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Sirius
2
Canopus
3
Rigel Kentaurus
4
Arcturus
5
Vega
6
Capella
7
Rigel
8
Procyon
9
Achernar
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Betelgeuse
 Brightest stars—The ten brightest stars in order of brightness. Sirius is the very brightest star in the sky (other than the Sun).
Brightest stars
The brightness of a star is described by a term called the stellar magnitude. The brightest stars are called first-magnitude stars. The next brightest stars
are 2.5 times as dim as the first- magnitude stars, and so on. A sixth- magnitude star is about 100 times as dim as a first-magnitude star.
The brightest star in the sky (other than the Sun) is Sirius. The second brightest is Canopus. Other very bright stars include Rigel and Betelgeuse. They can be clearly seen with the unaided eye. You can only see stars that are fainter than sixth magnitude using a telescope.
(See also: Capella and Vega.)
Cassiopeia A
 Binary star—Many stars are binary stars, although
they might not appear so without the help of a powerful telescope. The large picture shows how stars appear as single points of light; the inset shows how they are typically binaries when seen under high magnification.
Brown dwarf
A body that is too small to have acted like a star and been fueled by hydrogen fusion in its core, but which is still giving out large amounts of heat. The first brown dwarf was discovered by the Hubble Space Telescope in 1995.
C Callisto
The second largest moon of Jupiter and the farthest out of the group called the Galilean moons (because they were first described by Galileo). It is an icy world about 4,800km across. Its surface reflects little light, so the moon appears darker than the
other Galilean moons.
Capella
The common name for Alpha Aurigae, the sixth brightest star in the night sky. It appears as a single star, but is in fact a binary star. It is 41 light-years away.
Cassini
A space probe designed to study the atmosphere of Saturn. It will arrive at Saturn in June 2004. The probe is named after the Cassini family of Italian-French astronomers who lived in the 17th and 18th centuries. The Cassini Division is also the name of a gap in Saturn’s rings.
 Cassini—Launching of the Cassini probe.
Cassiopeia A
The brightest star of the Cassiopeia constellation and clearly visible in the night sky. It is about 10,000 light-years away and is thought to be the remains of a supernova. It is a strong source of radio waves.
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