The Long-Range Reconnaissance Imager (LORRI) on NASA’s New Horizons spacecraft has captured some spectacular new images of Pluto, revealing bright and dark regions on the planet’s surface.
This image of Pluto and Charon was taken by the New Horizons LORRI instrument on April 15, 2015. The image is part of several taken between April 12 and 18, as the spacecraft’s distance from Pluto decreased from about 69 million miles (93 million km) to 64 million miles (104 million km). Image credit: NASA / JHU-APL / SwRI.
“As we approach the Pluto system we are starting to see intriguing features such as a bright region near Pluto’s visible pole, starting the great scientific adventure to understand this enigmatic celestial object,” said Dr John Grunsfeld of NASA’s Science Mission Directorate in Washington.
Pluto is the second closest dwarf planet to the Sun and was at one point classified as the ninth planet. It was discovered in 1930 by the American astronomer Clyde Tombaugh (February 4, 1906 – January 17, 1997).
On average, the dwarf planet is more than 3.6 billion miles (5.8 billion km) away from the Sun. That is about 40 times as far from the Sun as our planet. It orbits the Sun in an oval like a racetrack and is sometimes closer to the Sun than at other times.
Pluto is only 1,400 miles (2,300 km) wide. It takes Pluto 248 years to go around the Sun. One day on the planet is about 6.5 days on Earth.
Pluto and Charon rotate around a center-of-mass once every 6.4 Earth days, and these images, taken with the LORRI, capture one complete rotation of the system. A 3x-magnified view of Pluto is displayed in the inset to the lower right, highlighting the changing brightness across the disk of Pluto as it rotates. Image credit: NASA / JHU-APL / SwRI.
The dwarf planet has five moons. Its largest moon, Charon, was discovered in 1978. Hubble observations in 2005 uncovered two smaller moons, Nix and Hydra. Two additional moons, Kerberos (P4) and Styx (P5), were found in Hubble data in 2011 and 2012.
Since it was discovered 85 years ago, Pluto has remained an enigma. Scientists have struggled to discern any details about its surface.
The latest images from New Horizons allow them to detect clear differences in brightness across the dwarf planet’s surface as it rotates.
One pole of Pluto appears to be brighter than the rest of the disk in all the images. NASA researchers suggest this brightening in the polar region might be caused by a cap of highly reflective snow on the surface. The snow in this case is likely to be frozen molecular nitrogen ice.
In addition to the polar cap, these images reveal changing brightness patterns from place to place as Pluto rotates, presumably caused by large-scale dark and bright patches at different longitudes on the planet’s surface.
An artist’s concept of Pluto. Image credit: NASA / Johns Hopkins University Applied Physics Laboratory / Southwest Research Institute.
Also captured in the images is Charon, rotating in its 6.4-day long orbit. The exposure times used to create this image set – a 1/10th of a second – were too short for the camera to detect Nix, Hydra, Kerberos, and Styx.
NASA’s New Horizons spacecraft was launched on January 19, 2006. It passed Jupiter for a gravity boost and scientific studies in February 2007.
Its flyby of the Pluto system on July 14, 2015 will complete the initial reconnaissance of the classical Solar System.
“As we get closer, the excitement is building in our quest to unravel the mysteries of Pluto using data from New Horizons,” Dr Grunsfeld said.
“We can only imagine what surprises will be revealed when New Horizons passes 7,800 miles (12,500 km) above Pluto’s surface this summer,” said Dr Hal Weaver of the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland.
