomagnetic charge or the so-called gravitomagnetic monopole exist in nature?   

    From Springer via phys.org : “The first black hole image-A gravitomagnetic monopole as an alternative explanation” 

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    From Springer

    via

    phys.org

    The Event Horizon Telescope (EHT) has recently mapped the central compact object of the galaxy M87 with an unprecedented angular resolution.

    EHT map.

    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 The Event Horizon Telescope Collaboration released on 10 April 2019 via National Science Foundation(US).

    Though the remarkable breakthrough has been interpreted based on theory that M87 contains a rotating or “Kerr” black hole, new research published in EPJ C. by Chandrachur Chakraborty and Qingjuan Yu at The Kavli Institute for Astronomy and Astrophysics at The Peking University [北京大学](CN) (KIAA-PKU), Masoumeh Ghasemi-Nodehi and Youjun Lu, at the The National Astronomical Observatories of China [ 国家天文台] at Chinese Academy of Sciences [中国科学院](CN), looks at possible alternative explanations for the image.

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    Shadow shapes resulting from the four different settings on the spin (a∗) and the NUT parameter (n∗), i.e., (a∗,n∗)=(0,0) (Schwarzschild metric), (1, 0) (extremely rotating Kerr metric), (0.9, 0.7) (KTN BH), and (5, 0.9) (KTN NS), respectively, for i=17∘. This Figure illustrates that the shadow shapes resulting from different KTN parameter settings are all nearly circular but the shadow sizes can be significantly different from each other. In the inset, although we display that the resulting deviation from circularity is only within 5% for these particular settings of parameters, it can be, in fact, higher for the different settings of a∗ and n∗.

    “The EHT collaboration has tried to show that the observed image is overall consistent with the expectations for the shadow of a Kerr black hole,” Chakraborty says. “As the alternatives to the Kerr BH have not been ruled out, we have investigated whether the EHT data is also consistent or not with alternative models for the central object of M87.”

    Chakraborty goes on to explain that he and his co-authors had one primary purpose to show how a gravitomagnetic monopole — or an NUT parameter — affects the shadow size and shape, and whether its existence can be ruled out or not in M87*. “To show this, we use the observational parameter values of the first image of M87* and found that a non-zero gravitomagnetic monopole is still compatible with the current EHT observations,” Chakraborty says.

    Chakraborty goes on to explain what a gravitomagnetic monopole is: “In nature, north and south magnetic poles always go hand in hand. Cutting a bar magnet in half just creates two magnets, each of which still has two poles, rather than creating separate north and south poles on each half. Yet their electrostatic cousins, positive and negative charges, exist independently.”

    The researcher adds that in theoretical physics, gravity and electromagnetism have analogous features. “Mass is considered as the analogous to electric charge. Therefore, we call mass the gravitoelectric charge,” Chakraborty says. “The next question is: does gravitomagnetic charge or the so-called gravitomagnetic monopole exist in nature?”

    In the paper the authors propose that M87* may contain a gravitomagnetic monopole and therefore could be described as a more general Kerr-Taub-NUT spacetime, with Kerr spacetime a special case of the Kerr-Taub-NUT spacetime with vanishing gravitomagnetic monopole.

    “In that sense, no models are incorrect, and this basically put a strong constraint on the spacetime structure of the central compact radio source in M87,” Chakraborty concludes, adding how competing theories could be tested. “Essentially, accurate measurements of both the shadow size and asymmetry could put strong constraints on Kerr parameter and NUT parameter, and break the degeneracies between the Kerr and Kerr-Taub-NUT spacetimes, including those between the black holes and naked singularities.”

     
  • richardmitnick 12:21 pm on March 24, 2021 Permalink | Reply
    Tags: "Astronomers image magnetic fields at the edge of M87’s black hole[Messier 87*]", , , , , , Event Horizon Telescope, ,   

    From ALMA [The Atacama Large Millimeter/submillimeter Array] (CL): “Astronomers image magnetic fields at the edge of M87’s black hole[Messier 87*]” 

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    Event Horizon Telescope Array


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    European Southern Observatory(EU)/MPG Institute for Radio Astronomy [MPG Institut für Radioastronomie](DE) ESO’s Atacama Pathfinder Experiment(CL) 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 Array for Research in Millimeter-wave Astronomy(US)), in the Inyo Mountains to the east of the California Institute of Technology Owens Valley Radio Observatory(US), 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.

    National Astronomy Observatory of Japan(JP) 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).


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    Caltech Submillimeter Observatory.


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    IRAM NOEMA, France.


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    Large Millimeter Telescope Alfonso Serrano.


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


    Caltech Owens Valley Radio Observatory.

    The Event Horizon Telescope (EHT) collaboration, which produced the first-ever image of a black hole, has today revealed a new view of the massive object at the center of the Messier 87 (M87) galaxy: how it looks in polarised light. With this data, astronomers measured polarization, a signature of magnetic fields, for the first time this close to the edge of a black hole. The observations are key to explaining how the M87 galaxy, located 55 million light-years away, can launch energetic jets from its core.

    “We are now seeing the next crucial piece of evidence to understand how magnetic fields behave around black holes, and how activity in this very compact region of space can drive powerful jets that extend far beyond the galaxy,” says Monika Mościbrodzka, Coordinator of the EHT Polarimetry Working Group and Assistant Professor at Radboud University [Radboud Universiteit](NL).

    On April 10, 2019, scientists released the first-ever image of a black hole, revealing a bright ring-like structure with a dark central region — the black hole’s shadow. Since then, the EHT collaboration has delved deeper into the supermassive object’s data at the heart of the M87 galaxy collected in 2017. They have discovered that a significant fraction of the light around the M87 black hole is polarized.

    “This work is a major milestone: the polarisation of light carries information that allows us to understand better the physics behind the image we saw in April 2019, which was not possible before,” explains Iván Martí-Vidal, also Coordinator of the EHT Polarimetry Working Group and GenT Distinguished Researcher at the University of Valencia [Universitat de València](ES). He adds that “unveiling this new polarised-light image required years of work due to the complex techniques involved in obtaining and analyzing the data.“

    Light becomes polarized when it goes through certain filters, like the lenses of polarized sunglasses, or when it is emitted in hot regions of space where magnetic fields are present. In the same way that polarized sunglasses help us see better by reducing reflections and glare from bright surfaces, astronomers can sharpen their view of the region around the black hole by looking at how the light originating from it is polarized. Specifically, polarization allows astronomers to map the magnetic field lines present at the inner edge of the black hole.

    “The newly published polarised images are key to understanding how the magnetic field allows the black hole to ‘eat’ matter and launch powerful jets,” says EHT collaboration member Andrew Chael, a NASA Hubble Fellow at the Princeton University Center For Theoretical Science(US) and the Princeton Gravity Initiative(US).

    The bright jets of energy and matter that emerge from M87’s core and extend at least 5000 light-years from its center are one of the galaxy’s most mysterious and energetic features. Most matter lying close to the edge of a black hole falls in. However, some of the surrounding particles escape moments before capture and are blown far out into space in the form of jets.

