COMPUTER GRAPHICS – This rocky world orbiting our nearest neighbor, Proxima Centauri, is located in a zone compatible with the existence of liquid water
fans of science fiction no longer believed: a planet revolves indeed around the nearest star to us, Proxima Centauri. Making it de facto closest exoplanet to Earth and therefore the best candidate for a putative extrasolar exploration mission. Better, it is likely rocky and located in the “habitable” zone of its star, that is to say at a distance compatible with the existence of liquid water on its surface, today announced an international team in the journal Nature. Caution remains the watchword. This does not mean that water runs on the surface, let alone that little green men splashing about happily. Recall that Venus as Mars, just as the moon moreover, are also located in the “habitable” zone around our sun. Yet they are home or rivers or oceans. As for life in any form whatsoever …
But it is not forbidden to dream a little and it could be quite different on Proxima Centauri b – the nickname of our new neighbor. “It is impossible to give a formal answer to that yet,” says Franck Selsis, team leader [exo] Lands in Astrophysical Laboratory of Bordeaux. In several related papers being published, researchers around the world have begun to speculate about the possible landscape on the surface of the newcomer.
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“Not an Earth twin ‘
It is indeed merely conjecture. So far, everything is imaginable: it could also harbor huge ocean being completely devoid of atmosphere. Be entirely frozen or hot as an oven. Although closer to us in astronomical terms, Proxima Centauri b rest located just over four light years, slightly less than 40,000 billion kilometers. It was detected by the gravitational influence it exercised over its star, a red dwarf almost ten times less massive than our Sun and 1000 times fainter. “When a planet orbits its star, it oscillates slightly it back and forth, changing its color Doppler,” says Julien Morin, a researcher at the laboratory universe and particle Montpellier, co-author of the discovery.
These are very tenuous changes from red to Proxima Centauri who betrayed the presence of the small planet after more than two months of daily observations beginning in 2016 with the telescope in La Silla (3.6 meters diameter), located in Chile and property of the European Southern Observatory (ESO). “If it had not been detected previously in spite of its proximity is that Proxima Centauri, as many red dwarfs, is a very active star that can produce these color changes” naturally “, explains Julien Morin. It was not easy to ensure that this was not the case. “
If you have the legs to the surface of the planet, you would a red sun almost three times bigger than ours, with two other small suns
This method of detection is not possible to know the radius of the planet but only a minimum mass. Namely 1.3 times that of Earth. The planet could weigh up to several Earth masses. Despite this uncertainty, it remains likely rocky. Proxima Centauri b is also 20 times closer to its star than the Earth from the sun. If you had the legs to the surface, you would see a red sun almost three times bigger than ours, with two other small suns, stars Alpha Centauri A and b that accompany our nearest neighbor. The planet must also undergo tidal forces (caused by the gravitational pull of its star) considerable. It is also likely that it is because of this “forced” to always present the same side to its star (the same way the Moon always shows the Earth the same side). This would induce very specific constraints on its possible atmosphere.
“Proxima Centauri b will not be an Earth twin, warns Franck Selsis. His sun is also very different. It emits far more extreme X and UV rays. “The question is whether this radiation and wind of intense particles emitted from the red dwarf or not have full blown its atmosphere. “If this is the case, the temperature difference between the day side and the dark side may be large enough for future US space telescope JWST will detect it,” said Martin Turbet, researcher at the Dynamic Meteorology Laboratory in paris.
for more favorable to the presence of liquid water, where the planet would still have an atmosphere, it will be the E-ELT (European Extremely Large Telescope) under construction at Chile, to study it. Scheduled for 2024, this behemoth of 39 meters will be the only one able to distinguish the small planet in the light of its star. It should then be possible to detect its possible atmosphere and determine its composition. With this slightly crazy hope. Found there traces of the first extraterrestrial life
If you leave now, you will arrive in 21 016 …
by Cyrille Vanlerberghe
Proxima Centauri may well be the closest star to the Sun, 4.2 light-years, potentially habitable planet that orbits remains no less inaccessible. For an order of magnitude colossal distances involved, it would 19,000 years to reach its destination with the fastest object ever sent by a rocket, the spacecraft Helios 2 NASA, which reached a speed of 240,000 km / h. You need to go faster.
With nuclear propulsion, study for decades to shorten the trip to Mars, the journey to Proxima would last “only” 1000 years. Still too long? It is then necessary to turn to even more futuristic technologies, close to science fiction. Thermonuclear fusion, which seeks to domesticate for the ITER reactor in southern France, could in theory allow to reach 12% of the speed of light. The journey to Proxima then would last 36 years
Russian billionaire Yuri Milner believes however that it will be possible to send by 2035 a tiny automated probe (weight: 1 g). Proxima towards propelling it with a shooting laser extremely powerful. At 20% the speed of light, the trip would take only 20 years. But the colossal acceleration at the start makes the unthinkable technology for manned flight.
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