the universe

3. nebula / the nebulosity surrounding a star: a star's shell or envelope of nebulosity.
4. star / is a star with an initial mass of 0.5 to 8 times that of Earth's Sun. It spends most of its time in the main sequence as an orange-yellow star.
6. / the amount of solar radiation reaching a given area.
9. / a region of space having a gravitational field so intense that no matter or radiation can escape.
10. / a star that suddenly increases greatly in brightness because of a catastrophic explosion that ejects most of its mass.
12. dwarf / a small very dense star that is typically the size of a planet.
13. star / a star at least eight times as massive as our sun.
15. / the natural satellite of the earth, visible (chiefly at night) by reflected light from the sun.
16. fusion / a nuclear reaction in which atomic nuclei of low atomic number fuse to form a heavier nucleus with the release of energy.
17. eclipse / an eclipse in which the moon appears darkened as it passes into the earth's shadow.
18. supergiant / An extremely large red giant star.
20. / A huge ball of gas held together by gravity.
21. / a cloud of gas and dust in outer space,
22. / the planet on which we live; the world.

1. / a system of millions or billions of stars, together with gas and dust, held together by gravitational attraction.
2. nebula / a ring-shaped nebula formed by an expanding shell of gas around an aging star.
5. / a group of stars forming a recognizable pattern that is traditionally named after its apparent form or identified with a mythological figure.
7. / the star around which the earth orbits.
8. / a celestial body moving in an elliptical orbit around a star.
11. / it has been expanding since its creation in the Big Bang about 13 billion years ago.
14. eclipse / the sun is obscured by the moon.
16. star / a celestial object of the very small radius (typically 18 miles/30 km) and very high density, composed predominantly of closely packed neutrons.
19. / the curved path of a celestial object or spacecraft around a star, planet, or moon, especially a periodic elliptical revolution.
20. / a continuous area or expanse which is free, available, or unoccupied.