A Pixel Of Charon Proves Pluto Probe Has Its Eye On The Target

Pluto’s the brighter object with its largest moon Charon at the 11 o’clock position in this composite image made last week by NASA’s New Horizon spacecraft. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

NASA’s New Horizons spacecraft just took its first picture of Pluto’s moon Charon. Not bad, not bad at all, especially considering the photo was snapped from 550 million miles away.

The probe made a beeline to Pluto starting on Day One January 19, 2006, when it left Earth at 36,373 mph (58,536 km/hr) – the greatest-ever launch speed for a man-made object.

Two years from tomorrow on July 14, 2015, New Horizons will pass just 7,750 miles (12,500 kilometers) above Pluto’s surface and photograph features as small as a football field.

The New Horizons spacecraft will fly by Pluto and its moons in July 2015 after a 9 1/2 year voyage through the solar system. Credit: NASA

We’ll get an eyeful instead of a few pitiful pixels of the dwarf planet and its family of five moons that summer with more satellites likely to be discovered during the flyby. Once the Pluto mission is complete, the spacecraft will blaze a trail into the Kuiper Belt. NASA officials hope to identify additional icy asteroids that could be targeted for flybys beyond 2015.

On July 1 and July 3 mission controllers pointed the probe’s telescopic camera at the Pluto system to spot the dwarf planet’s largest moon, Charon (pronounced KARE-un). Charon’s about 750 miles (1,200 km) across – half as big as Pluto – and covered in rock-hard water ice unlike Pluto which is encased in frozen methane and nitrogen. Surface temperatures at duo’s distance of 3.67 billion miles hover around -380 F (-229 C), cold enough to freeze even that liquid metal dude from the movie Terminator 2.

Pictures Jim Christy used to make his discovered of Pluto’s largest moon Charon, which shows up as a bump at the 1 o’clock position on the photo at left. Credit: NASA

Charon was discovered in 1978 by U.S. Naval Observatory astronomer James Christy who noticed a bump on Pluto’s image taken with the Observatory’s 61-inch telescope in Flagstaff, Arizona. It was first thought that the telescope hadn’t been guided correctly, causing the then-planet to smear out, but none of the stars in the image showed a similar elongation.

James Christy (left) and colleague Dr. Robert Harrington in 1978. At right is the clearest picture we have to date of Pluto (left) and Charon, which orbits 12,500 miles (19,400 km) from Pluto. Credit: U.S. Naval Observatory

Christy searched the archive for more photos, found them and discovered the “bump” came and went in a regular 6.39 day cycle. When a new set of photos confirmed the bulge in the predicted location, the discovery was announced to the world.

Christy picked “Charon” not only for its mythical association with the underworld but because the first four letters matched the name of his wife Charlene. What a guy.

4 Responses

  1. Edward M. Boll

    Funny that I just wrote a post about Pluto before I see that you put one out too. Mine was much shorter, without pictures.

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