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Beta Comae Berenices
Beta Comae Berenices (β Comae Berenices, β Com) is a main sequence dwarf star in the northern constellation of Coma Berenices. It is located at a distance of about from Earth. The Greek letter beta (β) usually indicates that the star has the second highest visual magnitude in the constellation. However, with an apparent visual magnitude of 4.3,〔 this star is slightly brighter than α Comae Berenices. It can be seen with the naked eye, but may be too dim to be viewed from a built-up urban area.
This star is similar to our own Sun, being only slightly larger and brighter in absolute magnitude. It has a stellar classification of G0 V,〔 compared to G2 V for the Sun. The effective temperature of the outer envelope is 5,936 K,〔 giving it a yellow hue of a G-type star.〔 In terms of age it is younger than the Sun, being about 3 billion years old.〔
Observations of short term variations in the chromatic activity suggest that the star undergoes differential rotation,〔 with a rotation period of about 11–13 days.〔 Its surface has a measured activity cycle of 16.6 years, compared to 11 years on our Sun. It may also have a secondary activity cycle of 9.6 years.〔 At one time it was thought that this star might have a spectroscopic companion. However, this was ruled out by means of more accurate radial velocity measurements. No planets have yet been detected around it, and there is no evidence of a dusty disk.
The habitable zone for this star, defined as the locations where liquid water could be present on an Earth-like planet, is 0.918–1.042 AU, where 1 AU is the average distance from the Earth to the Sun.〔
==References==
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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