Across
- 2. A planetary-mass object that does not orbit a star, but instead wanders through the galaxy directly orbiting the galactic center.
- 5. A star whose brightness changes over time, either due to internal pulsations (like expanding and shrinking) or being eclipsed by another object.
- 7. A small, rocky object orbiting the Sun, mostly found between Mars and Jupiter; they are remnants left over from the formation of the solar system.
- 8. A "failed star" that is massive enough to crush its own core but not massive enough to sustain hydrogen fusion like a true star.
- 11. The ultra-dense core left behind after a massive star explodes; a teaspoon of this material would weigh about 6 billion tons on Earth.
- 12. A celestial body made of ice, dust, and rock that orbits the Sun in an elongated path; when close to the Sun, it develops a glowing coma and tail.
- 14. A dying star in the late stages of stellar evolution that has exhausted its hydrogen fuel and expanded to many times its original size.
- 16. A type of neutron star with an extremely powerful magnetic field, capable of releasing intense bursts of X-rays and gamma rays.
- 18. The hot, dense remnant of a low-to-medium mass star (like our Sun) that has shed its outer layers; it will slowly cool over billions of years.
- 19. The extremely luminous center of a distant galaxy, powered by a supermassive black hole consuming vast amounts of gas and dust.
- 20. A small particle from an asteroid or comet orbiting the Sun; it is smaller than an asteroid but larger than a grain of dust.
Down
- 1. A hypothetical form of matter that is thought to account for approximately 85% of the matter in the universe but does not emit light.
- 3. A highly magnetized, rotating neutron star that emits beams of electromagnetic radiation from its magnetic poles, acting like a cosmic lighthouse.
- 4. A glowing shell of ionized gas ejected from a red giant star late in its life; despite the name, it has nothing to do with planets.
- 6. An early stage in the formation of a star, where a cloud of gas is collapsing under gravity but nuclear fusion has not yet begun.
- 9. A powerful and luminous stellar explosion that occurs at the end of a massive star's life, briefly outshining its entire host galaxy.
- 10. A giant interstellar cloud of dust, hydrogen, helium, and other ionized gases; often the site where new stars are born.
- 13. A system of two stars that are gravitationally bound to and orbit around a common center of mass.
- 15. A structure that consists of hundreds to thousands of galaxies bound together by gravity; one of the largest structures in the universe.
- 17. The stage in a star's life where it is stable and fusing hydrogen into helium in its core; our Sun is currently a Main Sequence star.