Aldebaran
Aldebaran - the brightest star in Taurus and the 14th-brightest in the sky, 66.6 light-years away, a cool orange giant more than 40 times the Sun's width. It gleams as the fiery 'eye' of the Bull, seen against (but well in front of) the Hyades cluster. A long-suspected giant planet is now regarded as unconfirmed - most likely a signal of the star's own churning surface.
Key facts
Science
Physical
- Mass
- 2.31 × 10³⁰ kg · 1.16 M☉
- Radius
- 0.21 AU · 45.1× wider than the Sun
- Density
- 0.0178 kg/m³ · 1.8e-05× water
- Spectral type
- K5III (orange giant)
Rotation
- Note
- A slowly-rotating giant; its surface pulsations produce the radial-velocity signal once mistaken for a planet.
Composition
- By mass
- An evolved orange giant of a bit over one solar mass that has swollen to more than 40 times the Sun's width and shines hundreds of times brighter. Cool and luminous, it is the classic red-giant end-state of a Sun-like star — and only appears set among the Hyades, which lie far beyond it.
Temperature
- Surface
- 3,900 K (3627 °C)
Radiation & temperature
- Luminosity
- 1.68 × 10²⁹ W · 439 L☉
- Surface temperature
- 3,900 K (3627 °C)
- Peak wavelength
- 743 nm · red light
Discovery & history
- Method
- Naked-eye star
- Name
- Its IAU name Aldebaran is from the Arabic al-dabaran, 'the follower' (it follows the Pleiades across the sky); it is Alpha Tauri, the eye of the Bull.
Aldebaran has marked the Bull's eye since antiquity and was occulted by NASA's Pioneer probes' target region studies of the Hyades. A periodic wobble hinted at a giant planet (proposed 2015), but by 2019 careful analysis showed it more likely arises from pulsations and starspots on the giant itself, so no planet is counted here.
Images
Images from open archives · credit shown per image