Sgr A *, the supermassive black hole in the center of the Milky Way, is surrounded by a group of stars that move at extreme speeds.
NASA / CXC / Univ. of Wisconsin / Y.Bai, et al.
At the center of our galaxy is Sagittarius A * (Sgr A *), a humongous black hole about four million times the mass of our Sun. So great are the gravitational effects extreme and they can be discovered by looking at the stars in their immediate vicinity. Orbiting Sgr A * are a handful of stars (and some mysterious objects), locked in a cosmic two-step with the invisible monster, moving with mind-melting speeds.
And astronomers have just discovered the fastest of fate, and its fastest speed around Sgr A * clocks at 8% the speed of light.
A study, published in The Astrophysics Journal on Tuesday, examined the area surrounding Sgr A *, looking for the signatures of stars. Earlier research has revealed dozens of stars move around the supermassive black hole on very unusual tracks. This population of stars is collectively known as the S-stars and some of them run incredibly close to the black hole, making them difficult to detect.
But the research team used instruments installed at the Very Large Telescope of the European Southern Observatory in Chile, by images taken between 2004 and 2016, and fought five new stars, S4711-S4715, to the population and follow them movements round Sgr A *. Their results show more evidence that a distinct population of stars revolves around Sgr A * at distances comparable to the size of our solar system.
And because they are so close to the horrible, bottomless abyss in the center of the Milky Way, they are a bit of extreme physics.
Florian Peissker, an astronomer at the University of Cologne in Germany, and his team studied intensively the region of space near the black hole. In January, they reported observations of the star S62. Their observations, published in the Astrophysics Journal, revealed that once in 9.9 years S62 orbited the black hole, it gave the shortest orbital period and made it the fastest star to flash around the black hole of and the Milky Way.
But Peissker and colleagues new data have dropped S62 both of their records.
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According to The Astronomer’s Telegram, one of the newly discovered stars, S4711, crawls the black hole of the Milky Way once every 7.6 years, and holds the record for the shortest orbital period.
Another star, S4714, is still extreme. It does not come as close to Sgr A * as S4711, but it travels around the black hole at 8% the speed of light. At that speed, the star moves every second about 15,000 miles (~ 24,000 kilometers), which would mean that it could make one complete round of the Earth in just over 1.5 seconds.
The very eccentric orbits of the S stars are also not just cosmic curiosity; the stars help establish more evidence for Einstein’s general theory of relativity. The theory predicts how space, time and gravity interact and suggests enormous, dense objects such as black holes can throw space around them. Studying the S stars, astronomers can see some of the motion proposed by Einstein’s theory. A team from the Max Planck Institute did just that, when they studied the star S2 earlier this year and found that it strictly followed Einstein’s theory.
The team believes that improved data analysis could provide even further insight into the space around Sgr A * and they expect that more stars on extremely tight orbits will be discovered in the near future. The Extremely Large Telescope, which is expected to become operational in 2025, will collect 13 times more light than any optical telescope in operation today and should help find a few more. Until then, S4714 will receive the crown.
