New images of the region around the Sagittarius A* black hole in the center of the Milky Way

I’ESO (European Southern Observatory) announces in these minutes a new series of pictures of the region around black hole Sagittarius A* which is located in the center of the Milky Way, our galaxy. This is parallel work to that carried out by the EHT which in the past showed new images of M87*.

recently still theESO announced the discovery of another black hole (much less massive than Sagittarius A*) in the star cluster NGC 1850 and called NGC 1850 BH1. These particularly elusive objects are at the center of a series of studies and research to try to understand their secrets. By using the VLTI (Very Large Telescope Interferometer) it has been possible to try to answer some fundamental questions to know these objects, as explained by Reinhard Genzel (director of the Max Planck Institute for Extraterrestrial Physics)”vWe want to know more about the black hole at the center of the Milky Way, Sagittarius A*: what is its mass exactly? Wheel? Do the stars around the black hole behave exactly as we expect from Einstein’s theory of general relativity? The best way to answer these questions is to track stars in orbits close to the supermassive black hole. And here we demonstrate that we can do it with unprecedented precision.“.

As written above, through the use of the Very Large Telescope Interferometer data was collected for the construction of two separate studies with titles Deep images of the galactic center with GRAVITY And The mass distribution in the galactic center from interferometric astrometry of several stellar orbits. The goal was to study the region closest to Sagittarius A* which is affected by the enormous gravity of this celestial object.

The region near the Sagittarius A* black hole in the new images

According toESO these are the images of this region “deeper and sharper so far”. With the new analyses, it has been possible to achieve a magnification twenty times higher than before thanks also to the technique ofinterferometry which uses data collected by four telescopes equipped with mirrors 8.2 meters in diameter VLT. The information was then analyzed using information field theory by first creating a theoretical model and then they simulated it as seen by GRAVITY and finally they compared the simulation and the real images. This made it possible, for example, to confirm the presence of a star (called S300 and visible in the image below).

milky way black hole

As has happened in the past, the movement of the stars around Sagittarius A* supermassive black hole was used to try to estimate its mass. The observations were carried out between March and July this year by cataloging the stars in the region as well as their movements.

For example the star call S29 is the closest to Sagittarius A* (in May 2021) arrival “only” 13 billion kilometers (90 AU) with a speed of 8740 km/s and an orbital period of about 90 years. While that may seem like a lot of distance, so is the size involved.

black hole

Also thanks to these studies, it was also possible to confirm once again the General relativity since the stars follow the theoretically predicted trajectories confirming the structure of the gravitational field of the large black hole at the center of the Milky Way. The data also allowed us to make a new estimate of the Sagittarius black hole mass A* which is now estimated at 4,297 (±0.012) million solar masses at a distance from the Earth of 27 thousand light years (also the result of new calculations).

black hole

Over the next few years, systems will be upgraded from GRAVITY to GRAVITY+. This will improve the sensitivity to detect new stars with orbits closer to the black hole Sagittarius A* compared to what is currently visible. First will come ELT, which will calculate the radial velocity of these new stars, while GRAVITY+ will triple the angular resolution. In the coming months or years, the Event Horizon Telescope (EHT) may also shed additional light on Sagittarius A*.

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