SDSS J090745.0+024507

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**SDSS J090745.0+024507**
Observation data Equinox J2000.0 (ICRS)
Constellation	Hydra
Right ascension	09^h 07^m 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). This is the fastest moving star so far detected (as of 2005). This is the first of a class of objects named hypervelocity stars. Warren Brown of the Harvard-Smithsonian center has called it "the Outcast Star". ^[1]

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.

The star is about 80 million years old, and is metal-rich (i.e., contains many elements heavier than hydrogen and helium), having formed in the evolved star-forming regions of the galactic core. The star is moving directly away from the galactic center. It is travelling at over 1,500,000 mph (420 miles, or 670 kilometers per second), which is twice as fast as the Milky Way's galactic escape velocity; therefore, the Milky Way's gravity will never be able to hold it. In the end, the star will never return to our galaxy.

This star 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.

The ejection scenario was proposed by astronomer Jack Hills in 1998, as a possibility for stars encountering a massive black hole.

[edit] External links

Press release
First Stellar Outcast Speeding at Over 1.5 Million Miles Per Hour (PhysOrg.com)
Discovery of an Unbound Hypervelocity Star in the Milky Way Halo, Warren R. Brown, Margaret J. Geller, Scott J. Kenyon, and Michael J. Kurtz, Astrophysical Journal 622 (March 2005), pp. L33–L36.
Three-body encounters in the Galactic Centre: the origin of the hypervelocity star SDSS J090745.0+024507, Alessia Gualandris, Simon Portegies Zwart, and Michael S. Sipior, Monthly Notices of the Royal Astronomical Society 363 (October 2005), pp. 223–228.
A Successful Targeted Search for Hypervelocity Stars, Warren R. Brown, Margaret J. Geller, Scott J. Kenyon, and Michael J. Kurtz, Astrophysical Journal 640 (March 2006), pp. L35–L38.
The Hypervelocity Star SDSS J090745.0+024507 Is Variable, Cesar I. Fuentes, K. Z. Stanek, B. Scott Gaudi, Brian A. McLeod, Slavko Bogdanov, Joel D. Hartman, Ryan C. Hickox, and Matthew J. Holman, Astrophysical Journal 636 (January 2006), pp. L37–L40.
Hypervelocity Stars: Predicting the Spectrum of Ejection Velocities, Benjamin C. Bromley, Scott J. Kenyon, Margaret J. Geller, Elliott Barcikowski, Warren R. Brown, and Michael J. Kurtz, Astrophysical Journal 653 (December 2006), pp. 1194–1202.