    Astronomers have relied on different models of how matter behaves near the black hole to understand this process better. But they still don’t know precisely how jets larger than the galaxy are launched from its central region, comparable in size to the Solar System, nor how exactly matter falls into the black hole. With the new EHT image of the black hole and its shadow in polarised light, astronomers managed for the first time to look into the region just outside the black hole where this interplay between matter flowing in and being ejected out is happening.

    The observations provide new information about the structure of the magnetic fields just outside the black hole. The team found that only theoretical models featuring strongly magnetized gas can explain what they see at the event horizon.

    “The observations suggest that the magnetic fields at the black hole’s edge are strong enough to push back on the hot gas and help it resist gravity’s pull. Only the gas that slips through the field can spiral inwards to the event horizon,” explains Jason Dexter, Assistant Professor at the University of Colorado Boulder(US), and Coordinator of the EHT Theory Working Group.

    To observe the heart of the M87 galaxy, the collaboration linked eight telescopes worldwide — including the northern Chile-based ALMA-Atacama Large Millimeter/submillimeter Array(CL) — to create a virtual Earth-sized telescope, the Event Horizon Telescope. The impressive resolution obtained with the EHT is equivalent to that needed to measure a credit card’s length on the Moon’s surface.

    “With ALMA [above] and APEX[above], which through their southern location enhance the image quality by adding geographical spread to the EHT network, European scientists were able to play a central role in the research,” says Ciska Kemper, European ALMA Programme Scientist at European Southern Observatory(EU). “With its 66 antennas, ALMA dominates the overall signal collection in polarised light, while APEX has been essential for the calibration of the image.”

    “ALMA data were also crucial to calibrate, image and interpret the EHT observations, providing tight constraints on the theoretical models that explain how matter behaves near the black hole event horizon,” adds Ciriaco Goddi, a scientist at Radboud University and Leiden Observatory(NL), who led an accompanying study that relied only on ALMA observations.

    “ALMA plays a central role in the entire process: it is centrally located to tie the EHT array together, and it is also the most sensitive telescope in the array, so it is crucial to making the most of the EHT data,” said Geoff Crew, Haystack Research Scientist. “In addition, the years of work on the ALMA polarimetry analysis has delivered far more than we imagined.”

    The EHT setup allowed the team to directly observe the black hole shadow and the ring of light around it, with the new polarised-light image clearly showing that the ring is magnetized. The results are published today in two separate papers in The Astrophysical Journal Letters by the EHT collaboration. The research involved over 300 researchers from multiple organizations and universities worldwide.

    “The EHT is making rapid advancements, with technological upgrades being done to the network and new observatories being added. We expect future EHT observations to reveal more accurately the magnetic field structure around the black hole and to tell us more about the physics of the hot gas in this region,” concludes EHT collaboration member Jongho Park, an East Asian Core Observatories Association Fellow at the Academia Sinica Institute of Astronomy and Astrophysics in Taipei.
    Additional Information

    This research was presented in two papers by the EHT collaboration published today in The Astrophysical Journal Letters: First M87 Event Horizon Telescope Results VII: Polarization of the Ring and First M87 Event Horizon Telescope Results VIII: Magnetic Field Structure Near The Event Horizon. Accompanying research is presented in the paper Polarimetric properties of Event Horizon Telescope targets from ALMA by Goddi, Martí-Vidal, Messias, and the EHT collaboration, which has been accepted for publication in The Astrophysical Journal Letters.

    The EHT collaboration involves more than 300 researchers from Africa, Asia, Europe, North and South America. The international collaboration is working to capture the most detailed black hole images ever obtained by creating a virtual Earth-sized telescope. Supported by considerable international investment, the EHT links existing telescopes using novel systems — creating a fundamentally new instrument with the highest angular resolving power that has yet been achieved.

    The individual telescopes involved are: ALMA, APEX, the Institut de Radioastronomie Millimetrique (IRAM) 30-meter Telescope, the IRAM NOEMA Observatory, the James Clerk Maxwell Telescope (JCMT), the Large Millimeter Telescope (LMT), the Submillimeter Array (SMA), the Submillimeter Telescope (SMT), the South Pole Telescope (SPT), the Kitt Peak Telescope, and the Greenland Telescope (GLT) [All above].

    The EHT consortium consists of 13 stakeholder institutes: the Academia Sinica Institute of Astronomy and Astrophysics(TW), the University of Arizona(US), the University of Chicago(US), the East Asian Observatory – Hilo, Hawaii(US), Goethe-Universitaet Frankfurt(DE), Institute of Radio Astronomy [Institut de Radioastronomie Millimétrique](ES), LMT – Large Millimeter Telescope Alfonso Serrano(MX), MPG Institute for Radio Astronomy [MPG Institut für Radioastronomie](DE), Massachusettes Institute of Technology-Haystack Observatory(US), National Astronomical Observatory of Japan [国立天文台](JP), Perimeter Institute for Theoretical Physics(CA), Radboud University [Radboud Universiteit](NL) and the Harvard Smithsonian Center for Astrophysics(US).

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    The Event Horizon Telescope (EHT) collaboration, who produced the first ever image of a black hole released in 2019, has today a new view of the massive object at the centre of the Messier 87 galaxy [Messier 87*]: how it looks in polarised light. This is the first time astronomers have been able to measure polarisation, a signature of magnetic fields, this close to the edge of a black hole. This image shows the polarised view of the black hole in Messier 87 [Messier 87*]. The lines mark the orientation of polarisation, which is related to the magnetic field around the shadow of the black hole. Credit: Event Horizon Telescope Collaboration.

    2
    This composite image shows three views of the central region of the Messier 87 galaxy in polarised light. The galaxy has a supermassive black hole at its centre [Messier 87*] and is famous for its jets, that extend far beyond the galaxy. One of the polarised-light images, obtained with ALMA shows part of the jet in polarised light. This image captures the part of the jet, with a size of 6000 light years, closer to the centre of the galaxy. The other polarised light images zoom in closer to the supermassive black hole: the middle view covers a region about one light year in size and was obtained with the National Radio Astronomy Observatory’s Very Long Baseline Array(US) in the US.

    The most zoomed-in view was obtained by linking eight telescopes around the world to create a virtual Earth-sized telescope, the Event Horizon Telescope. This allows astronomers to see very close to the supermassive black hole, into the region where the jets are launched. The lines mark the orientation of polarisation, which is related to the magnetic field in the regions imaged.The ALMA data provides a description of the magnetic field structure along the jet. Therefore the combined information from the EHT and ALMA allows astronomers to investigate the role of magnetic fields from the vicinity of the event horizon (as probed with the EHT on light-day scales) to far beyond the Messier 87 galaxy along its powerful jets (as probed with ALMA on scales of thousand of light-years). The values in GHz refer to the frequencies of light at which the different observations were made. The horizontal lines show the scale (in light years) of each of the individual images. Credit: EHT Collaboration; ALMA (ESO/NAOJ/NRAO), Goddi et al.; VLBA (NRAO), Kravchenko et al.; J. C. Algaba, I. Martí-Vidal.

