________________
1,490,000,000 kms. and light from Neptune takes four hours to reach us. In terms of light-year units, we can say that the moon is one and a quarter light seconds away from the earth, the sun about eight and a quarter light-minutes away and Neptune about four light-hours away from us. In astronomy, these distances within our solar system are, of course, comparable to the dimensions of one's backyard,
The nearest neighbour of our sun i.e. another 'sun' is so far away that its light takes about four years to reach us and this, astronomically speaking, is rather close neighbourly distance. There are other stars whose light takes fifty, hundred or five hundred years to reach us. For example, the light from the pole star takes about 450 light years to reach the earth. Our sun is a solitary star but in outer space, there are stars bunched together to form constellations which are scattered far and wide, the distant ones among them appearing nebulous. Our galactic formation contains an infinite number of stars, constellations and solar systems, probably more than hundred thousand million stars spread out in a biconvex elliptical shape of space with a diameter of about hundred thousand light years.
One of our neighbourly galaxy is Andromeda or May-31 that looks like a patch of smoke seen with naked eye but on telescopic viewing, appears as a galaxy of stars that is twentytwo hundred thousand light years away from us and radiotelescopes have picked up signals from over ten thousand million light years away which are stronger than the ones coming from known neighbourly galaxies. Modern astronomy has named these sources of powerful radio signals as quasi-stellar or star-like, because they are neither stars nor galaxies. No quasar is at a distance less than ten thousand million light years from earth. At such distances, it is not possible to see stars (or their light) while quasars are hundred times brighter than some of the brightest galaxies; however, they are quite
48
Jain Education International
For Private & Personal Use Only
www.jainelibrary.org