The stars are in the center of the universe.
A group of stars known as S-stars swoop on wild, years-long orbits when they are in the vicinity of the black hole in Sagittarius A. The scientists who won the physics prize were involved in the study of the Sgr A.
A team of researchers led by one of those scientists, Reinhard Genzel of the Max Planck Institute for Extraterrestrial Physics in Germany, has unveiled the fruits of their latest gaze into the abyss.
The team has identified an entirely new S-star, named S300, and refined estimates of the distribution of mass in the galactic center, thanks to the newly captured images.
Genzel wants to learn more about the black hole at the center of the Milky Way.
How big is it? Does it move? Einstein's general theory of relativity states that stars around it behave the same. The best way to answer these questions is to follow stars on their way to the black hole. We can do that to a higher degree than ever before.
Black holes are not visible to us even when they are active.
The distance from the black hole to the event horizon is not enough to escape the powerful gravity of the field.
The black hole is invisible because no radiation that we can currently detect emerges. Outside the event horizon, things can help measure the characteristics of the black hole.
It's important to have the most precise measurement we can get. The GRAVITY collaboration has been working on this. They have been using the Very Large Telescope Interferometer's GRAVITY instrument to measure the motions of the S-stars around Sgr A*.
Genzel said that following stars around Sagittarius A* allows us to precisely probe the gravity of the black hole, to test General Relativity, and to determine the properties of the black hole.
The stars were observed as they reached the closest point to the black hole, perinigricon.
The star S29, which was within 13 billion units of Sgr, reached speeds over 8 kilometers per second.
The team combined the GRAVITY observations with those of two former VLTI instruments and used a machine learning technique to increase the precision of the GRAVITY data.
The model of the S-star was created and then compared to the real observations.
This is how they found S300, and also obtained the most precise estimate of Sgr A*'s mass. The black hole in the Milky Way is 4.3 million times the mass of the Sun, with 0.25 percent uncertainty.
The collaboration's previous estimate was 4.154 million times the mass of the Sun, with 0.27 percent uncertainty.
Next year will see several S-stars reach perinigricon, which will allow us to study and refine our measurement of the galactic center.
Two papers about the team's research have been published. They can be found here.
