Question: How many stars are their exactly?

Alex Reid answered on 9 Nov 2018: last edited 9 Nov 2018 6:20 pm

Hi thanks for your question. It is impossible to know the exact number of stars for many reasons, the biggest of which is that many galaxies are so far away the light hasn’t reached us. Also, new stars are born and die every second, so by the time we counted them all the number would have changed. Even if these two issues were not a problem, the sheer number of stars involved still makes this pretty much an impossible task (imagine if someone asked you to count every grain of sand on earth). All we can do is estimate things based on our current understanding of the universe. I looked up one such estimate by other scientists and, assuming there are about 100 billion stars per galaxy, and 100 billion or so galaxies, this means that there are about 1,000,000,000,000,000,000,000 (1 billion trillion) stars in the observable universe. Going back to my sand example, that is 5-10 x more bits of sand than there is estimated to be on all of earth’s beaches combined. So to say there is a lot of stars a bit of an understatement!