Across
1
Icy body with a tail near the sun
3
Fourth state of matter
4
Gas form of a liquid
5
Center of an atom or cell
9
Unit of heredity
10
Path of a planet around the sun
11
Blocking of light by a celestial body
Down
2
Molten rock beneath Earth surface
3
Positive particle in nucleus
6
Unit of force
7
Biological catalyst
8
Glass that splits light into spectrum