Tonight's Sky: April 2011

Backyard stargazers get a monthly guide to the northern hemisphere's skywatching events with "Tonight's Sky." In April, Saturn reaches its closest point to Earth, the Big Dipper overflows with cosmic sights, and the Lyrid meteor shower streaks the sky. "Tonight's Sky" is produced by HubbleSite.org, online home of the Hubble Space Telescope. This is a recurring show, and you can find more episodes — and other astronomy videos — at HubbleSite.org.

Visit Tonight's Sky on HubbleSite.
http://hubblesite.org/explore_astronomy/tonights_sky

Dictionary: Star

A star is a celestial body whose temperature and density is high enough to allow energy to be generated by nuclear fusion.
A massive range of star types have been catalogued and described, ranging in size from less than 0.1 solar masses to about 100.
Most stars follow a simple, almost straight-line, relationship linking their mass to their light output or luminosity, the Hertzsprung-Russell diagram.
Stars are the basic study of most astronomers and astrophysicists, who in recent years have addressed issues including star formation, the later lives of stars after the major process of energy production – the production of helium by fusing hydrogen – has ceased, and the dynamics of interacting multiple stars, especially those involving a collapsed star and a normal one.
Astronomy Dictionary