Barnard's Star (star)
|Mass||0.144 (=150 MJ) MSol|
|Radius||0.2 (=1.75 RJ) RSol|
Barnard's Star (otherwise known as Proxima Ophiuchi) is a pinkish-orange "red dwarf" main sequence star of spectral type M4 that is classified as a BY Draconis type variable star with variable designation V2500 Ophiuchi.
- Though a comparatively dim star in the human-range of the visible spectrum of light, it is much brighter in the infrared part of the electromagnetic spectrum.
Barnard's Star has a mass of approximately 150 times that of Jupiter, but its radius is only about 1.75 times that of Jupiter due to its much higher density.
- At 7 to 12 billion years of age, Barnard's Star is considerably older than Sol and is classified as a Population II star, and in fact may be among the oldest stars in the universe. Barnard's Star has lost a great deal of rotational energy, and periodic changes in its light indicate it rotates just once every 130 days.
- Given its age, Barnard's Star was long assumed to be quiescent in terms of stellar activity. However astronomers have frequently observed intense stellar flares, making it a surprising flare star.
- The proper motion of the body corresponds to a relative lateral speed ("sideways" relative to Sol) of 90 km/sec. From the vantage point of the Sol system, the 10.3 seconds of arc covered annually amounts to a quarter of a degree in a human lifetime, roughly half the angular diameter of Terra's "full Moon" as perceived from the planetary surface.
- Because of its low mass, the interior of Barnard's Star is completely convective, causing energy to be transferred to the exterior by the movement of plasma rather than through radiative transport. This convection means that the helium ash left over from the thermonuclear fusion of hydrogen does not accumulate at the core, but instead circulates throughout the star. Unlike Sol, which will only burn through about 10% of its total hydrogen supply before leaving the main sequence, Barnard's Star will consume nearly all of its fuel before the fusion of hydrogen comes to an end, becoming smaller and hotter as the fuel is used up and turning into a "blue dwarf" as its end approaches. It will finally end its life as a white dwarf, without having passed through the red-giant phase.
The Barnard star system lies approximately 1.82pc from Terra, and is located in a roughly Coreward direction from Terra at bearing 031.0o Galactic Longitude and +14.1o North Galactic Latitude.
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