Astronomy

1. One of the two points within an ellipse; the Sun is located at one of these.
5. A large cloud of gas and dust where stars are born.
6. A rapidly spinning neutron star that emits beams of electromagnetic radiation.
7. The oval-shaped path that a planet travels around the Sun (Kepler's First Law).
10. The time it takes a planet to complete one full orbit around the Sun.
12. The element produced when hydrogen atoms are fused in the Sun's core.
14. The point in an orbit where a planet is farthest from the Sun.
15. The force that pulls matter together to form stars and governs planetary orbits.
17. The process by which material is added to a celestial body, like a growing star or black hole.

2. The extremely hot, central region of a star where nuclear reactions occur.
3. The total amount of energy a star radiates per unit of time (its intrinsic brightness).
4. A unit of astronomical distance, equivalent to about 3.26 light-years.
6. The point in an orbit where a planet is closest to the Sun.
8. The nuclear process in a star's core that generates energy by combining light elements.
9. A powerful and luminous stellar explosion that marks the death of a massive star.
11. A type of compact stellar remnant, often White or Brown.
13. The sequence on the Hertzsprung-Russell diagram where most stars spend their lives.
16. A star stage when its outer layers expand significantly after exhausting core hydrogen.