    3
    This composite image shows three views of the central region of the Messier 87 galaxy in polarised light and one view, in the visible wavelength, taken with the Hubble Space Telescope.

    The galaxy has a supermassive black hole at its centre [Messier 87*] and is famous for its jets, that extend far beyond the galaxy. The Hubble image at the top captures a part of the jet some 6000 light years in size. One of the polarised-light images, obtained with obtained with ALMA shows part of the jet in polarised light. This image captures the part of the jet, with a size of 6000 light years, closer to the centre of the galaxy. The other polarised light images zoom in closer to the supermassive black hole: the middle view covers a region about one light year in size and was obtained with the National Radio Astronomy Observatory’s Very Long Baseline Array (VLBA) in the US. The most zoomed-in view was obtained by linking eight telescopes around the world to create a virtual Earth-sized telescope, the Event Horizon Telescope or EHT. This allows astronomers to see very close to the supermassive black hole, into the region where the jets are launched. The lines mark the orientation of polarisation, which is related to the magnetic field in the regions imaged. The ALMA data provides a description of the magnetic field structure along the jet. Therefore the combined information from the EHT and ALMA allows astronomers to investigate the role of magnetic fields from the vicinity of the event horizon (as probed with the EHT on light-day scales) to far beyond the M87 galaxy along its powerful jets (as probed with ALMA on scales of thousand of light-years).

    The values in GHz refer to the frequencies of light at which the different observations were made. The horizontal lines show the scale (in light years) of each of the individual images. Credit: EHT Collaboration; ALMA (ESO/NAOJ/NRAO), Goddi et al.; NASA, ESA and the Hubble Heritage Team (STScI/AURA); VLBA (NRAO), Kravchenko et al.; J. C. Algaba, I. Martí-Vidal.

    4
    This image shows a view of the jet in the Messier 87 galaxy in polarised light. The image was obtained with ALMA and captures the part of the jet, with a size of 6000 light years, closer to the centre of the galaxy. The lines mark the orientation of polarisation, which is related to the magnetic field in the region imaged. This ALMA image therefore indicates what the structure of the magnetic field along the jet looks like.

    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 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 the supermassive black hole in the centre of Messier 87 and its shadow. The shadow of a black hole seen here is the closest we can come to an image of the black hole itself, a completely dark object from which light cannot escape. The black hole’s boundary — the event horizon from which the EHT takes its name — is around 2.5 times smaller than the shadow it casts and measures just under 40 billion km across. While this may sound large, this ring is only about 40 microarcseconds across — equivalent to measuring the length of a credit card on the surface of the Moon. Although the telescopes making up the EHT are not physically connected, they are able to synchronize their recorded data with atomic clocks — hydrogen masers — which precisely time their observations. These observations were collected at a wavelength of 1.3 mm during a 2017 global campaign. Each telescope of the EHT produced enormous amounts of data – roughly 350 terabytes per day – which was stored on high-performance helium-filled hard drives.

    Katie Bouman of Harvard Smithsonian Observatory for Astrophysics(US), headed to California Institute of Technology(US), with EHT hard drives from Messier 87.

    These data were flown to highly specialised supercomputers — known as correlators — at the MPG Institute for Radio Astronomy [MPG Institut für Radioastronomie](DE) and Massachusettes Institute of Technology(US) Haystack Observatory to be combined. They were then painstakingly converted into an image using novel computational tools developed by the collaboration. Credit: EHT Collaboration.

    5
    Messier 87 Captured by ESO’s Very Large Telescope. Credit: ESO

    European Southern Observatory(EU) , Very Large Telescope 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.

    6
    This artist’s impression depicts the black hole [Messier 87*] at the heart of the enormous elliptical galaxy Messier 87 . This black hole was chosen as the object of paradigm-shifting observations by the Event Horizon Telescope. The superheated material surrounding the black hole is shown, as is the relativistic jet launched by M87’s black hole. Credit: M. Kornmesser/European Southern Observatory(EU)/

    7
    This image shows the contribution of ALMA and ESO’s Atacama Pathfinder Experiment(CL) to the EHT. The left hand image shows a reconstruction of the black hole image using the full array of the Event Horizon Telescope (including ALMA and APEX); the right-hand image shows what the reconstruction would look like without data from ALMA and APEX. The difference clearly shows the crucial role that ALMA and APEX played in the observations. Credit: EHT Collaboration.

    The Event Horizon Telescope (EHT) collaboration, who produced the first ever image of a black hole, has today revealed a new view of the massive object at the centre of the Messier 87 galaxy: how it looks in polarised light. This is the first time astronomers have been able to measure polarisation, a signature of magnetic fields, this close to the edge of a black hole. This video summarises the discovery.

    This zoom video starts with a view of ALMA, a telescope in which ESO is a partner and that is part of the Event Horizon Telescope, and zooms-in on the heart of M87, showing successively more detailed observations. At the end of the video, we see the first ever image of a black hole — first released in 2019 — followed by a new image released in 2021: how this supermassive object looks in polarised light. This is the first time astronomers have been able to measure polarisation, a signature of magnetic fields, this close to the edge of a black hole.
    Credit: ESO/L. Calçada, Digitized Sky Survey 2, ESA/Hubble, RadioAstron, De Gasperin et al., Kim et al., EHT Collaboration. Music: Niklas Falcke.

    See the full article here .

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    The Atacama Large Millimeter/submillimeter Array (ALMA) (CL) , 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

    ALMA is a time machine!

    ALMA-In Search of our Cosmic Origins

     
  • richardmitnick 8:16 pm on January 6, 2020 Permalink | Reply
    Tags: "Famous Black Hole Has Jet Pushing Cosmic Speed Limit", , , , , Event Horizon Telescope, ,   

    From NASA Chandra: “Famous Black Hole Has Jet Pushing Cosmic Speed Limit” 

    NASA Chandra Banner

    NASA/Chandra Telescope


    From NASA Chandra

    1
    Credit: NASA/CXC/SAO/B.Snios et al.

    1.6.20

    The Event Horizon Telescope Collaboration released the first image of a black hole with observations of the massive, dark object at the center of Messier 87 last April.

    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 .

    EHT map

    This black hole has a mass of about 6.5 billion times that of the sun and is located about 55 million light years from Earth. The black hole has been called M87* by astronomers and has recently been given the Hawaiian name of “Powehi.”

    For years, astronomers have observed radiation from a jet of high energy particles — powered by the black hole — blasting out of the center of Messier 87. They have studied the jet in radio, optical, and X-ray light, including with Chandra. And now by using Chandra observations, researchers have seen that sections of the jet are moving at nearly the speed of light.

    “This is the first time such extreme speeds by a black hole’s jet have been recorded using X-ray data,” said Ralph Kraft of the Center of Astrophysics | Harvard & Smithsonian (CfA) in Cambridge, Mass., who presented the study at the American Astronomical Society meeting in Honolulu, Hawaii. “We needed the sharp X-ray vision of Chandra to make these measurements.”

