Across

1(astronomy) the luminous cloud of particles surrounding the frozen nucleus of a comet; forms as the comet approaches the sun and is warmed (4)
5(astronomy) a relatively small extraterrestrial body consisting of a frozen mass that travels around the sun in a highly elliptical orbit (5)
9A star cluster in the constellation Taurus. (Greek mythology) 7 daughters of Atlas and half-sisters of the Hyades; placed among the stars to save them from the pursuit of Orion (8)
12Any star around which a planetary system evolves (3)
14Any of the celestial bodies (other than comets or satellites) that revolve around the sun in the solar system (6)
15The abode of mortals (as contrasted with heaven or hell) (5)
16The (usually elliptical) path described by one celestial body in its revolution about another (5)
17A starlike object that may send out radio waves and other forms of energy; large red shifts imply enormous recession velocities (6)
19The comet discovered by Edmund Halley, the English astronomer who used Newton's laws of motion to predict the period of a comet (1656-1742)SETI (7,5)
20The international scientific organisation searching for extra terrestrial life using radio telescopes (4)
22A diffuse mass of interstellar dust or gas or both, visible as luminous patches or areas of darkness depending on the way the mass absorbs or reflects incident radiation. (7)
23The closest of Jupiter's moons; has active volcanoes (2)

Down

2The natural satellite of the Earth (4)
3(astronomy) a measure of time defined by Earth's orbital motion (11,4)
4The second nearest planet to the sun; visible as an early 'morning star' or an 'evening star'; rotates slowly clockwise (in the opposite direction from the normal rotation of the planets) (5)
6The largest planet and the 5th from the sun; has many satellites. (Roman mythology) supreme god of Romans; counterpart of Greek Zeus (7)
7A giant planet with a ring of ice particles; 7th from the sun. (Greek mythology) god of the heavens; son and husband of Gaea and father of the Titans in ancient mythology (6)
8The branch of physics that studies celestial bodies and the universe as a whole (9)

10Brightest star in Centaurus; second nearest star to the sun (5,8)
11(astronomy) the precise date that is the point of reference for which information (as coordinates of a celestial body) is referred (5)
13A constellation on the equator east of Taurus; contains Betelgeuse and Rigel (5)
18active galactic nuclei (abbreviation). A class of galaxies which spew massive amounts of energy from their centers, far more than ordinary galaxies. Many astronomers believe supermassive black holes may lie at the center of these galaxies and power their explosive energy output. (3)
21Any celestial body visible (as a point of light) from the Earth at night (4)


FreeWorldGroup Games and Puzzles - http://www.freeworldgroup.com