Universe Unit

2. A giant ball of hot gas (plasma) made primarily of hydrogen and helium that generates energy through fusion
4. Often called a "star nursery," this is a large cloud of gas and dust where stars are born
5. One of the possible final remnants of a high-mass star after it undergoes a supernova
6. An early, unstable phase of a star's life where gravity is actively pulling gas and dust together
9. A unit of measurement representing the distance that light travels in a single year
11. The fundamental force that pulls objects toward one another and governs the motion of all objects in the solar system
15. A galaxy shaped like an oval or "space football" that contains mostly older, redder stars
16. A stage in the life cycle of small to medium stars that occurs after the main sequence when fuel begins to run out
17. A very dim but hot star formed when a low-mass star runs out of fuel and sheds its outer layers
18. The region on an H-R diagram where 90% of stars, including our Sun, are categorized during the longest part of their life cycle
19. The specific spiral galaxy that contains our solar system
20. A measure of the amount of energy a star releases from its surface

1. A massive collection of stars, gas, and dust held together by the force of gravity
3. The tendency of a moving object to keep moving in a straight line, which works with gravity to maintain orbits
7. A galaxy characterized by a rotating disk and "arms" that contain younger stars
8. A scatterplot or chart used by astronomers to show the relationship between a star’s temperature and its luminosity
10. A galaxy with no definite shape, often smaller in size and full of young stars
12. The process of atoms smashing together to create energy, which is what causes stars to shine
13. A massive explosion that occurs at the end of a high-mass star's life cycle
14. The curved path an object (like a moon or planet) takes around another body due to gravitational pull