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| Astronomy: | The area of science that deals with celestial objects, space and the physical universe. People who work in this field are called astronomers. |
| Astrophysics: | An area of astronomy that deals with understanding the physical nature of stars and other objects in space. |
| Colleague: | Someone who works with another; a co-worker or team member. |
| Constellation: | Patterns formed by prominent stars that lie close to each other in the night sky. |
| Cosmos: | A term that refers to the universe and everything within it. |
| Exoplanet: | Short for extrasolar planet, it’s a planet that orbits a star outside our solar system. |
| Gas Giant: | A giant planet that is made mostly of the gases helium and hydrogen. |
| Infrared: | A type of electromagnetic radiation invisible to the human eye. The name incorporates a Latin term and means “below red. |
| Jupiter: | The solar system’s largest planet, it has the shortest day length (10 hours). |
| Light-Year: | The distance light travels in one year, about 9.48 trillion kilometers (almost 6 trillion miles). |
| Mass: | A term that means how much an object resists speeding up and slowing down — basically a measure of how much matter that object is made from. |
| Planet: | A celestial object that orbits a star, is big enough for gravity to have squashed it into a roundish ball and has cleared other objects out of the way in its orbital neighborhood. |
| Solar System: | The eight major planets and their moons in orbit around our sun, together with smaller bodies in the form of dwarf planets, asteroids, meteoroids and comets. |
| Star: | The basic building block from which galaxies are made. They develop when gravity compacts clouds of gas. |
| Sun: | The star at the center of Earth’s solar system. It is about 27,000 light-years from the center of the Milky Way galaxy. |
