Milky Way (thing)
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|The Milky Way is the name given to the faint band of light that stretches accross the night sky. This light comes from stars and nubulae in our galaxy, known as the Milky Way Galaxy or simply as the Galaxy.|
The galaxy is shaped like a spiral, with a dense central bulge that is encircled by four arms spiralling outwards and surrounded by a less dense halo. We are unable to see the spiral shape because the Solar System is in one of the spiral arms which is also known as the local arm.
From our position the centre of the galaxy is completely obscured by dust clouds. As a result, optical maps give only a limited view of the galaxy. However a more complete picture can be obtained by studying radio, infra-red and other radiation.
The central bulge of the galaxy is a relatively small, dense sphere that contains mainly older red and yellow stars. The halo is a less dense region in which the oldest stars are situated. Some of these stars may be as old as the galaxy itself (possibly 15 billion years). The spiral arms contain mainly hot, young blue stars as well as nebulae (clouds of dust and gas inside which stars are born).
The galaxy is about 100,000 light years across, in comparison the Solar System seems small at about 12 light hours across.
The entire galaxy is rotating in space, although the inner stars travel faster than those that are further out. The sun which is about two-thirds out from the centre, completes one lap of the Galaxy about every 220 million years.
SIDE VIEW OF OUR GALAXY:
Disc of spiral arms containing mainly young stars Surrounding halo contains oldest stars, | ___________ Central bulge containing mainly older | | stars | V V /**\ .....oo00OOOXXXXXXX<****>XXXXXXXOOO00oo..... \**/ | | |___________ 100,000 Light Years __________|
OVER HEAD VIEW OF OUR GALAXY:
Central bulge containing nucleus | | * | * * * *| * * | * * * | * * * * |* * * * * * ****|*** * * * * *** _V *** * * * Perseus ---------->* *** / \ **** *<----------- Sagittarius Arm * * ***| |*** * * Arm * * ****\ __ /*** * * * ** ******* * *<--- Orian Arm * * * * * * (Local Arm) * 0* * * * * ^ * * Crux-Centaurus --->* | * * * Arm * | | * | Location of Solar System
Note - The diagrams display a pictorial representation of the galaxy to the best of my HTML artistic capabalities, so please view with compassion.