| A | B |
|---|
| Fission | Process in which heavy nuclei split into smaller, lighter nuclei |
| Fusion | Process in a star’s core in which lightweight hydrogen nuclei combine into heavier helium nuclei |
| Spectrum | Arrangement of visible light ordered according to wavelength |
| Constellation | Group of stars that forms a pattern in the sky that resembles an animal, mythological, or everyday object |
| Luminosity | The rate of emission of radiation, visible or otherwise |
| Hubble constant | the unit of measurement used to describe the expansion of the universe |
| Big Bang theory | proposes that the universe began as a single point and has been expanding ever since |
| cosmology | the science of the origin and development of the universe |
| inflationary universe | the exponential expansion of space in the early universe |
| steady-state theory | a discredited expanding universe model alternative to the big bang theory of the universe and its origin |
