WONDER
OF THE UNIVERSE – MILKY WAY
Did you ever have a
look at the night sky? If not just go out and take a look. You will
see millions of stars twinkling. Most of these stars belong to the
Milky Way. After getting habituated you will be able to see a band of
stars. That’s what our milky way is. Milky Way is the galaxy in
which our solar system is present.
The diameter of our
milky way is 1, 20,000 light years (a light year is the distance
travelled by a ray of light in a time span of one year). The
thickness of the centre is about 2 thousand light years. Our sun is
located somewhere in between the centre and end of our milky way. The
sun revolves at an astonishing speed of 150 miles per second. It
takes about 25 crores of years to complete one revolution around the
galaxy.
Mostly we will see
stars in our milky way. Scientists have estimated that there are
about 20,000 crores to 40,000 crores of stars in our galaxy.
Stars which radiate
lot of heat and light get exhausted quickly because they use the
matter present inside them rapidly. New stars are born in the spiral
arms of the galaxy. That’s why these arms appear a little bit
different from the rest of the galaxy. Dust clouds and gases which
are the birth places of stars are mainly present in these spiral
arms.
The centre of the
Milky Way mainly consists of old stars. One of theory states that the
centres of the galaxies consist of a super massive black hole. The
mass of these super massive black holes would be nearly equal to
(guess what?) 30 lakhs of stars like our sun! So, how are these
scientists saying that there’s a super massive black hole in the
centre of our galaxy? That’s because the stars near the centre of
our galaxy are revolving at very high speeds. While our sun takes 25
crores of years to complete one revolution around the centre of our
galaxy a star near the centre takes 15.2 years only! But don’t
worry we are safe for now.
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