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BETELGEUSE
The great star Betelgeuse is one of the two that dominate mighty Orion of winter, the other Rigel, the pair respectively called Alpha and Beta Orionis. The name Betelgeuse is a corruption of the Arabic "yad al jauza," which means the "hand of al-jauza," al-jauza the ancient Arabs' "Central One," a mysterious woman. For us, it marks the upper left hand corner of the figure of the Greek's ancient hunter (and since he is facing you, his right shoulder). One of the sky's two first magnitude supergiants (the other Antares of summer), Betelgeuse is one of the larger stars that can be seen, indeed one of the larger stars to be found anywhere. At its most likely distance of 425 light years, its measured angular diameter yields a radius 630 times that of the Sun, 2.9 astronomical units. If placed at the Sun, the star would go 55% of the way to the orbit of the planet Jupiter. The star is so large that it is the first ever actually directly imaged as a disk from Earth (by the Hubble Space Telescope). From its size and temperature, allowing for its infrared radiation, Betelgeuse shines an amazing 60,000 times brighter than our Sun. The distance, however, is so great to be subject to some uncertainty, the possible radius ranging from 45% to 70% of Jupiter's orbit, the luminosity from 40,000 solar to 100,000 solar. Whatever the actual numbers, Betelgeuse is clearly a highly evolved star, one whose central hydrogen fuel supply has run out. As a result, the core contracted into a hot dense state, and the outer portions swelled outward. We do not really know the star's condition at the moment, but the odds are that it is now in the process of fusing helium into carbon and oxygen in its core. Betelgeuse is variable over long time periods, is ejecting part of itself through a strong wind, and is surrounded by a huge shell of dust of its own making. The wind and variability are perhaps related to huge hot spots on the star's surface, one of which was seen by Hubble. Betelgeuse is also surrounded by some controversy. From theory, its initial mass should have fallen somewhere between 12 and about 17 times that of the Sun. If at the high end, the core will fuse elements through neon, magnesium, sodium, and silicon all the way to iron. It will then collapse, and Betelgeuse will blow up as a "supernova", most likely leaving a compact neutron star about the size of a small town behind. If it were to explode today, it would become as bright as a crescent Moon, would cast strong shadows on the ground, and would be seen easily in full daylight. If the star is near or under the lower end of the range, then Betelgeuse may eventually become a shrunken and dense white dwarf about the size of Earth. Even then, however, it will be different. Most white dwarfs are made of carbon and oxygen, whereas Betelgeuse has enough mass to become one of the exceedingly rare neon-oxygen white dwarfs. The only way we will really know is to wait a few million years.