Earth/Astronomy

5. a star that suddenly increases greatly in brightness because of a catastrophic explosion that ejects most of its mass.
6. a fixed luminous point in the night sky that is a large, remote incandescent body like the sun
7. the force that attracts a body toward the center of the earth, or toward any other physical body having mass. For most purposes Newton's laws of gravity apply, with minor modifications to take the general theory of relativity into account.
9. a nuclear reaction in which atomic nuclei of low atomic number fuse to form a heavier nucleus with the release of energy.
10. an elastic wave in the earth produced by an earthquake or other means.
11. a region of space having a gravitational field so intense that no matter or radiation can escape.
12. is the ionizing radiation present in the environment.
14. is the change in frequency or wavelength of a wave for an observer who is moving relative to the wave source.
15. a part or aspect of something abstract, especially one that is essential or characteristic.

1. are a type of elastic wave, and are one of the two main types of elastic body waves, called seismic waves in seismology,
2. is a wave motion in a solid medium where the medium moves perpendicular to the direction of the travel of the wave.
3. a theory in astronomy: the universe originated billions of years ago in an explosion from a single point of nearly infinite energy density — compare steady state theory
4. the distance between successive crests of a wave, especially points in a sound wave or electromagnetic wave.
8. the wavelength of the light is stretched, so the light is seen as 'shifted' towards the red part of the spectrum.
13. a fixed luminous point in the night sky that is a large, remote incandescent body like the sun