Fastest known star speeds around Milky Way's black hole at 18 million mph

This article says

"During this rapid orbit of Sagittarius A*, which has an estimated diameter of 14.6 million miles (23.5 million kilometers), S4716 comes as close as 92 million miles (150 million km) to the supermassive black hole."

and

"While this may seem incredibly distant, it is just 100 times the distance between Earth and the sun, which is a relatively small distance in cosmic terms. "

Isn't the distance from the Earth to our Sun 93 million miles? What is this "100 times the distance between Earth and the sun" really talking about?
 
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rod

Oct 22, 2019
2,640
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Looks like a typo :)

Reference paper Observation of S4716—a Star with a 4 yr Orbit around Sgr A*, https://iopscience.iop.org/article/10.3847/1538-4357/ac752f, 05-July-2022. "Abstract The ongoing monitoring of the Galactic center and Sgr A*, the central supermassive black hole, produces surprising and unexpected findings. This goes hand in hand with the technical evolution of ground- and space-based telescopes and instruments, but also with the progression of image filter techniques such as the Lucy–Richardson algorithm. As we continue to trace the members of the S cluster close to Sgr A* on their expected trajectory around the supermassive black hole, we present the finding of a new stellar source, which we call S4716. The newly found star orbits Sgr A* in about 4.0 yr 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 shows an equivalent distance toward Sgr A* as S4711. These fast-moving stars undergo a similar dynamical evolution, since S4711–S4716 share comparable orbital properties. We will furthermore draw a connection between the recent finding of a new faint star called S300 and the data presented here. Additionally, we observed a blend-star event with S4716 and another newly identified S star S148 in 2017."

My observation, from the paper. "Moreover, Stephan et al. (2016) inferred a binary fraction of ∼ 70% for the stellar population of the most recent star formation episode in the nuclear star cluster ∼6 Myr ago (see, e.g., Lu et al. 2013)." "For S4716, we derive an orbital period of only 4 yr. With a distance of about 12 mas during its periapse, S4716 has the shortest known orbital period around an SMBH to date."...Here we incorporate both results because the averaged distance of the MCMC statistics for the S4716 orbit gives 8.028 ± 0.199 kpc or, alternatively, 8.028 kpc ± 2%."

My note, using 12 mas angular size and distance 8.028 kpc, I calculate using my spreadsheet 9.6336E+01 AU or 96.336 AU for distance from Sgr A* or very close to the 100 AU used in the paper. These folks are using better telescopes than I have :) If I can split double stars near 1.5 arcsecond or 1500 mas, I am happy :)

8,000 kilometers per second: Star with the shortest orbital period around black hole discovered, https://phys.org/news/2022-07-kilometers-star-shortest-orbital-period.html

My observation. Some comments in this report I note that show surprise, suggesting the fast orbiting star may not be stable over millions of years and very difficult to explain its origin near SgR A*. "By means of continuously refining methods of analysis, together with observations covering almost twenty years, the scientist now identified without a doubt a star that travels around the central supermassive black hole in just four years. A total of five telescopes observed the star, with four of these five being combined into one large telescope to allow even more accurate and 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 marks the limit that can be observed with traditional telescopes," said Peissker. Moreover, the discovery sheds new light on the origin and evolution of the orbit of fast-moving stars in the heart of the Milky Way. "The short-period, compact orbit of S4716 is quite puzzling," Michael Zajaček, an astrophysicist at Masaryk University in Brno who was involved in the study, said. "Stars cannot form so easily near the black hole. S4716 had to move inwards, for example by approaching other stars and objects in the S cluster, which caused its orbit to shrink significantly."
 
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The picture in the journal article that Rod posted shows the orbits of the close-in stars:
Intersesting that the periapses of several of those stars seem to be at the same point in space. Is that where some encounter took place that slung several stars from their more circular orbits?
 

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