NOTABLE STARS A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z           HOME ABOUT CATEGORIES SITE MAP COPYRIGHT ADVERTISE CONTACT entire Web this site Betelgeuse (Alpha Orionis) A red supergiant and irregular variable that is (usually) the tenth brightest star in the sky and second brightest in Orion, though it occasionally outshines Rigel (Beta Ori), with which it makes a striking color contrast. At an infrared wavelength of 2 microns, Betelgeuse is the brightest object in the sky. Its name (also written as “Betelgeuze” or “Betelgeux”) is a corruption of the Arabic yad al jauza, which means the “hand of al-jauza,” al-jauza being the ancient Arabs’ “Central One,” a mysterious woman; often pronounced “beetle-juice,” though “betel-jerze” is closer to the original Arabic. It marks the upper left-hand corner of the figure of the ancient hunter. One of the sky’s two first magnitude red supergiants (the other is Antares), Betelgeuse is among the larger stars on view to the naked eye, with a measured angular size of 0.05", corresponding to a radius of 2.9 AU at 425 light-years, so that if put in place of the Sun it would extend out as far as the asteroid belt. However, uncertainty about its distance allows a possible range in size of 45 to 70% of Jupiter’s orbit, and a corresponding luminosity range (including infrared) of 40,000 to 100,000 times the luminosity of the Sun. Its disk is so large that it was the first to be reconstructed by the technique of speckle interferometry (1975) and the first to be directly imaged, by the Hubble Space Telescope (1995). The Hubble image revealed a huge atmosphere with a mysterious hot spot on the star’s surface. The enormous bright spot, more than 10 times the diameter of Earth, is at least 2,000 K hotter than the rest of the star’s surface. Measurements by the International Ultraviolet Explorer found a 420-day period, during which the star rings like a bell. These oscillations, thought to be caused by turbulence below the surface of the star, may cause the bright spot’s position to change over time. Betelgeuse is also surrounded by a huge dusty circumstellar shell, extending up to one trillion kilometers from the star and composed of matter that has been ejected in the form of a vigorous stellar wind. The first image of the cloud was captured in 1998 using the Multiple Mirror Telescope and the technique of nulling interferometry.1. Dust is not the only thing surrounding Betelgeuse: in 1985 it was found to have two close companions. The inner orbits every two years or so at a mean distance of about 5 AU, while the outer lies some 40 to 50 AU away. The chances are that Betelgeuse is now fusing helium in its core. Theory suggests that its mass has now fallen to between 12 and 17 solar masses. If at the high end of this range, the core will fuse elements through neon, magnesium, sodium, and silicon all the way to iron. The star will then explode as a supernova. 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 predicted mass range, then it may eventually become a rare neon-oxygen white dwarf about the size of Earth. Visual magnitude 0.0 to 1.3 Absolute magnitude -5.14 Spectral type M2Iab Surface temperature 3,100 K Total luminosity 60,000 Lsun Radius 630 Rsun Distance 427 light-years Position R.A. 05h 55m 10.3s, Dec. +07° 24' 25" Reference Hinz, P. M., Angel, J. R. P., Hoffmann, W. F., McCarthy, D. W., Jr, McGuire, P. C., Cheselka, M., Hora, J. L., and Woolf, N. J. "Imaging Circumstellar Environments with a Nulling Interferometer," Nature, 395, 251 (1998). Related entry    • brightest stars Related category    • NOTABLE STARS Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) BACK TO TOP