Editing HE 0107−5240

{{Short description|Extremely metal poor star in the constellation Phoenix}}
{{Starbox begin}}
{{Starbox image
|image=[[File:Eso0228a.jpg|250px]]
|caption= The ultra-metal-poor star HE0107−5240
}}
{{Starbox observe
| epoch=[[J2000.0]] ([[International Celestial Reference System|ICRS]])
| constell=[[Phoenix (constellation)|Phoenix]]
| ra={{RA|01|09|29.1}}<ref name="aa">{{cite journal|bibcode=2003AcA....53..133U |title=The Optical Gravitational Lensing Experiment. Additional Planetary and Low-Luminosity Object Transits from the OGLE 2001 and 2002 Observational Campaigns |author1=A. Udalski |author2=G. Pietrzynski |author3=M. Szymanski |author4=M. Kubiak |author5=K. Zebrun |author6=I. Soszynski |author7=O. Szewczyk |author8=L. Wyrzykowski |journal=Acta Astronomica |volume=53 |date=June 2003 |pages=133–149|arxiv = astro-ph/0306444 }}</ref>
| dec={{DEC|-52|24|20}}
| appmag_v=15.86 
}}
{{Starbox astrometry
| prop_mo_ra = +2.357<ref name=dr3/>
| prop_mo_dec = −3.826<ref name=dr3/>
| parallax = 0.1064
| p_error = 0.0195
| parallax_footnote = <ref name=dr3>{{cite Gaia DR3|4927204800008334464}}</ref>
| dist_ly={{val|36000}}
}}
{{Starbox detail
| mass=1.789<ref name=dr3/>
| radius= 3.7<ref name=dr3/>
| luminosity= 14<ref name=dr3/>
| temperature= 5,765<ref name=dr3/>
| metal_fe = −5.3 <ref name=sp1/>
| rotation=
}}
{{Starbox catalog
| names=[[Hamburg/ESO Survey|HE]] 0107−5240, [[2MASS]] J01092916-5224341. }}
{{Starbox reference
| Simbad = HE+0107-5240
}}
{{Starbox end}}

'''HE0107−5240''' is an extremely [[metal (astronomy)|metal]]-poor [[metallicity#Stars|Population II]] star, located roughly {{val|36000|u=[[light-year]]s}} away from Earth. It is one of the most metal-poor stars known in our Galaxy, with a [[metallicity]] [Fe/H] = {{val|-5.2|0.2}};<ref name="sp1">{{cite journal |bibcode=2004ApJ...603..708C |title=HE 0107-5240, a Chemically Ancient Star. I. A Detailed Abundance Analysis |last1=Christlieb |first1=N. |last2=Gustafsson |first2=B. |last3=Korn |first3=A. J. |last4=Barklem |first4=P. S. |last5=Beers |first5=T. C. |last6=Bessell |first6=M. S. |last7=Karlsson |first7=T. |last8=Mizuno-Wiedner |first8=M. |journal=The Astrophysical Journal |year=2004 |volume=603 |issue=2 |page=708 |doi=10.1086/381237 |arxiv=astro-ph/0311173 |s2cid=7110470 }}</ref> i.e. it has just {{sfrac|{{val|160000}}}} of the metal that the Sun has. Because of its very low metallicity, it is believed to be one of the earliest Population II stars to have formed. If so, then it is also very old, with an age of roughly 13 billion years. Because the star is not completely metal-free, it does not belong to the first generation of stars (the hypothetical [[Population III star|Population III]]). These stars converted the pristine [[hydrogen]], [[helium]], and [[lithium]] formed by the Big Bang into heavier elements, such as [[carbon]], [[oxygen]], and [[metal]]s.

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]].<ref name="bb">{{cite journal|bibcode=2007MNRAS.378..563L |title=Carbon-rich extremely metal poor stars: signatures of Population III asymptotic giant branch stars in binary systems |author1=Lau, Herbert H. B. |author2=Stancliffe, Richard J. |author3=Tout, Christopher A. |date=2007 |journal=MNRAS |volume=378 |issue=2 |pages=563–568|arxiv = astro-ph/0703685 |doi = 10.1111/j.1365-2966.2007.11773.x |doi-access=free |s2cid=14996538 }}</ref>
<ref name="cc">{{cite journal|bibcode=2004ApJ...611..476S |title=Is HE 0107-5240 A Primordial Star? The Characteristics of Extremely Metal-Poor Carbon-Rich Stars |author1=Suda, Takuma |author2=Aikawa, Masayuki |author3=Machida, Masahiro N. |author4=Fujimoto, Masayuki Y. |author5=Iben, Icko Jr. |date=2004 |journal=Astrophysical Journal |volume=611 |issue=1 |pages=476–493 |arxiv = astro-ph/0402589 |doi = 10.1086/422135 |s2cid=13040221 }}</ref>

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 2.3 m Telescope]] and high-resolution spectra were taken at the [[European Southern Observatory]] in [[Chile]], using one of the units of the [[Very Large Telescope]]. In 2005, a second star with an even smaller iron abundance, [[HE 1327-2326]] ([Fe/H]=-5.4), was found, also in the Hamburg/ESO survey. In 2014 an even more metal poor star was announced: [[SMSS J031300.36−670839.3]].<ref name="Keller2014">{{cite journal|author1=S. C. Keller |author2=M. S. Bessell |author3=A. Frebel |author4=A. R. Casey |author5=M. Asplund |author6=H. R. Jacobson |author7=K. Lind|author7-link= Karin Lind |author8=J. E. Norris |author9=D. Yong, A. Heger |author10=Z. Magic |author11=G. S. Da Costa |author12=B. P. Schmidt |author13=P. Tisserand|date=2014|title=A single low-energy, iron-poor supernova as the source of metals in the star SMSS J031300.36−670839.3|journal=Nature|issn=0028-0836|doi=10.1038/nature12990|arxiv = 1402.1517 |bibcode = 2014Natur.506..463K|volume=506|issue=7489 |pages=463–466|pmid=24509711|s2cid=4457295 }}</ref>

== See also ==
Other ultra low metallicity / ultra metal poor stars
* [[Cayrel's Star]]
* [[HE 1327−2326]]
* [[SDSS J102915+172927]]

== References ==
<references/>
* 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)

== External links ==
* [http://simbad.u-strasbg.fr/sim-id.pl?protocol=html&Ident=he0107-5240 SIMBAD-Entry] ([[SIMBAD]])
* [http://cdsarc.u-strasbg.fr/viz-bin/Cat?J/A%2BA/484/721 Hamburg/ESO survey (Christlieb+, 2008)]
* [https://web.archive.org/web/20050305055859/http://space.com/scienceastronomy/relic_star_021030.html Relic Star Found, Pointing Way to Dawn of Time] ([[Space.com]])
* [https://web.archive.org/web/20051212113735/http://www.eso.org/outreach/press-rel/pr-2002/pr-19-02.html VLT UVES Observes Most Metal-Deficient Star Known] ([[European Southern Observatory]])
* [http://jumk.de/astronomie/special-stars/he0107-5240.shtml he0107-5240]

{{Stars of Phoenix}}

[[Category:Phoenix (constellation)]]
[[Category:Population II stars]]