Finding An Exoplanet That Takes 80,000 Earth Years To Orbit Its Sun

Brett Smith for – Your Universe Online

Using observations from multiple observation facilities, an international team of astronomers has identified a very unusual planet that takes around 80,000 Earth years to orbit its sun.

The planet, dubbed GU Psc b, was determined to be 2,000 times the distance between the Earth and the Sun from its own star – a new record for exoplanets. The team said they were able to detect this highly unusual planet by detecting the light coming from it at several different wavelengths.

“Planets are much brighter when viewed in infrared rather than visible light, because their surface temperature is lower compared to other stars,” said team member Marie-Ève Naud, a PhD student in the Department of Physics at the University of Montréal. “This allowed us to indentify GU Psc b.”

GU Psc, the star around which the new planet had been discovered, was considered an ideal candidate for exoplanet hunters because the star itself was only recently discovered and designated as a member of the young star group AB Doradus. Younger stars are very attracting for planet hunters since the planets around them are still cooling and are therefore more visible in the infrared spectrum.

Team member Étiene Artigau noted that finding a planet like this is an extremely rare event, which required observations from Gemini Observatories, the Observatoire Mont-Mégantic (OMM), the Canada-France-Hawaii Telescope (CFHT) and the W.M. Keck Observatory.

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

Since the astronomers cannot determine an exoplanet’s mass through observations alone – they used theoretical models of planetary evolution. To determine the mass of GU Psc b, the team used the light spectrum of the planet and compared it to their models to determine that it has a temperature of around 1500 degrees F. Using both this temperature information and the approximate age of the planet, the team was then able to calculate its mass, approximately 9-13 times that of Jupiter.

Using new instruments such as the Gemini Planet Imager (GPI) recently installed on Gemini South in Chile, astronomers aim to find even more exoplanets and these new instruments will allow for the detection of planets much closer to their stars. Calculations surrounding the discovery of GU Psc b are expected to inform models for future planet-hunting endeavors.

“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 René Doyon, co-supervisor of Naud’s thesis and OMM Director.

The research team said they have begun a project to watch many stars and find planets lighter than GU Psc b with comparable orbits. The discovery of GU Psc raises understanding of the substantial distance that are present between planets and their stars, opening up the search for planets with potent infrared cameras using more compact telescopes. The scientists said they also hope to learn more about the variety of such items in the next few years.

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