text: This is a tricky one.  The canonical number is around 200 billion, but the actual number might be twice as great.\n\nThe challenge lies in counting stars…  All the stars we see in our night sky are at most about 1,000 light years away, and the lion’s share are much closer.  But the entire Milky Way Galaxy has a diameter 100 times that size!  Even with our most powerful telescopes, we’re only seeing a tiny percentage of the stars in our galaxy.  Plus, our local region of the galaxy might be very different from the galaxy as a whole—we know that the density of stars is much greater at the center of the galaxy, but there may be other differences as well.\n\nFor example, based on the number of stars within approximately 16 light years of the Sun, astronomers estimate the total number of stars within about 80 light years to be at least 7,500, but we’ve only cataloged about a third that number.  Does that mean astronomers’ work is just beginning, or do we live in an unusually dense stellar neighborhood?  Almost certainly the former, possibly both.  One thing is for certain:  we have only begun to discover certain types of very low mass, dim stars that could up the total number of stars in our galaxy considerably (that’s where the 400 million number comes from).\n\nThus, extrapolating the total number of stars from the number that we observe proves tricky.  A safe answer to your question is “hundreds of billions,” but if you need to be more precise, you could do worse than to say something like 200 million.\n\n\nRyan Wyatt\nRose Center for Earth & Space\nNew York, New York