PLUTO can rest easy: it can hold its own against the newly discovered 10th planet. Xena, it seems, is only slightly larger than Pluto – not 30 per cent bigger as previously thought. But Xena’s downsizing means that Pluto, and indeed nearly every other object in the solar system, is rather dim compared with the newcomer.
“Xena is as bright as snow and more reflective than any other solar system body”
Xena, officially called 2003 UB313, was announced in July 2005 and lies about three times as far from the sun as Pluto. From estimates of Xena’s reflectance and temperature, astronomers…
