Carbon planet: A newly discovered kind of planet. It consist mainly of various substances which contain carbon. Carbon planets may have layers of diamonds which are several kilmetres thick.
Cassini: A space probe orbiting the planet saturn. A smaller probe was attached along with Cassini. It was sent down into the atmosphere of Titan and sent back historical images. The probe was named after the astronomer who discovered the large gap between saturn's rings.
Celestial: Another word of heavenly. Something related to the sky.
Cepheid Variable: A star which's luminosity (brightness) is related with it's period. In other words, the luminosity is periodical. Cepheid variables are used to measure distances in the universe.
Chandrasekhar limit: The mass limit which no white dwarf can pass: 1.4 Solar masses.
Chandra X-ray Telescope: A very advanced telescope sent into orbit around earth. It studies the universe in the X-ray field of the spectrum. The telescope was named after the astronomer Subrahmanyan Chandrasekhar who has contributed much to astrophysics.
Cromosphere: The lower layer of the sun's atmosphere.
Coma: The bright envelope of vaporized gases surrounding the nucleus of a comet.
Comet: A ball of dirty and snow orbiting the sun. When comets come close to the sun they start to vaporize, thus leaving a tail of gas behind it. This is what characterizes a comet. The tail always points away from the sun. When the earth crosses the orbit of a comet's many meteors become visible on the night sky.
Contact Binary: A binary star system in which the both stars are so close that they share a common envelope of gas.
Convection zone: A zone in a star where energy is mostly transferred through convection.
Corona: The outmost layer of the sun's atmosphere. This area has perplexed astronomers since it is much hotter than the surface (more than 1 million degrees hot!). The solar magnetic field is thought to play a role in this mystery.
Cosmic background radiation: This is the afterglow of the Big Bang. The glow is a radio signal with a temperature of 2.7 degrees Kelvin.
Crater: The mark of a impact by a comet, asteroid or meteor.
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