Astronomy Vocab

3. A morphological classification scheme for galaxies. Often described as a tuning fork, after the shape of the diagram created from it.
4. An assemblage of stars, oval in shape, that contains no conspicuous interstellar material.
5. The main portion of a galaxy. Consists of a nucleus, bulge, and spiral arms.
7. The outermost extent of a galaxy with a sparse distribution of stars.
10. A plot of luminosity against surface temperature or spectral type for a group of stars.
12. A spherical collection of stars that orbits a galactic core as a satellite.
13. A large assemblage of stars without radial symmetry.
14. A star of large luminosity and radius.
15. The surface at which the escape velocity of a collapsing star is equal to the speed of light.
16. Two stars that revolve around each other.
17. The upper boundary to the mass of a white dwarf.
18. A collapsed, massive body whose escape velocity is equal to or greater than the speed of light.

1. The rate at which an object must travel in order to break free of the influence of gravity.
2. A measure of the luminosity of an object like a star.
6. Stars that pulsate radially, varying in both temperature and diameter, to produce brightness changes with a well-defined stable period and amplitude.
8. A measure of the observed light received from a star or other object.
9. Large, cold, interstellar clouds with large diameters where massive stars form.
11. A large assemblage of stars, gas, dust, and dark matter orbiting a common center.
16. An object, midway in size between a planet and a star, with a mass about 1/100 that of the sun.