A
accretion--
accumulation of dust and gas into larger bodies.
albedo--
ratio of amount of light reflected by an object and the amount of incident light.(White's albedo is 1.0; black would have an albedo of 0.0)
albedo feature--dark or light marking on an object. It may be a topographical or geological feature.
aphelion--
point when a planet or other body is furthest from the sun.
artifical satellite--
man-made object that orbits a body in space (usually Earth).
asteroid--
a medium-sized rocky object made of rock and metal that orbits the sun.
asteroid number--
serial number assigned to asteroids when they are discovered. They don't have much meaning other than 'asteroid 257' was discovered after 'asteroid 256'.
astrology--
study that tries to link happenings in people's lives with the position of the stars and planets.
astronomical unit--
149, 597, 870 km. The average distance from the Earth to the sun.
astronomy--
branch of science that studies stars, planets, and all other heavenly bodies.
aurora--
glow in a planet's ionosphere cause by an interaction between the planet's magnetic field and charged particles from the sun.
aurora borealis--
caused by interaction between the solar wind, Earth's magnetic field, and the upper atmosphere. It is also know as "The Northern Lights". There is a similar effect in the Southern Hemisphere called "aurora australis".
B
Big Bang Theory--
theory about the beginning of the universe. It states that the universe began 15,000,000,000 (15 billion) years ago with a large explosion.
bolide--
a fireball that produces a sonic boom.
C
caldera--
crater formed by an explosion or collapse of a volcanic vent.
carbonate--
compound containing carbon and oxygen. One example is limestone.
catena--
chain of craters.
cavus--
hollow, irregular depression.
chos--
area of rugged terrain.
chasm--
canyon.
chromosphere--
lower level of the sun's atmosphere.
colles--
small hills.
coma--
the dust and gas surrounding a comet.
constellation--
a group of bright stars that form a pattern in the sky.
convection--
fluid circulation in a fluid that occurs because of differences of heat.
corona--
1. layer of atmosphere surrounding the sun
2. ring of colored light around a heavenly body
cosmic ray--
an extremely energetic charged particle that bombarded Earth from space.
crater--
bowl-shaped depression formed by the impact of a meteorite.
D
density--
ratio of mass of an object to its volume. It is measured in grams per cubic centimeter. Water's density is 1.0.
direct--
rotation orbit in a counterclockwise direction when viewed from the north pole.
dorsum--
ridge.
E
eclipse--
movement of one heavenly body across another, obscuring the view of the other heavenly body.
ellipse--
oval.
escarpments--
a long cliff.
explosive eruption--
dramatic volcanic explosion which throws debris high into the air.
F
farrum--
pancake-like structure.
filament--
a strand of cool gas.
fireball--
a meteor brighter than magnitude -3.
fissure--
narrow opening or crack of considerable length and depth.
flare--
sudden eruption of energy on the solar disk.
fossa--
long, narrow, shallow depression.
G
Gaia Hypothesis--
named for the Greek Earth goddess Gaea. It states that the Earth should be regarded as a living organism and that biological processes stabilize the enviorment.
Galilean Moons--
name given to the four moons of Jupiter.
geocentric theory--theory proposed by Ptolemy in which the earth is the center of universe.
geosynchronous orbit--
a direct, circular orbit.
granulation--
a pattern of small cells seen on the surface of the sun.
greenhouse effect--
increase in temperature due to a great difference in the outward thermal radiation and incoming solar radiation with the incoming being extremely greater than outward.
H
heliocentric theory--
theory proposed by Copernicus that stated that the sun was the center of the universe.
heliopause--
the point which the solar wind meets the interstellar medium or solar wind from other stars.
heliosphere--
space within the boundary of the heliopause containing the sun and other solar systems.
I
ice--
refers to water, methane, and ammonia which usually occur as solids outside the solar system.
inclination--
the angle between the plane of its orbit and the ecliptic.
inferior planets--
refers to the planets Mercury and Venus because they are closer to the sun than the earth.
interplanetary magnetic field--
the magnetic field carried with the solar wind.
interstellar--
between the stars
ionosphere--
region of charged particles in a planet's upper atmosphere.
K
Kelvin--
(K) system developed by William Thompson. 0 Kelvin is absolute zero; water melts at 273K; water boils at 373K.
L
labes--
landslide.
lacus--
lakes.
light-year--
distance light travels in a year. Six trillion miles.
M
macula--
dark spot.
magnetosphere--
region of space in which a planet's magnetic field dominates that of the solar wind.
magnetotail--
portion of a planetary magnetosphere which is pushed in the direction of the solar wind.
magnitude--
degree of brightness of a celestial body designated on a numerical scale.
mensa--
mesa, flat-topped elevation.
meteor--
bright streak of light in the sky caused by the entry into Earth's atmosphere. It is produced when a meteoroid burns up in Earth's upper atmosphere.
meteorite--
like a meteor, but doesn't burn up and it hits the ground.
minor planets--
official name for asteroids.
N
nebula--
bright or dark mass of interstellar gas and dust among the stars
nuclear fusion--
nuclear process where several small nuclei are combined to form a larger one
O
P
penumbra--
outer filamentary region of a sunspot.
perihelion--
point in which the orbit of a planet, comet, or asteroids closest to the sun.
photosphere--
visible surface of the sun.
planitia--
low plain.
planum--
plateau or high plain
prominence--
strand of relatively cool gas in the solar corona which appears bright when seen at the edge of the sun against the blackness of space.
Q
R
red giant--
a large red star that has low surface temperature and a diameter that is a hundred times that of the sun.
redshift--
a shift in the red part of the color spectrum when a star is moving away from the earth.
Relativity, Theory of--
describes the motion of bodies in strong gravitational fields of near the speed of light. It has a high degree of accuracy.
retrograde--
rotation or orbital motion in a clockwise direction when viewed from the north pole.
rift valley--
elongated valley formed by the depression of a block of the planet's crust between two faults or groups of faults of approximately parallel strikes.
S
satellite--
a small body that orbits around a large one in space.
shepherd satellite--
satellite which constrains the extent of a planetary ring through gravitational forces.
silicate--
compound containing silicon and oxygen (i.e. sand).
solar nebula--
cloud of dust and gas that began to collapse about five billion years ago to form the solar system.
solar wind--
tenuous flow of gas and energetic charged particles, mostly protons and electrons which stream from the sun. They are usually near 350 kilometers per second.
sublime--
to change directly from a solid to a gas without becoming a liquid.
sunspot--
area seen as a dark spot on the sun.
superior planets--
refers to Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto because their orbits are further away from the sun than the Earth's.
T
tectonic--
deformation forces acting on a planet's crust.
terra--
extensive land mass.
Tychonic theory--
theory that states that everything except the Earth and moon revolve around the sun, and that the sun and all its satellites orbit around the Earth. It was proposed by Tycho Brahe.
U
umbra--
1.dark central region of a sunspot.
2.the dark cone-shaped shadow from a planet or a satellite on the opposite side of the sun.
undae--
waves.
V
vallies--
sinuous valley.
vastitas--
widespread lowlands.
volatile--
refers to substances that are gases at normal temperatures. Examples include hydrogen, water, helium, ammonia, methane, and carbon dioxide.
W
white dwarf--
whitish star of high surface temperature and low brightness.
Y Z
