In the 1930s, when physicist and engineer Karl Jansky pointed his radio antenna toward the center of our galaxy, he detected a continuous source of radio waves. After some analysis, scientists realized that these radio waves were emitted by something much further away from our planet than the sun — but surprisingly, it is comparable to the energy of the waves we receive from the sun.
With this information, they begin to suspect that something really powerful must be hiding in the center of Milky Way.
Astronomers later realized that the source of these mysterious radio waves was none other than a supermassive black hole more than a million times larger than our own sun We call it today Sagittarius A*. Commonly abbreviated to Sgr A*, the massive object serves as a gravitational anchor for the entire Milky Way. Since these early observations, astronomers have learned quite a bit about Sgr A*; because astronomers can actually observe it, the black hole gives us the best chance to answer an interesting question – is star formation possible around black holes?
Related: The swirling gas is helping scientists pinpoint the mass of the supermassive black hole in the Milky Way
Sgr A* is surrounded by a mass of molecular clouds — interstellar haze from which you can see a star or two emerging. However, astronomers think that the proximity of these clouds to the black hole could disrupt any possible stellar nurseries cranking up inside, as the intense tidal and electromagnetic forces are thought to destroy those pocket of gas that usually accumulates to form. star.
“The combination of a low density medium and strong tidal forces [supermassive black hole] it is difficult for stars to form in the ‘standard’ way, which is from the collapse of dense gas clouds. They will break down before collapsing,” astrophysicist Rosalba Perna from Stony Brook University in New York told Space.com
More recent observationshowever, points to the possibility that star formation may occur closer to Sgr A* than we first realized.
Astronomers, for some PERIOD, observed stars around Sgr A*, but explained their presence at a distance possibly due to their migration towards the black hole after the original formation of distant clusters. The problem with this explanation, however, is that many of these newly discovered stars seem too young to be able to form far away and then travel across. space to reach Sgr A*.
Young Stars found near Sgr A*
Led by Florian Peißker, a postdoctoral researcher at the University of Cologne’s Institute of Astrophysics, the team of astronomers identified the young stellar object X3a.
“It turns out that there is a region at a distance of several light years from the black hole that fulfills the conditions for star formation. This region, a ring of gas and dust, is sufficiently cold and protected against of harmful radiation,” Peißker explained in a statement.
Surrounding Sgr A*, and other supermassive black holes for that matter, is an accretion disk of gas and dust falling toward the black hole due to its massive gravitational pull. The particular disk covering Sgr A* extends between 5 and 30 light-year from event horizon in the black hole.
The team believes that X3a may have formed in a gaseous envelope in the outer ring of the accretion disk surrounding Sgr A*. These gas clouds can grow large enough to collapse in on themselves to become protostars.
Researchers have also speculated about other possible explanations for the presence of stars close to Sgr A*.
“The presence of young stars around black holes has made astrophysicists expand their view of star formation, and various theories have been developed to explain it, such as the formation of a disk resulting from the breakup of a molecular cloud, the formation of a distant cluster is followed by inward migration and shock compression caused by a tidal disruption event,” Perna said.
Perna has just written a paper which suggests that tidal disruption events (TDEs) near black holes create the right conditions for stars to form. TDEs are events where gravitational instabilities can be introduced into the accretion disk of a black hole, an example would be a star falling into a black hole. These TDEs can interact with the accretion disk of a black hole in such a way that high gas densities and twilights occur, allowing the collapse of dense clusters into young stars.
Perna explained that star formation around black holes is likely to be affected by the evolutionary stage of that black hole. When a black hole is “active”, probably in its early stages when the galaxy surrounding it is a chaotic place, it is surrounded by a long disk of gas and dust. This accretion disk becomes fertile ground for star formation due to the accumulation of a high density of matter. However, now that the Milky Way is older, things have settled down, and star formation around Sgr A* has likely slowed down from what it used to be.
While black holes remain a cosmological enigma, astronomers are learning more about how they interact with their surroundings to give birth to new stars and affect the evolution of their home galaxies.
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Image Source : www.space.com