Bob the Alien's Tour of the Solar System
Bob the Alien's Tour of the Solar System
Space A to Z


Word Meaning
Caldera A volcano that has sunk into the collapsed land below it (usually because all the magma below has erupted and there is nothing to support the newly formed mountain). Fairly common on Earth. An example elsewhere in the Solar System is Olympus Mons on Mars.
Caliban moon of uranus
Callirrhoe Small moon of Jupiter discovered in 1999. About 7 km in diameter.
Callisto Second largest moon of Jupiter, third largest moon in the Solar System. 99% the size of planet Mercury. Discovered by Galileo in 1810, Callisto is the most cratered body in the Solar System.
Calypso moon of saturn
Carpo Small moon of Jupiter discovered in 2003, only about 2 km in diameter.
Carme Discovered in 1938, Carme became the eleventh moon known to orbit Jupiter. Irregularly shaped, about 48 km in diameter. The moon didn't receive its present name until 1975. Before then it was known as Jupiter XI, and between 1955 and 1975, some people knew it as Pan. Pan is now the name of a moon orbiting
Catena A chain of craters of similar size. They are believed to be created when an object like a comet is broken up into fragments and these fragments impact the surface of a planet or moon.
Celestial object Any object which appears in the sky - the Moon, Sun, planets, stars, galaxies, etc. are all celestial objects.
Chaldene Small moon of Jupiter, discovered in 2000, about 4 km in diameter.
Charon Moon of Pluto, discovered in 1978 and about one third the size of Pluto. Because Pluto and Charon orbit an invisible axis between the two objects, they are sometimes referred to as a Binary Planet.
Christie, James W. American astronomer who discovered Pluto's moon Charon in 1978. He was born in 1938.
Chromosphere Lower level of the Sun (or any other star's) atmopshere, above the photosphere and below the corona.
Cluster A group of stars or galaxies which stay in a cluster by their common gravity.
Coma The "ball" part of the comet, surrounds the nucleus.
Comet Small ball of dust and gas which orbits the Sun, often in elliptical (oval) orbits. Only visible when they are close enough to the Sun to start burning off their dust/gas. Some comets take a few decades to complete an orbit, others take thousands of years. Some comets are also known to orbit Jupiter.
Conjunction A term to describe the position of one planet in relation to Earth. An "inferior conjunction" is when an inferior planet (a planet closer to Earth: either Venus or Mercury) is in between Earth and the Sun. If the inferior planet is on the other side of the Sun to Earth, it is in "superior conjuction." A superior planet (any planet beyond Earth in the Solar System) is "in conjunction" when it is on the opposite side of the Sun. When the superior planet is on the same side of the Sun as Earth, it is then said to be "in opposition".
Constellation A group of stars, named by ancient astronomers because of their appearance (kind of like dot-to-dot). The twelve signs of the zodiac are named after twelve constellations.
Cordelia moon of uranus
Corona A uppermost part of the atmosphere surrounding a celestial object like the Sun. Can often be seen during a solar eclipse. The corona extends many millions of kilometres into space. Lower in density than the rest of the star, not as bright (the Sun's disc has to be covered for it to be visible), but much hotter.
Cosmonaut Russian/Soviet word for Astronaut.
Crater An bowl-shaped depression formed when a meteorite hits the surface of a planet or moon.
Cressida moon of uranus
Crust The thin rocky surface of a planet or moon.
Cupid moon of uranus

Bob the Alien's Tour of the Solar System
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