Artist’s concept of the New Horizons spacecraft as it approaches Pluto and its entourage of moons in summer 2015. Credit: Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute (JHUAPL/SwRI)
Two labeled images of the Pluto system taken by the Hubble Space Telescope’s Wide Field Camera 3 ultraviolet visible instrument with newly discovered fourth moon P4 circled. The image on the left was taken on June 28, 2011. The image of the right was taken on July 3, 2011. Credit: NASA, ESA, and M. Showalter (SETI Institute)
Researchers using the Hubble Space Telescope have found a fourth moon orbiting
the icy dwarf planet Pluto.
The discovery of the tiny, new satellite — temporarily designated P4 — was uncovered in a Hubble survey searching for rings around the dwarf planet.
And there’s more good news.
The finding adds to what the outbound NASA Pluto-bound New Horizons mission will be able to observe.
“We already know that when New Horizons provides the first close-up look at Pluto in July 2015, we’ll see planetary wonders we never could have expected,” says New Horizons Principal Investigator Alan Stern.
“Yet this discovery gives us another hint of what awaits us in the Pluto system, and we’re already thinking about how we want to study this new moon with New Horizons,” Stern added. “What a bonus for planetary science and for New Horizons!”
Smashup may have created moon system
The new moon is the smallest discovered around Pluto.
P4 has an estimated diameter of 8 to 21 miles (13 to 34 km). By comparison, Charon, Pluto’s largest moon, is 648 miles (1,043 km) across, and the other moons, Nix and Hydra, are in the range of 20 to 70 miles in diameter (32 to 113 km).
Pluto’s entire moon system is thought to have formed by a collision between Pluto and another planet-sized body early in the history of the solar system. The smashup flung material that coalesced into the family of satellites observed around Pluto.
According to the Space Telescope Science Institute (STScI) P4 was first seen in a photo taken with Hubble’s Wide Field Camera 3 on June 28. It was confirmed in subsequent Hubble pictures taken on July 3 and July 18. The moon was not seen in earlier Hubble images because the exposure times were shorter.
The STScI in Baltimore, Maryland conducts Hubble science operations.
Hubble is a project of international cooperation between NASA and the European Space Agency.
By Leonard David