Courtesy of the Space Telescope Science Institute and World Science staff
Astronomers using NASA’s Hubble Space Telescope are reporting the discovery of a fifth moon orbiting the icy ‘dwarf planet’ Pluto.
The object is thought to be irregularly shaped, 10-24km wide and to travel around Pluto in a 93 000km-wide circular orbit, a path thought to lie in the same plane as that of the other moons. They ‘form a series of neatly nested orbits, a bit like Russian dolls,’ said research team leader Mark Showalter of the SETI Institute in Mountain View, Calif.
The scientists called it intriguing that such a small planet can have such a complex collection of satellites.
The finding also provides new clues to how the Pluto system formed and evolved. The favoured theory is that all the moons are relics of a billions-of-years-old collision between Pluto and something else in its area of orbit, called the Kuiper belt.
The new finding is expected to help scientists navigate NASA’s New Horizons spacecraft through the Pluto system in 2015, when it makes an historic and long-awaited high-speed flyby of the distant world.
The team is using Hubble’s powerful vision to scour the Pluto system to uncover potential hazards to the New Horizons spacecraft. Moving past Pluto at 50 000km/h, New Horizons could be destroyed in a collision with even a BB-shot-size piece of orbital debris.
A dangerous passage
‘The discovery of so many small moons indirectly tells us that there must be lots of small particles lurking unseen in the Pluto system,’ said Harold Weaver of the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland. ‘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,’ added Alan Stern of the Southwest Research Institute in Boulder, Colorado, the mission’s principal investigator.
Pluto’s largest moon, Charon, was discovered in 1978 in observations made at the US 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. The latest moon, provisionally designated S/2012 (134340) 1, was detected in nine sets of images taken by Hubble’s Wide Field Camera 3 this month and last month.
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 is expected to be able to measure Pluto’s surface chemistry, its moons, and many other bodies that lie in the distant Kuiper Belt along with Pluto.
Source: World Science, http://www.world-science.net