CEMP star

{{Short description|Chemically peculiar stars}}

Carbon-enhanced metal-poor stars, usually referred to as CEMP stars, are a class of chemically peculiar star. CEMP stars have [C/Fe] > +1, which means compared to the Sun these stars have carbon enhanced at least ten times more than iron, and [Fe/H] < -1, meaning that iron is less than a tenth that in the Sun.

These are further categorized by whether r-process or s-process elements are enhanced. CEMP-no stars have no enhancement. Some of these are the earliest formed in the Milky Way. The others are termed CEMP-r, CEMP-s, or CEMP-r/s.{{cite web|title=Carbon-Enhanced Metal-Poor Stars in the Milky Way|url=https://www.aao.gov.au/files/palmcove2014/Kennedy.pdf|archive-url=https://web.archive.org/web/20151019101610/https://www.aao.gov.au/files/palmcove2014/Kennedy.pdf|url-status=dead|archive-date=October 19, 2015|author=Catherine r. Kennedy|location=Canberra|date=29 May 2014|accessdate=18 December 2016}}{{Cite journal|last1=Carollo|first1=Daniela|last2=Freeman|first2=Ken|last3=Beers|first3=Timothy|last4=Placco|first4=Vinicius|last5=Tumlinson|first5=Jason|last6=Martell|first6=Sarah|title=Carbon-Enhanced Metal-Poor Stars: CEMP-s and CEMP-no Sub-Classes in the Halo System of the Milky Way|journal=The Astrophysical Journal|volume=788|issue=2|pages=180|doi=10.1088/0004-637X/788/2/180|date=20 June 2014|arxiv=1401.0574|bibcode=2014ApJ...788..180C|s2cid=59932382}} Metal-poor stars are more likely to be CEMP stars, and once [Fe/H] < -5.0, then all the stars are CEMP stars.