Groombridge 1830
A high-proper-motion, metal-poor halo star with superflare activity.
Groombridge 1830, sometimes called Argelander's Star, lies 29.9 light-years away in Ursa Major. Its apparent magnitude of 6.4 puts it just at the edge of what the unaided eye can see in perfect conditions. The star is metal-poor and is considered a superflare star.
British astronomer Stephen Groombridge recorded it using his Transit Circle between 1806 and the 1830s, and it appeared posthumously in his 1838 Catalogue of Circumpolar Stars—hence the designation Groombridge 1830 (or, in older texts, 1830 Groombridge). In 1842, Friedrich Wilhelm Argelander noted its high proper motion, leading to the name Argelander's Star, first used in an 1853 paper. Its rapid movement across the sky also earned it the nicknames Flying Star and Runaway Star, similar to 61 Cygni and Barnard's Star. Other identifiers include HD 103095, HR 4550, and Gliese 451. The variable star designation CF Ursae Majoris originally referred to a supposed flaring companion, but that companion is no longer thought to exist.
The star’s classification has varied: it has been called a K-type main-sequence star, a G-type main-sequence star, or a G-type subdwarf. Its low metallicity makes some spectral lines resemble those of a G-class star, and it serves as a spectral standard for class G7V. At 29.9 light-years (nearly 10 parsecs) from the Sun—a distance measured by the Gaia spacecraft—its absolute magnitude is almost identical to its apparent magnitude. It belongs to the galactic halo, a population that accounts for only 0.1 to 0.2 percent of stars near the Sun. Like most halo stars, it has a low abundance of elements heavier than hydrogen and helium.
Once suspected of being a binary with a red dwarf flare star, astronomers now agree it is single. Earlier observations of flares, thought to come from a companion, were likely superflares on the primary star—similar to solar flares but hundreds to millions of times more energetic. It was among the first nine stars identified as superflare stars.
At the time of its discovery, Groombridge 1830 had the highest known proper motion of any star, surpassing 61 Cygni. Kapteyn’s Star and Barnard’s Star have since been found with even higher proper motions, but Groombridge 1830 is much farther away, giving it a greater transverse velocity.
Quick Facts
- Distance
- 29.9 light-years
- Constellation
- Ursa Major
- Apparent magnitude
- 6.4
- Other designations
- HD 103095
- HR 4550
- Gliese 451
- CF Ursae Majoris
- Spectral classification
- variously classified as K-type main-sequence
- G-type main-sequence
- or G-type subdwarf; spectral standard for G7V
Facts from the source article.
Lore & Background
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. Its high proper motion was noted by Friedrich Wilhelm Argelander in 1842, and so it is sometimes called Argelander's Star, a name first used in an 1853 paper. Due to its high proper motion, it has also been called the Flying Star or Runaway Star.
Groombridge 1830 has been variously classified as a K-type main-sequence star, a G-type main-sequence star, or a G-type subdwarf. The low metallicity of this star makes some of its spectral lines resemble those of a G-class star, and it has been given as a spectral standard for the class G7V. It is 29.9 ly from the Sun as measured by the Gaia spacecraft, 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.
Once suspected to be a binary star with a red dwarf flare star companion, the current consensus is that it is single. 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.
Reader's Guide
Groombridge 1830 holds a notable place in the history of stellar astronomy due to its exceptionally high proper motion, which when discovered surpassed that of 61 Cygni. Although later surpassed by Kapteyn's Star and Barnard's Star, its greater distance means its transverse velocity is larger than either of those stars. Its membership in the galactic halo—a population comprising only 0.1 to 0.2 percent of nearby stars—underscores its rarity and its value for studying the early chemical composition of the Milky Way. The star's low metallicity and its classification as a superflare star have made it a subject of ongoing interest. The initial interpretation of observed flares as evidence of a binary companion has been revised; the current consensus is that the star is single and that the flares are superflares originating from the primary star itself. As one of the first nine identified superflare stars, it contributes to the understanding of stellar magnetic activity and the potential for extreme energy releases on stars similar to the Sun.
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