Multifrequency Observations of M87*
Telescopes unite in unprecedented observations of the famous black hole
In April 2019, scientists released the first image of a black hole using the Event Horizon Telescope (EHT). However, that remarkable achievement was just the beginning of the science story to be told. New results are being released today that promise to give unparalleled insight into this black hole, and to improve tests of Einstein’s General Theory of Relativity. The collaborative effort includes a substantial contribution from the Max-Planck-Institut für Radioastronomie including observations with the 100-m radio telescope in Effelsberg.
New results from nineteen observatories are being released today that promise to give unparalleled insight into the black hole in the galaxy Messier 87 (M87), and to improve tests of Einstein’s General Theory of Relativity.
The immense gravitational pull of a supermassive black hole does not only accrete matter into it, but also powers an energetic matter outflow with particles that travel at almost the speed of light through vast distances. M87’s jets produce light across the entire electromagnetic spectrum, from radio waves to gamma rays. This pattern is different for each black hole. Collecting this “fingerprint” gives crucial insight into a black hole’s properties, but is a challenge because the pattern changes with time.
During the EHT observations of M87, scientists compensated for this volatility by coordinating observations with many of the world’s most powerful telescopes on the ground and in space, collecting light across the spectrum. This is the most extensive, simultaneous observing campaign ever undertaken on a supermassive black hole with jets. “This unique data set is crucial for our understanding of the physical conditions in the immediate vicinity of one of the most massive black holes in our cosmic neighborhood", says Stefanie Komossa, astronomer at the MPIfR, member of the team supporting multi-wavelength observations of the EHT, and one of the leading authors of this work.
Today, astronomers are releasing this vast reservoir of data as part of a new study being published in The Astrophysical Journal Letters. This will allow anyone interested to examine the data and use it for their own studies. Each telescope delivers critical pieces of information about the behavior and impact of the 6.5-billion-solar-mass black hole at the center of M87, which is located about 55 million light years from Earth.
“We knew that the first direct image of a black hole would be groundbreaking”, says Kazuhiro Hada of the National Astronomical Observatory of Japan, a co-author of the new study. “But to get the most out of this remarkable image, we need to know everything we can about the black hole’s behavior at that time by observing over the entire electromagnetic spectrum.”
“The combination of VLBI data obtained in the radio mm-band with close in time measurements performed at other wavelength like near-infrared, optical, X- and gamma-rays provides an excellent base for the detailed understanding of the physical processes acting near the black hole and in the jet launching region”, adds Thomas P. Krichbaum, astronomer at the Max-Planck-Institut für Radioastronomie (MPIfR) in Bonn, Germany, member of the EHT Science Council, and one of the leading authors of the present work.
The data were collected by a team of seven-hundred sixty scientists and engineers, from nearly two-hundred institutions, and thirty-two countries or regions, using nineteen observatories telescopes funded by agencies and institutions around the globe – including MPIfR’s telescopes Effelsberg and APEX – concentrated from the end of March to the middle of April 2017.
“There are multiple groups revving up to see if their models are a match for these rich observations, and we’re excited to see the whole community use this public data set to help us better understand the deep links between black holes and their jets,” says co-author Daryl Haggard of McGill University.
“This incredible set of observations includes many of the world’s best telescopes, with a combined record of three-hundred years of operation”, says co-author Juan Carlos Algaba of the University of Malaya in Kuala Lumpur, Malaysia. “This is a wonderful example of astronomers around the world working together in the pursuit of science.”
The results show that the amount of electromagnetic radiation produced by material around of M87’s supermassive black hole was the lowest that had ever been seen. This gave ideal conditions for studying the black hole, from regions close to the event horizon out to tens of thousands of light-years.
The combination of data from these telescopes, used in conjunction with the current and future EHT observations, will allow scientists to conduct important lines of investigation into some of astrophysics’ most significant and challenging fields of study. For example, scientists plan to use these data to improve tests of Einstein’s Theory of General Relativity. Currently a major hurdle in applying such tests to M87 involves uncertainties about the material rotating around the black hole and being blasted away in jets, in particular the properties that determine the emitted light.
“Understanding the particle acceleration is really central to our understanding of both the EHT image as well as the jets, in all their ‘colors’,” says co-author Sera Markoff, from the University of Amsterdam. “These jets manage to transport energy released by the black hole out to scales larger than the host galaxy, like a huge power cord. Our results will help us calculate the amount of power carried, and the effect the black hole’s jets have on its environment”.
The release of this new treasure trove of data coincides with the EHT's 2021 observing run, which leverages a worldwide array of radio dishes, the first since 2018. This very week, EHT astronomers are targeting M87, the supermassive black hole in our galaxy (Sgr A*), and several more distant black holes for six nights. “With the release of data, combined with the resumption of observing and an improved EHT, we know many exciting new results are on the horizon,” says co-author Mislav Baloković of Yale University.
