Groombridge 1830
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Groombridge 1830 is a star 29.9 light-years away in the constellation Ursa Major. With an apparent magnitude of 6.4, it is near the limit of naked eye visibility under ideal conditions. It has a low metallicity and is thought to be a superflare star.
Discovery and naming
The star was catalogued by British astronomer Stephen Groombridge with the Groombridge Transit Circle between 1806 and the 1830s and published posthumously in his star catalog, Catalogue of Circumpolar Stars (1838). The designation Groombridge 1830 comes from this catalog; in older sources it may be written as 1830 Groombridge.<ref name=Peters1853/> Its high proper motion was noted by Friedrich Wilhelm Argelander in 1842,<ref name=Argelander1842/> and so it is sometimes called Argelander's Star, a name first used in an 1853 paper.<ref name=Peters1853/> Due to its high proper motion, it has also been called the Flying Star or Runaway Star<ref name=allen1899/> (compare 61 Cygni and Barnard's Star).
Other designations for this star include HD 103095, HR 4550, and Gliese 451. It has the variable star designation CF Ursae Majoris, which originally referred to a supposed flaring companion star that is no longer believed to exist.<ref name=SIMBAD/><ref name=GCVS/><ref name=Heintz1984/>
Description
Groombridge 1830 has been variously classified as a K-type main-sequence star,<ref name=nstars/> a G-type main-sequence star,<ref name=keenan1953/> or a G-type subdwarf.<ref name=Heintz1984/> The low metallicity of this star makes some of its spectral lines resemble those of a G-class star,<ref name=abt1986/> and it has been given as a spectral standard for the class G7V.<ref name=keenan1953/>
It is Template:Convert from the Sun as measured by the Gaia spacecraft,<ref name="Gaia DR3"/> which, as the distance is nearly 10 parsecs, means its absolute magnitude is almost equal to its apparent magnitude. It is a member of the galactic halo; such stars account for only 0.1 to 0.2 percent of the stars near the Sun. Like most halo stars, it has a low abundance of elements other than hydrogen and helium—what astronomers term a metal-poor star.<ref name=solstation/>
Once suspected to be a binary star with a red dwarf flare star companion,<ref name=Beardsley1974/> the current consensus is that it is single.<ref name=Heintz1984/> Previous observations of stellar flares, suspected to be from a companion star, were probably "superflares" on the primary star—analogous to the Sun's solar flares, but hundreds to millions of times more energetic. It was one of the first nine identified superflare stars.<ref name=solstation/><ref name=as89_1_38/>
Proper motion
When discovered, Groombridge 1830 had the highest known proper motion of any star, replacing 61 Cygni. Kapteyn's Star and Barnard's Star have since been identified as having even higher proper motions. It is considerably farther away than either of those stars, however, which means its transverse velocity is greater.Template:Cn