    When matter gets close enough to a black hole, it enters into a swirling pattern called an accretion disk. Some material from the inner part of the accretion disk falls onto the black hole and some of it is redirected away from the black hole in the form of narrow beams, or jets, of material along magnetic field lines. Because this infall process is irregular, the jets are made of clumps or knots that can sometimes be identified with Chandra and other telescopes.

    The researchers used Chandra observations from 2012 and 2017 to track the motion of two X-ray knots located within the jet about 900 and 2,500 light years away from the black hole. The X-ray data show motion with apparent speeds of 6.3 times the speed of light for the X-ray knot closer to the black hole and 2.4 times the speed of light for the other.

    “One of the unbreakable laws of physics is that nothing can move faster than the speed of light,” said co-author Brad Snios, also of the CfA. “We haven’t broken physics, but we have found an example of an amazing phenomenon called superluminal motion.”

    Superluminal motion occurs when objects are traveling close to the speed of light along a direction that is close to our line of sight. The jet travels almost as quickly towards us as the light it generates, giving the illusion that the jet’s motion is much more rapid than the speed of light. In the case of M87*, the jet is pointing close to our direction, resulting in these exotic apparent speeds.

    Astronomers have previously seen such motion in Messier 87*’s jet at radio and optical wavelengths, but they have not been able to definitively show that matter in the jet is moving at very close to the speed of light. For example, the moving features could be a wave or a shock, similar to a sonic boom from a supersonic plane, rather than tracing the motions of matter.

    This latest result shows the ability of X-rays to act as an accurate cosmic speed gun. The team observed that the feature moving with an apparent speed of 6.3 times the speed of light also faded by over 70% between 2012 and 2017. This fading was likely caused by particles’ loss of energy due to the radiation produced as they spiral around a magnetic field. For this to occur the team must be seeing X-rays from the same particles at both times, and not a moving wave.

    3
    Illustration of the Supermassive Black Hole at the Center of Messier 87 (Credit: NASA/CXC/M.Weiss)

    4
    Chandra Wide-field View of Messier 87; box shows the approximate location of the wide-field jet image above (Credit: NASA/CXC)


    A Quick Look at the Black Hole Jet in Messier 87

    “Our work gives the strongest evidence yet that particles in Messier 87*’s jet are actually traveling at close to the cosmic speed limit”, said Snios.

    The Chandra data are an excellent complement to the EHT data. The size of the ring around the black hole seen with the Event Horizon Telescope is about a hundred million times smaller than the size of the jet seen with Chandra.

    Another difference is that the EHT observed Messier 87 over six days in April 2017, giving a recent snapshot of the black hole. The Chandra observations investigate ejected material within the jet that was launched from the black hole hundreds and thousands of years earlier.

    “It’s like the Event Horizon Telescope is giving a close-up view of a rocket launcher,” said the CfA’s Paul Nulsen, another co-author of the study, “and Chandra is showing us the rockets in flight.”

    In addition to being presented at the AAS meeting, these results are also described in a paper in The Astrophysical Journal led by Brad Snios.
    Other materials about the findings are available at:
    http://chandra.si.edu

    For more Chandra images, multimedia and related materials, visit:
    http://www.nasa.gov/chandra

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

    See the full article here .


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

     
  • richardmitnick 8:38 am on May 4, 2019 Permalink | Reply
    Tags: , , , , Event Horizon Telescope, ,   

    From JPL-Caltech: “The Giant Galaxy Around the Giant Black Hole” 

    NASA JPL Banner

    From JPL-Caltech

    1

    The galaxy Messier 87, imaged here by NASA’s Spitzer Space Telescope, is home to a supermassive black hole that spews two jets of material out into space at nearly the speed of light. The inset shows a close-up view of the shockwaves created by the two jets.Credit: NASA/JPL-Caltech/IPAC

    NASA/Spitzer Infrared Telescope

    On April 10, 2019, the Event Horizon Telescope (EHT) unveiled the first-ever image of a black hole’s event horizon, the area beyond which light cannot escape the immense gravity of the black hole.

    The first image of a black hole, Messier 87 Credit Event Horizon Telescope Collaboration, via NSF and ERC 4.10.19

    That giant black hole, with a mass of 6.5 billion Suns, is located in the elliptical galaxy Messier 87. EHT is an international collaboration whose support in the U.S. includes the National Science Foundation.

    This image from NASA’s Spitzer Space Telescope shows the entire M87 galaxy in infrared light. The EHT image, by contrast, relied on light in radio wavelengths and showed the black hole’s shadow against the backdrop of high-energy material around it.

    EHT map

    Located about 55 million light-years from Earth, Messier 87 has been a subject of astronomical study for more than 100 years and has been imaged by many NASA observatories, including the Hubble Space Telescope, the Chandra X-ray Observatory and NuSTAR.

    NASA/ESA Hubble Telescope

    NASA/Chandra X-ray Telescope

    NASA/DTU/ASI NuSTAR X-ray telescope

    In 1918, astronomer Heber Curtis first noticed “a curious straight ray” extending from the galaxy’s center. This bright jet of high-energy material, produced by a disk of material spinning rapidly around the black hole, is visible in multiple wavelengths of light, from radio waves through X-rays. When the particles in the jet impact the interstellar medium (the sparse material filling the space between stars in M87), they create a shockwave that radiates in infrared and radio wavelengths of light but not visible light. In the Spitzer image, the shockwave is more prominent than the jet itself.

    The brighter jet, located to the right of the galaxy’s center, is traveling almost directly toward Earth. Its brightness is amplified due to its high speed in our direction, but even more so because of what scientists call “relativistic effects,” which arise because the material in the jet is traveling near the speed of light. The jet’s trajectory is just slightly offset from our line of sight with respect to the galaxy, so we can still see some of the length of the jet. The shockwave begins around the point where the jet appears to curve down, highlighting the regions where the fast-moving particles are colliding with gas in the galaxy and slowing down.

    The second jet, by contrast, is moving so rapidly away from us that the relativistic effects render it invisible at all wavelengths. But the shockwave it creates in the interstellar medium can still be seen here.

    Located on the left side of the galaxy’s center, the shockwave looks like an inverted letter “C.” While not visible in optical images, the lobe can also be seen in radio waves, as in this image from the National Radio Astronomy Observatory’s Very Large Array.

    Close-up from VLA of a jet near black hole in Messier 87

    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)

    By combining observations in the infrared, radio waves, visible light, X-rays and extremely energetic gamma rays, scientists can study the physics of these powerful jets. Scientists are still striving for a solid theoretical understanding of how gas being pulled into black holes creates outflowing jets.

    Infrared light at wavelengths of 3.6 and 4.5 microns are rendered in blue and green, showing the distribution of stars, while dust features that glow brightly at 8.0 microns are shown in red. The image was taken during Spitzer’s initial “cold” mission.

    The Jet Propulsion Laboratory in Pasadena, California, manages the Spitzer Space Telescope mission for NASA’s Science Mission Directorate in Washington. Science operations are conducted at the Spitzer Science Center at Caltech in Pasadena. Space operations are based at Lockheed Martin Space Systems in Littleton, Colorado. Data are archived at the Infrared Science Archive housed at IPAC at Caltech.

