|Astronomers from the Université de Montréal and the CRAQ discovered an errant planet, lost in space|
An errant planet, not orbiting any star, has been discovered with the Canada France Hawaii Telescope (CFHT) and the Very Large Telescope (VLT) of the European Southern Observatory (ESO), by a team of researchers from the Université de Montréal (UdeM) and their european colleagues."This type of young and cold planet, while predicted by astrophysicists, had not been discovered until now, said Etienne Artigau, astrophysicist at the UdeM. This first object is also the nearest ever found to our Solar System."
The absence of any parent star for this planet allowed the precise study of the planet's atmosphere. This work will also help astronomers to better understand exoplanets that are orbiting stars.
Planets erring in space are planets that are not gravitationally tied to any star. "In the past few years, several such objects had been noticed, but the lack of age measurement did not allow for any confirmation, explained Jonathan Gagné, PhD student at the UdeM. Astronomers were not able to distinguish them from brown dwarfs, which are 'failed' stars that are too small to initiate nuclear burning in their core."
The astrophysicists of the CRAQ and the physics department of UdeM - Jonathan Gagné, Lison Malo, Etienne Artigau and Loïc Albert - managed to detect with planet in a collaboration with French astronomers, including Phillipe Delorme, from the Laboratoire d'Astrophysique de l'Observatoire de Grenoble (France), and principal investigator on the project. Named CFBDSIR2149, this planet appears to belong to a group of young stars called Young Association AB Doradus.
"This group of stars is composed of about thirty stars of the same age and composition, and moving together in space. The association of this planet with AB Doradus made possible the determination of its age, and therefore its classification as a planet," said Lison Malo, PhD student at the UdeM.
The team of researchers first collected infrared images of CFBDSIR2149 with the 3.6m telescope of the CFHT before using the 8m VLT of the ESO to deduct the planet's mass, temperature and age. CFBDSIR2149 is between 50 and 120 million years old, has a temperature close to 400 degrees Celsius, and has a mass of about 4 to 7 times the mass of Jupiter. It is important to know that passed 13 times the mass of Jupiter, a celestial object is not considered a planet but a brown dwarf star because this value is the minimum mass required to fuse deuterium in the core of the object.
"The etymology of the word 'planet' comes from the greek 'planeta', or 'planêtês' which designated moving stellar objects, or errant stellar objects, in contrast with stars that appear immobile on the celestial sphere", reminded Olivier Hernandez, astrophysicist at the UdeM.
This is the first isolated planet, non-gravitationally tied to a host star, for which we know the mass, temperature and age fairly well. This result supports the theories of planet and star formation, but it also provides arguments to the theories claiming that isolated planets are more numerous than we think.
"This errant planet was found in a very large survey of the sky covering the equivalent of 1000 times the surface of the full moon, explained Etienne Artigau. We basically observed hundreds of millions of stars and planets, and we only found a single errant planet, very close to us. These objects are not necessarily rare, but we only see that ones that are nearby. In addition, we have to find them among millions of more distant objects. It is like looking for a single needle in thousands of haystacks."
This artist’s impression shows the free-floating planet CFBDSIR J214947.2-040308.9. This is the closest such object to the Solar System. It does not orbit a star and hence does not shine by reflected light; the faint glow it emits can only be detected in infrared light. Here we see an artist’s impression of an infrared view of the object with an image of the central parts of the Milky Way from the VISTA infrared survey telescope in the background. The object appears blueish in this near-infrared view because much of the light at longer infrared wavelengths is absorbed by methane and other molecules in the planet's atmosphere. In visible light the object is so cool that it would only shine dimly with a deep red colour when seen close-up.
This closeup of an image captured by the SOFI instrument on ESO’s New Technology Telescope at the La Silla Observatory shows the free-floating planet CFBDSIR J214947.2-040308.9 in infrared light. This object, which appears as a faint blue dot at the centre of the picture, is the closest such object to the Solar System. It does not orbit a star and hence does not shine by reflected light; the faint glow it emits can only be detected in infrared light. The object appears blueish in this near-infrared view because much of the light at longer infrared wavelengths is absorbed by methane and other molecules in the planet's atmosphere. In visible light the object is so cool that it would only shine dimly with a deep red colour when seen close-up.
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