Universe and Stars Crossword Puzzle

3. The average length of a star's main sequence stage in billions of years
5. A unit of number used to measure the extreme ages and temperatures of stars
6. The longest and most stable adult stage of a star's life cycle
11. The estimated temperature in millions of degrees needed to fuse heavier elements
12. A star that swells up and turns red as its core runs out of hydrogen
15. The process inside a star's core that smashes atoms together to release energy
16. An enormous star that expands and cools after using up its main hydrogen fuel
18. A gigantic, powerful explosion caused by a dying massive star
19. Stars that burn through fuel very quickly and end in giant explosions

1. An object with gravity so strong that not even light can escape it
2. The super-dense remains of a massive star created after a supernova
4. A glowing shell of gas blown off by a dying medium-sized star
6. The amount of matter in a star, which controls how long it lives and how it dies
7. The hot, dense core left behind after a medium star dies
8. A measure of how bright a star looks from Earth
9. A early "baby" star made of contracting gas and dust before fusion begins
10. A huge cloud of dust and gas in space where new stars are born
13. The metal element created at the core of a massive star right before it explodes
14. A cooled-down white dwarf that no longer shines or gives off light
17. Newly formed stars that have recently started shining on the main sequence