Earth Sky | Whooshing sound! Fast star orbiting the Milky Way's black hole

This image shows the center of our Milky Way galaxy. It shows the position of stars in the so-called S star cluster, a small group of high-speed stars orbiting our Milky Way’s central black hole (at the black cross). Speedy star S4716 has set a new record as the fastest known of all these stars. Image via Peissker et al.

Fast star orbiting the Milky Way’s black hole

Scientists in Europe said on July 5, 2022 that they had found the fastest star known to orbit a black hole. And not just any black hole… it orbits Sagittarius A*, the giant black hole at the center of our Milky Way galaxy. Our central black hole weighs about 4 million times the mass of our sun. The newly discovered star is called S4716. It reaches an orbital speed of 5,000 miles per second (8,000 kps) around the black hole, or about 5,000 times faster than the fastest fighter jet.

Imagine seeing star – a huge ball of turbulent gas that glows on its own – shooting at this speed! By the way, on the other hand, our Earth is moving at 18 miles per second (about 30 kps) around our sun.

The scientists who made this discovery are at the University of Cologne and Masaryk University in Brno (Czech Republic). Their work is published in peer-review Astrophysics Journal.

When you look at this image, you’re looking toward the center of our Milky Way galaxy, toward the supermassive black hole called Sagittarius A*. Image via Chandra X-ray Observatory.

Our earth takes one year to orbit our sun once. And S4716 takes four years to once circle the black hole. Consider that the Earth is one astronomical unit from the sun: it is about 90 million miles (about 150 million km). S4716 is about 100 times the Earth-Sun distance to the black hole (100 astronomical units). That’s a small distance by astronomical standards.

A statement from these scientists explains:

Around the black hole at the center of our galaxy is a dense cluster of stars. This cluster, called the S cluster, is home to more than a hundred stars that differ in brightness and mass. Star S moves very fast…

Florian Peisker of Masaryk University led the research and explained:

One prominent member, 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. But, in a short time, we can observe around the center of the black hole.

These scientists used a total of five telescopes to observe the star, with four of the five combined into one large telescope, “to allow for more accurate and detailed observations,” the scientists said. They say their discovery sheds light on the origin and evolution of the orbit of the fast-moving star at the heart of the Milky Way.

Michael Zajaek of Masaryk University in Brno was also involved in the research. He says:

‘S4716’s short and dense orbit is quite confusing. Stars do not 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.’

Peissker added:

A star being in a stable orbit so close and fast around a supermassive black hole is completely unexpected and marks the limit that can be observed with traditional telescopes.

Bottom line: The newly discovered fast star S4716 is the fastest star known to orbit our Milky Way’s central black hole.

Source: Observation S4716: Star with a 4-year orbit around Sgr A*

Through the University of Cologne

Deborah Byrd

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About the Author:

Deborah Byrd created the radio series EarthSky in 1991 and founded EarthSky.org in 1994. She is currently the Editor-in-Chief of this website. He has won numerous awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in his honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. “Being an EarthSky editor is like throwing a big global party for cool nature lovers,” he says.

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