Anton Zensus, Founding Chairman of the Event Horizon Telescope and director at the MPIfR, concludes: “In this observing campaign many telescopes in the World and in Space have teamed up with the EHT Collaboration, to jointly and simultaneously probe the properties of M87 across the full electromagnetic spectrum. This takes us a big step forward in our understanding of the nature of black-hole-powered systems and their jets. We are learning how to better probe magnetic fields, cosmic rays, jet structure, emission and absorption processes, and the role of general relativity.”
This research is presented in a publication at The Astrophysical Journal on April 14, 2021. 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. 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 release of this new treasure trove of data coincides with the first observing run by the EHT’s array of worldwide radio dishes since 2018. Last year’s campaign was canceled because of the COVID-19 pandemic, and the previous year was suspended because of operational problems and poor weather. This very week, EHT astronomers are targeting primarily the supermassive black hole in our galaxy (Sgr A*), M87, and a more distant black hole for six nights. Compared to 2017 the array has been improved by adding three more telescopes: the Greenland Telescope, the Kitt Peak 12m Telescope, and the NOrthern Extended Millimeter Array (NOEMA).
The research presented includes observations of different telescopes, including the 100-m radio telescope in Effelsberg as part of the High Sensitivity Array and the Global Millimetre VLBI Array.
The EHT consortium consists of thirteen stakeholder institutes: the Academia Sinica Institute of Astronomy and Astrophysics, the University of Arizona, the University of Chicago, the East Asian Observatory, Goethe-Universität Frankfurt, Institut de Radioastronomie Millimétrique, Large Millimeter Telescope, Max-Planck-Institut für Radioastronomie, MIT Haystack Observatory, National Astronomical Observatory of Japan, Perimeter Institute for Theoretical Physics, Radboud University, and the Smithsonian Astrophysical Observatory.
The 2017 campaign involved a large number of observatories and telescopes. At radio wavelengths it involved: the European Very Long Baseline Interferometry (VLBI) Array Network (EVN) on May 9, 2017, including the Effelsberg 100-m radio telescope; the High Sensitivity Array (HSA), which includes the Very Large Array (VLA), the Effelsberg 100-m radio telescope and the 10 stations of the National Radio Astronomy Observatory (NRAO) Very Long Baseline Array (VLBA) on May 15, 16 and 20; the VLBI Exploration of Radio Astronomy (VERA) over 17 different times in 2017; the EAVN/KaVa array, which combines the East Asian VLBI Network (EAVN) and KaVA, which is composed of the Korean VLBI Network (KVN), and VERA, over 14 epochs between March and May 2017; the KVN over seven epochs between March and December 2017; the VLBA on May 5, 2017; the Global Millimeter-VLBI-Array (GMVA) on March 30, 2017, also including the Effelsberg 100-m radio telescope; the Atacama Large Millimeter/submillimeter Array (ALMA); the Submillimeter Array (SMA) as part of an ongoing monitoring program. At ultraviolet (UV) wavelengths it involved the Neil Gehrels Swift Observatory (Swift) with multiple observations between March 22 and April 20, 2017; and at optical wavelengths: Swift; and the Hubble Space Telescope on April 7, 12 and 17, 2017. (The Hubble data were retrieved from the Hubble archive because it was part of an independent observing program.) At X-ray wavelengths it involved the Chandra X-ray Observatory on April 11 and 14, 2017; the Nuclear Spectroscopic Telescope Array (NuSTAR) on April 11 and 14, 2017; and Swift. At gamma-ray wavelengths it involved Fermi from March 22 to April 20, 2017; the High Energy Stereoscopic System (H.E.S.S); the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescopes, and the Very Energetic Radiation Imaging Telescope Array System (VERITAS).
The EHT is supported by considerable international investment and a big commitment from the MPI für Radioastronomie since the 1990s in the development of the millimetre-VLBI technique. More recently additional funding came through the ERC-funded Black Hole Camera project, for which Michael Kramer, director at the MPI für Radioastronomie, is one of the three principal investigators.
The following thirty-four researchers affiliated to MPIfR are co-authors of the paper (listed in order of appearance): Jae-Young Kim, Stefanie Komossa, Thomas P. Krichbaum, Ru-Sen Lu, Walter Alef, Rebecca Azulay, Anne-Kathrin Baczko, Silke Britzen, Ralph P. Eatough, Michael Janßen, Ramesh Karuppusamy, Dong-Jin Kim, Michael Kramer, Rocco Lico, Jun Liu, Kuo Liu, Andrei P. Lobanov, Karl M. Menten, Nicholas R. MacDonald, Cornelia Müller, Aristeidis Noutsos, Gisela N. Ortiz-León, Felix M. Pötzl, Eduardo Ros, Helge Rottmann, Alan L. Roy, Tuomas Savolainen, Lijing Shao, Pablo Torné, Efthalia Traianou, Jan Wagner, Norbert Wex, Robert Wharton, and J. Anton Zensus.