New moons for Pluto?

The Hubble Space Telescope may have observed two new moons orbiting Pluto.
By | Published: October 31, 2005 | Last updated on May 18, 2023
New Pluto moons
These Hubble Space Telescope images, taken by its Advanced Camera for Surveys, reveal Pluto, its moon Charon, and the planet’s two new candidate satellites. Provisionally designated P1 and P2, these appear to rotate counterclockwise around Pluto.
October 31, 2005
In July 1978, James Christy discovered Pluto’s moon Charon. Twenty-seven years later, astronomers may have found more company for the distant planet.

Using the Hubble Space Telescope (HST), a team of astronomers has imaged what may be two new moons orbiting Pluto. Provisionally known as S/2005 P1 and S/2005 P2, these bodies were seen 27,000 miles (44,000 kilometers) away from the planet — about 2 to 3 times the distance between Pluto and Charon.

“If, as our new Hubble images indicate, Pluto has not one, but two or three moons, it will become the first body in the Kuiper Belt known to have more than one satellite,” says Hal Weaver of the Johns Hopkins Applied Physics Laboratory and coleader of the team that made this discovery.

In May 2005, the astronomers used HST to hunt for undiscovered moons around Pluto. Knowing what to look for, they referred back to HST images taken in 2002, which confirmed the existence of P1 and P2.

“Our result suggests that other bodies in the Kuiper Belt may have more than one moon. It also means that planetary scientists will have to take these new moons into account when modeling the formation of the Pluto system,” adds Alan Stern the Southwest Research Institute and coleader of the research team.

Another team member, Marc Buie of Lowell Observatory, told Astronomy about the team’s future plans.

“We still hope to obtain additional observations with HST in February 2006,” explains Buie. “Beyond that I would expect lots of people will try their hand at observing these new objects — myself included.”