WHAT’S UP WITH NEPTUNE?
When Voyager 2 reached Neptune in 1989, just 12 years after setting off on its historic journey through the Solar System, it discovered six new moons, took the first images of the planet's rings and noted a particularly violent storm.
This was something of a surprise. In the southern hemisphere there was a swirling, counter-clockwise wind of up to 2,414 kilometres (1,500 miles) per hour – the strongest ever recorded in the Solar System. Astronomers called it the Great Dark Spot, and while it had gone by the time the Hubble Space Telescope looked at the planet five years later, they were keen to learn why the winds were so extreme.
They were also perplexed by another issue: Voyager 2 revealed that Neptune is warmer than Uranus, despite being further from the Sun. As Professor Brian Cox discussed in his BBC documentary, The Planets: “The source of this extra heat remains a mystery.” But does that mean we have a double-puzzle on our hands, and can one mystery help to explain the other in some way?
Before we begin to address the two issues at hand, we must first look at what is actually meant by ‘warmer’. Since Neptune is
