User:RainbowWiki

Some people get very excited by the possibility of living in space cities. Perhaps

they have forgotten they already live ‘in space’.

If you look at the sky on a clear night you might be able to see at least 3000 stars. All of them, plus millions more invisible to the naked eye, are part of the Milky Way

Galaxy. You and I and solar system, are part of this vast galaxy of at least another

200 billions stars. Earth is just a small planet, part of one star system out of billions

in the Milky Way Galaxy. When we look up at night sky, we may see a white or milky band of light. Above and

below the band is the darkness of space. This is the Milky Way Galaxy. We see the

stars as a band because, from our position on Earth, the stars are so far away they

appear to be clustered together in space. If you look at this Galaxy from a spaceship

in outer space, it would look like a flat, slowly spiralling disc with curved arms

protruding from it. It sparkles with light rather like a spiralling wheel-shaped firework. The Milky Way Galaxy is enormous; a ray of light travelling at the ‘speed of the

universe’, 300 000 kn/sec, would take 100 000 years to cross it. This means that the

Milky Way Galaxy measures 100 000 light years across its diameter. If you compare

this with the fact that light from the Sun takes only 8 light minutes to reach the Earth, you will get some idea of the vastness of this Galaxy. Many of the stars in Milky Way Galaxy are much bigger than our Sun. Our star

system or what we call the ‘solar system’ lies within the Galaxy, about two-thirds of

the way out from the centre. What we are able to see in the sky are mostly stars but

there are also star clusters, dark gas clouds, even planets which are too far away

for us to see. The youngest and the closest stars occupy different parts of the Milky Way Galaxy. The oldest, coolest stars give off red light and usually surround the central hub, which was the first part to form 13 billion years ago. On the other hand, the

youngest stars are sprinkled along the arms of the Galaxy and are still forming. When gas and dust clump together, they form enormous, heavy clouds. These

clouds become so heavy that they collapse and heat up, causing hot white-blue

stars to form from the gas and dust inside these clouds. These new stars shine

brightly in the night sky. One such group, called the Pleiades, was formed only 60

million years ago. Sometimes new stars come about due to collisions with other, smaller galaxies resulting in the stars of the smaller galaxy being absorbed into the

Milky Way Galaxy. The galaxy we live in is a dynamic one and it continues to develop and evolve. From

Earth we can only see the Milky Way Galaxy as luminous band, but scientist using

powerful telescopes are able to observe many changes that occur within it. They

record the changes they find and continually update the star map of our ever.