Asteroid This is a large, rocky body found in space. It often orbits the sun in a belt between Mars and Jupiter.
Astronomical Unit This is the distance between the sun and the earth. It is the standard unit for distance within
our solar system.
Astronomy This is the study of celestial bodies and extra-terrestrial phenomena.
Aurora This is a spectacular "light show" formed by collisions between fast-moving particles (electrons) from
space and the oxygen and nitrogen gas in Earth's atmosphere.
Big Bang Theory This is a scientific theory that the universe was created about 4 to 5 billion years ago as the
result of explosions from expanding matter.
Centripetal Force This is the force on a rotating or orbiting body in the direction of the center of rotation.
Chromosphere (in the sun) a narrow layer above the photosphere that raises in temperature with height;
normally can't be seen because of the intensity of the light from the photosphere
Comet This is a small rocky body that orbits the Sun, and when close to the sun exhibit a small tail of ice and
gas.
Corona The layer of the Sun above the chromosphere which is hotter than the Sun's surface and where many
solar events, such as solar flares and prominences, can be seen. It is where solar wind originates
Density This is a measure of mass per unit volume.
Distance This is the measured value (always positive) from one point to another.
Earth Revolution This is the elliptical orbit of the Earth around the Sun. It takes 365.25 days to complete one
orbit.
Earth Rotation This refers to the spinning of our planet on its axis. This takes twenty four hours and is
responsible for day and night.
Elliptical Galaxy This is a galaxy consisting of mostly older stars that has no dust lane and is fairly featureless.
The shape can range from spherical to highly elongated.
Elliptical Orbit This when a satellite orbits in an oval-shaped path around a central object.
Fusion The process in which nuclei with small masses are combined to form a nucleus with a larger mass.
Galaxy This is a massive, gravitationally bound system consisting of stars, interstellar gas and dust, and dark
matter.
Ionosphere This is the outermost layer of Earth's atmosphere where many atoms are have gained or lost
electrons so they have a net electrical charge. This layer is very thin, is where the aurora take place, and is also
responsible for absorbing the most energetic photons from the Sun.
Light Year This is the distance that a light travels in 365.25 earth days. 9.46 x 1015m
Lunar Eclipse This occurs when the Moon passes through some portion of the Earth's shadow. This can occur
only when the Sun, Earth, and Moon are aligned exactly, or very closely.
Mass This is a measure of the quantity of matter.
Meteor This is the visible event that occurs when a meteoroid or asteroid enters Earth's atmosphere and
becomes visible.
Photosphere visible surface of the sun which is about 100 km thick and is composed of gas; it is the region of
the sun that produces visible light
Radiation Heat transfer by electromagnetic waves.
Satellite This is an object which is in orbit around another celestial body in space. It can be natural or artificial.
Solar Eclipse This occurs when the Moon passes between the Sun and the Earth so that the Sun is completely
or partially obscured.
Solar Energy This is the utilization of radiation from the sun.
Solar Flare a magnetic storm on the Sun which is a very hot, bright spot that usually occurs near sunspots; an
explosion that releases huge amounts of high-energy particles and gases and are ejected thousands of miles from
the surface of the Sun; can also cause sunquakes
Solar System This is the Sun and the celestial objects bound to it by gravity. This includes the eight planets and
their 166 known moons,four dwarf planets, and billions of small bodies, including asteroids, comets,
meteoroids, and interplanetary dust.
Solar Wind This consists of particles streaming away from the sun and being blown into space at speeds of
200-800 km/sec. These particles are responsible for auroral lights and a planet's magnetosphere.
Spiral Galaxy This is a galaxy with a characteristic pinwheel shape with a flat disk, central bulge, and graceful
arms containing regions where young stars form.
Star This is a massive ball of plasma that shines because of thermonuclear fusion in its core.
Sunspots dark spots that are visible on the surface of the sun that are caused by intense magnetic activity that
disrupts convection forming areas of reduced surface temperature
Telescope Equipment used to magnify objects far away.
Tides These are caused by the gravitational pull of the moon.
Universe This is all matter and energy, including Earth, the galaxies, and the contents of intergalactic space.