The supermassive black hole at the heart of our Milky Way galaxy has been imaged for the first time by astronomers. This finding confirms that the object is a black hole and sheds light on how such massive objects, which are expected to exist at the center of most galaxies, function. The Event Horizon Telescope (EHT) Collaboration, a multinational research group, created the picture using data from a global network of radio telescopes.
The picture represents a long-awaited glimpse of the huge object in the galaxy’s core. Scientists have previously seen stars around the Milky Way’s center, which was invisible, compact, and huge. This strongly suggests that Sagittarius A* (Sgr A*, pronounced “sadge-ay-star”) is a black hole, and today’s photograph is the first direct visible proof of it.
Because the black hole is entirely dark, we can’t see it, but blazing gas surrounding it shows a telltale signature: a dark center area (called a “shadow”) encircled by a light ring-like structure. The new image shows light being distorted by the black hole’s enormous gravity, which is four million times that of our Sun.
“We were astounded by how closely the ring’s size corresponded to Einstein’s General Theory of Relativity predictions,” says the author “Geoffrey Bower of the Academia Sinica’s Institute of Astronomy and Astrophysics, Taipei, is an EHT Project Scientist. “These groundbreaking discoveries have substantially increased our knowledge of what occurs at the very heart of our galaxy, and have revealed new details about how these massive black holes interact with their environment.” The findings of the EHT team have been published in a special edition of The Astrophysical Journal Letters today.
Because the black hole is around 27,000 light-years distant from Earth, it looks to us like a doughnut in the sky. To visualize it, the team built the EHT, a powerful virtual telescope that joined eight existing radio observatories across the world into a single “Earth-sized” virtual telescope . The EHT studied Sgr A* throughout many nights, capturing data for several hours at a time, much like a camera with a longer exposure period.
The accomplishment comes after the EHT team published the first photograph of a black hole at the center of the more distant Messier 87 galaxy, dubbed M87*, in 2019.
Even though our galaxy’s black hole is thousands of times smaller and less massive than M87* , the two black holes seem very similar. “Sera Markoff, Co-Chair of the EHT Science Council and a professor of theoretical astrophysics at the University of Amsterdam, the Netherlands, says, “We have two completely different types of galaxies and two very different black hole masses, but close to the edge of these black holes they look amazingly similar.” “This indicates that General Relativity rules these things up close, and whatever changes we perceive from afar must be attributable to variances in the material that surrounds the black holes.”
Even though Sgr A* is substantially closer to us, this feat was far more difficult than M87 *’s. “The gas in the region of the black holes flows at the same speed — almost as fast as light — around both Sgr A* and M87*,” said EHT scientist Chi-Kwan (‘CK’) Chan of the University of Arizona’s Steward Observatory and Department of Astronomy and the Data Science Institute. Whereas gas takes days to weeks to circle M87*, it takes just minutes to orbit Sgr A*. As the EHT Collaboration observed Sgr A*, the brightness and pattern of the gas surrounding it changed rapidly, similar to attempting to capture a clear image of a dog chasing its tail.
The researchers had to develop complex new techniques.
The scientists had to create complex new techniques to account for the gas migration near Sgr A*. Unlike M87*, which was a much simpler and more consistent target with almost identical pictures, Sgr A* was not. The picture of the Sgr A* black hole is a composite of the several photographs obtained by the team, showing for the first time the behemoth hiding at the center of our galaxy.
The EHT Collaboration, which includes over 300 researchers from 80 institutions across the globe, made the endeavor feasible. The team labored for five years, utilizing supercomputers to integrate and analyze their data while collecting an extraordinary library of simulated black holes to compare with the observations.
Scientists are especially ecstatic to have photographs of two black holes of very different diameters, which will allow them to compare and contrast them. They’ve also started putting the new data to the test to see how gas behaves near supermassive black holes, using theories and simulations. Although this mechanism is not completely understood, it is considered to play a significant role in galaxies’ creation and development.
On May 12th, 2022, at 13:00 UT, the Event Horizon Telescope consortium will reveal ground-breaking Milky Way findings.
On May 12th, 2022, at 13:00 Universal Time, two simultaneous press conferences will be held to announce groundbreaking results from the Event Horizon Telescope collaboration. These will be held in collaboration with the National Science Foundation of the United States of America, the European Southern Observatory, the Joint ALMA Observatory, and other funding agencies and institutions. These events will be broadcast live on the internet as well. The events are organized alphabetically by location (local times are provided).
ESO Media Advisory (15:00 CEST) – Live streaming at ESO Website and ESO YouTube Channel – Garching bei München, European Southern Observatory
CONACyT Media Advisory (08:00 CDT) – Live streaming at CONACyT YouTube Channel – Mexico City, CONACyT
ALMA Media Advisory from Santiago de Chile, Joint ALMA Observatory (09:00 CLT)
Shanghai Astronomical Observatory Media Advisory (21:00 CST)
Academia Sinica Institute for Astronomy and Astrophysics, Taipei, Taiwan (21:00 CST), YouTube Live Streaming.
National Astronomical Observatory of Japan, Tokyo (22:00 JST), YouTube Live Streaming
National Press Club, Washington, D.C.
There will be additional events, including:
Madrid (15:00 CEST, see CSIC YouTube streaming)
Korean Peninsula (22:00 KST, see YouTube Live Streaming)