{"id":1116380,"date":"2026-07-28T16:19:22","date_gmt":"2026-07-28T16:19:22","guid":{"rendered":"https:\/\/www.europesays.com\/uk\/1116380\/"},"modified":"2026-07-28T16:19:22","modified_gmt":"2026-07-28T16:19:22","slug":"this-star-is-racing-around-the-milky-ways-black-hole-at-8-the-speed-of-light","status":"publish","type":"post","link":"https:\/\/www.europesays.com\/uk\/1116380\/","title":{"rendered":"This Star Is Racing Around the Milky Way\u2019s Black Hole at 8% the Speed of Light"},"content":{"rendered":"

\"Illustration<\/a>Illustration of a sunlike star passing very close to a supermassive black hole. Credit: ESO, ESA\/Hubble, M. Kornmesser<\/p>\n

A fast-moving star near the Milky Way\u2019s central black hole could test gravity under unusually extreme conditions.<\/strong><\/p>\n

General relativity provides a remarkably precise description of gravity, but most everyday calculations do not require it. Newton\u2019s law of universal gravitation is accurate enough to guide spacecraft across the solar system and describe the motion of most stars circling Sag A*, the supermassive black hole at the Milky Way\u2019s center.<\/p>\n

Einstein\u2019s theory predicts effects that Newton\u2019s does not, including gravitational waves, yet the two models produce nearly identical results in many situations. Distinguishing general relativity from other relativistic theories of gravity is even harder because their predictions differ only under extreme conditions. A recently identified star may offer a rare opportunity to test those boundaries.<\/p>\n

A star enters gravity\u2019s extreme regime<\/p>\n

The star is called S301 because it is the 301st recognized member of the S-stars, a group that orbits Sag A*. Slightly more massive than the Sun, S301 completes one orbit every 8.7 years, the shortest period known for any S-star, and follows a highly elongated path.<\/p>\n

At its closest point, it passes within roughly 140 Sag A* radii, equivalent to about 24 AU. If Sag A* replaced the Sun, its event horizon would lie just inside Mercury\u2019s orbit, while S301 at its nearest approach would travel between the orbits of Uranus and Neptune. At that point, the star would reach more than 8% of the speed of light.<\/p>\n

Its orbit magnifies relativistic effects<\/p>\n

This makes S301 the most relativistic star we have observed. It will allow us to test some of the limits of general relativity. For example, we have already observed that the orbit of S301 precesses. We\u2019ve observed orbital precession in the motion of Mercury.<\/p>\n

It was one of the classic tests<\/a> of GR. But the precession of Mercury is tiny. The difference in motion between Einstein\u2019s prediction and Newton\u2019s is less than the span of a human heartbeat<\/a> with each orbit. For S301, its perihelion advances about 2\u00b0 with each orbit.<\/p>\n

\"Observed<\/a>The observed orbit of the star S301. Credit: Dayem, et al.<\/p>\n

This motion is so extreme that secondary relativistic effects come into play. For example, gravitational redshift<\/a> and the transverse Doppler effect.<\/a> We\u2019ve observed these effects in the lab, but S301 gives us a chance to study them in nature. But more significantly, in time we can use S301 to study alternatives to general relativity.<\/p>\n

Future telescopes could test deeper theories<\/p>\n

One of the big difficulties with GR is that it doesn\u2019t play well with quantum theory. There are several models that try to unify the two, but they only differ from GR in extreme cases. Some of these differences might be seen at relativistic speeds, since the effects are at the order of (v\/c)2 or (v\/c)3.<\/p>\n

The effects of the black hole\u2019s spin and its interaction with the rotation of the star also come into play on these orders of magnitude. Future large telescopes such as the Giant Magellan Telescope (GMT) will be able to observe the spectra of S301 with enough precision to measure second- and third-order effects.<\/p>\n

For now, however, observing S301 remains a challenge. The center of our galaxy is veiled in cloud and dust,<\/a> meaning we can\u2019t observe it in optical light. Since S301 is a Sun-like star, it isn\u2019t particularly bright, even in the infrared. We can observe its motion, but we can\u2019t yet gather any significant spectral data.<\/p>\n

But as with all things relativity, it\u2019s only a matter of time.<\/p>\n

Reference: \u201cDiscovery of a star sensitive to the spin of Sgr A*\u201d by K. Abd El Dayem, R. Abuter, N. Aimar, P. Amaro-Seoane, A. Berdeu, J. -P. Berger, G. Bourdarot, W. Brandner, A. Burkert, D. Calderon, C. Correia, J. Cuadra, R. Davies, D. Defrere, L. Delit, A. Drescher, F. Eisenhauer, L. Esteras Otal, M. Fabricius, H. Feuchtgruber, N. M. Foerster Schreiber, A. Foschi, P. Garcia, R. Garcia Lopez, A. Generozov, R. Genzel, S. Gillessen, F. Gonte, X. Haubois, S. F. Hoenig, M. Houlle, S. Joharle, A. Kaufer, J. Kammerer, P. Kervella, J. Kolb, L. Kreidberg, L. Labadie, S. Lacour, O. Lai, R. Laugier, J. -B. Le Bouquin, J. Leftley, B. Lopez, D. Lutz, F. Mang, A. Merand, F. Millour, M. Montarges, N. Morujao, H. Nowacki, M. Nowak, S. Oberti, J. Osorno, T. Ott, T. Paumard, C. Paladini, H. B. Perets, K. Perraut, G. Perrin, R. Petrov, P. O. Petrucci, T. Piran, N. Pourre, S. Rabien, D. C. Ribeiro, S. Robbe-Dubois, M. Sadun Bordoni, J. Sanchez Bermudez, D. Santos, R. Sari, J. Sauter, S. Scheithauer, J. Scigliuto, J. Shangguan, T. T. Shimizu, F. Soulez, J. Stadler, C. Straubmeier, E. Sturm, M. Subroweit, C. Sykes, L. J. Tacconi, P. Thevenet, I. Urso, F. Vincent, J. Woillez and G. Zins, July 13, 2026, arXiv.
DOI: 2607.12664<\/a><\/p>\n

Adapted from an article originally published in UniverseToday<\/a>.<\/p>\n

Never miss a breakthrough: Join the SciTechDaily newsletter.<\/a><\/b>
Follow us on Google<\/a> and Google News<\/a>.<\/b><\/p>\n","protected":false},"excerpt":{"rendered":"Illustration of a sunlike star passing very close to a supermassive black hole. Credit: ESO, ESA\/Hubble, M. Kornmesser…\n","protected":false},"author":2,"featured_media":1116381,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_share_on_mastodon":"0"},"categories":[3845],"tags":[901,5632,7021,46122,65178,74,70,16,15],"class_list":["post-1116380","post","type-post","status-publish","format-standard","has-post-thumbnail","category-physics","tag-astronomy","tag-astrophysics","tag-black-hole","tag-general-relativity","tag-milky-way","tag-physics","tag-science","tag-uk","tag-united-kingdom"],"share_on_mastodon":{"url":"https:\/\/pubeurope.com\/@uk\/116998517965325067","error":""},"_links":{"self":[{"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/posts\/1116380","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/comments?post=1116380"}],"version-history":[{"count":0,"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/posts\/1116380\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/media\/1116381"}],"wp:attachment":[{"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/media?parent=1116380"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/categories?post=1116380"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/tags?post=1116380"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}