| A | B |
|---|
| Distance between us and Andromeda Galaxy | ~3 million light years |
| Age of Universe | 13.7 billion years |
| ~200,000 years | when stars began to form |
| Edwin Hubble | astronomer who introduced a law about the expansion of the universe |
| cosmic background radiation | leftover thermal energy from the Big Bang |
| electromagnetic radiation | energy that travels through space in the form of waves |
| dark matter | matter that doesn't give off electromagnetic radiation |
| 23% | amount of dark matter in the universe |
| Vera Rubin | discovered dark matter |
| 90% | amount of stars in the main sequence |
| dark energy | causing the expansion of the universe to accelerate |
| Hertzsprung-Russell Diagram | used to classify stars and to see how stars change over time |
| Radio Waves | Longest wavelength of the electromagnetic spectrum |
| Gamma Rays | Shortest wavelength of the electromagnetic spectrum |
| Red | Longest wavelength of the visible light spectrum |
| Violet | Shortest wavelength of the visible light spectrum |
| Galileo | Invented the spectroscope, first to see the moon through a telescope, and given credit for inventing the telescope |
| 3 types of galaxies | spiral, elliptical, irregular |
| irregular galaxy | made of mostly young stars |
| spiral galaxy | main feature are the spiral arms, has the most stars |
| elliptical galaxy | made of mostly older stars |
| Milky Way | our home galaxy |
