Aldebaran is the bright orange star that marks the eye of Taurus, the Bull. It is an orange giant 65 light-years away, about 44 times wider than the Sun, and roughly the 14th-brightest star in the night sky. It is easy to find by following Orion’s Belt up and to the right, and it is well placed on evenings from November to March.
Where is Aldebaran in your sky right now?
Location: not set
Calculating for your location…
Aldebaran at a glance
| Other names | Alpha Tauri, Rohini (India) |
|---|---|
| Constellation | Taurus (the Bull) |
| Brightness | Magnitude about +0.86, about 14th-brightest star |
| Distance | 65 light-years |
| Type | Orange giant (K5 III) |
| Mass | About 1.2 Suns |
| Size | About 44 times the Sun’s diameter |
| Luminosity | About 400 times the Sun |
| Temperature | About 3,900 K |
| Best time to see it | Evenings around January (highest at about 9 p.m.) |
| Where on Earth | Visible from everywhere north of about 73°S |
How to find Aldebaran
Start with Orion. From the Northern Hemisphere, follow the line of Orion’s Belt up and to the right (the opposite direction from Sirius) and the first bright star you meet is Aldebaran, glowing orange. It sits at one tip of a V-shaped group of stars, the Hyades cluster, which forms the Bull’s face, and a little farther along the same line is the Pleiades (the Seven Sisters). In November Aldebaran rises in the early evening in the east-northeast and is high in the south around midnight; it is a fine evening star from December to March.
Aldebaran and the Hyades: a trick of perspective
Aldebaran looks like the brightest member of the Hyades, but it is not part of the cluster at all. The Hyades lie about 150 light-years away, while Aldebaran is only 65 light-years from us, less than half the distance, simply lined up in front. The Hyades are the nearest open star cluster to the Sun, and binoculars show dozens of its stars around Aldebaran.
What kind of star is Aldebaran?
Aldebaran is an orange giant, a star slightly more massive than the Sun that has exhausted the hydrogen in its core and expanded to about 44 times the Sun’s diameter. Its surface is cool, about 3,900 K, giving its orange glow. It is a preview of the Sun’s future, several billion years from now. Aldebaran varies very slightly in brightness, by about a tenth of a magnitude, too little to see easily.
Lunar occultations and a space probe
Aldebaran is one of only four first-magnitude stars close enough to the ecliptic to be covered by the Moon (the others are Regulus, Spica and Antares). These occultations come in series lasting a few years; a long series ended in 2023, and the next one is not expected until the 2030s. Aldebaran is also the rough direction of the Pioneer 10 spacecraft, launched in 1972, which will pass in its general direction in about 2 million years.
The name
Aldebaran comes from Arabic al-dabarān, “the follower”, because it appears to follow the Pleiades across the sky. In Indian astronomy it is Rohini, the “red one”, one of the most important nakshatras.
Does Aldebaran have a planet?
In 2015 astronomers reported a possible giant planet, several times the mass of Jupiter, orbiting Aldebaran every 629 days, detected through small regular shifts in the star’s spectrum. Later studies argued that the signal could be caused by the star’s own surface activity rather than a planet, so its existence is still debated. Giant stars like Aldebaran pulsate and have large spots, which can mimic the wobble produced by a planet.
Aldebaran is also a great colour comparison star. Look at it next to the blue-white stars of the Pleiades, a short way to the west, and its orange tint is obvious. In binoculars the field around it is full of the scattered stars of the Hyades, one of the loveliest sights of the winter sky.
Frequently asked questions about Aldebaran
Where is Aldebaran in the sky?
Follow Orion’s Belt up and to the right (from the Northern Hemisphere). The bright orange star at the tip of the V-shaped Hyades cluster is Aldebaran.
How far away is Aldebaran?
About 65 light-years. The Hyades cluster behind it is about 150 light-years away.
Is Aldebaran a red giant?
Yes. Aldebaran is an orange (red) giant star, about 44 times wider than the Sun.
When is Aldebaran visible?
It is best on evenings from November to March. It is close to the Sun and hidden in May and June.
Why is it called the eye of the Bull?
Aldebaran marks the eye of Taurus, whose face is drawn by the V-shaped Hyades star cluster.
Sources: Aldebaran overview and references. Star data from standard catalogues; positions and rise/set times are calculated by SpaceTracker.live with the Astronomy Engine library.