Across
- 1. Velocity: The rate at which an object must travel in order to break free of the influence of gravity.
- 4. dwarf: A low-mass star that has exhausted most or all of its nuclear fuel and has collapsed to a very small size.
- 7. brightness: A measure of the observed light received from a star or other object.
- 12. limit: The upper boundary to the mass of a white dwarf.
- 13. sequence: A morphological classification scheme for galaxies. Often described as a tuning fork, after the shape of the diagram created from it.
- 17. galaxy: A flattened, rotating, large assemblage of stars with pinwheel-like arms of interstellar material and stars winding out from its nucleus.
- 19. star: A star of extremely high density composed almost entirely of neutrally charged subatomic particles.
- 21. bulge: The central part of a galaxy.
- 22. horizon: The surface at which the escape velocity of a collapsing star is equal to the speed of light.
- 24. The apparent displacement of a nearby star caused by the revolution of the Earth around the sun.
- 25. A star of very high luminosity and relatively low temperature.
- 28. magnitude: A measure of the luminosity of an object like a star.
- 29. A variable radio source of small angular size that emits very rapid radio pulses in very regular periods.
- 30. An explosion that marks the final stage of stellar evolution.
- 31. radius: The distance from the center of a black hole to its event horizon.
- 32. A large assemblage of stars, gas, dust, and dark matter orbiting a common center.
- 33. molecular clouds: Large, cold, interstellar clouds with large diameters where massive stars form.
Down
- 2. Variables: Stars that pulsate radially, varying in both temperature and diameter, to produce brightness changes with a well-defined stable period and amplitude.
- 3. cluster: A spherical collection of stars that orbits a galactic core as a satellite.
- 5. galaxy: An assemblage of stars, oval in shape, that contains no conspicuous interstellar material.
- 6. classes: The classification of stars according to their temperatures using the characteristics of their spectra.
- 8. Diagram (HR diagram): A plot of luminosity against surface temperature or spectral type for a group of stars.
- 9. An object of very high redshift that looks like a star but is extragalactic and highly luminous.
- 10. hole: A collapsed, massive body whose escape velocity is equal to or greater than the speed of light.
- 11. galaxy: A large assemblage of stars without radial symmetry.
- 14. sequence: Middle-age stars that can be found running diagonally through the middle of an HR diagram.
- 15. A star that experiences a sudden outburst of radiant energy, temporarily exponentially increasing its luminosity.
- 16. system: Two stars that revolve around each other.
- 18. disk: The main portion of a galaxy. Consists of a nucleus, bulge, and spiral arms.
- 20. A cloud of interstellar gas or dust.
- 23. Object: One of the 107 galaxies, nebulas, star clusters, and other deep sky objects classified with an M followed by a number.
- 26. dwarf: An object, midway in size between a planet and a star, with a mass about 1/100 that of the sun.
- 27. The outermost extent of a galaxy with a sparse distribution of stars.
- 31. A theoretical point of zero volume and infinite density to which any black hole must collapse.
- 32. A star of large luminosity and radius.