12) Regulus, in astronomy. The Columbia Encyclopedia, Sixth Edition. 2001
...in astronomy, (reg´yls) (KEY) , brightest star in the constellation Leo; Bayer designation Alpha Leonis; 1992 position R.A. 10h08m, Dec. +12°00´. A bluish-white main-sequence...

13) Arcturus. The Columbia Encyclopedia, Sixth Edition. 2001
...in the constellation Bootes and 4th-brightest star in the entire sky; Bayer designation Alpha Bootis; 1992 position R.A. 14h15.3m, Dec. +19°13´. An orange giant of...

14) Centaurus. The Columbia Encyclopedia, Sixth Edition. 2001
...located N and E of Crux, the Southern Cross. It is known especially for its bright stars Alpha Centauri and Hadar. It also contains Centaurus A, a radio galaxy, as...

15) radioactive isotope. The Columbia Encyclopedia, Sixth Edition. 2001
...created isotope of a chemical element having an unstable nucleus that decays, emitting alpha, beta, or gamma rays until stability is reached. The stable end product...

16) Perseus, in astronomy. The Columbia Encyclopedia, Sixth Edition. 2001
...constellation lying E of Cassiopeia and N of Taurus. It contains the bright star Mirfak (Alpha Persei) and Algol (Beta Persei), a visible variable star of the type...

17) Andromeda, in astronomy. The Columbia Encyclopedia, Sixth Edition. 2001
...located to the NE of Pegasus and to the S of Cassiopeia. Its brightest star, Alpheratz (Alpha Andromedae), marks the northeast corner of the Great Square in Pegasus....

18) Geiger counter. The Columbia Encyclopedia, Sixth Edition. 2001
...instrument for the detection and quantitative determination of ionizing radiation such as the alpha and beta rays given off by radioactive minerals and cosmic rays....

19) light-year. The Columbia Encyclopedia, Sixth Edition. 2001
...light travels in one sidereal year. It is 9.461 × 1012 km (about 6 million million mi). Alpha Centauri and Proxima Centauri, the stars nearest our solar system, are...

20) A. The Columbia Encyclopedia, Sixth Edition. 2001
...A, first letter of the alphabet. A is a usual symbol for a low central vowel, as in father; the English long a (a) is pronounced as a diphthong of e and y. The corresponding...