PLUTO is warming up as its orbit takes it further from the Sun. The finding is baffling astronomers, who had expected it to cool.
The planet moves in a 248-year elliptical orbit, and has been retreating from the Sun since its closest approach in 1989, when it was 4.4 billion kilometres out, just inside Neptune’s orbit. It will reach its most distant point, 7.4 billion kilometres from the Sun, in 2114. Astronomers had worried that the atmosphere would freeze before NASA could send a spacecraft to explore the planet. But Pluto may be more complex than they thought. “We just…
