These new images provide the New Horizons spacecraft’s first extended look at Hydra (identified by a yellow diamond) and its first-ever view of Nix (orange diamond). The right-hand image set has been specially processed to make the small moons easier to see. Click the picture to see a seven-frame movie. Image credits: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research InstituteThe moons Nix and Hydra are visible in a series of images taken by the New Horizons spacecraft from 27th January—8th February, at distances ranging from about 125 million to 115 million miles (201 million to 186 million kilometres). The long-exposure images offer New Horizons’ best view yet of these two small moons circling Pluto, which Tombaugh discovered at Lowell Observatory in Flagstaff, Arizona, on 18th February 1930.
“Professor Tombaugh’s discovery of Pluto was far ahead its time, heralding the discovery of the Kuiper Belt and a new class of planet,” says Alan Stern, New Horizons principal investigator from Southwest Research Institute, Boulder, Colorado. “The New Horizons team salutes his historic accomplishment.”
Assembled into a seven-frame movie, the new images provide the spacecraft’s first extended look at Hydra (identified by a yellow diamond) and its first-ever view of Nix (orange diamond). The right-hand image set has been specially processed to make the small moons easier to see.
“It’s thrilling to watch the details of the Pluto system emerge as we close the distance to the spacecraft’s July 14th encounter,” says New Horizons science team member John Spencer, also from Southwest Research Institute. “This first good view of Nix and Hydra marks another major milestone, and a perfect way to celebrate the anniversary of Pluto’s discovery.”
These are the first of a series of long-exposure images that will continue through early March, with the purpose of refining the team’s knowledge of the moons’ orbits. Each frame is a combination of five 10-second images, taken with New Horizons’ Long-Range Reconnaissance Imager (LORRI) using a special mode that combines pixels to increase sensitivity at the expense of resolution. At left, Nix and Hydra are just visible against the glare of Pluto and its large moon Charon, and the dense field of background stars. The bright and dark streak extending to the right of Pluto is an artefact of the camera electronics, resulting from the overexposure of Pluto and Charon. As can be seen in the movie, the spacecraft and camera were rotated in some of the images to change the direction of this streak, in order to prevent it from obscuring the two moons.The right-hand images have been processed to remove most of Pluto and Charon’s glare, and most of the background stars. The processing leaves blotchy and streaky artifacts in the images, as well as a few other residual bright spots that are not real features, but makes Nix and Hydra much easier to see. Celestial north is inclined 28° clockwise from the “up” direction in these images. Image credits: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research InstituteNix and Hydra were discovered by New Horizons team members in Hubble Space Telescope images taken in 2005. Hydra, Pluto’s outermost known moon, orbits Pluto every 38 days at a distance of approximately 40,200 miles (64,700 kilometres), while Nix orbits every 25 days at a distance of 30,260 miles (48,700 kilometres). Each moon is probably between 25-95 miles (approximately 40- 150 kilometres) in diameter, but scientists won’t know their sizes more precisely until New Horizons obtains close-up pictures of both of them in July. Pluto’s two other small moons, Styx and Kerberos, are still smaller and too faint to be seen by New Horizons at its current range to Pluto; they will become visible in the months to come.
Clyde Tombaugh discovered Pluto over 85 years ago. He died in 1997, but during the historic 14 July flyby of NASA’s New Horizons spacecraft, Clyde’s children Alden and Annette Tombaugh will be special guests at mission headquarters. Here they reflect on their father’s legacy.
What is the origin of the large heart-shaped nitrogen glacier on Pluto revealed by NASA’s New Horizons spacecraft in 2015? Two French researchers show that Pluto’s peculiar insolation and atmosphere favour nitrogen condensation near the equator, in the lower altitude regions, leading to an accumulation of ice at the bottom of Sputnik Planum, a vast topographic basin.
The first colour images of Pluto’s atmospheric hazes returned by NASA’s New Horizons spacecraft last week — seen here backlit by the Sun — reveal that the hazes are blue. Also, in a second significant finding, New Horizons has detected numerous small, exposed regions of water ice on the dwarf planet.
