The nearest potentially habitable planet, Proxima b, apparently, not always turned to its star to one side.
Robert brown of the Science Institute space telescope (USA) has done the calculations as to how elongated the orbit of the planet Proxima b around its star. As it turned out, rather, it revolves in an orbit far enough from the circular. This means that it, with high probability, no tidal capture, and, conversely, there is a change of day and night, making the climate milder. Relevant article sent for publication in The Astrophysical Journal, and its text can be found on the Preprint server at Cornell University.
The researcher used the method of Monte Carlo simulation for the selection of such values of elongation of the orbit of the exoplanet, which would in the least degree contradict the available observations on the fluctuations of the radial velocity of its star, Proxima Centauri. As you know, Proxima b was detected by the method of radial velocities, that is, light podergivaniah that its gravity caused its own star. Because the planet is very small — only 1.3 times more massive than Earth, such podragivanija have its lights very small. However, using the model of this influence for different possible orbits Proxima b, found out that the eccentricity of its orbit, most likely close to 0,25.
This is a fairly high degree of elongation of the orbit. In the Solar system is the same Pluto, causing its orbit is far from circular. The closest to the Sun point of the orbit of Pluto has been removed from it approximately 30 times more than earth is from the Sun, and the farthest is about 49 times further away.
Information about the shape of the orbit of Proxima b is essential. For this planet, because of its proximity to its star, there are only two options daily rotation or lunar, or Mercurian. At first she looks at the star on one side, ever day like the Moon on the Earth. There can be quite hot, but always on the night side very cold. This planet is presumed to be inhabited only if its atmosphere is much thicker and the earth is able to endure the heat on the night side. Otherwise, greenhouse gases, carbon dioxide and water vapor will freeze solid from the atmosphere to the ever-cold non-illuminated side, which will lead to problems with the climate and daily.
However, with orbital eccentricity of 0.25 is unlikely. When eccentric orbit, the planet needs all the time to look at the light for one side — it will synchronize the rotation with him at the Mercurian scenario, when the day of the planet is equal to 2/3 of its year. For Proxima b is a matter of weeks, that is excessive heat or cool in such a situation is less likely than in the eternal day in one hemisphere, and perpetual night in the other. For the planet in the zone of potential habitability, this may be an important factor stabilizing the climate and increase the possible isnapshot.