SDSS J090745.0+024507

SDSS J090745.0+024507

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Hydra
Right ascension	09h 07m 44.99 s
Declination	+02° 45′ 06.9″
Spectral type	B9
Other designations
SDSS J090744.99+024506.8

SDSS J090744.99+024506.8 (SDSS 090745.0+024507), is a star that is leaving the Milky Way galaxy at twice the galactic escape velocity (0.002 the speed of light). Christened by the astronomer Warren Brown as the Outcast Star, it is the first of a class of objects named hypervelocity stars, and as of 2005 is the fastest yet detected.^[1]

It was discovered at the MMT Observatory of the Harvard-Smithsonian Center for Astrophysics (CfA), by astronomers Warren Brown, Margaret J. Geller, Scott J. Kenyon and Michael J. Kurtz.^[2]

Scientists theorize that the star was ejected out of a binary star system approximately 80 million years ago when it encountered a black hole in the center of the Milky Way galaxy.^{[citation needed]}

The star is about 80 million years old, and as it contains many elements heavier than hydrogen and helium, having formed in the evolved star-forming regions of the galactic core, is considered metal-rich. It is moving directly away from the galactic center at over 1,500,000 miles per hour (2,400,000 km/h), twice as fast as the Milky Way's galactic escape velocity. Eventually the star will be ejected from the galaxy completely.

This scenario was proposed by astronomer Jack G. Hills in 1988, as a possibility for stars encountering a massive black hole.^[3]

References

1. ^ Berardelli, Phil (February 10, 2005), "In The Stars: Odd Stars, Odder Planets", Space Daily, http://www.spacedaily.com/news/extrasolar-05h.html 
2. ^ Brown, Warren R.; Geller, Margaret J.; Kenyon, Scott J. & Kurtz, Michael J. (2005), "Discovery of an Unbound Hypervelocity Star in the Milky Way Halo", Astrophysical Journal 622 (1): L33–L36, arXiv:astro-ph/0501177, Bibcode 2005ApJ...622L..33B, doi:10.1086/429378 
3. ^ Hills, J. G. (1988), "Hyper-velocity and tidal stars from binaries disrupted by a massive Galactic black hole", Nature 331 (6158): 687–689, Bibcode 1988Natur.331..687H, doi:10.1038/331687a0 

Further reading

• Gualandris, Alessia; Portegies Zwart, Simon & Sipior, Michael S. (2005), "Three-body encounters in the Galactic Centre: the origin of the hypervelocity star SDSS J090745.0+024507", Monthly Notices of the Royal Astronomical Society 363 (1): 223–228, arXiv:astro-ph/0507365, Bibcode 2005MNRAS.363..223G, doi:10.1111/j.1365-2966.2005.09433.x 
• Brown, Warren R.; Geller, Margaret J.; Kenyon, Scott J. & Kurtz, Michael J. (2006), "A Successful Targeted Search for Hypervelocity Stars", Astrophysical Journal 640 (1): L35–L38, arXiv:astro-ph/0601580, Bibcode 2006ApJ...640L..35B, doi:10.1086/503279 
• Fuentes, Cesar I.; Stanek, K. Z.; Gaudi, B. Scott; et al. (2006), "The Hypervelocity Star SDSS J090745.0+024507 Is Variable", Astrophysical Journal 636 (1): L37–L40, arXiv:astro-ph/0507520, Bibcode 2006ApJ...636L..37F, doi:10.1086/499233 
• Bromley, Benjamin C.; Kenyon, Scott J.; Geller, Margaret J.; et al. (2006), "Hypervelocity Stars: Predicting the Spectrum of Ejection Velocities", Astrophysical Journal 653 (2): 1194–1202, arXiv:astro-ph/0608159, Bibcode 2006ApJ...653.1194B, doi:10.1086/508419 

External links

• Press release
• First Stellar Outcast Speeding at Over 1.5 Million Miles Per Hour (PhysOrg.com)