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A world 500 light-years away, Kepler-186f became the first planet known since the size of the Earth outside the solar system that revolves around a star in the habitable zone, with a stable climate and a seasonal variation.
This means that it is the appropriate distance from its star for the water the liquid to accumulate on the surface.
The study of Georgia Tech used simulations to analyze and identify the dynamics of the axis of rotation of the exoplanet . This dynamic determines how well a planet tilts on its axis and how this inclination angle evolves with time. Axial inclination contributes to seasons and climate because it affects how sunlight hits the surface of the planet .
The researchers suggest that the Axial tilt of Kepler-186f is very stable, like the Earth, which makes it likely to have regular seasonal variations and a stable climate. The Georgia Tech team thinks it's the same for Kepler-62f, a planet the size of a super Earth that revolves around a star about 1200 light-years away from US.
What is the importance of axial inclination for the climate?
The great variability of the axial tilt could be one of the main reasons why Mars was transformed from a wet landscape billions of years ago to an arid desert.
" March ] is in the habitable zone of our solar system, but its axial tilt has been very unstable, ranging from zero to 60 degrees," said Gongjie Li, assistant professor of Georgia Tech, who led the study with Yutong Shan of the Harvard-Smithsonian Center for Astrophysics. This instability probably contributed to the decomposition of the Martian atmosphere and the evaporation of surface water. "
By way of comparison, the axial tilt of the Earth oscillates more harmoniously, between 22.1 and 24.5 degrees, going from one end to the other about all the 10,000 years.
The angle of orientation of the orbit of a planet around its host star may oscillate from gravitational interaction with other planets in the system . If the orbit oscillated at the same speed as the precession of the axis of rotation of the planet (similar to the circular motion presented by the axis of rotation of a top or gyroscope), the axis of rotation would also wobble towards the front and back, sometimes dramatically.
Mars and Earth strongly interact with each other, as well as with Mercury and Venus, resulting in their axes of rotation They should be preloaded with the same speed as the orbital oscillation, which can cause large variations in their axial inclination.
Fortunately, the moon maintains the variations of Earth under control. The moon increases the rate of precession of the axis of rotation of our planet and makes it different from the orbital oscillation rate. Mars, on the other hand, has no satellite large enough to stabilize its tilt .
"It seems that the two exoplanets are very different from Mars ] and the Earth because they have a weaker link with their sister planets," he said. Li, a faculty member of the Faculty of Physics, in a statement. "We do not know if they have moons, but our calculations show that even without satellites Kepler-186f and 62f rotation axes would have remained constant for tens of millions of years." years. "
Kepler-186f less than radius of 10% than the Earth but its mass, composition and density remain a mystery. Orbit your star every 130 days. According to NASA, the brightness of this star at noon, in 186f, would look as bright as the sun just before sunset here on Earth. Kepler-186f is in the constellation of Cygnus as part of a star system of five planets
Kepler-62f was the exoplanet the closest to the Earth until scientists found it 186f in 2014. It is about 40 percent larger than our planet and is likely to be a terrestrial or oceanic world . It is in the constellation of Lyra and is the outermost planet among five exoplanets which orbit around a single star . ]
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