    More information on Spitzer can be found at its website: http://www.spitzer.caltech.edu/

    See the full article here .


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    NASA JPL Campus

    Jet Propulsion Laboratory (JPL)) is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. Although the facility has a Pasadena postal address, it is actually headquartered in the city of La Cañada Flintridge, on the northwest border of Pasadena. JPL is managed by the nearby California Institute of Technology (Caltech) for the National Aeronautics and Space Administration. The Laboratory’s primary function is the construction and operation of robotic planetary spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA’s Deep Space Network.

    Caltech Logo

    NASA image

     
  • richardmitnick 8:03 pm on March 16, 2016 Permalink | Reply
    Tags: , , , Event Horizon Telescope,   

    From NOVA: “Are Black Holes Real?” This is a MUST READ 

    PBS NOVA

    NOVA

    10 Mar 2016
    Kate Becker

    Not so long ago, black holes were like unicorns: fantastical creatures that flourished on paper, not in life. Today, there is wide scientific consensus that black holes are real. Even though they can’t be observed directly—by definition, they give off no light—astronomers can infer their hidden presence by watching how stars, gas, and dust swirl and glow around them.

    But what if they’re wrong? Could something else—massive, dense, all-but-invisible—be concealed in the darkness?

    While black holes have gone mainstream, a handful of researchers are investigating exotic ultra-compact stars that, they argue, would look exactly like black holes from afar. Well, almost exactly. Though their ideas have been around for many years, researchers are now putting them to the most stringent tests ever, looking to show once and for all that what looks and quacks like a black hole really is a black hole. And if not? Well, it could just spark the next revolution in physics.

    The game-changer is a new experiment called the Event Horizon Telescope (EHT).

    Event Horizon Telescope map
    EHT map

    The EHT is a network of telescopes that are sensitive to radio waves about a millimeter long and linked together using a technique called very long baseline interferometry. Baseline refers to the distance between the networked telescopes: the longer the distance, the finer the details the telescope can pick out. It’s impossible—or at least impractical—to build a single telescope as big as planet Earth, but astronomers can achieve the same “zoom” factor by linking telescopes on opposite continents. Just like that, the universe goes from standard-definition to HD: a switch powerful enough to tell a black hole from an exotic imposter.

    Meanwhile, scientists have directly detected gravitational waves for the first time using the Laser Interferometer Gravitational-Wave Observatory, also known as LIGO.

    MIT Caltech  Advanced aLIGO Hanford Washington USA installation
    MIT Caltech Advanced aLIGO, Hanford, Washington, USA installation

    Gravitational waves—ripples in the fabric of space-time that [Albert] Einstein predicted should radiate out from the site of any gravitational disturbance—represent an entirely new way to see the cosmos, and with enough data, they could finally confirm—or contradict—the existence of black holes.

    Black Hole Anatomy

    On its own, a black hole looks like nothing: black-on-black, indistinguishable from the empty space that surrounds it. But supermassive black holes, which are believed to sit at the core of almost every galaxy in the universe, surrounded by stars and other galactic detritus that accumulates around the edge like soap suds circling the bathtub drain. By studying those “suds,” astronomers can answer questions about the central black hole.

    The best-studied black hole candidate in the universe is the one called Sagittarius A* [Sag A*], which lives at the center of our very own Milky Way galaxy.

    Sag A prime
    Sag A*

    By tracking the orbits of stars circling around Sagittarius A*, they have deduced that Sagittarius A* packs some 4 million times the mass of the Sun into a region of space much smaller than the solar system. Their conclusion: it could only be a supermassive black hole.

    To confirm that suspicion, they would like to see up to the edge of the black hole—the event horizon, a sort of line in the sand that separates the “inside” of the black hole from the “outside” and beyond which nothing can escape. From the perspective of a telescope on Earth, the event horizon should look like a dark shadow surrounded by a bright ring of light. The exact shape of this ring and shadow are predicted by the equations of general relativity, plus the properties of the black hole and its surroundings.

    An Earth-Sized Telescope

    That’s where the EHT comes in. Since the EHT first started taking data, it has been building its telescope roster, and with each new member, it gets closer to making the first true image of a black hole shadow.

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

    Atacama Pathfinder EXperiment (APEX)

    ESO APEX

    Atacama Submillimeter Telescope Experiment (ASTE)

    Atacama Submillimeter Telescope Experiment (ASTE) (ASTE)

    Combined Array for Research in Millimeter-wave Astronomy (CARMA)

    CARMA Array

    Caltech Submillimeter Observatory (CSO)

    Caltech Submillimeter Observatory

    Institut de Radioastronomie Millimetrique (IRAM) 30m

    IRAM 30m Radio telescope

    James Clerk Maxwell Telescope (JCMT)

    East Asia Observatory James Clerk Maxwell telescope

    The Large Millimeter Telescope (LMT) Alfonso Serrano

    Large Millimeter Telescope Alfonso Serrano

    The Submillimeter Array (SMA)

    CfA Submillimeter Array Hawaii SAO

    Future Array/Telescopes

    Atacama Large Millimeter/submillimeter Array (ALMA)

    ALMA Array

    Plateau de Bure interferometer

    Plateau de Bure interferometer

    The EHT is like an all-star team of telescopes: Most days, its millimeter-wave dishes run their own experiments independently, but for one or two weeks a year, they team up to become the EHT, taking new data and running tests during the brief window when astronomers can expect clear weather at sites from Hawaii to Europe to the South Pole.

    “It sounds too good to be true that you just drop telescopes around the world and ‘poof!’ you have an Earth-sized telescope,” says Avery Broderick, a theoretical astrophysicist at University of Waterloo and the Perimeter Institute. And in a way, it is. The EHT doesn’t make pictures. Instead, it turns out a kind of mathematical cipher called a Fourier transform, which is like the graphic equalizer on your stereo: it divvies up the incoming signal, whether its an image of space or a piece of music, into the different frequencies that make it up and tells you how much power is stored in each frequency. So far, the EHT has only given astronomers a look at a few scattered pixels of the Fourier transform. When they compare those pixels to what they expect to see in the case of a true black hole, they find a good match. But the job is like trying to figure out whether you’re listening to Beethoven or the Beastie Boys based only on a few slivers of the graphic equalizer curve.

    Now, the EHT is about to add a superstar player: the [ESO/NRAO/NAOJ]Atacama Large Millimeter Array, a telescope made up of 66 high-precision dishes sited 16,000 feet above sea level in Chile’s clear, dry Atacama desert. With ALMA on board, the EHT will finally be able to make the leap from fitting models to seeing a complete picture of the black hole’s shadow. EHT astronomers are now rounding up time at all of the telescopes so that they can take new data and assemble that first coveted image in 2017.

    And if they don’t see what they expect? It could mean that the black hole isn’t really a black hole at all.

    That would come as a relief to many theorists. Black holes are mothers of cosmic paradox, keeping physicists up at night with the puzzles they present: Do black holes really destroy information? Do they really contain infinitely dense points called singularities? Black holes are also the battlefield on which general relativity and quantum mechanics clash most dramatically. If it turns out that they don’t actually exist, some physicists might sleep a little better.

