Thanks to the Kepler Space Telescope, a team of astronomers from the Universities of Washington and Harvard discovered two really extraordinary planets orbiting the star Kepler-36. In fact they’re two planets completely dissimilar but with very close orbits.
Kepler-36 is a star in the Cygnus constellation about 1,500 light years from the solar system. It’s a subgiant star, which means that its spectral class is brighter than a normal main sequence star but less bright than a giant star.
Some subgiants stars seem to be simply very brilliant and metal-rich but it’s deemed that in general those stars have exhausted hydrogen fusion in their cores. In this case, in the near future – in astronomical terms – they’ll become giants after new nuclear fusion reactions around the nucleus will be triggered.
Thanks to asteroseismology, which is the study of the stars by observing their natural oscillations, it was possible to measure the size, mass and age of Kepler-36 with precision. This star appears to have a radius about 1.6 times the Sun for a mass almost identical to the Sun. I’ts a few billion years older than the Sun.
The two planets found orbit very close to the star Kepler-36, too much to fit in its habitable zone, in which water can be in the liquid state on the surface of a planet with the possibility of developing life forms similar to those on Earth.
The planet Kepler-36b is a super-Earth, so it’s rocky with a significant component of iron, a size about 1.5 times the Earth with a mass about 4.5 times the Earth. Its year lasts almost 14 Earth days with an average distance from its star of about 18 million kilometers (about 11 million miles).
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The planet Kepler-36c is gaseous but probably has a rocky core, has a size about 3.7 times the Earth with a mass about 8 times the Earth, about half the mass of Neptune. Its year lasts a little more than 16 Earth days with an average distance from its star of about 20 million kilometers (about 12 million miles).
Every 97 days, there’s the junction between these two planets, which means the moment in which the distance between them is minimal. The extraordinary thing is that this distance is less than 2 million chilometers (about 1.2 million miles), only 5 times the distance between Earth and the Moon. Curiously, on the surface of Kepler-36c, in that moment Kepler-36b appears about as big as the Moon. Instead, on the surface of Kepler-36b, in that moment Kepler-36c seems huge, a show that must be wonderful.
The periodic proximity between the two planets surely causes a significant gravitational influence. