| Term | Meaning |
| red dwarf | a small, cool very faint, main sequence star whos surface temp. is under 4000k. Red dwarfs are the most common type of star. Proxima Centauri is one. |
| Red Giant | a relatively old star whose diameter is about 100 percent bigger than it was originally, and had become cooler. they are frequently orange in color. Betelgeuse is one. |
| supergiant | the largest known type of star;some are almost as large as our entire solar system. Betelgeuse and Rigel are these. |
| White Dwarf | a small, very dence, hot star that is made mostly of carbon |
| Brown Dwarf | a star whose mass is too small to have nuclear fusion occur at its core. They are not very luminous. |
| Neutron Star | a very small, super dense star which is composed mostly of tightly packed neutrons has a thin atmosphere of hydrogen. It has a diamerter of about 5-10 miles and a density of 10000000000000000gm/cm3. |
| pulsar | a rapidly spinning neutron star that emits energy in pulses |
| Double star | two stars that appear close to one another in the sky. Some are true binaries, others just appear together from the Earth because thy are both in the same line of sight. |
| Binary star | is a system of two stars that rotate around a common center of mass. About half of all stars are in a group of at least two stars Polaris is an example. |
| Eclipsing Binary | two close stars that appear to be a single star varying in brightness. The variations in brightness is due to the stars periodically obscuring or enhancing one another. The binary star sysetem is titledso that its orbital plane is viewed from its edge. |
| X Ray Binary star | are special type of binary star in which one of the stars is a collapsed object such as a white dwarf, neutron star, or black hole. As a matter is stripped from the normal star, it falls into the collapsed star, producin X Rays |
| asteroid | a small, rocky chunk of matter orbiting the sun, also called a minor planet, most asteroids orbit in the asteriod belt |
| asteroid belt | a band between mars and jupiter where most asteroids orbit |
| barycenter | the center of mass in a system of two orbiting bodies |
| celestial sphere | a huge, imaginary sphere around theEarth, used to model the positions and motions of celestial bodied |
| centripetal force | the force acting upon a body moving along a curved path that is directed toward the center of curvature of the pathe and constains the body to the path |
| circumpolar stars | stars that never rise or set because their star trails do not intersect the horizon |
| comet | massof fromzen gases revolving around the sun, generally in a highly eccentric orbit |
| eclipse | the darkening of a celestial body as it passes throughthe shadow of another body, the obscuration of all or part of the sun by a celestial body |
| equinox | the time when the sun crosses the plane of the earth's equator making night and day of approximately equal lenght all over the world |
| fixed star | a star that occupies a fixed point on the celestial sphere |
| gibbous moon | a phase between quarther and full that shows a surface that is more than half illuminated |
| lunar eclipse | an eclipse in which parts of the Moon are darkened be the Fearth's shadow, lunar eclipses occur at times of the full moon |
| meteor | the luminous trail of heated air produced by a meteoroids passage through the earth's atmosphere |
| meteorite | a meteorid that reaches the surface of the Earth or another planet or moon |
| meteoroid | a rock in space on a collision couse with the earth, sources of meteorids include comets and colliding asterois |
| meteor shower | an eventcaused by the earths passage through the orbit of a comet, where it will collide with an increased number of meteoroids, it happens at the same piont in the Earth's orbit and thus on the same date every year |
| partial lunar eclipse | an eclipse in whic only part of the moon enters the umbra and isdarkende |
| penumbra | the light shadow outside the dark shadow of an opaque body, where the light from te source of illumination is partially cut off |
| solar corona | a faint halo of gases surrounding the sun visible during a toatal solar eclipse |
| star trails | a streak made by stars on photographs of the sky, caused b Earth's rotation |
| umbra | the dark shadow of an opaque body,ehere diret light from the source of illuminationis completely cut off |
| waxing moon | any phase during with the illuninationfraction of the face increases |
| zenith | the point in the sky directly above the observer, opposite the nadir |
| nadir | the point in the celestial spher directly beneath the observer, opposite the zenith |
