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Pale Blocky Dot: Dwarf Planet Ceres in Dawn Probe’s Sights

It's only nine pixels wide, but the Dawn probe's latest picture of Ceres already shows that the dwarf planet is true to form.

The Dec. 1 view was taken when NASA's Dawn spacecraft was about 740,000 miles (1.2 million kilometers) from 590-mile-wide (950-kilometer-wide) Ceres, the most massive object in the main asteroid belt. Dawn is on its way to a rendezvous with Ceres early next year after studying Vesta, the second most massive asteroid.

The International Astronomical Union lumped Ceres in with Pluto and several other worlds as dwarf planets in 2006 — due to the fact that it's massive enough to maintain a round shape, but not big enough to "clear the neighborhood of its orbit." That definition may be a bit problematic; nevertheless, Dawn's view certainly provides a sense of Ceres' roundness.

This picture was taken primarily to calibrate Dawn's camera. It's not as detailed as the view that the Hubble Space Telescope captured in 2004. For better views — perhaps including glimpses of ice caps, ice volcanoes and clouds — check back in March, when Dawn goes into orbit around the first dwarf planet to be seen close up. (Pluto gets its turn in July.)

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— Alan Boyle