Scientists photograph remote planet
A planet in a star system 155 light years from the Sun has been photographed by astronomers.
It is a rare example of an exoplanet being directly imaged from Earth, rather than its presence being inferred from light data.
The gas giant circles the young star GU Psc in the constellation Pisces at a record distance 2,000 times the size of the gap separating the Earth and Sun.
As a result the planet's year - the length of time it takes to complete one orbit of its star - is 80,000 Earth years long.
Astronomers identified the planet, known as GU Psc b, by combining observations from four Earth-based telescopes.
"Planets are much brighter when viewed in infrared rather than visible light, because their surface temperature is lower compared to stars," said Canadian astronomer Marie-Eve Naud, from the University of Montreal who led the team.
The scientists focused on GU Psc because it had been identified as a member of the young star group AB Doradus. Young stars only around 100 million years old are prime candidates for planetary detection through imaging because the fledgling worlds orbiting them are still cooling and unusually bright.
"We observed more than 90 stars and found only one planet, so this is truly an astronomical oddity," said astrophysicist Dr Etienne Artigau, also from the University of Montreal.
The light from the planet suggests it has a surface temperature of around 800C. Knowing the age of the parent star allowed the scientists to calculate its mass as being nine to 13 times that of Jupiter.
In future astronomers hope to image other planets using powerful infrared cameras.
Co-author Professor Rene Doyon, director of the Mont-Megantic Observatory in Canada, said: "GU Psc b is a true gift of nature. The large distance that separates it from its star allows it to be studied in depth with a variety of instruments, which will provide a better understanding of giant exoplanets in general."
Details of the discovery will appear in the Astrophysical Journal on May 20.