chapter 9: cosmos exam 2

cryovolcanism

low-temperature volcanism in which the magmas are composed of molten ices rather than rocky material

photodissociation

breaking apart of molecules into smaller fragments or individual atoms by the action of photons

near-earth asteroid

an asteroid whose orbit brings it close to the orbit of earth

near-earth object (NEO)

an asteroid, comet, or large meteoroid whose orbit intersects earth’s orbit

active comet

a comet nucleus that approaches close enough to the sun to show signs of activity, such as the production of a coma and tail

oort cloud

a spherical distribution of comet nuclei stretching from beyond the kuiper belt to more than 50,000 AU from the sun

short-period comet

a comet with an orbital period of less than 200 years

long-period comet

a comet with an orbital period of greater than 200 years

coma

the nearly spherical cloud of gas and dust surrounding the nucleus of an active comet

nucleus

the dense, central part of an atom; the central core of a galaxy, comet, or other diffuse object

head

the part of a comet that includes both the nucleus and the inner part of the coma

tail

a stream of gas and dust swept away from the coma of a comet by the solar wind and by radiation pressure from the sun

ion tail

one type of comet tail, consisting of ionized gas; particles in the ion tail are pushed directly away from the comet’s head in the antisunward direction at hight speeds by the solar wind

dust tail

one type of comet tail, consisting of dust particles that are pushed away from the comet’s head by radiation pressure from the sun

meteor shower

a larger-than-normal display of meteors that occurs when earth passes through the orbit of a disintegrating comet and sweeps up some of its debris

radiant

the direction in the sky from which the meteors in a meteor shower seem to come

stony meteorite

a meteorite composed primarily of silicate minerals, similar to those found on earth

chondrule

a small, crystallized, spherical inclusion of rapidly cooled molten droplets found inside some meteorites

chondrite

a stony meterorite containing chondrules

achondrite

a stony meteorite that does not contain chondrules

carbonaceous chrondrite

a primitive stony meteorite that contains chondrules and is rich in carbon and volatile materials

iron meteorite

a meteorite composed primarily of iron-nickel alloys

stony-iron meteorite

a meteorite composed of a mixture of silicate minerals and iron-nickel alloys

c-type asteroid

an asteroid made of material that has largely been unmodified since the formation of the solar system; most primitive type of asteroid

s-type asteroid

an asteroid made of material that has been modified from its original state, likely as the outer part of a larger, differentiated body that has since broken into pieces

m-type asteroid

an asteroid that was once part of the metallic core of a larger, differentiated body that has since been broken into pieces; made mostly of iron and nickel