Alien Planet is Similar to Neptune but Has a Comet-Like Tail

A weird alien planet orbiting a star 33 light-years from Earth has a tail. The Neptune-sized planet, named Gliese 436b, was seen transiting its star in 2007, but now, new observations of the world from the Hubble Space Telescope shows that the planet's atmosphere is actually evaporating. Gliese 436b is sloughing its hydrogen atmosphere out into space as it closely orbits its dim star, giving the world a tail that makes it resemble a comet.