In Archival Photos, Astronomer Discovers Neptune’s 14th Moon

The little moon had ignored detection until a veteran moon hunter spotted it in old photos

Neptune’s new moon, S/2004 N 1, is the planet’s 14th.
Neptune’s new moon, S/2004 N 1, is the planet’s 14th. NASA, ESA, M. Showalter/SETI Institute

SETI Institute astronomer Mark Showalter just discovered a new moon around Neptune, a roughly 12-mile-wide rock that zips around the azure planet once every 23 hours. The discovery of the new moon, S/2004 N 1, was just the latest in Showalter’s recent string of celestial successes. NASA:

“On a whim, Showalter looked far beyond the ring segments and noticed the white dot about 65,400 miles from Neptune, located between the orbits of the Neptunian moons Larissa and Proteus. The dot is S/2004 N 1.”

Showalter was looking through old photos of Neptune, trying to study the planet’s faint rings, says New Scientist.

The rings around our outermost planet are too faint to see without taking very long-exposure pictures. However, the rings orbit so fast that taking one long shot would smear them across the frame. Showalter and colleagues gathered multiple shorter-exposure images and developed a technique to digitally rewind the orbits to the same point in time. Then they could stack several images on top of each other to reveal details of the rings.

“I got nice pictures of the arcs, which was my main purpose, but I also got this little extra dot that I was not expecting to see,” says Showalter.

Stacking eight to 10 images together allowed the moon to show up plain as day, he says. When he went back and repeated the process using Hubble pictures taken in 2004, the moon was still there and moving as expected.

Showalter is a prolific moon hunter. Earlier this year he led the discovery of Pluto’s two newest moons, now named Styx and Kerberos. He’s also found moons and rings orbiting Uranus.

Showalter was one of the driving forces behind the controversial contest to name Pluto’s two newest moons. Traditionally, the discoverer of a celestial body gets first dibs at proposing a name for their find. Who knows, maybe he’ll turn to the public once more to select a name for Neptune’s new satellite?

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