Astronomy

4. A group of apparently near by objects; clusters of stars or galaxies.
6. spectrum Spectrum that consists of emission lines.
7. Large number of stars with their interstellar gas and dust, grouped into a region that is well separated from other galaxies.
8. Blocking of light from one body by another that passes in front of it. Eclipse can be total or partial.
9. Bright band that stretches across the sky, produced by large number of stars and other bright objects that lie near the equatorial plane of our galaxy.
10. A system in which the positions of the Sun, Moon, and Planets are supposed to exert an influence on events on Earth.
11. Distance above the surface of a planet, used in describing an atmosphere or a spacecraft orbit.
12. Observed once each month, when the Earth lies between the Sun and Moon, and the fully illuminated disk of the Moon can be seen.
14. A measure of compactness: mass of an object divided by its volume.
15. Glowing trail in the upper atmosphere, produced by meteoroid burning up as it moves at high speed.

1. Central region of a planet. The Earth's core is liquid, possible with a small, solid inner core.
2. Path traced out by one object around another.
3. A group of stars that seemed to suggest the shape of some god, person, animal or object.
5. Distance that light travels in 1 year.
9. Scale for describing brightness of a celestial object. See apparent magnitude, absolute magnitude.
13. Phase of the moon when its motion brings it between the Earth and Sun, and thus appears to us not to be illuminated.