Project Science Magazine Crossword Puzzle

This printable crossword puzzle on the topic of Astronomy & Space has 10 clues. Answers range from 4 to 19 letters long. This crossword is also available to download as a Microsoft Word document or a PDF.

When the conditions are "just right" for something new and complex to happen
Gas element represented by "He" on the periodic table
Smallest unit of matter
A positively charged particle
A negatively charged particle
A large system of stars, for example: The Milky Way
A word that describes everything, meaning all space, time, and matter
The most widely accepted theory for how the universe began
A glowing ball of gas containing hydrogen and helium
A heavy body that orbits the sun