Le Monde | • Updated | By
Read also: a planet like Earth discovered by NASA
the dramatic enrichment of Kepler catalog results from new method of identifying exoplanets. The American telescope detects changes in brightness of stars, which result from the passage into his line of sight of a planet – but other phenomena can explain these variations in brightness, it is important to rule before declaring an exoplanet ” confirmed. ” As explained Tim Morton (Princeton University), “must unmask impostors , a process that requires time and resources” . It must indeed point ground-based telescopes to each candidate planet to obtain independent confirmation of that obtained by observing transits dear to Kepler.
He had the idea speed things up by calculating the probability that the received signal emanates much of an exoplanet, not an “impostor”. When the probability was greater than 99%, the planet was classified as confirmed. “This statistical classification method was presented at a conference in Hawaii in December 2015 , says Anne-Marie Lagrange (Observatoire de Grenoble), a specialist in exoplanets. It led to rather tense sessions because the proposed tests were variable from one team to another. “ This statistical classification remains further information poor: a number of planets seem to be in the habitable zone – at a distance from their star where water can be liquid and may help the appearance of life. But to determine whether they are rocky, like Earth, it will take more observations.
The exact nature of the new planets are thus unaware regarded as being in the habitable zone, shown below orange (blue are those which had already been verified).
to learn more, another great method for detecting exoplanets, called radial velocity, must be put to use in order to provide the additional information can be inferred from the density of the star, and support the assumptions about its composition. It involves measuring the color variation of the star caused by the motion of the planet around it. Dance this changes the location of the star around their common center of gravity. As the sound of the siren of a fire engine, more acute when it approaches, more serious as it moves away, these periodic movements relative to an outside observer change the perception of the wavelength the light emitted by the star. “But these checks are time and Kepler observed fairly bright stars, difficult to follow radial velocity” , says Anne-Marie Lagrange, stressing that the European telescope Plato, scheduled for 2024 , will observe her brightest stars.
“Almost all planets have a non-zero probability of false alarms. “Jean Schneider, an astronomer.
The question is how Kepler newcomers them will be classified in the exoplanet online encyclopedias. In his presentation, NASA maintains a fuzzy terminology: the 1284 new planets are “validated” , but not “verified” . John Schneider (Observatoire de Paris Meudon), which holds the oldest day (February 1995) and one of the most comprehensive (2125 to May 9 units) of these encyclopedias will add “1284 planets” validated, “since they are the 99%” . This addition will take time, because the data format of
Read also: Exoplanets: neighboring the Trappist-1 dwarf star are they really “living”?
A countdown to the nearest unit of John Schneider has no meaning: “I must say that (almost) all the planets have a nonzero probability (ranging from 0.1 ~ % to ~ 10-50%) to be false alarms. So there is a certain arbitrary to say that a planet is validated. “ Especially, he adds, there is no consensus on the definition of a planet: ” So what mass that it is a planet and not a brown dwarf? I myself have advocated a maximum limit of 60 times the mass of Jupiter (temporarily!). “
But the” quality control “these extrasolar planets seem to him satisfactory final. “Experience shows that the 2100 planets” validated “to date, only a dozen was struck,” he notes. One of them has even been, to then be “rehabilitated.”
Read also: Everything understand exoplanets, distant and fascinating worlds
No comments:
Post a Comment