HE0107-5240

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**HE0107-5240**
Observation data Epoch J2000.0 (ICRS)
Constellation (pronunciation)	Phoenix
Right ascension	01^h 09^m 29.1^s^[1]
Declination	-52° 24′ 20″
Astrometry
Spectral type	K5+III/dM2 V
Apparent magnitude (V)	15.86
Distance	36.000 Ly
Details
Mass	0.8 M_☉
Radius	? R_☉
Luminosity	? L_☉
Temperature	? K
Metallicity	?
Rotation	?
Age	13.6 billion years
Other designations
HE 0107-5240, 2MASS J01092916-5224341.

HE0107-5240 is a newly discovered giant star roughly 36,000 light years away from Earth and 80% the mass of the Sun.

It is largely metal-free, having just 1/200,000 of the metal that the Sun has. It is one of the oldest stars yet found and is thought to be nearly 13 billion years old, having formed shortly after the Big Bang. This means it was one of first population II stars. Because the star has tiny amounts of heavier elements, it does not belong to the first generation of stars (the hypothetical population III). These stars converted the pristine hydrogen, helium, and lithium formed by the Big Bang into heavier elements, such as carbon, oxygen, and metals.

Its metallicity [Fe/H] = -5.4 +/- 0.2.

The star is relatively small for a star of the early universe, which accounts for its old age: massive stars die quickly. To help explain why this star is so small, it is hypothesized it was once part of a binary star system.

HE0107-5240 was found by Norbert Christlieb and colleagues at the University of Hamburg in Germany as a byproduct of the Hamburg/ESO Survey for faint quasars with the 1m ESO Schmidt telescope. Follow up observations were made at the Siding Spring Observatory 2.3m telescope and high-resolution spectra were taken at the European Southern Observatory in Chile, using one of the units of the Very Large Telescope.

[edit] See also

HE1327-2326

[edit] References

^ The Optical Gravitational Lensing Experiment. Additional Planetary and Low-Luminosity Object Transits from the OGLE 2001 and 2002 Observational Campaigns, A. Udalski, G. Pietrzynski, M. Szymanski, M. Kubiak, K. Zebrun, I. Soszynski, O. Szewczyk, and L. Wyrzykowski, Acta Astronomica 53 (June 2003), pp. 133–149.

CHRISTLIEB N., BESSELL M.S., GUSTAFSSON B., KORN A., BARKLEM P.S., KARISSON T., MIZUNO-WIEDNER M., ROSSI S., A stellar relic from the early Milky Way, Nature, 419, 904-906 (2002)