A star orbits the Milky Way's black hole at 18 million miles per hour

A newly discovered star, now called S4716, is moving at 5,000 miles (8,000 km) per second around the black hole at the center of our galaxy, the Milky Way, space.com reported.

The vast expanse of our universe means that astronomers are always discovering something they’ve never seen before. Earlier this week, astronomers spotted two asteroids the size of a bus heading for Earth, which will pass just a quarter of the distance that separates the Moon from us.

In addition to asteroids, our galaxy is also attracting the attention of astronomers looking for signs of other planets that support life. Right at the center of the Milky Way, there is a supermassive black hole dubbed Sagittarius A* or Sgr A* and S4716 orbits this black hole at high speed.

What we know about S4716

From observations made so far, we know that at 5,000 miles (8,000 km) per second or 18 million miles (29 million km) per hour, S4716 is the fastest star orbiting Sgr A*. It completes an orbit around a black hole with a diameter of 14.6 million (23.5 million km) in just four years.

S4716 is part of another dense group of stars also orbiting Sgr A* which astronomers call the S cluster. All the stars in this cluster move at high speeds but differ in their mass and brightness. Another star in this cluster, known as S2, is better known and much larger than S4716.

However, S2’s orbit around the black hole takes 16 years and is close to 11 billion miles (18 billion km) from Sgr A*. In comparison, S4716 comes as close as 9.2 billion miles (150 million km) to the black hole, that’s about 100 times the distance between Earth and the Sun.

The discovery of a star so close to a black hole could change our understanding of the evolution of our galaxy and its fast-moving stars. “S4716’s short, dense orbit is quite puzzling,” said Michael Zajaček, an astrophysicist at Masaryk University in a study. statement. “Star cannot form easily near black holes. S4716 must move inward, for example by approaching stars and other objects in the S cluster, causing its orbit to shrink significantly.”

How do astronomers spot the fastest stars?

While S2 has helped us understand in more detail about Sgr A*, Sgr A* has its drawbacks. “The S2 behaves like the big guy sitting across from you in the cinema — it blocks your view of what’s important. The view of the center of our galaxy is therefore often obscured by S2,” said Florian Peissker, an astrophysicist at the University of Cologne, who was involved in the research, said in a statement.

Peissker and his team used data from five telescopes, NIR2 and OSIRIS, at the Keck Observatory in Hawaii, and the SINFONI, NACO, and GRAVITY Very Large Telescopes and refined their analytical techniques over more than two decades to confirm S4716’s orbital period. “For a star to be in a stable orbit so close and fast around a supermassive black hole is completely unexpected,” Peissker added.

This research was published in Astrophysics Journal.

Abstract

Continuous monitoring of the center of the Galaxy and Sgr A*, the central supermassive black hole, yielded surprising and unexpected findings. This is in line with the technical evolution of ground and space-based telescopes and instruments, but also with the development of image filtering techniques such as the Lucy–Richardson algorithm. As we continue to track members of the S cluster close to Sgr A* on the expected trajectory around the supermassive black hole, we present the discovery of a new stellar source, which we call S4716. The newly discovered star orbits Sgr A* in about 4.0 years and can be detected with NIRC2 (Keck), OSIRIS (Keck), SINFONI (VLT), NACO (VLT), and GRAVITY (VLTI). With a periapse distance of about 100 au, S4716 exhibits an equivalent distance to Sgr A* as S4711. These fast-moving stars undergo similar dynamic evolution, as S4711–S4716 has comparable orbital properties. We will next draw the connection between the recent findings of a new faint star called S300 and the data presented here. In addition, we observed a mixed stellar event with S4716 and another newly identified S star S148 in 2017

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