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Groombridge 1618
Groombridge 1618 is a star in the constellation Ursa Major. It is located close to Earth, at a distance of less than 16 light years. It is an orange dwarf star of spectral type K8 V.
==Properties==
This star was first identified as entry number 1618 in the work ''A Catalog of Circumpolar Stars'', published posthumously by Stephen Groombridge in 1838. It has a high proper motion across the sky, which is normally taken as an indicator that the star is located nearby—making it an early candidate for parallax measurement of its distance. In 1884 the parallax angle was measured as , which is larger than the modern value of 0″.205.
Groombridge 1618 has a stellar classification of K8 V, which means it is a K-type main sequence star that is generating energy by fusing hydrogen at its core. It has 67% of the mass of the Sun, 61% of the Sun's radius,〔 but radiates only 15% of the Sun's energy and only 4.6% of the Sun's energy in the visible light spectrum. The effective surface temperature of the star's photosphere is about 4,000 K, giving it an orange hue.
It is a BY Draconis variable with a surface magnetic field strength of 750 G.〔 The chromosphere is relatively inactive〔 and possesses star spots comparable to Sun spots. However, like the star UV Ceti, it has been observed to undergo increases in luminosity as a flare star.〔 It has a greater luminosity than most flare stars, which are typically red dwarfs, but is less active. The level of activity suggests that this is a somewhat youthful star.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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