Alien planet. Artwork of a gas giant planet seen from the surface of one of its moons. This planet orbits a binary star system (upper right) comprising a white dwarf (upper star) and a pulsar (lower star). A pulsar is a rapidly-spinning neutron star that emits beams of energy in opposite directions. The pole of the gas giant (centre) is ringed with aurorae, a glow produced by the action of charged particles from the stars colliding with the planet's upper atmosphere. This planet was confirmed to exist in 2003, when calculations showed that it had a mass 2.5 times that of Jupiter. It lies in the globular star cluster M4, some 5600 light years from Earth.