Betelgeuse
Betelgeuse, also called α Orionis, is a large red star in the constellation of Orion. It is the 12th brightest star in the sky, a red giant, and is a vertex of the Winter Triangle.
The name is a contraction of the Arabic Yad al-Jauza`, translated as the "armpit of the central one," indicating its position in the constellation of Orion. Because of its rich reddish color the star has frequently been referred to as the "martial one," and in Astrology portends military or civic honors. Because it is the first star of Orion to rise, the title of "roarer" or "announcer" has been assigned to it by ancient writers. Other names are:
Betelgeuse is of great interest astronomically. It is also one of the first stars to have its diameter measured with a stellar interferometer. The diameter was found to be variable, ranging from 290,000,000 km to 480,000,000 km. At maximum diameter, the star would extend out beyond the orbit of Mars if put in the Sun's place.
Physical and other characteristics
Observation data Semiregular Variable, type SR c
Right ascension (RA, α) (J2000,00)
05 h 55 m 10.29 s Declination (Dec, δ) (J2000,00)
+07° 24' 25.3" Distance from Earth
427 ± 92 LY (131 pc) Visual brightness (V)
+0.45m (+0.3m to +0.6m (+1.3m)) Absolute magnitude
-5.3m to -5.0m Physical characteristics Mean Diameter (dS = 1,392,000 km) 385,000,000 km | ~ 276.6 dS
2.57 AU | (452 s.u.) Surface area Volume Mass ~ 40 × 1030 kg Relative mass to the Sun
(mS = 1.9891 × 1030 kg) ~ 20 mS Density Surface gravity Spectral type M1-2 Ia-Iab (Red Super Giant) Surface temperature 3600 K Age Color (B-V) +1.850 (Orange-red) | (1.500) V-I 2.32 Luminosity (LS = 3.827 × 1026 J s-1)
~ 10,000 LS Orbital characteristics Period of rotation Period ~ 2070 d to 2355 d