Across
- 3. the natural satellite of Earth
- 4. the curved path of an object round a star, planet or moon
- 5. the force that attracts a body towards objects with mass
- 6. a cloud of gas and dust in outer space
- 7. a star that suddenly increases greatly in brightness because of a catastrophic explosion that ejects most of its mass
- 8. a hypothetical space object about the size of Mars that many astronomers believe once existed in the solar system, following an orbit similar to that of Earth and that collided with Earth
Down
- 1. a celestial body moving in an elliptical orbit round a star
- 2. the rapid expansion of matter
- 5. a system of millions or billions of stars, together with gas and dust, held together by gravitational attraction
- 7. a fixed luminous point in the sky, remote incandescent body like the Sun