AS THE newest kid in its class Pluto may not be the biggest, but it can claim to have more friends – even if they are only its moons.
In 2006, Pluto was demoted to “dwarf planet” status, and last week it suffered a new blow. Observations pinned down the mass of an even larger icy world in the outer solar system called Eris, revealing that it outweighs Pluto by a hefty 27 per cent. Michael Brown and Emily Schaller at the California Institute of Technology, Pasadena, measured how long Eris’s single moon took to orbit, and used this figure to calculate the dwarf planet’s mass at 17 billion billion tonnes (…
