Across
1
Icy body with a tail near the sun
4
Precious yellow metallic element
5
Center of an atom or cell
8
Fourth state of matter
9
Path of a planet around the sun
10
Preserved remains of ancient life
11
Blocking of light by a celestial body
Down
2
Group of similar cells
3
Compound containing oxygen
6
Unit of energy
7
Element found in all living things