US 708
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Star US 708 |
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| AladinLite | |||
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Observation dates equinox : J2000.0 , epoch : J2000.0 |
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| Constellation | Big Bear | ||
| Right ascension | 09 h 33 m 20.86 s | ||
| declination | + 44 ° 17 ′ 5.5 ″ | ||
| Apparent brightness | 18.8 mag | ||
| Typing | |||
| B − V color index | −0.3 | ||
| Spectral class | sdOHe | ||
| Astrometry | |||
| Radial velocity | (708 ± 15) km / s | ||
| distance | (60300 ± 8500) Lj (18500 ± 2600) pc |
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| Proper movement | |||
| Rec. Share: | (−5.36 ± 0.39) mas / a | ||
| Dec. portion: | (+1.29 ± 0.38) mas / a | ||
| Physical Properties | |||
| Effective temperature | (44600 ± 700) K. | ||
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Other names and catalog entries |
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US 708 or HVS 2 is a star from the rare group of hyper-speed runners , i.e. an object that moves faster than the escape speed of the Milky Way , and which therefore flies out of it without its gravity being able to prevent it. With a speed of about 1200 km per second, it was the fastest known unbound star in the Milky Way in March 2015. Seen from Earth, it is located in the constellation Great Bear .
In contrast to most other known hyper-fast runners, US 708 is not a main sequence star , but a hot sub-dwarf . In addition, it probably did not get its high speed from a close encounter with the supermassive black hole in the center of the Milky Way , but from the supernova explosion of a nearby companion .
The star was recorded, among others, in a specialist article published by Usher, Mattson and Warnock in the ApJS in 1982 on low-luminosity stars with a high UV excess. It was then cataloged by the Sloan Digital Sky Survey as SDSS J093320.86 + 441705.4 . In 2008 it was classified as HVS because at that time a speed of 751 km / s was observed relative to the Milky Way. In 2015, a speed of 1157 km / s and a rotation speed of 115 km / s were observed. This would make US 708 the fastest known, non-gravitationally bound star in the Milky Way and also the star with the fastest rotation.
Individual evidence
- ↑ a b c d e US 708. In: SIMBAD . Center de Données astronomiques de Strasbourg , accessed on November 3, 2018 .
- ^ A b c Warren R. Brown, Jay Anderson, Oleg Y. Gnedin, Howard E. Bond, Margaret J. Geller, Scott J. Kenyon: Proper Motions and Trajectories for 16 Extreme Runaway and Hypervelocity Stars . In: The Astrophysical Journal . 804, 2015, p. 49. arxiv : 1502.05069 . bibcode : 2015ApJ ... 804 ... 49B . doi : 10.1088 / 0004-637X / 804/1/49 .
- ^ Stephan Geier et al .: The fastest unbound star in our Galaxy ejected by a thermonuclear supernova. In: Science , March 2015 ( abstract )
- ^ HA Hirsch, U. Heber, SJ O'Toole, F. Bresolin: US 708 - An unbound hyper-velocity subluminous O star . February 5, 2008, arxiv : astro-ph / 0511323 (English).
- ^ S. Geier, F. Fürst, E. Ziegerer, T. Kupfer, U. Heber, A. Irrgang, B. Wang, Z. Liu, Z. Han, B. Sesar, D. Levitan, R. Kotak, E Magnier, K. Smith, WS Burgett, K. Chambers, H. Flewelling, N. Kaiser, R. Wainscoat, C. Waters: The fastest unbound star in our Galaxy ejected by a thermonuclear supernova . March 5, 2015, arxiv : 1503.01650 (English).