The Keck telescope has so-called adaptive optics. An adjustable mirror and special sensors eliminate the distortions that cause turbulence in the atmosphere. Thanks to this new technology, the images of the Keck telescope are sometimes sharper than those of the Hubble Space Telescope. Tholen shot a total of 16 pictures of the dwarf planet and its three moons over a period of one hour. The tiny satellites Nix and Hydra, whose luminosity is about a five-thousandth of Plutos, but were only visible by combining all 16 images.
"It is our intention to make further shots of the system of similar quality to track several rounds of Nix and Hydra around Pluto, " says Tholen. So far, the size and mass of the little satellites are not known exactly. "Extremely precise orbit rules allow us to determine their mass and perhaps their size, " Tholen hopes.
Planet researchers estimate that Nix and Hydra are less than a hundred kilometers in size. Apart from the two chunks, Pluto still has the moon Charon, which has a diameter of 1, 200 kilometers and was discovered in 1978. The latest Pluto images are particularly interesting for the scientists involved in NASA's New Horizons mission: if they know how big and bright Nix and Hydra are, they can choose suitable camera settings in advance. New Horizons will reach Pluto 2015. displayUte Kehse