In April 2019, scientists released the first image of a black hole in the M87 galaxy using the Event Horizon Telescope (EHT). However, this remarkable achievement was only the beginning of the scientific story to tell.
Data from 19 observatories released today promise to provide unparalleled insight into this black hole and the system it powers, and improve tests of Einstein’s general theory of relativity.
“We knew the first direct image of a black hole would be revolutionary,” says Kazuhiro Hada of the National Astronomical Observatory of Japan, co-author of a new study published in Letters from the astrophysical journal which describes the large dataset. “But to get the most out of this remarkable picture, we need to know all we can about the behavior of the black hole at that time by observing across the electromagnetic spectrum.”
The immense gravitational pull of a supermassive black hole can propel jets of particles that move almost at the speed of light over vast distances. The M87’s jets produce light spanning the entire electromagnetic spectrum, from radio waves to visible light to gamma rays. This model is different for each black hole. Identifying this model provides crucial insight into the properties of a black hole – for example, its spin and energy production – but is a challenge because the model changes over time.
Scientists have compensated for this variability by coordinating observations with many of the world’s most powerful telescopes on the ground and in space, collecting light across the spectrum. These 2017 observations were the largest simultaneous observation campaign ever undertaken on a supermassive black hole with jets.
Three observatories managed by the Center for Astrophysics | Harvard & Smithsonian participated in the historic campaign: the Submillimeter Array (SMA) in Hilo, Hawaii; the Chandra X-ray space observatory; and the High Energy Radiation Imaging Telescope Array System (VERITAS) in southern Arizona.
Beginning with the now iconic EHT image of M87, a new video takes viewers on a journey through the data of each telescope. Each consecutive image shows data on many scale factors of ten, both wavelengths of light and physical size.
The footage begins with the April 2019 image of the black hole. It then moves through images from other radio telescope arrays around the world (MAS), moving outward into the field of view with each step. Then the sight transforms into telescopes which detect visible light, ultraviolet light and x-rays (Chandra). The screen splits to show how these images, which cover the same amount of sky at the same time, compare to each other. The sequence ends by showing what the gamma telescopes on the ground (VERITAS), and Fermi in space, detect from this black hole and its jet.
Each telescope provides different information about the behavior and impact of the 6.5 billion solar mass black hole at the center of M87, located about 55 million light years from Earth.
“Several groups are eager to see if their models match these rich observations, and we’re excited to see the entire community use this public dataset to help us better understand the deep links between black holes and their jets,” says co-author Daryl Haggard of McGill University in Montreal, Canada.
The data was collected by a team of 760 scientists and engineers from nearly 200 institutions, covering 32 countries or regions, and using observatories funded by agencies and institutions around the world. Observations were concentrated from the end of March to mid-April 2017.
“This incredible set of observations includes many of the best telescopes in the world,” says co-author Juan Carlos Algaba of the University of Malaysia in Kuala Lumpur, Malaysia. “He is a wonderful example of astronomers around the world working together in the pursuit of science.”
The first results show that the intensity of the light produced by the material around the supermassive black hole of M87 was the lowest ever observed. This produced ideal conditions for visualizing the “shadow” of the black hole, as well as being able to isolate light from regions near the event horizon tens of thousands of light years away from the black hole.
Combining data from these telescopes with current (and future) EHT observations will allow scientists to conduct important lines of inquiry in some of the most important and challenging areas of study in astrophysics. For example, scientists plan to use this data to improve tests of Einstein’s theory of general relativity. Currently, the uncertainties about the material revolving around the black hole and projected in the jets, in particular the properties that determine the light emitted, represent a major obstacle for these tests of general relativity.
A related question that is addressed by today’s study concerns the origin of energetic particles called “cosmic rays,” which continually bombard Earth from space. Their energies can be a million times higher than what can be produced in the world’s most powerful accelerator, the Large Hadron Collider. The huge jets launched from black holes, like those shown in today’s images, are believed to be the most likely source of the most energetic cosmic rays, but there are many questions about the details, including including the precise locations where particles are accelerated. Because cosmic rays produce light through their collisions, higher-energy gamma rays can locate this spot, and the new study says these gamma rays are probably not produced near the event horizon – at least not. in 2017. A key to settling this debate will be a comparison with the observations of 2018, and the new data collected this week.
“Understanding particle acceleration is really essential to understanding both the EHT image and the jets, in all their ‘colors’,” says co-author Sera Markoff of the University of Amsterdam. “These jets manage to carry the energy released by the black hole on scales larger than the host galaxy, like a huge power cord. Our results will help us calculate the amount of energy carried and the effect of the jets. of the black hole on its environment. “
The release of this new data treasure coincides with the EHT’s 2021 Observation Race, which operates a global range of radio antennas, the first since 2018. Last year’s campaign was canceled due to the COVID-19 pandemic, and the previous year was put on hold due to unforeseen technical issues. This very week, for six nights, the EHT astronomers target several supermassive black holes: that of M87 again, that of our galaxy called Sagittarius A *, and several black holes further away. Compared to 2017, the network has been improved by adding three additional radio telescopes: the Greenland Telescope, the Kitt Peak 12-meter Telescope in Arizona and the NOrthern Extended Millimeter Array (NOEMA) in France.
“With the release of this data, combined with resumption of observation and improved EHT, we know that many exciting new results are on the horizon,” says co-author Mislav Balokovi? from Yale University.
“I’m really excited to see these results come out, as well as my colleagues working on the ADS, some of whom were directly involved in collecting some of the data for this spectacular sight on M87,” says co-author Garrett Keating, a scientist from the Submillimeter Array project. “And with the results of Sagittarius A * – the massive black hole at the center of the Milky Way – coming out soon, and the resumption of observation this year, we have been looking forward to even more astonishing results with the EHT for many years. years. come. “