Our methods of finding planets outside the solar system are still very primitive, but we're now getting a stage where we can start taking photos of them. And doing just that, known as direct imaging, a gas giant has been spotted around a star three times less massive than our sun.
But what is most striking about this planet, dubbed GU Psc b, is the huge distance at which it orbits its host star - about 2,000 times further than Earth is from the sun, a record among exoplanets.
The international research team, led by Marie-Ève Naud, a PhD student in the Department of Physics at the Université de Montréal, was able to find this planet by combining observations from the the Gemini Observatories, the Observatoire Mont-Mégantic (OMM), the Canada-France-Hawaii Telescope (CFHT) and the W.M. Keck Observatory.
Given its distance from its star, it takes approximately 80,000 Earth years for GU Psc b to make a complete orbit. 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 (or colors) from the OMM and CFHT, they were able to correctly detect the planet.
Naud says, 'Planets are much brighter when viewed in infrared rather than visible light, because their surface temperature is lower compared to other stars. This allowed us to identify GU Psc b.'
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.
This does not mean that planets similar to GU Psc b exist in large numbers, as noted by by Étiene Artigau, co-supervisor of Naud's thesis and astrophysicist at the Université de Montréal. 'We observed more than 90 stars and found only one planet, so this is truly an astronomical oddity,' he says.
Here the planet GU Psc b and its star GU Psc A are composed of visible and infrared images. Because infrared light is invisible to the naked eye, astronomers use a color code in which infrared light is represented by the color red. GU Psc b is brighter in infrared than in other filters, which is why it appears red in this image
To determine other characteristics of the planet, including its mass, researchers used theoretical models of planetary evolution. The light spectrum of the planet 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°C (1,500°F).
Knowing the age of the star GU Psc due to its location in AB Doradus, the team was able to determine the mass of the planet, which is nine to 13 times that of Jupiter. In the coming years, the astrophysicists hope to detect planets that are similar to GU Psc but much closer to their stars, thanks, among other things, to new instruments such as the GPI (Gemini Planet Imager) recently installed on Gemini South in Chile.
The proximity of these planets to their stars will make them much more difficult to observe. GU Psc b is therefore a model for better understanding these objects.
The discovery was made by combining observations from the the Gemini Telescope (in the foreground), the Observatoire Mont-Mégantic (OMM), the Canada-France-Hawaii Telescope (CFHT, shown in the background) and the W.M. Keck Observatory
René Doyon, co-supervisor of Naud's thesis and OMM Director says, '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.'
The team has started a project to observe several hundred stars and detect planets lighter than GU Psc b with similar orbits. The discovery of GU Psc, a rare object indeed, raises awareness of the significant distance that can exist between planets and their stars, opening the possibility of searching for planets with powerful infrared cameras using much smaller telescopes such at the one at the Observatoire du Mont-Mégantic.
The researchers also hope to learn more about the abundance of such objects in the next few years using instruments such as NASA’s upcoming James Webb Space Telescope.
Source DailyMail.