Spaceflight Insider

Image montages show one full day on Pluto and Charon

Pluto and Charon

A composite image with enhanced colors of Pluto, lower right, and Charon as New Horizons passed through the system on July 14, 2015. Image Credit: Johns Hopkins University Applied Physics Laboratory / NASA

The best images of each side of Pluto and Charon taken by NASA’s New Horizons spacecraft have been compiled together by the mission team to illustrate one full day on each body. 

The montage of images were taken by the Long Range Reconnaissance Imager (LORRI) and by the Ralph/Multispectral Visible Imaging Camera (MVIC). One full day on Pluto and Charon is equal to 6.4 Earth days. Because Pluto and Charon are tidally locked to one another, the length of each body’s day is the same.

Both objects always show the same face to each other. Charon is always visible from Pluto’s “far side”, which faced away from New Horizons its July 14, 2015, encounter day. Charon is never seen from the “near side”, which features the iconic heart-shaped Tombaugh Regio.

The same is true for Charon, with Pluto always visible to one hemisphere and never visible to the other.

Charon is half Pluto’s size. The two objects orbit a center of mass, known as a barycenter, outside of Pluto, leading some scientists to consider it a binary planet system.

LORRI and Ralph/MVIC took the images between July 7 and 13 of this year as the spacecraft headed toward its rendezvous with the Pluto system.

The distance between the spacecraft and Pluto decreased from five million miles (eight million kilometers) to 400,000 miles (645,000 kilometers) over the 6.4-day period. As a result, the images taken from further away are less detailed than those acquired from close up.

For Pluto, the most distant contributing are at the 3 o’clock position, with Tombaugh Regio rotating out of view. The lower resolution images between the 12 o’clock and 3 o’clock position show strange bumps, possibly impact craters, on Pluto’s far side.

The highest resolution and greatest detail are at the 6 o’clock position, which features the encounter side, with Tombaugh Regio front and center.

A few of the Pluto images show what appear to be “dimples” or bumps on the southern edge of the planet’s disk, but these are artifacts produced during the process of combining the images and not actual features.

Day on Pluto

The best images taken of each side of Pluto are combined here show the dwarf planet conduct one full rotation. Image Credit: Johns Hopkins University Applied Physics Laboratory / NASA

According to a statement released by the mission team, “The best available images of each side of Pluto taken during approach have been combined to create this view of a full rotation.”

The images show details of the contrasting terrains that make up Pluto’s surface.

The same process was used to create the montage Charon’s day using images also taken between July 7 and 13 by LORRI and Ralph/MVIC. They cover a range of 6.4 million miles (10.2 million kilometers) as the spacecraft raced toward the system.

Charon’s most distant and, therefore, lowest resolution, images are at the 9 o’clock position. Surface features such as canyons,  craters, and the rolling plains of the region informally known as Vulcan Planum are difficult to see on this “far” side.

The “near side” of Charon, which New Horizons photographed in the most detail, is visible at the 12 o’clock position.

As with Pluto, “dimples” or bumps visible on the southern edge of Charon’s disk are artifacts of the process through which the images were combined rather than actual features.

While Pluto’s encounter side is very different from its far side, Charon’s two hemispheres appear very similar.

Day on Charon

The best images taken of each side of Charon are combined here show the moon conduct one full rotation. Image Credit: Johns Hopkins University Applied Physics Laboratory / NASA


Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.

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