    But if they’re not black holes, then what could they be? One possibility is that they are dark stars made up of bosons, subatomic particles that, unlike more familiar electrons and protons, obey strange rules that allow more than one of them to be in the same place at the same time. Boson stars are highly speculative—astronomers have never seen one, as far as they know—but theorists like Vitor Cardoso, a professor of physics at Técnico in Lisbon and a distinguished visiting researcher at Sapienza University of Rome, hypothesize that some or all of the objects we think are supermassive black holes could actually be boson stars in disguise.

    Physicists classify particles into two different categories: fermions, which include protons, electrons, neutrons, and their components; and bosons, like photons (light particles), gluons, and Higgs particles. Every star that we’ve ever seen shining is dominated by fermions. But, Cardoso says, given a starting environment rich in bosons, bosons could “clump” together gravitationally to form stars, just as fermions do. The early universe might have had a high enough density of bosons for boson stars to form.

    But not every boson is a suitable building block for a boson star. Gravity won’t hold together a clump of massless photons, for instance. Higgs particles are massive enough to be bound together by gravity, but they aren’t stable—they only exist for tiny fraction of a second before decaying away. Theorists have speculated about ways to stabilize Higgs particles, but Cardoso is more intrigued by the prospect that other, yet-undiscovered heavy bosons, like axions, could make up boson stars. In fact, some physicists hypothesize that massive bosons like these could be responsible for dark matter—meaning that boson stars wouldn’t just be a solution to the riddle of black holes, they could also tell us what, exactly, dark matter is.

    Gravastars

    Boson stars aren’t the only black hole doppelgänger that theorists have dreamed up. In 2001, researchers proposed an even more speculative oddity called a gravastar. In the gravastar model, as a would-be black hole collapses under its own weight, extreme gravity combines with quantum fluctuations that are constantly jiggling through space to create a bubble of exotic spacetime that halts the cave-in.

    Theorists don’t really know what’s inside that bubble, which is both good and bad news for gravastars: Good news because it gives theorists the flexibility to revise the model as new observations come in, bad news because scientists are rightly skeptical of any model that can be patched up to match the data.

    When the data does come in, physicists have a checklist of sorts that should help them know which of the three—black hole, boson star, or gravastar—they’re looking at. A gravastar should have a bright surface that’s distinguishable from the glowing ring predicted to loop around a black hole. Meanwhile, if the object at the center of the Milky Way is actually a boson star, Cardoso predicts, it will look more like a “normal” star. “Black holes are black all the way through,” Cardoso says. “If really the object is a boson star, then the luminous material can in principle pile up at its center. A bright spot should be detected right at the center of the object.”

    A New View

    Most physicists have placed their bets on Saggitarius A* and other candidates being black holes, though. Boson stars and gravastars already have a few strikes against them. First, when it comes to scientific credibility, black holes have a major head start. Astronomers have a solid understanding of the process by which black holes form and have direct evidence that other ultra-dense objects, like white dwarfs and neutron stars, which could merge to form black holes, really do exist. The alternatives are more speculative on every count.

    Furthermore, Broderick says, astronomers have looked for the telltale signature of boson stars and gravastars at the center of the Milky Way—and haven’t found it. “The stuff raining down on the object will give up all its kinetic energy—all the gravitational binding energy tied up in the kinetic energy of its fall—resulting in a thermal bump in the spectrum,” Broderick says —that is, a signature spike in infrared emission. In 2009, astrophysicists reported that they had found no such bump coming from Sagittarius A*, and in 2015, they announced that it was missing from the nearby massive galaxy [Messier]87, too.

    Cardoso doesn’t see this as a death-knell for the boson star model, though. “The field that makes up the boson star hardly interacts with matter,” he says. To ordinary matter, the surface of a boson star would feel like frothed milk. “We do not yet have a complete model of how these objects accrete luminous matter,” Cardoso says, “so I think that it’s fair to say that this is still an open question.” He is less optimistic about gravastars, which he describes as “artificial constructs” that are likely ruled out by the latest observations.

    As the LIGO experiment gathers more data, theorists will get more opportunities to test their exotic hypotheses with gravitational waves. As two massive objects—say, a supermassive black hole and a star—spiral toward each other on the way toward a collision, gravitational waves carry away the energy of their motion. If one member of the spiraling pair is a black hole, the gravitational wave signal will cut off abruptly as the star passes through the black hole’s event horizon. “It gives rise to a very characteristic ringdown in the final stages of the inspiral,” Cardoso says. Because the alternative models have no such horizon, the gravitational wave signal would keep on reverberating.

    Most astronomers believe that the waves LIGO detected were given off by the collision of two black holes, but Cardoso thinks that boson stars shouldn’t be ruled out just yet. “The data is, in principle, compatible with the two colliding objects being each a boson star,” he says. The end result, though, is probably a black hole “because it rings down very fast.”

    LIGO is not designed to pick up signals at the frequency at which supermassive objects like Sagittarius A* are expected to “ring.” (LIGO is tuned to recognize gravitational waves from smaller black holes and dense stars like neutron stars.) But supermassive black holes and boson stars are in the sweet spot for the planned space-based gravitational wave telescope ESA/LISA (the Evolved Laser Interferometer Space Antenna), slated for launch in 2034.

    ESA LISA Pathfinder
    ESA/LISA

    “To confirm or rule out boson stars entirely, we need ‘louder’ observations,” Cardoso says. “EHT or eLISA are probably our best bet.”

    Taking the Pulse

    In the meantime, astronomers could measure waves from these extremely massive objects by precisely clocking the arrival times of radio pulses from a special class of dead stars called pulsars. If astronomers spot pulses arriving systematically off-beat, that could be a sign that the space they’ve been traveling across is being stretched and squeezed by gravitational waves. Three collaborations—NANOGrav in North America, the European Pulsar Timing Array, and the Parkes Pulsar Timing Array in Australia—are already scanning for these signals using radio telescopes scattered around the globe.

    To Broderick, though, the big question isn’t which model will win out, it’s whether these new experiments can find a flaw in general relativity. “For 100 years, general relativity has been enormously successful, and there’s no hint of where it breaks,” he says. Yet general relativity and quantum mechanics, which appears equally shatterproof, are fundamentally incompatible. Somewhere, one or both must break down. But where? Boson stars and gravastars might not be the answer. Still, exploring these exotic possibilities forces physicists to ask the questions that might lead them to something even more profound.

    “We expect that general relativity will pass the EHT’s tests with flying colors,” Broderick says. “But the great hope is that it won’t, that we’ll finally find the loose thread to pull on that will unravel the next great revolution in physics.”

    See the full article here .

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    NOVA is the highest rated science series on television and the most watched documentary series on public television. It is also one of television’s most acclaimed series, having won every major television award, most of them many times over.

