What is ...
An Aurora
An aurora is nature's light show. Triggered by violent storms on the Sun, the Earth's magnetosphere is stimulated by the solar particles that come from these storms. This produces wondeful curtains of dancing green glows. In good displays, the whole sky is lit up and the colour red appears. With luck you may see these rare, wonderous, and unpredictable displays of light in the coming years.
A Star
A star is a sustained thermonuclear reaction. The same nuclear reaction that occurs in a hydrogen bomb, and causes mass destruction is also responsible for giving us life. Without the Sun, our Star, we could not exist. Stars come in all sizes, colours, temperatures and densities. Even shape can vary. Compact starts such as neutron sizes are so dense that a teaspoon of it would weight as much as a mountain.
A Nebula
In astronomy, a localized conglomerate of the gaseous and finely divided dust particles that are spread throughout interstellar space. Before the invention of the telescope, the term nebula (Lat., "cloud") was applied to all celestial objects of a diffuse appearance. As a result, many objects now known to be star clusters or galaxies were called nebulas.
A Galaxy
A massive ensemble of hundreds of millions of stars, all gravitationally interacting, and orbiting about a common center. All the stars visible to the unaided eye from earth belong to the earth's galaxy, the Milky Way. The sun with its associated planets is just one star in this galaxy. Besides stars and planets, galaxies contain clusters of stars; atomic hydrogen gas; molecular hydrogen; complex molecules composed of hydrogen, nitrogen, carbon, and silicon, among others; and cosmic rays.
A Constellation
In astronomy, any of 88 imagined groupings of bright stars that appear on the celestial sphere and that are named after religious or mythological figures, animals, or objects. The term also refers to the delimited areas on the celestial sphere that contain the named groups of stars.
A Lunar Eclipse
A lunar eclipse occurs whenever the Earth's shadow falls on the Moon. If the Earth did not have an atmosphere, the Moon would simply disappear into the shadow. However, instead of disappearing the Moon becomes dim and takes on the colour red. This red is the light from all the sunsets and sunrises refracted onto the surface of the Moon.Total lunar eclipse of Feb 20, 2008
Click on above image for everything you ever wanted to know about eclipses.
Photo credit: B McGaffney - Thanks Brian