New Horizons: I Spy Pluto and Charon!

by Nancy Atkinson on July 10, 2013

New Horizons LOng Range Reconnaissance Imager (LORRI) composite image showing the detection of Pluto’s largest moon, Charon, cleanly separated from Pluto itself. (Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute)

New Horizons LOng Range Reconnaissance Imager (LORRI) composite image showing the detection of Pluto’s largest moon, Charon, cleanly separated from Pluto itself. (Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute)

The New Horizons spacecraft is still about 880 million kilometers (550 million miles) from Pluto, but on July 1 and 3, 2013, the spacecraft’s LOng Range Reconnaissance Imager (LORRI) was able to detect not only Pluto, but its largest moon, Charon, visible and cleanly separated from Pluto itself. Charon orbits about 19,000 kilometers (12,000 miles) away from Pluto, and seen from New Horizons, that’s only about 0.01 degrees away.

“The image itself might not look very impressive to the untrained eye, but compared to the discovery images of Charon from Earth, these ‘discovery’ images from New Horizons look great!” said New Horizons Project Scientist Hal Weaver. “We’re very excited to see Pluto and Charon as separate objects for the first time from New Horizons.”

The frame on the left in the grouping of images above is an average of six different LORRI images, each taken with an exposure time of 0.1 second. The frame to the right is the same composite image but with Pluto and Charon circled; Pluto is the brighter object near the center and Charon is the fainter object near its 11 o’clock position. The circles also denote the predicted locations of the objects, showing that Charon is where the team expects it to be, relative to Pluto. No other Pluto system objects are seen in these images.

These images are just a hint of what’s to come when New Horizons gets closer to the Pluto system. On July 14, 2015, the spacecraft is scheduled to pass just 12,500 kilometers (7,750 miles) above Pluto’s surface, where LORRI will be able to spot features about the size of a football field.

“We’re excited to have our first pixel on Charon,” said New Horizons Principal Investigator Alan Stern, “but two years from now, near closest approach, we’ll have almost a million pixels on Charon –and I expect we’ll be about a million times happier too!”

Pluto has five known moons (and naming them has been a bit controversial). Will New Horizons find even more?

Source: New Horizons

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Nancy Atkinson is Universe Today's Senior Editor. She also works with Astronomy Cast, and is a NASA/JPL Solar System Ambassador.

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