A supermassive dark hole (SMBH), is likely to be located at the center the Milky Way and other galaxies. However, it has never been observed. It was found by looking at a cluster of star near the galactic center called S stars.
The presence of a large object in the Milky Ways center was indicated by the motions of the S stars. Most scientists agreed that it must have been an SMBH. Its named Sagittarius A*.
Some scientists are unsure if it is really a black hole. One of the S stars could help answer this question, as well as other questions about black holes.
Over 20 years, scientists have been studying and monitoring the S stars. They have gathered detailed astrometric data on the group of stars and measurements of the stars' positions and movements around galactic centers have revealed that there is a large object. Astronomers may be able to identify the object's nature by looking at one star in the group named S2 (or S0-2).
A new research letter examines the behaviour of S2s and asks a potentially awkward question. The study is called What lies at the Milky Way Centre? The preprint site arxiv.org contains insights from the S2 star orbit precession. C. R. Argelles, Fac. de Ciencias Astron. y Geofsicas, Universidad Nacional de La Plata, Paseo del Bosque.
It is now clear what the Milky Ways Center actually looks like. Three scientists were awarded the 2020 Nobel Prize in Physics. Reinhard Genzel and Andrea Ghez were awarded the prize for their work on the object at its center. According to the Nobel Prize Organization press release, Reinhard Genzel (left) and Andrea Ghez (right), they discovered that the orbits of the stars in the center of our galaxy are controlled by an invisible and very heavy object. The only explanation currently available is a supermassive dark hole.
Artist's impression of the orbits three stars located very close to the supermassive dark hole at the center the Milky Way Credit: ESO/M. Parsa/L. Calada
There is uncertainty.
It is possible that dark matter could be the source of the huge object in the middle of our galaxy. This is fermionic dark material. The authors claim that both a Schwarzschild black hole (BH) and a dense concentration (DM) of self-gravitating fermionic darkness (DM) can be used to explain the exact astrometric data (positions, radial velocities, etc.) of the S stars orbiting Sgr. A*.
This question has a second cosmic actor. It's not a star but a cloud made up of gas called G2. G2 was close to the Milky Ways center in 2014. Astronomers believe it was within 36 light hours from Sgr A*. Astronomers had previously simulated the impact of this encounter before it came to a close. They imagined that the black hole would release gas from the cloud and cause a noticeable brightening of Sgr A*, as it accreted mass form G2. It never happened.
This simulation shows a gas cloud moving close to the supermassive dark hole at the center of the galaxy in mid-2013. ESO's Very Large Telescope observations have confirmed that the cloud has stretched to the point where the front is moving away from the black holes at more than 10,000,000 km/h. The tail is still falling towards them. Image credit: ESO/S. Gillessen/MPE/Marc Schartmann
Why wasn't there fireworks as G2 passed so near to Sgr. A*? G2 might not have been a cloud of gas. G2 actually consists of two components. One is a low-mass cloud of gas and the other is a dusty star object. The close passage of G2 by Sgr. A* did not shed much light on the nature and origin of the object at the galactic center.
Return to S2.
The authors explain that there are two models that can describe the nature of a massive object. They differ in one key way. The Schwarzschild BH scenario for S2 predicts a prograde precession, but the DM scenario can either indicate retrograde or prograde. The amount of DM mass in S2s orbit will determine whether S2s precession occurs progradely or retrograde.
Researchers are still not able to decide which model is correct, despite all the data and observations of S2 stars. There is an opportunity to see S2 in the near future, which should help determine whether the Milky Ways center contains dark matter or a black hole. They write that the next S2 astrometry near the next apocentre passage could possibly establish if Sgr. A* is governed either by a classic BH or a quantum DM.
The majority of matter in the Universe is made up dark matter and not baryonic material. It is not surprising that some of the largest objects in the Universe are made of dark matter, rather than regular matter. Yes. It would be huge to confirm that Sgr. A* isn't a black hole, but a mass dark matter.
We will have to wait and watch. S2's orbital period is 16 years. The last time Sgr A* came within striking distance of S2 was in 2018. S2 will pass by Sgr. A* in 2034, which is the next best time to see it.
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