Betelgeuse (α Ori / α Orionis / Alpha Orionis) is the second brightest star in the constellation Orion and the tenth brightest star in the nighttime sky. Although it has the Bayer designation "alpha", it is not as bright as Rigel (Beta Orionis).

Betelgeuse is vertex of the Winter Triangle.

Betelgeuse is a red supergiant star, one of the physically largest stars known. If it was placed at the center of our Solar System, the Earth would be engulfed and would be inside it. Its proximity to Earth combined with its enormous size make it the star with the third largest angular diameter as viewed from Earth [1], smaller only than the Sun and R Doradus, and one of only a dozen or so stars that telescopes can image as a visible disk as of 2005. (See photo, at right and picture of hotspots on Betelgeuse in External links section below). The angular diameter of Betelgeuse was first measured in 1920-1921 by Michelson and Pease using an interferometer on the Mount Wilson 100-inch telescope.

Because Rigel is a blue star and Betelgeuse is a red star, Betelgeuse is actually brighter than Rigel at infrared wavelengths, but not at visual wavelengths.

Origin of the name "Betelgeuse"

The name is a corruption of the Arabic يد الجوزا yad al-jawzā, or "hand of the central one". Jauza, the central one, initially referred to Gemini among the Arabs, but at some point they decided to refer to Orion by that name. During the Middle Ages the first character of the name, y (ﻴ, with two dots under it), was misread as a b (ﺒ, with one dot under it) when transliterating into Latin, and Yad al-Jauza became Bedalgeuze. Then, during the Renaissance, someone tried to derive the original Arabic from this corrupted name, and decided that it was originally written as Bait al-Jauza. This imaginative person then declared that Bait meant "armpit" in Arabic, to the surprise of Arabs everywhere. The nameless Renaissance linguist then "corrected" the transliterated spelling to Betelgeuse, and the modern rendering was born. In order for Betelgeuse to have meant "armpit of the central one", the original rendering would have to have been ابط Ibţ (al-Jauza).

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. Other names are:

• Al Dhira (the Arm),
• Al Mankib (the Shoulder)
• Al Yad al Yamma (the Right Hand)
• Ardra (Hindi),
• Bahu (Sanskrit),
• Bed Elgueze
• Beit Algueze
• Besn (Persian) (the Arm),
• Beteigeuze
• Beteiguex
• Betelgeuze(Bet El-geuze),
• Betelgeza (Slovene),
• Betelguex
• Gula (Euphratean),
• Ied Algeuze (Orion's Hand),
• Klaria (Coptic) (an Armlet)
• Yedelgeuse

Distinguishing characteristics

Betelgeuse is of great interest astronomically. It is 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. Though only 15 times as massive as the Sun, it is as much as 40 million times larger in volume, like a beach ball compared to Texas Stadium. It was also the first star to have its disk resolved in an optical image by a telescope, from observations by the COAST telescope in 1995.

Astronomers confidently predict that Betelgeuse will ultimately undergo a type II supernova explosion. Opinions are divided as to the likely timescale for this event. Some regard the star's current variability as suggesting that it is already in the carbon burning phase of its life cycle, and will therefore undergo a supernova explosion at some time in the next thousand years or so. Skeptics dispute this contention and regard the star as being likely to survive much longer. There is a consensus that such a supernova would be a spectacular astronomical event, but would not represent any significant threat to life on Earth given the star's enormous distance.

But the star will at least brighten 10000 times which means brighten to the brightness of a crescent Moon, but some think it will brighten to about full Moon brightness (mv = -12.5). This will probably last for a few months. It would look like a bright point, the brightness of a full Moon with the color of an incandescent bulb at night, and easily visible in daylight. After that period the star will gradually dim until after some months or years the star completely disappears and Orion misses the left shoulder.

External links

• Images of hotspots on the surface of Betelgeuse taken at visible and infra-red wavelengths using high resolution ground-based interferometers.

References in fiction

In science fiction, Ford Prefect, a character in the Hitchhiker's Guide to the Galaxy, hails from a world "in the vicinity of Betelgeuse".

Betelgeuse is also the name of the main character of the 1988 comedy/fantasy film Beetlejuice.