(ORDO NEWS) — New observations of stars orbiting the supermassive black hole Sgr A * made it possible to refine its mass and find a new record holder for the speed of orbital motion.
In the very center of the Milky Way lies the compact source of Sagittarius A * (Sgr A), emitting in all wavelengths. It is believed to be a supermassive black hole weighing about 4.3 million times the mass of the Sun, surrounded by an even heavier and hotter cloud of matter falling into it.
The stars of the Sagittarius A * cluster revolve even further , which are held by the gravity of the black hole. The orbits of these S-stars pass so close to the hole that some manage to complete a full revolution in a couple of decades of our years.
Two new articles ( 1 , 2 ) published in the journal Astronomy & Astrophysics present the results of the most accurate observations of the Sagittarius A * star cluster to date. Among the authors is the German astrophysicist Reinhard Henzel, who received the Nobel Prize in 2020 for his discovery of Sgr A *. It was made on the basis of just such data: long and careful tracking of the trajectories of stars, the movements of which indicated the size and mass of the central object.
This time, scientists used the European Southern Observatory (ESO) telescopes in Chile for more accurate observations. They were conducted from March to July 2021. Information from all four 8.2-meter instruments was combined using the GRAVITY interferometer.
In addition, astronomers took into account data previously obtained by the VLTI, Keck and Gemini observatories. As a result, it was possible to achieve 20 times better resolution than has been available until now.
The behavior of the star S29 turned out to be the most extreme: at its closest approach, it passed only 13 billion kilometers from the black hole, only three times farther than Pluto – from the Sun. Its orbital speed exceeds 8700 kilometers per second (almost three percent of the speed of light) – this can be called a record. In addition, observations made it possible to notice a new, relatively faint S-star, dubbed S300.
But most importantly, the motions of the stars helped to clarify the mass of the central black hole and the distance to it. Both values are in excellent agreement with available estimates: about 4.3 million solar masses and about 27 thousand light years.
Finally, observations have shown that there is no additional hidden mass in the vicinity of the black hole. Neither the presence of other black holes, nor other gravitating objects any longer distort the trajectories of S-stars, which means that, as a whole, the structure of the center of the Milky Way is fully known to us.
Contact us: [email protected]