An illustration of a star traveling around a black hole. Depositphotos.

Star at the Heart of the Milky Way Orbits a Black Hole at 8,000km/s

It takes the star dubbed S4716 to orbit the massive black hole at the center of the Milky Way Galaxy, Sagittarius A*, only four years. This means it travels at a staggering speed of 8,000 kilometers per second (or 4970.97 miles per second).

According to a research paper published in The Astrophysical Journal, a newly discovered star travels around our galaxy’s black hole at a staggering speed of 8,000 kilometers per second (or 4970.97 miles per second). In other words, it takes four years to orbit the supermassive black hole.

A team of researchers from the University of Cologne and Masaryk University in Brno (Czech Republic) has uncovered the fastest star ever discovered, which takes record time to orbit a black hole.

At 8000 kilometers per second, in four years, S4716 orbits Sagittarius A*, the black hole at the center of our Milky Way. As far as astronomical standards are concerned, S4716 comes within 100 AU (astronomical units) of the black hole. A distance of one AU is 149,597,870 km. A study published in The Astrophysical Journal describes the results of the study.

A dense cluster of stars

There is a dense cluster of stars near the black hole at the center of our galaxy. There are more than a hundred stars in this cluster, known as the S cluster, which varies in brightness and mass. The movement of S stars is particularly rapid. But there is one that seems to stand out from the rest.

“One prominent member, S2, behaves like a large person sitting in front of you in a movie theatre: it blocks your view of what’s relevant,” explained Dr. Florian Peissker, lead author of the new study.

“The view into the center of our galaxy is therefore often obscured by S2. However, in brief moments we can observe the surroundings of the central black hole,” Dr. Peissker revealed.

Observations spanning almost two decades and continuously refining methods of analysis allowed the scientist to confirm that the star is traveling around the supermassive black hole in a mere four years.

Observation of S4716 in 2020 with OSIRIS. Image Credit: University of Cologne.
Observation of S4716 in 2020 with OSIRIS. Image Credit: University of Cologne.

A combination of telescopes

Five telescopes were used to observe the star, with four of those telescopes combined into one large telescope to make even more detailed observations.

“For a star to be in a stable orbit so close and fast in the vicinity of a supermassive black hole was completely unexpected and marked the limit that can be observed with traditional telescopes,” explained Peissker.

A new understanding of how fast-moving stars orbit the Milky Way is also revealed as a result of the discovery.

And according to Michael Zajaček, a scientist at Masaryk University in Brno, S4716’s short period and compact orbit are quite puzzling.

“Stars cannot form so easily near the black hole. So S4716 had to move inwards by approaching other stars and objects in the S cluster, which caused its orbit to shrink significantly,” he added.

Sagittarius A*

Sgr A* is one of only a few black holes in the universe where we can witness the flow of matter within its vicinity, at just 26,000 light-years away.

Our Milky Way galaxy’s Black Hole, located at its very center and dubbed Sagittarius A*, is located in the direction of the Sagittarius constellation. Check out this for the first-ever photograph of the Black hole at the center of our galaxy.

Black holes are measured by their event horizons, the distance from their centers beyond which nothing can escape. The diameter of Sagittarius A* was previously estimated to be 16 million miles (26 million kilometers).

As compared to black holes created when massive stars die, the Milky Way’s black hole is huge. Almost all galaxies are believed to have supermassive black holes at their centers. The size and significance of Sagittarius A* seem meager compared to most of these. In addition, scientists also believe that there are “free-floating” black holes that can travel through space.


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Written by Ivan Petricevic

I've been writing passionately about ancient civilizations, history, alien life, and various other subjects for more than eight years. You may have seen me appear on Discovery Channel's What On Earth series, History Channel's Ancient Aliens, and Gaia's Ancient Civilizations among others.

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