The planet, TrES-4, is roughly 1.7 times the size of Jupiter, but has the density of balsa wood. This puts it in a strange class of objects known as “puffy” planets, which have extremely low densities. Astrophysicist Georgi Mandushev of the Lowell Observatory in Arizona told Space.com that the planet is “way bigger than it’s supposed to be.” In other words, standard planets of that mass should be much tinier.
Located about 1,400 light years from Earth, the planet orbits its sun in just three and a half days. When it passes in front of that star, astronomers can calculate its size. As for why it’s puffy, they're still trying to work that out.—Gregory Mone
(Image credit: Jeffrey Hall, Lowell Observatory)
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.