Across
1
Center of an atom or cell
3
Force that attracts objects together
8
Second lightest element
9
Molten rock beneath Earth surface
11
Amplified beam of light
12
Unit of energy
Down
2
Ball of burning gas in space
4
Blocking of light by a celestial body
5
Natural satellite of Earth
6
Biological catalyst
7
Preserved remains of ancient life
10
Gas form of a liquid