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“Another Earth. “ NASA had found the words to draw attention to the press conference it organized, Thursday, July 23, on the latest results of its Kepler space telescope, which specializes in the hunt for exoplanets, these planets located in other solar systems than ours. The US space agency has met the expectations of enthusiasts of astronomy: a new planet with a size close to Earth was detected by the satellite, for the first time in the habitable zone around a star similar our Sun -. but distant from 1400 light years
Dubbed Kepler-452b, it brings the number of confirmed exoplanets in 1030, says NASA, the deputy director said that John Grunsfeld its detection “made us one step closer to Earth 2.0″ . With a diameter 60% larger than the Earth, Kepler-452b goes around its star in three hundred eighty-five days and is 5% further away from it than we are from the sun. It is battery in the habitable zone, one where liquid water, essential to life, would be likely to be present.
The star Kepler-452 (known as the 2MASS J19440088 + 4416392) is aged 6 billion years, 1.5 billion more than our star, and also 20% brighter and 10% larger. These results will be submitted to the journal Astrophysical Journal .
“A substantial opportunity for life to emerge”
“It strikes the imagination to think that this planet spent six billion years in the habitable zone, the longer that the Earth , says Jon Jenkins, head of the analysis of Kepler data to NASA . This is a substantial opportunity for life to emerge, if all the ingredients and conditions necessary for life existed on this planet. “
It is however too early to say. Kepler is not able to determine the mass of the new planet, “an essential parameter to determine its nature, rocky, gaseous, or a combination of both, and whether it is home to an atmosphere” says astrophysicist Anne-Marie Lagrange (Grenoble Observatory). The researcher, who was not associated with the discovery, welcomes it, because it “shows that we can detect very weak signals over periods that correspond to that of the Earth. “ Many super Earth had indeed already been identified, but much closer to the star orbits, where the radiation they would have every opportunity to nip in the bud any activity organic.
Didier Queloz (Cambridge University), co-discoverer in 1995 of the first exoplanet, a “super Jupiter,” says he, too, progress for twenty years. “Today, we speak of a cousin of the Earth, even if one is not sure of his ground , he said. This is just the beginning of a very long journey. We will soon have access to information on the composition of the atmosphere. This is not science fiction. “
New instruments necessary
This is not the first time that Kepler claims to have found a new Earth. In April 2014, Elisa Quintana (NASA Ames Research Center, SETI Institute) and colleagues showed in Science Kepler-186f, a planet barely larger than ours, but orbiting a dwarf red in the constellation Cygnus, distant 500 light years. A red dwarf is a star at the lowest brightness, and smaller in size than our sun.
However, Kepler-186f showed the interest to be in the habitable zone, good distance to harbor water in the liquid state. But, as with Kepler 452-b, it was impossible to know which was its mass, its exact composition and even less if it had an atmosphere conducive to chemical reactions that on Earth led to the emergence of life.
Read also: From the looks fixed on a new exoplanet
Kepler can not tell. The first instrument entirely dedicated to exoplanets, launched in 2009, is now an undead: the loss of gyroscopes no longer allows him to perform accurate monitoring of the portion of the sky that was assigned. “If the catalog is that it has established a gold mine, to go further, we have to combine a series of instruments and detection techniques, in orbit and on the ground” warns Stéphane Udry (Geneva University). Like Plato, a space telescope of the European Space Agency, which has to fly in 2024, or small space telescopes that will focus on a single star, and successors like Harps spectrograph, the European Southern Observatory (ESO ).
The length of the trip, insurmountable
The ideas abound to detect exoplanets, but two methods stand out. In 1995, the first exoplanet was discovered around a solar-type star, by Michel Mayor and Didier Queloz (then at the Geneva Observatory), by the radial velocity method. This involves measuring the color variation of the star induced by the motion of the planet around it: this dance changes the location of the star around their common center of gravity. As the sound of the siren of a fire engine, more acute as it approaches more serious as it moves away, these periodic movements relative to an outside observer alter the perception of the wavelength the light emitted by the star – there is talk of Doppler effect. This method allows for time to detect giant planets, Jupiter type. – Like the discovery in 1995 by Mayor and Queloz around the star 51 Peg
Kepler uses him, technique so-called “transit”, which comprises detecting variations in brightness of a star at the passage of a planet in the observer’s line of sight. It allows to deduce the size of the planet and its distance from the star – so whether it is in the habitable zone, that is to say at a distance that makes possible the presence of liquid water. But do not reveal the mass, so crucial.
Future progress in the hunt for more land will come from the combination of these techniques. For there is no question yet to observe these stars directly in visible light, except bigger, gas giants that are ten to twenty times the mass of Jupiter: the light they reflect is lost in that emitted by their star, or too weak to be detected. This is also the case of the Earth, that hypothetical aliens attempt to see from Kepler-452b: the pale light reflected by our “blue marble” is embedded in the lighthouse one billion times brighter Sun
Will it be possible one day to explore more directly these systems cousins of ours? The length of the trip is an insurmountable obstacle for comparison, the New Horizons probe, the device that holds the speed record at launch, almost 60 000 km / h, took nine and a half years to reach Pluto, Remote currently 3.8 billion kilometers, on the fringes of the solar system. Kepler-452b is 3.5 million times farther … And assuming that being smart is ready to receive a radio signal, it would take nearly three thousand years for its eventual response reaches us …
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