     
  • richardmitnick 7:02 pm on January 27, 2016 Permalink | Reply
    Tags: , , , Event Horizon Telescope, ,   

    From WIRED.com: “The Death of General Relativity Lurks in a Black Hole’s Shadow” 

    Wired logo

    Wired

    01.27.16
    Lizzie Wade

    Black hole in color
    Chi-kwan Chan, Feryal Ozel, and Dimitrios Psaltis

    Nothing gets out of a black hole—not even light. Once a star, a planet, a piece of dust, or even a single photon crosses the limit known as the event horizon, it’s not coming out again. Pulled into the crushing gravity of the singularity at the black hole’s heart, it vanishes from the universe.

    That’s a big problem if what you really want from a black hole is a photograph. By definition, it’s impossible. All light getting sucked in means no light reflects back—so a black hole is invisible, across the spectrum. And, duh, invisible objects don’t show up in photographs.

    But thanks to a new telescope, Tim Johannsen, an astrophysicist at the Perimeter Institute and the University of Waterloo in Ontario, Canada, may be able to get a black hole pic after all. A loophole in physics means he might be able to see not the black hole itself, but its shadow. And, no big deal, but that photo just might overturn Albert Einstein’s theory of general relativity.

    So…wait. Black holes have shadows? Sort of. As gas and dust and other cosmic material approaches a black hole, “that stuff heats up, like millions and millions of degrees,” Johannsen says. That superheated matter swirls around the black hole in what’s called an accretion disk; because it’s so hot, the accretion disk emits a lot of light.

    Some of those photons zoom out towards Earthbound telescopes, while others cross the event horizon and fall into the void. So when astronomers look at a black hole, what they expect to see is a ring of bright light—the accretion disk—surrounding a circle of nothingness. That circle of nothingness is the shadow. (The black hole itself is just a single point within.) You can see a model of that here:


    Download mp4 video here .

    At least, that’s the idea. No one has ever actually seen a black hole’s shadow. “Despite their enormous mass, black holes are also exceedingly small,” says Avery Broderick, Johannsen’s colleague at the Perimeter Institute and the University of Waterloo. Seen from Earth, the shadow of Sagittarius A*, the supermassive black hole at the center of the Milky Way (also known as Sgr A*, which astrophysicists pronounce “Saj-A-star”) is just 1/35,000,000th the width of the Moon, or 50 microarcseconds wide.

    Sag A prime
    Sgr A*

    Here’s where that new telescope comes in. Maybe. Johannsen, Broderick, and their colleagues hope the Event Horizon Telescope will be able to resolve Sgr A*’s shadow. The EHT is actually nine [radio] telescopes (and counting), all working together and each located in a different spot on Earth.

    Event Horizon Telescope map
    EHT map

    Telescopes of the EHT

    ALMA

    ALMA Array
    APEX

    ESO APEX

    Arizona Radio Observatory (U. of Arizona)

    Arizona Radio Observatory

    Caltech Submillimeter Observatory

    Caltech Submillimeter Observatory

    CARMA

    CARMA Array

    Harvard Smithsonian Center for Astrophysics Submillimeter Array

    SMA Submillimeter Array

    Institut de Radioastronomie Millimetrique (IRAM) 30m

    IRAM

    James Clerk Maxwell Telescope (JCMT)

    The Large Millimeter Telescope Alfonso Serrano (LMT)

    Plateau de Bure interferometer

    IRAM Interferometer Submillimeter Array of Radio Telescopes

    South Pole Telescope]

    South Pole Telescope

    Coordinating those telescopes’ observations allows them to work as one big telescope that is, in essence, as big as the planet. The bigger your telescope, the higher your resolution. “The Event Horizon Telescope has the capability to produce the highest-resolution images in the history of astronomy”, Broderick says. “That means, for the first time, we can see what happens right down in the immediate vicinity of black hole event horizons.”

    Scientists working on the EHT hope to see images in the spring of 2017. But they already have some ideas of what they’ll get. General relativity describes gravity not as a force drawing two objects together, but rather as the warped spacetime that governs each of those objects movements.

    Spacetime with Gravity Probe B
    Artist concept of Gravity Probe B orbiting the Earth to measure space-time, a four-dimensional description of the universe including height, width, length, and time. NASA

    Concentrate a big enough mass in a small enough region of spacetime, and its gravity will be inescapably huge—voila, you’ve got a black hole. If that sounds weird to you, well, it took 50 years for astronomers to discover that black holes were real objects, not just a quirk of general relativity’s math.

    The problem is, general relativity is really good at describing giant things like stars, but breaks down utterly when it comes to really teeny tiny things like photons and quarks. To talk about those, you need a different theory: quantum mechanics. The central problem in physics today is that the theories are fundamentally incompatible. To figure that out, physicists are keen to find places where the theories overlap or break down—like, for example, the event horizon of a black hole.

    General relativity doesn’t just predict the existence of black holes. It also precisely describes the size and shape of their shadows. Sgr A*’s shadow is supposed to be perfectly circular and 50 microarcseconds wide. “What would it look like if general relativity were wrong?” wonders Broderick (and just about every other astrophysicist on the planet). There are two possibilities. “The shadow could be more egg shaped,” says Johannsen. “That would be a smoking gun for a GR violation.” It might also be slightly smaller or bigger than general relativity predicts. All he needs to figure it out is the picture from the EHT. (Johannsen and Broderick just published a paper outlining their strategy in Physical Review Letters.)

    And what if Sgr A*’s shadow doesn’t look the way general relativity says it should? Well, that would be great. If the results held up, physicists could start looking for alternative theories of gravity that did predict the shadow’s size and shape. Success wouldn’t mean the new theory would automatically be the successor to general relativity, of course. But it’s a good way to figure out which theories might be on the right track, so you can give their other predictions a closer look.

    Johannsen’s favorite possibility involves extra dimensions. A shortcoming of general relativity is that it doesn’t explain why gravity is so much weaker than the other fundamental forces. “Let’s assume there is another space dimension. Gravity would immediately penetrate that and become kind of diluted,” Johannsen says. In other words, gravity isn’t weak, it’s just working across more dimensions than the other forces. Amazingly, theories that predict those extra dimensions also predict a different size for Sgr A*’s shadow. In a couple years, finally proving—or falsifying—this weird new physics could “literally be as ‘easy’ as putting a ruler across the image,” Johannsen says.

    “We’re getting this amazing opportunity to finally put Einstein to the test around the most enigmatic and striking predictions of this theory,” Broderick says. If Einstein is wrong, general relativity won’t go away—it’s too good at what it does. It just won’t be the whole story anymore. Isaac Newton was plenty right about how gravity worked here on Earth; Einstein revolutionized our understanding of the universe. But the universe is big enough to have room for someone to come along and do it again.

    See the full article here .

