They are the closest and sharpest images yet of the core of the Milky Way, where the giant black hole Sagittarius A * is located
The destination is far away, the center of the Milky Way galaxy is about 27,000 light years from us. To get there, you first have to cross a region invaded by cosmic dust in the constellation Sagittarius (the Archer). Behind the dust, a swarm of stars appears, orbiting an invisible monster, Sagittarius A *.
Sagittarius A * is a super massive black hole , 4.3 million times the mass of the Sun. As the images get closer to it, it is possible to see a group of stars, observed by the NACO instrument of the Very Large Telescope of ESO (the last observation is from 2019). But the zoom increases even more, until almost everything is dark. But it is possible to see the last stars, the ones closest to the black hole, observed with the GRAVITY instrument in the interferometry of ESO’s Very Large Telescope in mid-2021. The video that captures the journey into the interior of the galaxy has been created by ESO / GRAVITY / L Calçada / N Risinger / DSS. The music is by Johan Monel. The journey begins here:
THE LAST STARS OF THE MILKY WAY
There are many stars surrounding the black hole . In fact, there are estimated to be millions within a 1.6 light-year radius of the Milky Way’s central black hole. S29 is the closest known star to Sagittarius A *, and in their observations, astronomers have seen it approach the black hole at a distance of only 13 billion kilometers. That’s only about 90 times the distance from Earth to the sun . The star was moving at a record speed of 8,740 kilometers per second.
Another of the stars close to the cosmic monster is S62, which is the fastest (known) star orbiting Sgr A *, with an orbital period of 9.9 years.
This animation, made with images obtained with the GRAVITY instrument on the ESO Very Large Telescope (VLTI) Interferometer between March and July 2021, shows stars orbiting very close to Sgr A *, the supermassive black hole at the heart of the Via Milky.
UNLOCKING SECRETS OF THE SAGITTARIUS A BLACK HOLE *
The inner black hole in the center of the Milky Way does not emit light, it cannot be observed directly. Astronomers can only learn about its properties by studying the motions of stars in its vicinity.
“Following stars in close orbits around Sagittarius A * allows us to accurately probe the gravitational field around the massive black hole closest to Earth, test general relativity, and determine the properties of the black hole,” explains Reinhard Genzel , director of El Max Planck Institute for Extraterrestrial Physics and winner of the 2020 Nobel Prize in Physics for his research on Sagittarius A *
Measurements, made between March and July 2021, revealed that Sagittarius A * has a mass of 4.3 million suns and is located at a distance of 27,000 light years from Earth. Both figures are the most accurate estimates of their kind to date.
The research is part of an international project called GRAVITY, which is developing new techniques to analyze images of the Milky Way’s galactic center in order to map the surroundings of Sagittarius A * in as much detail as possible. The project takes place at the Very Large Telescope , one of the most advanced optical space observatories in the world. It consists of four main telescopes, each 8.2 meters in diameter, and four auxiliary telescopes, 1.8 m in diameter. It can detect stellar objects four billion times fainter than what can be seen with the naked eye.
In his permanent exploration of the deepest interior of our galaxy, he has detected dancing stars near the mysterious Sagittarius A * the measurements and images obtained have been made possible thanks to GRAVITY, an instrument of ESO’s VLTI. GRAVITY combines the light from the four telescopes using a technique called interferometry. This technique is complex, “but in the end you get images 20 times sharper than those from individual VLT telescopes, revealing the secrets of the Galactic Center,” says Frank Eisenhauer of MPE, principal investigator at GRAVITY. And this is how they have managed to observe the movement of stars very close to the black hole in the center of our galaxy.
The new research has been published in two articles published in the journal Astronomy & Astrophysics