The Number of Stars
Name: pam j byrne
Date: 1993 - 1999
How many stars are there?
Well, you could try counting them :-) From my house you can
only see about 200 or 300 most nights, because the street lights
get in the way. In principle, on a dark night in some isolated
area of the country, there should be several thousand visible.
You'll also notice a kind of hazy band extending diagonally across
the sky - this is the Milky Way, our home galaxy. The hazy band
actually consists of millions of stars too faint for us to
resolve without using at least binoculars, or of course telescopes.
Nobody's counted all the stars in the galaxy - I believe the number
that have been counted is on the order of a million. But in fact,
by looking at other galaxies that seem to be about the size of
the Milky Way, their overall brightness implies that they contain
roughly 10 billion stars - much much more than we can see, or count
easily. Put another way, that's several stars in our own galaxy
for each person here on earth. But there are also lots of
galaxies out there - in fact, you can even see a few of them
on those dark nights when you can see the Milky Way with your bare eyes.
Using telescopes, we find more and more of them, out to immense
and almost unimaginable distances - billions of light years.
Again, nobody's counted all the galaxies, although I believe
several hundred thousand have been catalogued. But just from
the immensity of the space we can observe, and the average
distribution of galaxies in it, we can guess there are 10s of billions
of them also. That means the number of stars in the universe
is really enormous - 1 followed by 20 or more zeros!
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Update: June 2012