Ask a child how many stars they can see on a clear night, and the answer is likely to be some rather precise and yet strangely diffuse number like 200 and twenty-nine billion million thousand. An adult might suggest millions(?) with an inflection in their tone of voice to suggest that they are uncertain of that number and think it might be much higher.
Of course, the real answer is way, way lower. On a really clear night away from city lights and air pollution and with the best eyes in the world you would struggle to count just a couple of thousand visible to the naked eye. With a decent telescope you could see many more and, of course, there are literally (to paraphrase the late, great Carl Sagan) billions upon billions of the astral orbs in the universe as a whole. See “Ask a Scientist” on the ANL site where they suggest that there are 10 billion stars in the Milky Way and a possible 10 billion galaxies, which means 10 billion billion stars (that’s a 10 followed by 18 zeroes).
However, Sciencebase reader Luke McGuiness alerted me to an even more unimaginable estimate from Marcus Chown. In his book The Never-Ending Days of Being Dead, Chown suggests that there are 150 billion observable galaxies and probably about 500 billion in total in the universe, which puts the star count at 5000 billion billion, a few orders of magnitude higher than the ANL estimate. Although even more recent Hubble estimates suggest 300 billion stars per galaxy. So could be 150,000 billion billion stars…a number that’s starting sound like the kind of child’s exaggeration I mentioned earlier.
This brief post was inspired by a post on a futurology blog that suggested one might see millions and by a quick google that revealed the answer (Universe Today) I already thought of as being a couple of thousand. Across the globe their are probably about 6000 stars visible to the unaided eye.
More about stars and galaxies
- What’s eating the stars out of our galaxy’s heart? (newscientist.com)
- Distant Spiral Galaxy May Reveal Clues About Our Milky Way (space.com)
- Hubble snaps a cosmic photobomb (blogs.discovermagazine.com)
- Top 10 Summer Sky Objects to See Before Fall (space.com)
- What is a Galaxy, Anyway? (astrobasics.blogspot.com)