Exploring The Real Wonders of The Universe: The Night Sky

Exploring The Real Wonders of The Universe: The Night Sky

By Mr Ghaz, February 19, 2011

Image Credit

Exploring The Real Wonders of The Universe: The Night Sky

Image Credit

Core Facts

Constellations are star patterns which are visible in the night sky. Other bright night sky objects include planets, nebulae, galaxies and supernovae.

Forty-eight constellations in the Northern Hemisphere were listed by Ptolemy in the 2nd century AD and many were first recorded in Babylonian times.

Eight-eight constellations are currently identified. The constellations name refers to the whole area of sky occupied by a constellations, as well as to  the star pattern

Different star patterns are seen in the Northern and Southern Hemispheres.

Northern Hemisphere constellations known today were listed by Helvelius in 1687.

Image Credit

The Moving Sky

Image Credit

Since the Ancient Greeks, astronomers have called the night sky the celestial sphere because, seen from Earth, it looks like a transparent sphere with the stars attached to it. Earth’s Equator and poles are projected onto the sphere to give the celestial equator and celestial north and south poles, which are used to map the position of stars in the sky. Because the Earth is spinning, the constellations appear to move across the sky. The portion of the celestial sphere that can be seen by the observer depends on their position on the Earth and the Earth’s position in its orbit. An observer always has part of the sphere blocked out by the Earth itself. Although constellations look flat, the stars in them vary in distance from Earth. Stars Betelgeuse and Mintaka in Orin, for example, are 330 and 2300 light years away. Over time, constellations change shape because individual stars change position in relation to each other.