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Scientists, for the first time, have detected something unexpected hovering in the vicinity of Sagittarius A*, the supermassive black hole sitting in the centre of our galaxy.
A binary star system, which is a pair of two gravitationally bound stars that orbit each other, was shown to exist near the Sagittarius A* despite conditions being hostile, according to a paper published in Nature Communications.
Binary stars are quite common in the Universe. Scientists estimate that some 85 per cent of stars exist in binary star systems, with a few in systems containing three or more stars. But the new findings are unusual as the intense gravity near the supermassive black holes makes it hard for stellar bodies to exist.
Our findings show “that binaries indeed can exist in the vicinity of a supermassive black hole. This is not limited to our supermassive black hole Sagittarius A*. But it raises the question about the formation process of the binary and the evolution of the other stars”, Florian Peißker, a researcher at the University of Cologne, Germany, and lead author of the study, told Down To Earth.
The binary star system named D9 formed near the supermassive black hole. It is estimated to be only 2.7 million years old. The researchers expect the strong gravitational force from the nearby black hole could force the stars to merge into one within just one million years.
[This image indicates the location of the newly discovered binary star D9, which is orbiting Sagittarius A*, the supermassive black hole at the centre of our galaxy. It is the first star pair ever found near a supermassive black hole. The cut-out shows the binary system as detected by the SINFONI spectrograph on ESO’s Very Large Telescope. While the two stars cannot be discerned separately in this image, the binary nature of D9 was revealed by the spectra captured by SINFONI over several years. These spectra showed that the light emitted by hydrogen gas around D9 oscillates periodically towards red and blue wavelengths as the two stars orbit each other.
Credit: ESO/F. Peißker et al., S. Guisard]
“The D9 system shows clear signs of the presence of gas and dust around the stars, which suggests that it could be a very young stellar system that must have formed in the vicinity of the supermassive black hole,” Michal Zajacek, a researcher at Masaryk University, Czechia and University of Cologne and co-author of the study, said in a statement.
The researchers arrived at this by analysing data from the Very Large Telescope (VLT), one of the main optical telescopes installed in Chile's Atacama Desert. The combined data from VLT’s ERIS instrument along with archival data from the SINFONI instrument showed recurring variations in the velocity of the star. This suggested that D9 was actually two stars orbiting each other. “I thought that my analysis was wrong,” Peißker said, adding that the spectroscopic pattern covered about 15 years, indicating that the detection was the first binary observed.
Though this the first time that a binary system has been detected, several young stars have been found in close proximity to Sagittarius A*. Scientists are yet to understand the precise nature of many of the objects orbiting the supermassive galaxy and how they could have formed in such extreme environments.
Peißker theorises that D9 could be a missing link in the overall evolution of stars in the vicinity of Sagittarius A*. “It furthermore raises the question about the existence of planets. If binary stars can form, planets should also be possible, speculatively speaking,” the expert added.
Going forward, the researcher hopes to find more such binaries and study them closely to understand their existence better. “It seems plausible that the detection of planets in the Galactic centre is just a matter of time,” Peißker noted.