Across
- 2. a unit of astronomical distance equivalent to the distance that light travels in one year, which is 9.4607 × 1012 km (nearly 6 trillion miles)
- 3. a cloud of gas and dust in outer space, visible in the night sky either as an indistinct bright patch or as a dark silhouette against other luminous matter
- 4. a small very dense star that is typically the size of a planet. A white dwarf is formed when a low-mass star has exhausted all its central nuclear fuel and lost its outer layers as a planetary nebula
- 6. a spot or patch appearing from time to time on the sun's surface, appearing dark by contrast with its surroundings.
- 7. a system of millions or billions of stars, together with gas and dust, held together by gravitational attraction
- 8. a law stating that the redshifts in the spectra of distant galaxies (and hence their speeds of recession) are proportional to their distance
- 10. an ionized gas consisting of positive ions and free electrons in proportions resulting in more or less no overall electric charge, typically at low pressures (as in the upper atmosphere and in fluorescent lamps) or at very high temperatures (as in stars and nuclear fusion reactors)
- 12. a celestial object consisting of a nucleus of ice and dust and, when near the sun, a “tail” of gas and dust particles pointing away from the sun
- 13. a celestial body moving in an elliptical orbit around a star
- 14. a fixed luminous point in the night sky which is a large, remote incandescent body like the sun
- 15. It means that all the distances in the universe are stretching out at the same rate
- 19. the rarefied gaseous envelope of the sun and other stars. The sun's corona is normally visible only during a total solar eclipse, when it is seen as an irregularly shaped pearly glow surrounding the darkened disk of the moon
- 20. the cooled remnant of the first light that could ever travel freely throughout the Universe
- 21. a celestial object of very small radius (typically 18 miles/30 km) and very high density, composed predominantly of closely packed neutrons. Neutron stars are thought to form by the gravitational collapse of the remnant of a massive star after a supernova explosion, provided that the star is insufficiently massive to produce a black hole
Down
- 1. a star that suddenly increases greatly in brightness because of a catastrophic explosion that ejects most of its mass
- 5. The Doppler effect or Doppler shift is the apparent change in frequency of a wave in relation to an observer moving relative to the wave source
- 9. a region of space having a gravitational field so intense that no matter or radiation can escape
- 11. the branch of science that deals with celestial objects, space, and the physical universe as a whole
- 16. a very large star of high luminosity and low surface temperature. Red giants are thought to be in a late stage of evolution when no hydrogen remains in the core to fuel nuclear fusion
- 17. a contracting mass of gas which represents an early stage in the formation of a star, before nucleosynthesis has begun
- 18. the luminous envelope of a star from which its light and heat radiate