Giant Exo-planet Puzzles Astronomers

Artist’s view of the planet GU Psc b (at right) and its distant star GU Psc (at left). Courtesy of Lucas Granito

Talk about a cosmic outsider! A newfound exoplanet sets the record for orbital distance from a host star.
Dubbed GU Psc b, the giant planet is on an orbit more than 2,000 times farther away from its star than the one the Earth circles around the sun. You wouldn’t see many birthdays on this exotic world, since it takes about 80,000 years to make a single trip around its star!
For comparison, the farthest large planet in our solar system, Neptune, orbits at only 30 times the Earth-sun distance. Its “year” is just shy of 165 Earth-years.
The newly discovered exoplanet lies some 155 light-years from Earth in the constellation Pisces, and it is huge, estimated at about 11 times the mass of Jupiter.
Current theories, however, cannot explain how a large planet like GU Psc b could form at such a great distance from its star, so the discovery may refine our understanding of how planets are born.
The international discovery team, led by Marie-Ève Naud of the Université de Montréal in Quebec, found and directly imaged the planet by combining observations from observatories in Canada, Hawaii, and Chile. The announcement made this week, published in the Astrophysical Journal, comes hot on the heels of the release of the best direct image ever taken of an exoplanet.

The planet GU Psc b and its star GU Psc A are shown in a composite picture of visible and infrared images from the Gemini South telescope and an infrared image from the Canana-France-Hawaii Telescope. Credit: Gemini Observatory