The Sciences

Quadrillions and Quadrillions of Stars

By Elizabeth SvobodaDec 3, 2003 6:00 AM


Sign up for our email newsletter for the latest science news

An eagle-eyed sky gazer could count more than 2,000 stars on a good clear night, but Simon Driver, an astronomer at Australian National University, can do a lot better. Using two large telescopes in Australia and the Canary Islands, he has determined that the visible universe contains about 70,000 million million million stars—that’s a 7 followed by 22 zeros. Driver arrived at this number by quantifying the brightness of a sample strip of sky containing about 10,000 galaxies. “What we’ve actually measured is an estimate of the blue-wavelength photon density of the universe—how many particles there are per unit volume in a certain wavelength range,” he says. He multiplied this figure by current estimates of the volume of the universe. Since the brightness of galaxies is directly related to the number of stars they contain, Davis was able to derive a reasonably accurate star count. His estimated total is far more than all the grains of sand on all of Earth’s beaches, yet he says there are probably many more stars out there. “The universe is so big that light from its farthest regions hasn’t reached us yet,” he says.

1 free article left
Want More? Get unlimited access for as low as $1.99/month

Already a subscriber?

Register or Log In

1 free articleSubscribe
Discover Magazine Logo
Want more?

Keep reading for as low as $1.99!


Already a subscriber?

Register or Log In

More From Discover
Recommendations From Our Store
Shop Now
Stay Curious
Our List

Sign up for our weekly science updates.

To The Magazine

Save up to 70% off the cover price when you subscribe to Discover magazine.

Copyright © 2023 Kalmbach Media Co.