Aldebaran is the bright orange star that marks the eye of Taurus the Bull. Located about 65 light-years away, it is one of the brightest stars in the night sky and can easily be found using Orion’s Belt. Here are some interesting facts about Aldebaran.
Easy to Find Using Orion’s Belt
Aldebaran is one of the easiest bright stars to find because Orion points almost directly toward it. Follow the line of Orion’s Belt in the direction of Taurus and you will reach Aldebaran, a distinctive orange star sitting among the V-shaped pattern of the Hyades. Continue along the same general line beyond Aldebaran and you will eventually reach the Pleiades star cluster.
The Bright Orange Eye of Taurus
Aldebaran is the brightest star in Taurus and forms the fiery orange eye of the Bull. With an apparent magnitude of about 0.9, it is also roughly the 14th-brightest star in the night sky. Its distinctive orange color makes it particularly easy to recognize among the surrounding stars.
Not Actually Part of the Hyades
Aldebaran appears to sit within the V-shaped Hyades star cluster, but this is just a line-of-sight effect. Aldebaran is only about 65 light-years from Earth, while the Hyades lie roughly 150 light-years away. This means the bright orange star that seems to complete the Bull’s face is actually a foreground object, unrelated to the cluster behind it.
Its Name Means “the Follower”
The name Aldebaran comes from the Arabic al-Dabarān, meaning “the Follower,” because the star appears to follow the Pleiades across the night sky as Earth rotates. The name is particularly fitting when viewing Taurus, where the Pleiades appear ahead of Aldebaran and the Hyades as they travel from east to west across the sky.
Around 44 Times Wider Than the Sun
Aldebaran has expanded to around 44 times the Sun’s radius, making it nearly 90 times wider from one side to the other. To put that into perspective, if the Sun were shrunk to the size of a basketball, Aldebaran would be roughly 10 meters (33 feet) across. Despite its enormous size, Aldebaran contains only a little more mass than the Sun. Its huge diameter is instead the result of the star expanding dramatically as it evolved into a giant.
An Aging Orange Giant Star
Aldebaran is a K5 III orange giant that has already exhausted the hydrogen fuel in its core and left the main sequence. As its outer layers expanded, its surface cooled to around 3,900 K, giving the star its distinctive orange color. Yet its enormous surface area means it still radiates several hundred times more energy than the Sun. Eventually, Aldebaran will shed its outer layers and leave behind a small, dense white dwarf.
May Have a Giant Planet — But We’re Not Sure
For years, astronomers thought Aldebaran might be orbited by a giant planet after detecting a repeating wobble in the star’s motion. The proposed planet, Aldebaran b, would have been several times more massive than Jupiter. Later studies, however, found that the signal may instead be caused by activity and oscillations within Aldebaran itself. For now, the planet remains unconfirmed — a good example of how giant stars can sometimes mimic the signals astronomers use to discover distant worlds.
Pioneer 10 Is Heading Its Way — Very Slowly
Pioneer 10, the first spacecraft to travel through the asteroid belt and make a close encounter with Jupiter, is now heading out into interstellar space in the general direction of Aldebaran. But even at its enormous speed, the distances between the stars are difficult to comprehend: it will take Pioneer 10 more than 2 million years to reach Aldebaran’s vicinity.