Astronomy

Across

4. A planet that exists outside the orbit of the Earth. All of the planets in our solar system are superior except Mercury and Venus. These two planets are inferior planets.
5. A group of stars that form a pattern in the night sky.
8. A term used to describe anything originating on the planet Earth.
11. The gaseous envelope of a celestial body (such as a planet).
13. An ellipse is an oval shape. Johannes Kepler discovered that the orbits of the planets were elliptical in shape rather than circular.
18. Material from beneath the surface of a body such as moon or planet that is ejected by an impact such as meteor and distributed around the surface. Ejecta usually appears as lighter color than the surrounding surface.
19. A type of volcanic crater that is extremely large, usually formed by collapse of a volcanic cone or by a violent volcanic explosion.
20. Outer edge or border of a planet or other celestial body.
22. Any of 88 arbitrary configurations of stars or an area of the celestial sphere covering one of these configurations.
25. A state that occurs when compression due to gravity is balanced by a pressure gradient which creates a pressure gradient force in the opposite direction. Hydrostatic equilibrium is responsible for keeping stars from imploding and for giving planets their spherical shape.
26. A shift in the lines of an object's spectrum toward the blue end. Blueshift indicates that an object is moving toward the observer. The larger the blueshift, the faster the object is moving.
27. Also known as the southern lights, this is an atmospheric phenomenon that displays a diffuse glow in the sky in the southern hemisphere. It is caused by charged particles from the Sun as they interact with the Earth's magnetic field. Known as the Aurora Borealis in the northern hemisphere.
28. A body that gives light.
29. A celestial body that orbit around the Sun.
30. The point in the orbit of a planet or other celestial body where it is the farthest from the sun.

Down

1. The area of partial illumination surrounding by the darkest part of the shadow caused by an eclipse.
2. A ball-shaped gaseous celestial body that shines by its own light.
3. The point in the orbit of a planet or other body where it is closest to the Sun.
6. The explosion of a star in which the star may reach a maximum intrinsic luminosity one billion times that of the sun.
7. A term used to describe matter in the universe that cannot be seen, but can be detected by its gravitational effects on other bodies.
9. The collapsed core of a massive star. Stars that are very massive will collapse under their own gravity when their fuel is exhausted. The collapse continues until all matter is crushed out of existence into what is known as a singularity. The gravitational pull is so strong that not even light can escape.
10. A system of two stars that revolve around a common centre of gravity.
12. The invisible boundary around a black hole past which nothing can escape the gravitational pull - not even light.
14. A large grouping of stars. Galaxies are found in a variety of sizes and shapes. Our own Milky Way galaxy is spiral in shape and contains several billion stars. Some galaxies are so distant the their light takes millions of years to reach the Earth.
15. A region at the center of a galaxy that produces an extremely large amount of radiation.
16. A relatively compact group of stars forming a gravitating unit and containing either not more than a few hundred stars or tens of thousands of stars.
17. A star that leads or guides.
21. Any of numerous clouds of gas or dust in interstellar space.
23. The process by which dust and gas accumulate into larger bodies such as stars and planets.
24. The two points at which the Sun crosses the celestial equator in its yearly path in the sky. The equinoxes occur on or near March 21 and September 22. The equinoxes signal the start of the Spring and Autumn seasons.