Have you ever tried to count stars in the sky? When we look up the star filled sky, we often wonder about how many stars are out there in the universe. It is said that there are more stars in the universe than the sand particles on all the beaches of the world. Well, let’s find out!
It is estimated that the observable universe contains about one billion trillion (1,000,000,000,000,000,000,000 or 1021) stars!
How do we reach this estimation? From images like Hubble Extreme Deep Field, it is now estimated that there are about 10 billion galaxies in the observable universe. We also know that our own galaxy, the Milky Way, contains 100 to 400 billion stars. Thus, even if we take the lower average of 100 billion stars per galaxy, we get the figure of one billion trillion stars in the observable universe.
According to some other estimates, the observable universe contains 1×1024 stars. Most of these stars are invisible to the naked eye from Earth, including all stars outside our galaxy, the Milky Way.
We can only try to make informed estimates about the number of stars in the universe. The Universe is so vast that it is almost infinite (or probably it is indeed infinite, we don’t know!). In such a case it is easier to say the the universe contains infinite number of stars. Scientists and astronomers around the world, however, try to keep refining this number based on the new information available.
Besides stars, the universe also has other bodies like planets and asteroids etc. The Sun has eight confirmed planets (which collectively have over a hundred satellites). Counting even the exact number of galaxies in the universe is so difficult — but what if we set out to find the number of all the bodies in the universe?!