Pluto’s new moons confirmed

Thursday, February 23rd, 2006 at 11:19 AM by Administrator

NASA and Alan Stern’s research group have announced that new Hubble Space telescope photographs of Pluto shot last week (February 15) have now confirmed the existence of two additional moons. dubbed “S/2005 P 1″ and “S/2005 P 2″ whose discovery was announced last Holloween. There really wasn’t any doubt as to the reality of the moons, but the nice bit is that

[T]he team [was] happy to see the moons show up very close to the locations predicted from the earlier Hubble observations.

(Click on image for full-size version.) A Hubble Space Telescope Image of Pluto and its three moons taken February 15, 2005.

Why would they be happy? Because it confirms the new moons are in the same orbital plane as Charon, the much larger previously known moon of Pluto. This would not be expected if “S/2005 P 1″ and “S/2005 P 2″ were simply “captured” Kuiper Belt Objects. Instead, this suggests that Charon and the newly discovered moons share a common origin. The currently favored model for the formation of the Pluto/Charon system is one similar to the formation of the Earth/Moon system.

The origin of the Moon has been one of the chief puzzles of planetary scientists during the 20th century. The manned missions to the Moon returned a large number of moon rocks (Yes, we did actually go to the moon). The moon rocks proved to be extremely similar to Earth rock with one glaring exception… they had almost no volatiles (molecules like water or CO2 that are easily vaporized). The model was eventually developed (and computer simulations show it is reasonable) that within the first few hundred million years of the solar sytem’s formation, the Earth, having achieved roughly its current size, had a grazing impact with another planetesimal roughly the size of Mars. This impact vaporized the crust of the earth and blew it and a good chunk of the Earth’s mantle off the surface of the Earth and into orbit. This orbiting material eventually collected to form the Moon. A nice page with illustrations of the model is available at the Planetary Science Institute website..

A similar model is now proposed for Pluto in that it was an early impact by a large object that formed Charon. Presumably, in Pluto’s case, some of the smaller debris stuck around, and that is why Alan Stern’s team, the folks behind the recently launched Horizons mission to Pluto, have been doing deep imaging of Pluto. They are looking for evidence of a ring or other moon’s from this image. Looks like they have it.

Posted in Astronomy News

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