How Many Stars Are There?

How many stars are there? This is a question most of us have asked, maybe as children (who ask just about everything), or maybe as adults (who are more selective.)

Well, each clear night, far from city lights, we can see (with our unaided eyes) about two thousand stars. And since so many stars come and go with the seasons, over the course of a year we can see about six thousand.

That's only the tip of the iceberg. In our own Milky Way galaxy, there are over a hundred billion stars. (That's how much mass is needed for gravity to hold the Sun in its orbit around the Galactic Central.)

And that's just one galaxy. Looking at a seemingly vacant place in the Big Dipper, astronomers reported seeing dozens of galaxies where they thought there were none. They concluded that, if all of space is as crowded as this spot, there must be billions of other galaxies, each as big as our own.

In total, then, there are vas many stars as there are grains of sand covering all the beaches of the world. What an almost endless job it would be to fill just one bucket with grains of sand, one at a time...and then bucket after bucket, until the beach was cleared...and then beach after beach, all over the world. Thatıs how many stars there are.

And now we are told that about half the stars in the sky have planets. How many solar systems there must be. If only the smallest fraction of those planets harbor life....

(11/01/06)