NASA’s New Horizons spacecraft has captured images of four small moons of Pluto – Hydra, Nix, Kerberos and Styx.
Hydra (red), Nix (yellow), Kerberos (orange), Styx (green) and their orbits. Image credit: NASA / JHU-APL / SwRI.
“New Horizons is now on the threshold of discovery. If the spacecraft observes any additional moons as we get closer to Pluto, they will be worlds that no one has seen before,” said Dr John Spencer of the Southwest Research Institute in Boulder, Colorado, who is a member of the New Horizons Science Team.
Drawing ever closer to Pluto in mid-May, New Horizons will begin its first search for new moons or rings.
The new images were taken with New Horizons’ most sensitive camera, the Long Range Reconnaissance Imager (LORRI), from April 25-May 1.
They are allowing the mission team to refine the techniques they will use to analyze those data, which will push the sensitivity limits even deeper.
These images of Hydra, Nix, Kerberos and Styx were taken with the LORRI instrument aboard NASA’s New Horizons spacecraft. Image credit: NASA / JHU-APL / SwRI.
Nix and Hydra (the outermost known moon of Pluto) were discovered using the images taken by NASA’s Hubble Space Telescope in May, 2005.
Hydra has been calculated to have a diameter of between 61 and 167 km. Nix is about 25 percent fainter than Hydra, so could be a 10 to 15 percent smaller.
Hydra orbits Pluto every 38 days at a distance of 64,700 km, while Nix orbits every 25 days at a distance of 48,700 km.
Kerberos and Styx were discovered in 2011 and 2012, respectively. Styx, circling Pluto every 20 days between the orbits of Charon and Nix, is likely just 4 to 13 miles (7-21 km) in diameter, and Kerberos, orbiting between Nix and Hydra with a 32-day period, is just 6 to 20 miles (10-30 km) in diameter.
“Detecting these tiny moons from a distance of more than 55 million miles is amazing,” said Dr Alan Stern of the Southwest Research Institute, New Horizons Principal Investigator.
