Across
- 4. the envelope of gases surrounding the earth or another planet
- 6. the force that attracts a body towards the centre of the earth
- 7. a Spaceship
Down
- 1. a person who is trained to travel in a spacecraft
- 2. a system of millions or billions of stars,held together by gravitational attraction
- 3. explosion of stars that marks the end of their lives
- 5. the usa measure unit