Across
- 1. The characteristic way in which the intensity of radiation emitted by a hot object depends on frequency. The frequency at which the emitted intensity is highest is an indication of the temperature of the radiating object.
- 4. The very largest of the large, hot, bright stars at the uppermost, left end of the main sequence on the Hertzsprung-Russell diagram.
- 5. Fragments of collapsing gas and dust that did not contain enough mass to initiate core nuclear fusion. Such an object is then frozen somewhere along its pre-main-sequence contraction phase, continually cooling into a compact dark object. Because of their small size and low temperature, these are extremely difficult to detect observationally.
- 7. A star that suddenly increases in brightness, often by a factor of as much as 10,000 then slowly fades back to its original luminosity. These are the result of an explosion on the surface of a white-dwarf star, caused by matter falling onto its surface from the atmosphere of a binary companion.
- 8. Objects that emit radiation in the form of rapid pulses with a characteristic pulse period and duration. Charged particles, accelerated by the magnetic field of a rapidly rotating neutron star, flow along the magnetic field lines, producing radiation that beams outward as the star spins on its axis.
- 11. Bright lines in a specific location of the spectrum of radiating material, corresponding to emission of light at a certain frequency. A heated gas in a glass container produces these in its spectrum.
- 12. Explosive death of a star, caused by the sudden onset of nuclear burning (Type 1), or an enormously energetic shock wave (Type 2).
- 14. The brightness of a star as it appears from Earth, expressed using the magnitude scale.
- 16. One of the basic properties used to characterize stars, it is defined as the total energy radiated by a star each second, at all wavelengths.
- 17. A plot of luminosity against temperature (or spectral class) for a group of stars.
- 18. An imaginary spherical surface surrounding a collapsing star, with radius equal to the Schwarzschild radius, within which no event can be seen, heard, or known about by an outside observer.
Down
- 1. Stars found on the main sequence of the Hertzsprung-Russell diagram, but which should already have evolved off the main sequence, given its location on the diagram. These are thought to have formed from mergers of lower mass stars.
- 2. A dense ball of neutrons that remains at the core of a star after a supernova explosion has destroyed the rest of the star. These are typically about 20 km across, and contain more mass than the Sun.
- 3. Two stars orbiting around each other.
- 6. The apparent magnitude a star would have if it were placed at a standard distance of 10 parsecs from Earth, expressed using the magnitude scale.
- 9. Dark lines in an otherwise continuous bright spectrum, where light within one narrow frequency range has been removed.
- 10. A region of space where the pull of gravity is so great that nothing, not even light, can escape. A possible outcome of the evolution of a very massive star.
- 13. A giant star whose surface temperature is relatively low so that it glows red.
- 15. A small star with sufficiently high temperature that it glows white. These are the end product of low to mid-mass stars at the end of their lives.