By David Ward
How many stars do you think you can see up in the night sky? I often ask this question at my stargazing events. Usually the answer I hear is “millions at least” or “ billions and billions.” Actually, if you have really good eyes and there is no moon to wash out the fainter stars, and you are looking up from a dark place like the Methow Valley, you might see about 4,000 or 5,000 individual stars.
That is just a drop in the bucket, so to speak, to what is really out there. Our galaxy, the Milky Way, has an estimated 300 billion stars in it, of which our sun is just one. That sounds like a big number and it is — $300 billion would amount to a stack of $1,000 bills about 20 miles high.
Up until 100 years ago, we thought the Milky Way Galaxy made up the entire universe. Back in the 1920s, the famous astronomer Edwin Hubble figured out there were lots of other galaxies out there, greatly expanding our view of the universe.
One of the most amazing pictures I have seen was one of the first taken by the Hubble orbiting telescope named for the astronomer. A random spot in the constellation of the Big Dipper was picked to photograph a piece of sky not much bigger than a grain of sand held at arm’s length. Astronomers were amazed to count over 3,000 galaxies in that tiny piece of sky. Each of those galaxies would hold tens of billions to hundreds of billions of stars. Extrapolate how many grains of sand it would take to cover the entire sky and astronomers realized there are hundreds of billions of galaxies out there.
Since that picture was taken, additional ones have been imaged showing many more galaxies. Estimates vary but the total number of galaxies we can see could be in the trillions. Now wait a minute. A trillion sounds like a really big number, and it is. A billion seconds ago happened in 1986, but a trillion seconds ago happened in the year 29,692 B.C.!
Bigger numbers
If each of those galaxies has many billions of stars in them, how many stars are up there? We need to find a really big number. Suppose we counted every individual grain of sand in the Sahara Desert. A single handful is several thousand, so the whole desert of sand grains would be a really big number. Would that be a big enough number to equal the number of stars in the sky? Not even close. How about all the grains of sand in all the deserts on earth? We need a bigger number yet so let’s throw in all the beaches too.
The number of sand grains on the entire planet earth is a really, really big number, but it is still not big enough. According to people who have got way too much time on their hands and sit around thinking about things like this, there are probably at least 10 times more stars in the sky than grains of sand on earth and that is a low estimate.
The most amazing thing to me is that there are as many molecules in just 10 drops of water as there are stars out there. We are surrounded by vastness both in the stars and galaxies above us and in the tiny world right under our noses.
Coming back closer to home, be sure to check out the beautiful planets in the evening sky. Venus is bright and low in the southwest just after sunset. Next above and to the left you can see almost as bright Jupiter. Then farther left yet, dimmer Saturn shines when it is almost dark. Reddish Mars is over in the southeast.
Notice how they form a beautiful arc across the sky. That is the plane of our solar system projected out to where we can see it. Starting about mid-September, the moon will dance with each of the planets in turn as it makes its way from west to east across the sky for the following week. While you are looking up, be sure to think about all those grains of sand up there.
