Washington: Astronomers using the Hubble Space Telescope have discovered Pluto’s fifth moon, a little more than three years before a NASA space probe is due to sail past the dwarf planet and its tribe of satellites.
The irregular moon, estimated to be 6 to 15 miles (10 to 25 kilometers) across, was found in the course of checking out the potential collision hazards facing NASA’s New Horizons spacecraft for the Bastille Day flyby on July 14, 2015.
Experts believe the exciting discovery will give them more clues to how Pluto’s complex system of satellites formed and evolved.
It is the fifth known moon to be discovered around Pluto. The largest was spotted in 1978, and Hubble operations have uncovered three others since 2006.
The new mass is believed to be in line with the other satellites, on a 58,000-mile-diameter circular orbit around the dwarf planet.
Lead astronomer Mark Showalter, of the SETI Institute in Mountain View, California, said: ‘The moons form a series of neatly nested orbits, a bit like Russian dolls.’
The most popular theory to explain the formation of the Pluto system is that all the moons are relics of a collision between the dwarf planet and another large Kuiper belt object billions of years ago.
The new detection will help scientists navigate NASA’s New Horizons spacecraft on its long-awaited flight through the Pluto system in 2015.
The team of astronomers is using Hubble’s powerful vision to scour the Pluto system for potential hazards which could affect the historic mission.
New Horizons is due to travel past the dwarf planet at a speed of 30,000 miles per hour and could be destroyed if it collides with even a pellet-sized piece of orbital debris.
Harold Weaver, of the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, said: ‘The discovery of so many small moons indirectly tells us that there must be lots of small particles lurking unseen in the Pluto system.’
The New Horizons mission’s principal investigator, Alan Stern, of the Southwest Research Institute in Boulder, Colorado, said: ‘The inventory of the Pluto system we’re taking now with Hubble will help the New Horizons team design a safer trajectory for the spacecraft.’
Pluto’s largest moon, Charon, was discovered in 1978 in observations made at the United States Naval Observatory in Washington, D.C.
Hubble observations in 2006 uncovered two additional small moons, Nix and Hydra. In 2011 another moon, P4, was found in Hubble data.
Provisionally designated S/2012 (134340) 1, the latest moon was detected in nine separate sets of images taken by Hubble’s Wide Field Camera 3 on June 26, 27, 29, and July 3 and 9.
In the years following the New Horizons Pluto flyby, astronomers plan to use the infrared vision of Hubble’s planned successor, NASA’s James Webb Space Telescope, for follow-up observations.
The Webb telescope will be able to measure the surface chemistry of Pluto, its moons, and many other bodies that lie in the distant Kuiper Belt along with Pluto.