Night Sky Identifier

The Stars

Star Fact File

Nearest star

Proxima Centauri, red dwarf, distance 4,25 light years.

Brightest star in the sky

Sirius, white star, radius 1.7 Suns, distance 8.7 light years, true brightness 25 Suns.

Dying stars

There comes a time in a star's life when the source of its power simply starts to run out. Whe this happens its central core gradually starts to collapse inwards, causing its temperature to rise as it does so. Some of the heat energy released causes the remainder of the star to expand outwards, and it becomes a giant or supergiant.

Death of a normal star

After a start exhausts the supply of hydrogen in its core, there is no longer any source of power to support the core against the force of gravity. The core of the star collapses under gravity's pull until it reaches enough density to start burning helium to carbon. [...] The carbon core will eventually cool and become a white dwarf [...]

Death of a massive star

When a start ten times larger than the Sun uses up all the helium in its core, the nuclear burning cycle continues. The carbon cores contraccts even further and reaches a high enough temperature to burn carbon into oxygen, neon, silicon, sulphur, and finally to iron. Iron is the most stable form of nuclear matter and there is no energy to be gained by burning it to any heavier element.
Without any source of heat to balance the gravity, the iron core collapses until it reaches nuclear densities. This high density core resists further collapse causing the infalling matter to literally 'bounce' off the core, and it is this bounce that causes a supernova explosion.
For one brilliant month, a single star burns brighter than a whole galaxy of a billion stars.

Watching the Sky

Andromeda

The Great Spiral

The Andromeda Galaxy is one of the showpiece objects of the northern heavens. [...] Of about the fourth magnitude in brightness, the Great Spiral is easily seen near Nu. It lies about 2.3 million light years away, which makes it easily the furthest naked-eye object in the night sky.