The most well-studied object in the Kuiper Belt is undoubtedly Pluto, a body that was a couple of years ago demoted from the rank of full-fledged planet to that of dwarf planet. The object features a large Moon called Charon, as well as two smaller satellites, dubbed Nix and Hydra. The latter two were only discovered in 2005 with the Hubble Space Telescope, and a heated debate is currently taking place in scientific circles as to what they're made up of, and what their origins might be. Researchers are, however, aware of the fact that they will soon get the answer to these questions, when the NASA New Horizons probe reaches the Pluto system.
The point of closest approach is scheduled to take place around 1200 GMT, on July 14, 2015. The ion engine-propelled spacecraft, which came with a hefty price tag of $719 million, is currently more than halfway to the outer fringes of the solar system, where the Kuiper Belt lies. Astronomers believe that the formation is made up of the rocky debris that did not contribute to forming planets, moons and larger asteroids when the solar system took shape, some 4.6 billion years ago. Pluto is the largest object in this belt, alongside other celestial bodies, such as Haumea, Makemake and Eris.
Last week, the Baltimore, Maryland-based Space Telescope Science Institute (STSI) organized a workshop on Nix and Hydra, where experts on the Pluto system could share opinions and coordinate ideas. Studies presented at the conference suggest that the two satellites are actually elongated in shape, and not spherical. This hints at the fact that they may be asteroids, captured in Pluto's orbit over time, and not moons that formed at the same time and location the dwarf planet did. Participants said that the meeting was the first formal discussion on these two moons since they were discovered 5 years ago.
Nix and Hydra are incredibly small. Astronomers say that they are both between 30 and 150 kilometers in diameter. For comparison, Pluto itself is some 2,400 kilometers wide, about 70 percent the size of Earth's Moon. The bodies orbit very far away from the dwarf planet, at 49,000, and 65,000 kilometers, respectively. New Horizons will observe them best on July 14, 2005, when it will reach its point of closest approach to Pluto, at 10,000 kilometers. Some of the mission's specific observation phases have already been established, researchers say, though some slots have remained open.
“These are wholly different beasts; mostly ice with some rock and organic materials. We're just starting to understand how they work geologically,” says Lowell Observatory astronomer Will Grundy. New Horizons will be able to produce images with a resolution of 100 meters per pixel. This should be enough to provide numerous data on the two peculiar moons, including the number of craters they contain and other major features. The probe will also be able to make out the moons' sizes, shapes, temperatures and surface compositions,
Nature News reports.
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