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Barnard’s Star is the fastest-moving star and fourth closest to the Sun. It’s a red dwarf star, too dim to see with the naked eye, and may have an Earth-sized planetary companion. It was once considered for an interstellar probe, but it would have been expensive.
Barnard’s Star is the fourth closest star to the Sun, after the three members of the Centauri system, and the fastest-moving star in the sky. It is sometimes called Barnard’s Runaway Star to refer to its significant movement relative to other stars. Located in the constellation Ophiuchus, just 5.98 light-years from Earth, Barnard’s Star is not yet visible to the naked eye. This is because it is a red dwarf star with only 17% the mass of the Sun and 04% more luminosity. Red dwarfs are so faint that we are only aware of those within about 100 light-years of ourselves.
Barnard’s star is currently moving in the general direction of our solar system at about 140 km/sec, and will become the closest star other than the Sun in just about 11,700 years, at a distance of only 3.8 light-years. Unfortunately, even then it will still be too dim to see with the naked eye. Even now, the star is so dim that if it were to replace the Sun, it would only have about 100 times the brightness of a full Moon. There is much debate as to whether a red dwarf could have habitable planets for life. The “Habitable Zone” for planets around a red dwarf would be similar in distance to the orbit of Mercury. Barnard’s star has a surface temperature of only about 3000 K.
From about 1963 to 1973, some astronomers believed that there was a Jupiter-sized planet orbiting Barnard’s star, based on the small wobble motions supposedly observed against photographic plates. Unfortunately for this group, subsequent attempts to verify the swing were unsuccessful. Much higher resolution observations with the Hubble Space Telescope have also ruled out observable wobbles. Barnard’s star may still have an Earth-sized planetary companion, but definitely not a Jupiter-sized one in a close orbit.
Barnard’s star’s proximity to and possible planetary companion made it popular in the 1960s as a target for an interstellar probe. A design has been conceived for a probe, called Daedalus, by the British Interplanetary Society. Such a probe would have been extremely expensive and powered by nuclear pulse propulsion, although it would have been feasible with 1960s technology.
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