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Star discovered with the shortest orbital period around a black hole

8000 Kilometer pro Sekunde: Stern mit der kürzesten Umlaufzeit um Schwarzes Loch entdeckt

The K-band view of the GC observed with NIRC2 (Keck) in 2019.30. This image is high-pass filtered and shows the position of several S stars near Sgr A*, indicated by a black cross. The star in the white dashed circle shows a K-band magnitude of 16.3 mag, while the star in the blue circle is faint at 17.0 mag. Both K-band sizes agree with the values ​​reported for S62 by Peißker et al. match. (2020a) and those for S29 by Gillessen et al. (2017) and Peißker et al. (2021b). Here north is up and east is to the left. Recognition: The Astrophysical Journal (2022). DOI: 10.3847/1538-4357/ac752f

Researchers from the University of Cologne and Masaryk University in Brno (Czech Republic) have discovered the fastest known star to orbit a black hole in record time. The star S4716 orbits Sagittarius A*, the black hole at the center of our Milky Way, in four years, reaching a speed of around 8,000 kilometers per second. S4716 comes as close as 100 AU (astronomical units) to the black hole — a small distance by astronomical standards. One AU corresponds to 149,597,870 kilometers. The study was published in The Astrophysical Journal.

A tightly packed star cluster resides near the black hole at the center of our galaxy. This cluster, called the S cluster, is home to well over a hundred stars that vary in brightness and mass. S stars move particularly fast. “A celebrity member, S2, behaves like a tall person sitting in front of you in a movie theater: it blocks your view of what’s important,” says Dr. Florian Peißker, first 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.”

Through increasingly refined analysis methods and observations over almost twenty years, the scientist has now unequivocally identified a star that migrates around the central supermassive black hole in just four years. A total of five telescopes observed the star, with four of those five being combined into one large telescope for even more accurate and detailed observations. “For a star in a stable orbit to be so close and fast to a supermassive black hole was completely unexpected and marks the limit that can be observed with conventional telescopes,” Peissker said.

In addition, the discovery sheds new light on the origin and evolution of the orbits of fast-moving stars at the heart of the Milky Way. “S4716’s brief, compact orbit is quite puzzling,” said Michael Zajaček, an astrophysicist at Masaryk University in Brno who was involved in the study. “Stars cannot form so easily near the black hole. S4716 had to move inward, for example by getting closer to other stars and objects in the S cluster, causing its orbit to shrink significantly.”

The fastest star ever observed

More information:
Florian Peißker et al, Observation of S4716 – a Star with a 4 yr orbit around Sgr A*, The Astrophysical Journal (2022). DOI: 10.3847/1538-4357/ac752f

Provided by the University of Cologne

Citation: 8,000 kilometers per second: Star with shortest orbital period around black hole discovered (2022, July 5), retrieved July 6, 2022 from https://phys.org/news/2022-07-kilometers-star-shortest- orbital-period .html

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