space

3. Jupiter and Saturn are sometimes called the gas ______.
6. The ____ Cloud is considered to mark the edge of the solar system.
8. Black holes are among the most ________ cosmic objects.
10. Pluto is truly way out there and on a wildly ______, elliptical orbit.
12. The ___ defines a true planet as a body that circles the sun without being some other object's satellite.
13. The sun is by far the largest object in our solar system, __________ 99.8% of the solar system's mass.
15. Black holes huge concentrations of ______ packed into very tiny spaces.
16. The four large outer worlds — Jupiter, Saturn, Uranus and Neptune — are sometimes called the ______ or "Jupiter-like" planets.
17. The solar system stretches outward from the ___.
18. A star’s ___ provides its fuel.
19. Stars are giant balls of hot gas – mostly ________.

1. The _____ _______ isn’t a surface like Earth’s or even the Sun’s.
2. NASA has a _____ of spacecraft observing the sun.
4. At the beginning of the end of a star’s life, its ____ runs out of hydrogen to convert into helium.
5. Stars form in large clouds of gas and dust called _________ clouds.
7. Astronomers estimate that the universe could contain up to one __________ stars.
9. A real term that describes what happens when ______ gets too close to a black hole.
11. The nearest known black hole, called ____ BH1, is about 1,500 light-years away.
14. Astronomers call stars that are stably undergoing nuclear fusion of hydrogen into ______ main sequence stars.
19. Black holes aren’t really _____.