Download Astronomy Terms

Astronomy Terms
Solar System/Galaxy:
Galaxy = huge collection of stars
Milky Way Galaxy = the name of our galaxy; a spiral galaxy
Big Bang Theory = theory that states that the universe began to expand with the
explosion of concentrated matter and energy and has been expanding ever since
Copernicus = Polish astronomer who first stated the theory that Earth and other planets
revolve around the sun
Light-year = the distance that light travels in one year
Gravity = force of attraction between objects
Orbits = path an object takes when moving around another object in space
The Sun:
Nuclear Fusion = process that converts matter into energy; process by which hydrogen
atoms are fused, or joined together, to form helium atoms
Core = center of the sun; composed of hydrogen and helium stirring in nuclear reaction
Middle Layer = called the radiation zone; the next layer out from the core of the sun
Outer Layer = called the convection zone; helps move heat from the core to the surface
Photosphere = the visible surface of the sun; innermost layer of the sun’s atmosphere
Chromosphere = the middle layer the sun’s atmosphere
Corona = a cloud of gas surrounding the sun; the outermost layer of the sun’s
atmosphere
Prominence = bright arches of gases; violent solar storm on the sun that can be seen
from Earth as a huge bright arch or loop of hot gases
Solar Flare = powerful explosions which burst from sunspots; solar storm on the sun that
shows up as a bright burst of light on the sun’s surface
Sunspot = area where gases have broken through the surface of the sun; dark area on the
sun’s surface
Solar Wind = continuous stream of high-energy particles released into space in all
directions from the sun’s corona
Eclipses:
Eclipse = when one object blocks out another from sight
Lunar Eclipse = when the earth passes between the moon and the sun and the moon is
blocked from sight; blocking of the moon that takes place when the Earth comes
directly between the sun and the full moon; occur more frequently than solar
eclipses
Solar Eclipse = when the moon passes between the sun and the Earth and the sun is
blocked from view; blocking of the sun that occurs when the new moon comes
directly between the sun and the Earth; very rare occurrence
Full Eclipse = when the entire sun or moon is blocked from view
Partial Eclipse = when only a portion of the sun or moon is blocked from view
Umbra = inner part of the shadow created during an eclipse; total shadow
Penumbra = outer part of the shadow created during an eclipse; partial shadow
The Moon:
Phases = different views of the moon dependent upon the position of the moon in
relation to the sun and Earth and how much sunlight is refelcted
Waxing = when the visible portion of the moon is getting larger
Waning = when the visible portion of the moon is getting smaller
Gibbous = when more than a quarter of the moon is visible
Crescent = when less than a quarter of the moon is visible
Crater = hole on the surface of the moon created by meteoroids impacting the surface
Maria = “seas” on the moon’s surface; smooth lowland plains on the surface of the moon
Rilles = long, narrow valleys on the moon’s surface probably caused by flowing lava
Highlands = mountain ranges on the surface of the moon
Full Moon = when the moon is aligned with the sun and Earth with the Earth being in the
middle and the entire side of the moon facing the Earth is bright and visible
New Moon = when the moon lies between the sun and Earth and the side of the moon
facing the Earth is not visible
First Quarter = when the moon has moved east from the new moon phase to a 90 degree
angle with the Earth and sun and appears half bright and half dark
Third Quarter = when the moon has moved from the full moon phase to a 90 degree
angle with the Earth and sun and appears half bright and half dark
Meteoroids, Meteors, Meteorites:
Meteor = luminous streak seen in the sky; stray bits of rock that fall from space in
uncontrollable flight
Meteoroid = tiny piece of rock or metal traveling through space
Meteorite = piece of material from space that lands on Earth; a meteor that hits the
ground
Shooting Star = a meteor that vaporizes in the Earth’s atmosphere; a tiny asteroid or
asteroid fragment
Comet:
Comet = large frozen mass of gas and dust that has a regular orbit around the sun; an icy
body that orbits the sun in an elliptical orbit
Nucleus = solid part of a comet made mainly of ice; tiny solid part of a comet made up of
bits of rock and dust frozen in ice
Tail = gaseous part of a comet that points away from the sun because of the solar wind
Halley’s Comet = famous comet that orbits every 76 years
Kuiper Belt = origin of most comets
Oort Cloud = origin of most comets; giant cloud of as many as 100 billion comets
Coma = haze around a comet created by the ice evaporating directly to a gas as the comet
nears the sun; fuzzy glowing ball that forms around the nucleus
Head = the coma and nucleus form the head of a comet
Asteroid:
Asteroids = pieces of rock; large space rocks
Asteroid Belt = gap between mars and Jupiter containing a large collection of asteroids
orbiting the sun
Minor Planets = celestial bodies too small to be called planets; asteroids
Kirkwood Gap = area near Jupiter that contains no asteroids because of Jupiter’s strong
gravitational pull
Ceres = the largest known asteroid
Stars/Constellations:
Star =
Constellation = group of stars that form a pattern
Red Giant =
White Dwarf = small, dense star
Supernova = tremendous explosion in which a star breaks apart, releasing energy and
newly formed elements
Neutron Star = smallest of the stars
Pulsar = neutron star that gives off pulses of radio waves
Quasar = quasi-stellar radio source; distant object that gives off mainly radio waves and
x-rays
Black Hole = core of a supernova star that remains after a supernova; the gravity of the
core is so strong that not even light can escape