The Many Moons of Saturn

Edward Ashton helped to discover two thirds of the planet's known moons

- MEGHAN BARTELS

A MERE DECADE AGO astronomers knew of just 62 moons around Saturn. Today the ringed planet boasts a staggering 274 official satellites. That's more than any other world in the solar system—and far too many for most people to keep track of. Astronomer Edward Ashton is no exception, even though he has helped discover 192 of them—he thinks that's the total, anyway, after pausing to do some mental math.

Ashton is now a postdoctoral fellow at the Academia Sinica Institute of Astronomy and Astrophysics in Taiwan. He fell into the hunt for Saturn's moons in 2018, when his then academic adviser suggested the project for his Ph.D. at the University of British Columbia. It has been a fruitful search. Most recently, in March, Ashton and his colleagues announced a batch of 128 newfound Saturnian satellites.

SCIENTIFIC AMERICAN spoke with Ashton about the science of discovering so many relatively tiny moons—most of them just a few kilometers wide—using vast amounts of data gathered by the Canada-France-Hawaii Telescope (CFHT), located in Hawaii.

An edited transcript of the interview follows.

How have you found these moons?

To detect the moons, we use a technique known as shifting and stacking. We take 44 sequential images of the same patch of sky over a three-hour period because in that time frame, the moons move relative to the stars at a rate similar to Saturn's. If we just stack the images normally, then the moon appears as a streak across the images, and that dilutes the signal of the moon.