| |
cannibal coronal mass ejections
fast-moving solar eruptions that appear to overtake and often devour their slower-moving kin
|
carbon star
a red giant star with much more carbon than oxygen in its surface layers
|
carbonaceous chondrites
a class of stony meteorites and asteroids which contain organic (carbon) compounds and may be the most primitive samples of the early solar system
|
cataclysmic variable
a close binary system which includes a white dwarf accreting matter from a less massive companion
|
catadioptric telescope
a telescope that combines the primary mirror of a reflector with a lens placed in front of the mirror that corrects for aberrations; most catadioptric telescopes for amateurs are Schmidt-Cassegrain telescopes
|
celestial pole
the imaginary projection of Earth’s rotational axis onto the celestial sphere
|
celestial sphere
the apparent sphere of the sky; an imaginary sphere of immense radius centered on Earth often used to plot the coordinates of objects in the sky
|
charge-coupled device
a silicon chip used to detect light; charge-coupled devices (CCDs) are far more efficient at collecting light than conventional film
|
chondrite
a stony meteorite containing small, round, silicate granules called chondrules
|
chromosphere
a layer in a star’s atmosphere lying below the corona and above the photosphere
|
circumpolar
Circumpolar stars are permanently above the horizon from a given observing point on Earth; that is to say, they never set. At Earth's Geographical North Pole (90° north latitude), all stars in the sky are cirumpolar. On Earth's equator, no stars are circumpolar.
|
clock drive
a motor attached to an equatorial mount that compensates for Earth’s rotation and thus keeps the telescope pointing at the same area of sky
|
coated optics
optics treated with a thin, uniform coating that greatly reduces scattered light and thus makes the image brighter
|
collapsar
a giant star that collapses of its own weight at the end of its normal lifetime
|
collimation
the act of putting a telescope’s optics into perfect alignment
|
coma
the bright shroud of gas that surrounds a comet’s nucleus
|
comet
a small piece of ice and rock that orbits a star usually in a highly elongated orbit; long-period comets have orbital periods longer than 200 years, short-period comets have orbital periods less than 200 years
|
comet nucleus
a solid, compact mass of rock and ice that heats up when exposed to sunlight and releases gas and dust
|
conjunction
a time when two or more bodies appear close together in the sky
|
constellation
one of the 88 patterns of stars in the sky, often named for a mythological god, hero, or animal
|
convection
the transfer of heat energy by moving currents of material
|
core
the central region of a planet, brown dwarf, star, or galaxy
|
corona
the outer atmosphere of the sun or a star
|
coronagraph
an instrument designed to block light from the solar disk, allowing the corona to be observed
|
coronagraphic mask
an disk-shaped instrument designed to block light from the disk of a star, allowing the region very close to a target star to be studied
|
coronal mass ejection
a huge eruption of electrified, magnetic gas ejected from the solar corona; this gas is hurled into space with speeds from 12 to 1,250 miles per second (about 20 to 2,000 kilometers per second); CMEs can produce geomagnetic storms and auroral displays on Earth
|
coronal mass ejections
huge eruptions of electrified, magnetic gas ejected from the solar corona; this gas is hurled into space with speeds from 12 to 1,250 miles per second (about 20 to 2,000 kilometers per second); CMEs can produce geomagnetic storms and auroral displays on Earth
|
cosmic background radiation
microwave radiation that permeates the universe and represents the still-cooling heat generated from the Big Bang
|
cosmic microwave background
microwave radiation that permeates the universe and represents the still-cooling heat generated from the Big Bang
|
cosmic ray
an atomic nucleus (most are protons) moving at a speed approaching that of light
|
cosmological constant
a term in the equations of general relativity that represents a repulsive force in the universe
|
cosmology
the branch of science concerned with the structure and evolution of the universe
|
cosmos
a synonym for universe
|
crescent
the phase of a planet or moon during which less than half the surface is illuminated
|
critical density
the density of the universe that provides just enough gravity to bring the expansion to a halt after an infinite time
|
crust
the thin, outermost geological layer of a planet, moon, or asteroid
|
cryovolcanism
the eruption of water and other liquid or vapor-phase volatiles, together with gas-driven solid fragments, onto the surface of a planet or moon due to internal heating
|