The newly-found star, named S4716, reaches a speed of 8,000 km/sec and comes as close as 98 astronomical units (AU) to Sagittarius A*, a supermassive black hole in the center of our Milky Way Galaxy.
The view of the Galactic center observed with the NIRC2 instrument on the Keck II telescope at the W.M. Keck Observatory. This image is high-pass filtered and shows the position of several S stars close to Sgr A*, which is indicated by a black cross. The star in the white dashed circle shows a magnitude of 16.3 mag, while the star in the blue circle is 17 mag faint. Here north is up and east is to the left. Image credit: Peissker et al., doi: 10.3847/1538-4357/ac752f.
At the center of our Milky Way Galaxy lies the 4-million-solar-mass black hole named Sagittarius A* (Sgr A*).
This gravitational monster is surrounded by a cluster of stars, dubbed the S cluster, orbiting around it at high speed.
First identified in 1996, these S stars can be characterized by speeds up to several thousand kilometers per second, with some of them moving on highly eccentric orbits.
It is a remarkable achievement on both the technological and scientific level to analyze orbits of these stars that pass around Sgr A* at distances comparable to the size of our Solar System.
“One prominent member, S2, behaves like a large person sitting in front of you in a movie theatre: it blocks your view of what’s important,” said Dr. Florian Peissker, an astronomer at the I.Physikalisches Institut der Universität zu Köln.
“The view into the center of our Galaxy is therefore often obscured by S2.”
“However, in brief moments we can observe the surroundings of the central black hole.”
Using data from with NIRC2 and OSIRIS instruments on Keck I and Keck II telescopes at the W.M. Keck Observatory, SINFONI and NACO instruments on ESO’s Very Large Telescope, and the GRAVITY instrument on ESO’s Very Large Telescope Interferometer, Dr. Peissker and colleagues detected a new S-cluster member.
Named S4716, the star belogns to the B8/9 class and orbits Sgr A* in 4 years at distances between 98 and 702 AU.
“For a star to be in a stable orbit so close and fast in the vicinity of a supermassive black hole was completely unexpected and marks the limit that can be observed with traditional telescopes,” Dr. Peissker said.
The discovery of S4716 sheds new light on the origin and evolution of the orbit of fast-moving stars in the heart of the Milky Way.
“The short-period, compact orbit of S4716 is quite puzzling,” said Dr. Michael Zajaček, an astrophysicist at Masaryk University.
“Stars cannot form so easily near the black hole. S4716 had to move inwards, for example by approaching other stars and objects in the S cluster, which caused its orbit to shrink significantly.”
The study was published in the Astrophysical Journal.
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Florian Peißker et al. 2022. Observation of S4716 – a Star with a 4 yr Orbit around Sgr A*. ApJ 933, 49; doi: 10.3847/1538-4357/ac752f
Source link: https://www.sci.news/astronomy/s4716-star-10974.html
