Aldebaran
For the Fallen Angel Aldebaran, see Aldebaran (demon).Aldebaran, (α Tau / α Tauri /
Alpha Tauri), is the brightest star in the constellation
Taurus and
one of the brightest stars in the nighttime sky. Because of its location in the head of Taurus, it has historically been called the
Bull's Eye.
Its name is derived from the
Arabic الدبران al-dabarān meaning "the follower", a reference to the way the star follows the
Pleiades star cluster in its nightly journey across the sky. Aldebaran has the appearance of being the brightest member of the more scattered
Hyades cluster, which is the closest star cluster to Earth. However, it is merely located in the line of sight between the Earth and the Hyades, and is actually an independent star.
Aldebaran is a K5 III star, which means it is orangish, large, and has moved off of the
main sequence by using all its
hydrogen fuel. It has a minor companion (a dim M2 dwarf orbiting at several hundred
AU). Now primarily fusing
helium, the main star has expanded to a diameter of approximately
5.3 × 10
7 km, or about 38 times the diameter of the
Sun. The
Hipparcos satellite has measured it as 65.1
light years away, and it shines with 150 times the Sun's luminosity. Taken together this distance and brightness makes it the
14th brightest star, having an
apparent magnitude of 0.87. It is slightly variable, of the
irregular variable type, by about 0.2 magnitude.
In 1997, a possible large planet (or small
brown dwarf) companion was reported, with a mass equalling that of 11
Jupiters and orbiting at a distance of 1.35 AU.
Aldebaran is one of the easiest stars to find in the
night sky, partly due to its brightness and partly due to its spatial relation to one of the more noticeable asterisms in the sky. If one follows the three stars of
Orion's belt from left to right (in the Northern Hemisphere) or right to left (in the Southern), the first bright star found by continuing that line is Aldebaran.
The unmanned
Pioneer 10 spacecraft was last reported to have been heading toward Aldebaran. Assuming the spacecraft avoids some form of
collision, the spacecraft will arrive at Aldebaran in 2 million years.
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Size comparison between Aldebaran and the Sun |
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Radio scan of Aldebaranrad, brightness temperature measures at all frequencies |
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