Young, hot exoplanet takes title for longest year

Nearly 156 light-years from Earth, the planet GU Psc b likes to keep its distance — at least from its sun. The planet orbits 2,000 times farther from its cool, red star than Earth does around the sun, making it possibly the longest planetary orbit known.

One year on GU Psc b, which sits in the constellation Pisces, lasts nearly 163,000 Earth years.

Astronomers spotted the planet as a speck of infrared light following its sun across the sky, as described in the May 20 Astrophysical Journal. The planet glows in infrared because it’s young — just 100 million years old — and still cooling.

The escaping heat warms the planet to roughly 800º Celsius. Based on its age and brightness, astronomers estimate that the body is nine to 13 times as massive as Jupiter. While the star’s companion is most likely a very massive planet, there’s a chance it may actually be a very dim, lightweight star.