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  • richardmitnick 4:43 pm on January 27, 2016 Permalink | Reply
    Tags: , , , Event Horizon Telescope, ,   

    From U Cambridge via CfA: “The Event Horizon Telescope project” – Interview of Shep Doelman – Worth Your Time 

    HarvardSmithsonian

    Harvard-Smithsonian Center for Astrophysics

    U Cambridge bloc

    Cambridge University

    Shep Doelman, MIT Haystack Observatory and Harvard Smithsonian Centre for Astrophysics

    Event Horizon Telescope map
    EHT map

    The event horizon at the mouth of a black hole is the point of no return: once light crosses this threshold, there is no going back. This means it’s proved impossible for astronomers to physically see what’s going on beyond this point. But there might be a way to do it by looking at the shadow cast by the event horizon and using this to infer what made that shadow. Shep Doelman is an astronomer at the MIT Haystack Observatory and Harvard Smithsonian Centre for Astrophysics, and he’s part of an initiative called The Event Horizon Telescope project, which aims to get the first image of the shadow cast by the black hole at the centre of our own galaxy, as he explains to Georgia Mills…

    Shep – There’s a part of the Universe that is forever separate from our experience, and that’s inside inside the event horizon, and the size and the shape of that event horizon is predicted by [Albert] Einstein’s equations which have withstood all the tests that we’ve subjected them to in the solar system and the larger universe, and now we’d like to go to the one place where they might break down, at the event horizon itself.

    Georgia – Past the event horizon, by its very nature, you can’t really see into it. How would you be able to study something like that?

    Shep – Well, in a paradox of their own immense gravity, black holes, which by definition are dark are some of the brightest objects in the Universe. You can think of it this way: the black hole is insanely powerful and it’s trying to attract all of this gas, dust, and ionised plasma into a very small volume and you get a cosmic traffic jam. Everything is rubbing up against each each and, just as your hands get warm when you rub them together, all this gas and dust heats up to billions of degrees. So it’s a little bit like trying to suck an elephant through a straw; it’s very hard to do and, when you ultimately do it, it’s a big mess. So the black hole and the event horizon are illuminated by this three dimensional flashlight that lights up the space time, and one of the characteristics of the event horizon is that the light gets bent by gravity and so you wind up with a shadow feature. The way you can think about the shadow is that the light that is moving away from you, from the back side of the black hole, gets bent around in these curve trajectories back toward you so it illuminates a ring of light around the event horizon, and it’s the size and shape of that ring that we’re after with the Event Horizon Telescope Project.

    Georgia – So how are you planning to find this shadow?

    Shep – Black holes are the smallest objects that we know of and to see something that small you’ve got to make an entirely new kind of telescope. So we need something, to put it in perspective, that has a magnifying power that’s at least 2,000 times better than the Hubble Space Telescope.

    NASA Hubble Telescope
    NASA/ESA Hubble

    The best candidate for us to observe one of these black hole shadows is in the centre of our own Milky Way galaxy and radio waves are the perfect medium for that. They can pierce the gas, and the dust, and the ionised plasma that lies between us and the centre of our galaxy. So we need to make a telescope that has 2,000 times the magnifying power of the Hubble that sees radio waves.

    Georgia – So the problem here is that you need a radio telescope that’s 2,000 times stronger and that, to me, would seem like it would need to be bigger. How are you going to go about this?

    Shep – The magic of the Event Horizon Telescope is that we don’t make one single telescope, but we use radio dishes that are spread around the globe and we link them together using GPS to synchronise them perfectly, and then we install atomic clocks at each of the sites. And all of the telescopes swivel to look at the black hole at the centre of our galaxy at the same exact moment and, when that happens, you get an earth sized virtual telescope and the radio waves are recorded perfectly at each of the sites. Then hard discs are shipped back on a 747, or the airliner of your choice, to a central facility and when you do that we wind up getting a data set that’s equivalent to having a telescope the size of the Earth. And I would hasten to add that when you’re making and Earth sized telescope you need and Earth sized group and I’m just pleased as punch to work with some of the most talented astronomers on the face of the Earth from: Taiwan, Japan, Chile, the United States, Europe. It’s a really big enterprise.

    Georgia – This kind of massive collaboration thing; it seems to me that’s what science is all about. How did you get all these different telescopes on board with you?

    Shep – Part of the secret sauce of the Event Horizon Telescope is that we’re not building any new telescopes. We are developing all the instrumentation that allows us to turn telescopes that already exist into this global linked array. So, what we have done is we’ve gone to the directors and boards of telescopes around the world; we’ve explained this project to them and the science payoff is so interesting and exciting to the community that they’ve allowed us to come in with specialised equipment, install it at the telescopes and make these observations, and we’ve had some very interesting results so far. We wouldn’t really be having this conversation if we hadn’t already seen very small shadow sized features towards the black hole at the centre of the galaxy, and now we’re going to take those size measurements one step further and see if we can make an actual image.

    [Telescopes of the EHT

    ALMA

    ALMA Array
    APEX

    ESO APEX

    Arizona Radio Observatory (U. of Arizona)

    Arizona Radio Observatory

    Caltech Submillimeter Observatory

    Caltech Submillimeter Observatory

    CARMA

    CARMA Array

    Harvard Smithsonian Center for Astrophysics Submillimeter Array

    SMA Submillimeter Array

    Institut de Radioastronomie Millimetrique (IRAM) 30m

    IRAM

    James Clerk Maxwell Telescope (JCMT)

    The Large Millimeter Telescope Alfonso Serrano (LMT)

    Plateau de Bure interferometer

    IRAM Interferometer Submillimeter Array of Radio Telescopes

    South Pole Telescope]

    South Pole Telescope

    Georgia – And then at some point in the near future – well when is this going to happen, when are we going to get the telescopes to join up and assemble and all point at the same direction at once?

    Shep – Well we’re on, as they say, an aggressive timeline. We have already made these precursor observations which show us that we’re on the right track and we are, over the next year, finishing the build out across the entire global array. The first possibility for us to really make an image would be in the spring of 2017, that’s when of the larger telescopes (The Alma Array, in Chile), will join the Event Horizon Telescope and that will increase our sensitivity by a factor of ten, and also increase our resolution by a factor of two, and that would be the first time when we would have a shot at making a credible image. Knowing that all those 4 millions suns are within that ring would be the strongest evidence that we have, as least as humans (aliens might have better evidence), that black holes actually exist.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    U Cambridge Campus

    The University of Cambridge[note 1] (abbreviated as Cantab in post-nominal letters[note 2]) is a collegiate public research university in Cambridge, England. Founded in 1209, Cambridge is the second-oldest university in the English-speaking world and the world’s fourth-oldest surviving university.[6] It grew out of an association of scholars who left the University of Oxford after a dispute with townsfolk.[7] The two ancient universities share many common features and are often jointly referred to as “Oxbridge”.

    Cambridge is formed from a variety of institutions which include 31 constituent colleges and over 100 academic departments organised into six schools.[8] The university occupies buildings throughout the town, many of which are of historical importance. The colleges are self-governing institutions founded as integral parts of the university. In the year ended 31 July 2014, the university had a total income of £1.51 billion, of which £371 million was from research grants and contracts. The central university and colleges have a combined endowment of around £4.9 billion, the largest of any university outside the United States.[9] Cambridge is a member of many associations and forms part of the “golden triangle” of leading English universities and Cambridge University Health Partners, an academic health science centre. The university is closely linked with the development of the high-tech business cluster known as “Silicon Fen”.

     
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