The → red supergiant that is the second brightest star in the
constellation → Orion.
Betelgeuse is one of the biggest stars known with a size of almost 1,000 times larger
than the Sun, corresponding to an angular diameter of 43.76 ± 0.12 milli-arcseconds
(Perrin et al. 2004, A&A 418, 675).
It is a → semiregular variable whose
→ apparent visual magnitude varies between 0.2 and
1.2 shining very rarely more brightly than its neighbor → Rigel.
The energy released by Betelgeuse is estimated to be only 13% in the form of
visible light, with most of its radiation being at → infrared
wavelengths.
The distance of Betelgeuse is
643±146 → light-years (Harper et al. 2008, AJ 135, 1430),
while its luminosity
is about 140,000 times that of the Sun (→ solar luminosity).
Its → spectral type is M2 Iab, its
→ surface temperature about 3,600 K, and its
→ initial mass 10 to 20 → solar masses
(Msun).
Neilson & Lester (2011, arXiv:1109.4562) recently proposed a mass of
11.6 (+5.0, -3.9) Msun
for Betelgeuse, while
Dolan et al. (2008, BAPS 53, APR.S8.6)
obtained about 21 Msun.
Its → rotation period is estimated to be about 17 years
(Uittenbroek et al. 1998, AJ 116, 2501).
Recent observations with the → Very Large Telescope
resolve not only the apparent surface of Betelgeuse, but also reveal a large and previously
unknown plume of gas extending into space from the surface of the
star (Kervella et al. 2009, A&A 504, 115).
The plume extends to at least six times the diameter of the star, corresponding to
the distance between the Sun and Neptune.
This detection suggests that the whole outer shell of Betelgeuse is not shedding
matter evenly in all directions.
More recently, an image of the surface of the star was obtained using
long → baseline → interferometry
at infrared wavelengths (Haubois et al. 2009, A&A 508, 923). It shows the presence of
an irregular flux distribution possibly caused by enormous
→ convective cells.
A very large dusty envelope has also been observed at larger distances from the star
(Kervella et al. 2011, A&A 531, A117).
Etymology (EN): Betelgeuse, from Ar. Ibt al-Jauza’ (ابطالجوزاء)
“the armpit of Jauza’,”
from ibt “armpit” + Jauza’ “Orion.”
Etymology (PE): Ebtoljowzâ, from Ar. Ibt al-Jauza’.
