| A | B |
|---|
| nebula | a huge cloud of gas and dust |
| neutron star | the dense remains of a massive star's core after a supernova explosion |
| black hole | a dense, collapsed core with a very strong gravitational pull |
| protostar | a dense pocket of matter that is the beginning of a star |
| supernova | an enormous explosion of a giant star |
| red giant | an expanded star, with cooling outer layers |
| white dwarf | a dim star that forms from a collapsed red giant |
| constellation | a group of stars that forms a pattern in the night sky |
| meteorite | a meteor that falls to Earth |
| rotation | the spinning of the Earth on its axis |
| revolution | Earth's yearly trip around the Sun |
| trajectory | the curved course a probe takes through space |
| solar system | a star and the objects that revolve around it |
| Big Bang Theory | the idea that all the matter in the universe was once concentrated in a dense ball that then exploded |
| meteor | space debris that gets burned when it enters Earth's atmosphere |
| refracting telescope | uses lenses to focus light from distant objects |
| reflecting telescope | uses mirrors to gather light from distant planets |
| light year | unit of measure; the distance light can travel in one year |
| universe | everything that exists |
| solar eclipse | occurs when the Moon blocks the Sun |
| lunar eclipse | occurs when the Earth comes directly between the Sun and the Moon |
| astronauts | travels in a spacecraft |
