Thursday 16 April 2015

Dwarf Planets

That's the first ever full colour photograph of dwarf planet Pluto and its major moon Charon. OK, it may not look like much, but it's a significant first. No spacecraft has ever been close enough to Pluto before to take a quality image, but now NASA's New Horizons space probe is closing in on the Plutonian system, snapping photos using its special long exposure colour imager (which is, charmingly, called Ralph). The resolution is low at the current distance, but even in this image we can see that Pluto has a brighter appearance than Charon, indicating different surface materials. The New Horizons team on Earth are now refining the image to make it clearer, and better, more detailed images will come as the probe gets closer to Pluto. As I write this, it's 89 days away from closest approach.

Meanwhile, NASA's Dawn spacecraft is in orbit around Ceres, the nearest of the dwarf planets, in the asteroid belt. Dawn is the first spacecraft to achieve orbit around a dwarf planet, and has been stable in orbit for around a month, since March 6th, although frustratingly much of that time it has been on the dark side of the orbit and unable to take photos. We do have some excellent images taken from its approach though. Above are two excellent monochrome shots of Ceres, half in shadow due to the position of the spacecraft relative to both the planetoid and the sun, while below is a composite colour image of the Cererean surface. This is not a true colour image, but is enhanced to show the diversity of surface features more clearly. From both images, we can see that the Cererean surface is heavily cratered and displays considerable variation. The bottom image shows several shots of the surface taken using an infrared mapping spectrometer, clearly showing the two mysterious bright spots on the surface of Ceres which are as yet unexplained and are provoking debate. It's an exciting time for space exploration. Makes up for that tragically disappointing solar eclipse.

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