2023-04-26 17:00:09
The vast majority of galaxies harbor a supermassive black hole at their center. Ours, the Milky Way, has its own. Also our neighboring galaxy, Messier 87, which is 53 million light-years from Earth. Its central giant was the first to be ‘portrayed’ by human telescopes, in a historic image showing the event horizon and the glow of the surrounding material spinning at full speed just before being engulfed by the blackness of the celestial object. from which not even light escapes.
This artist’s rendering shows a rapidly spinning supermassive black hole, surrounded by an accretion disk. This thin disk of rotating material is composed of the remains of a star similar to our Sun that was torn apart by tidal forces from the black hole. The black hole is marked, showing the anatomy of this fascinating object.
But black holes aren’t just darkness: These supermassive monsters can launch powerful jets of matter that extend beyond their own galaxies. Now, an international team in which researchers from the Instituto de Astrofísica de Andalucía (IAA-CSIC) also participate, have just managed to capture for the first time in a single image the black hole of Messier 87 (M87) along with its powerful jet. The results have just been published in the journal ‘Nature’.
“We know that the jets are ejected from the region around black holes,” explains Ru-Sen Lu of the Shanghai Astronomical Observatory in China. “However, we still don’t really fully understand how it happens. To study it directly we need to observe the source of the jet as close as possible to the black hole.” That is why this image will be key to unraveling one of the mysteries that most intrigues scientists: the mechanism behind these powerful emanations.
Previous observations had managed to obtain separate images of the region near the black hole, which is 6.5 billion times more massive than our Sun, and the jet: this is the first time the two have been observed together. Now, thanks to this capture, it will be possible to study the phenomena that unite both. “Now, by showing the region around the black hole and the jet at the same time, we already have the full picture,” says Jae-Young Kim of Kyungpook National University in South Korea and the Max Planck Institute for Radio astronomy, in Germany.
A virtual telescope the size of Earth
The image was obtained with GMVA, ALMA and the GLT, forming a global network of radio telescopes that have worked together as a virtual Earth-sized telescope. Such a large grating can discern very small details in the region around M87’s black hole.
The new image shows the jet emerging near the black hole, as well as what scientists call the black hole’s shadow. As matter orbits the black hole, it heats up and emits light. The black hole bends and captures some of this light, creating a structure around the black hole that, when viewed from Earth, looks like a ring.
Light from M87 is produced by the interaction between highly energetic electrons and magnetic fields, a phenomenon known as synchrotron radiation. The new observations reveal novel details about the location and energy of these electrons, and also introduce a note about the nature of the black hole itself: It’s not very hungry. It consumes matter at a low rate, converting only a small fraction to radiation. In addition, the new data brings surprising aspects: the radiation of the inner region close to the black hole is broader than expected, which could mean that there is something more than gas falling inside it. There could also be a type of galactic wind, which produces turbulence around the black hole.
Pictures taken in 2018
These new observations of M87’s black hole were made in 2018 with GMVA, which consists of 14 radio telescopes in Europe and North America. In addition, two other facilities were linked to GMVA: the Greenland Telescope and ALMA, of which ESO is a partner. ALMA consists of 66 antennas in the Chilean Atacama Desert, and played a key role in these observations. The data collected by all these telescopes around the world is combined using a technique called interferometry, which synchronizes the signals taken by each individual facility. But to adequately capture the true shape of an astronomical object it is important that telescopes are spread all over the Earth.
GMVA’s telescopes are mostly aligned from east to west, so the addition of ALMA in the southern hemisphere was essential to capture this image of M87’s black hole jet and shadow. “Thanks to ALMA’s location and sensitivity, we were able to reveal the shadow of the black hole and, at the same time, get a deeper look at the emission from the jet,” explains Lu.
The high resolution and sensitivity of the intercontinental network of telescopes used have allowed us to obtain this panorama. The diameter of the ring as measured by the Global Millimeter VLBI Array is 64 microarcseconds, which corresponds to the size of a football on the Moon as seen from Earth. “These amazing results are just the beginning of a fascinating era in radio astronomy. Our research team will continue to explore M87 and other similar objects using the unprecedented resolution that large antenna combinations such as GMVA, KVN and EHT can offer”, says Thalia Traianou, a researcher at the IAA-CSIC who is participating in the work.
Looking at the future
In the future, observations with this network of telescopes will continue to unravel how powerful jets can be launched by supermassive black holes. “We plan to observe the region around the black hole at the center of M87 at different radio wavelengths to further study the emission from the jet,” confirms Eduardo Ros from the Max Planck Institute for Radio Astronomy.
These simultaneous observations would allow the team to unravel the complicated processes taking place near the supermassive black hole. “The next few years will be exciting, as we will be able to learn more about what is happening near one of the most mysterious regions of the Universe,” concludes Ros.
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