Summer on Neptune

Martian-mooncat writes "According to New Scientist Neptune is now entering a 40-year summer. The report says that cloud cover changes show Neptune has its own seasons, despite being 4.5 billion miles from the Sun. There are some pretty Hubble pics too!"

Comments

Re:Where's it coming from?

[CheshireCatCO]

Jupiter does indeed emit about twice as much energy asn it absorbs (not reflects) from the Sun. This indicates an internal heat source. "Core temperature" isn't a very accurate description, based on what we think is going on, though. Jupiter isn't a failed star, especially in the standard planet formation scenario where it forms an icy core before accreting gases. So don't look to fusion to create the heat, the planet's structure is likely (we're not absolutely certain that there is a core) wrong for that. What powers Jupiter is probably slow, continued contraction. As the planet shrinks, it loses gravitational energy and emits that as heat.

Saturn has the same input/output disconnect. In the case of Saturn, I believe that the current model is helium rain. (Also releasing gravitational energy.) And Neptune also emits more energy than it takes in. (Oddly, Uranus doesn't.) Neptune's heat source is somewhat more ambiguous, but helium rain could be it. However, we know that Uranus and Neptune have very large icy cores (well, large proportional to their overall size), so there is definately no fusion there. It's doubtful that the core could be responsible for the extra heat, since there aren't many ways for ices to generate heat.