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“The Hubble picture reveals a huge ultraviolet atmosphere with a
mysterious hot spot on the stellar behemoth's surface. The
enormous bright spot, more than 10 times the diameter of Earth,
is at least 2,000 degrees Kelvin hotter than the star's surface.
Credit: Andrea Dupree (Harvard-Smithsonian CfA), Ronald
Gilliland (STScI), NASA and ESA”
This information obtained from
http://hubblesite.org/newscenter/archive/1996/04/. |
Rigel:
According to the Macmillan Encyclopedia, “the star
β Orionis…at magnitude 0.18
…is the seventh brightest star in the sky, and though designated
β is actually the brightest
star in Orion. Betelgeuse (β
Orionis), now an irregular variable, may have been the brighter
star when the Bayer letters were allocated in 1603” (6).
According to data listed in MegaStar version 5.0, Rigel (Beta
Orionis, 19 Orionis) has a spectral type B81a, which means its
spectrum should show neutral helium and some hydrogen (4).
Rigel has an enormous luminosity estimated from 40,000 to
700,000 times that of the Sun (see below discussion), and it has
a high surface temperature of 12,000K. Rigel is also a variable
star and is a spectroscopic binary as well as having a companion
9.5 arcseconds away. The companion is easily visible in a small
telescope. Rigel is part of a large association of bright, blue
stars, including the stars of Orion's Belt, the Orion Nebula and
its embedded stars, and many of the other hot blue-white stars
in Orion, except Bellatrix which is a closer foreground star
(5). |
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