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Chaos near Pluto?


According to a study in Nature, Pluto forms a pair with the largest moon, Charon, around which they dance in a seemingly broken four smaller moons. According to Douglas Hamilton, one of the two authors, “the chaos may be a common feature of binary systems.”
Although they have downgraded Pluto to dwarf planet in 2006, astronomers have certainly not diminished their interest in the more distant cousin of the Earth and its handful of moons. A publication output in the journal Nature, the result of a complete analysis of the data obtained with the Hubble Space Telescope, reveals now for the first time the details of the models orbital and rotational of that cloud a bit ‘abnormal consists of Pluto and its five moons known.

Pluto-System-Illustration

Credit: NASA, ESA, Mark Showalter (SETI Institute)

The study describes a system dominated by Pluto and its largest moon, Charon, which together constitute what may be considered a “binary planet”, around which orbit four smaller moons. Beyond providing the techniques used to find in recent years the two smaller moons, Kerberos and Styx (Styx and Cerberus), the new research also provides a detailed description of the strange and unpredictable rotation of the two moons were a bit ‘bigger, Nix and Hydra (Night and Hydra), discovered in 2005.
“As good children, moons generally held face carefully turned on their home planet, showing – as does our moon – the same side,” said Douglas Hamilton, a professor of astronomy at the University of Maryland and co-author of the new study. “What we have learned is that the moons of Pluto appear quite as surly teenagers who refuse to follow the rules.”
The gravitational field, unbalanced and dynamically unstable, created by Pluto and Charon is forcing smaller moons to prance so unpredictable. The effect is amplified by the fact that the satellites have approximately the shape of a rugby ball, rather than spherical.
In contrast to these rotational motions apparently random, moons follow a pattern surprisingly predictable as they orbit the planet binary format by Pluto and Charon. Three of them – Nix, Hydra and Styx – are linked by an orbital resonance, exerting mutual and regular gravitational influence that stabilizes their orbits. The same effect, called Laplace resonance, which can be observed in the three large Jovian moons Io, Europa and Ganymede.
“The relationship of resonance between Nix, and Hydra Styx makes their orbits more regular and predictable, preventing that go banging against each other,” says Hamilton. “This is one of the reasons why the small Pluto is able to have so many moons.”
The study also revealed that Kerberos is dark as coal, while other moons are as brilliant white sand. “This is a very exciting result,” says the other author of the study, Mark Showalter of the SETI Institute. According to forecasts of astronomers, in fact, the dust created by meteorite impacts should cover all the moons evenly, making their surfaces similar in appearance.

Pluto-System-Hubble

Credit: NASA, ESA, Mark Showalter (SETI Institute)

“Before the Hubble observations, no one appreciated properly the complex dynamics of the Pluto system,” continues Showalter. The planned close flyby, the probe New Horizons will perform in the month of July, will help solve the mystery of the dark surface of Kerberos, and certainly will refine the understanding of orbital and rotational extravagant models discovered thanks to Hubble. The New Horizons team is already using these discoveries to optimize the upcoming activities of scientific inquiry.
Researchers believe, in fact, that a more detailed study of the chaotic system Pluto-Charon would be useful to visualize how to behave planets around a binary star. In fact, even if they were tracked down many extrasolar planets around binary stars, these star systems are still too far away to be able to deduct their rotation patterns with existing technology.
“We are learning that the chaos may be a common feature of binary systems,” he says in conclusion Hamilton. “This could also have consequences for the possible development of life on planets orbiting pairs of stars.”

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