New, odd, planet discovered

Written by PTI | Toronto | Updated: May 15 2014, 18:40pm hrs
Scientists have identified a massive new exoplanet that takes a record 80,000 Earth years to make a complete orbit around its star, 155 light years away from our solar system.

The gas giant has been added to the short list of exoplanets discovered through direct imaging. It is located around GU Psc, a star three times less massive than the Sun and located in the constellation Pisces.

The international research team, led by Marie-Eve Naud, a PhD student at Universite de Montreal's Department of Physics, was able to find this planet by combining results from several observatories.

GU Psc b is around 2,000 times the Earth-Sun distance from its star, a record among exoplanets. Given this distance, it takes approximately 80,000 Earth years for GU Psc b to make a complete orbit around its star.

The researchers also took advantage of the large distance between the planet and its star to obtain images. By comparing images obtained in different wavelengths from the Observatoire Mont-Megantic (OMM) and the Canada-France-Hawaii Telescope (CFHT), they were able to correctly detect the planet.

"Planets are much brighter when viewed in infrared rather than visible light, because their surface temperature is lower compared to other stars," Naud said.

"This allowed us to identify GU Psc b," Naud said.

The researchers were looking around GU Psc because the star had just been identified as a member of the young star group AB Doradus.

Young stars (only 100 million years old) are prime targets for planetary detection through imaging because the planets around them are still cooling and are therefore brighter, researchers said.

This does not mean that planets similar to GU Psc b exist in large numbers, noted Etiene Artigau, co-supervisor of Naud's thesis and astrophysicist at Universite de Montreal.

"We observed more than 90 stars and found only one planet, so this is truly an astronomical oddity!" Artigau said.

Observing a planet does not directly allow its mass to be determined. Instead, researchers use theoretical models of planetary evolution to determine its characteristics.

The light spectrum of GU Psc b obtained from the Gemini North Observatory in Hawaii was compared to such models to show that it has a temperature of around 800 degrees Celsius.

Knowing the age of GU Psc due to its location in AB Doradus, the team was able to determine its mass, which is 9-13 times that of Jupiter.

"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," said Rene Doyon, co-supervisor of Naud's thesis and OMM Director.