Solar System Challenge

2. I am a hypothetical planet in which researchers have found evidence of my existence, but I am found in deep space.
3. _________ comet is the most famous comet and takes about 76 years to travel around the Sun.
7. Which planet is named after a Roman god, who is known as Zeus to those in Greek mythology?
10. This is the only planet that rotates on it's side.
12. This is a dwarf planet that is extremely cold and only 1/9 of the radius of Earth.
13. Is the name for a celestial body in our solar system that is not one of our 8 planets, and is another name for the god Hades.
14. considered to be a giant spherical shell surrounding the universe.
17. I was discovered by William Lassell who was an amateur astronomer in 19th century England.
18. This planet's moons orbit the closest to the planet itself compared to the other moons and planets in the solar system.

1. This amino acid _____ was found in comet dust and here on Earth is used by organisms to make proteins.
4. This show first aired in 1966 and took inspiration from the cosmos.
5. Our Solar system makes up the _______ arm of the Milky Way galaxy.
6. This was the first planet in our solar system that was explored by a spacecraft.
8. Our sun is considered a ___________ (hint 2 words, no space) star.
9. the name of Pluto's largest moon.
11. this planet has 5 main rings, and is not the planet saturn.
15. There are roughly ____ billion galaxies in the universe.
16. Our Sun is a giant ball of ______.