Uranus at Opposition

Hundreds of planets have been found in other star systems. They’re all so far away, though, that they’re seen as no more than squiggly lines on a computer screen. Yet astronomers are slowly starting to tease details out of some of those squiggles.

To understand how difficult the problem is, consider that there’s still a lot to learn about the planets of our own solar system, even though by astronomical standards they’re just next door.

One mystery, for example, is why the planet Uranus radiates so little energy into space.

The four outermost planets — Jupiter, Saturn, Uranus, and Neptune — are all giants. They’re so heavy that their gravity squeezes their interiors tightly, producing heat that radiates into space. In fact, three of the four worlds emit a good bit more energy than they receive from the Sun. The exception is Uranus, where the energy is roughly balanced — and scientists are trying to figure out why.

Another mystery is the planet’s climate. Uranus orbits the Sun on its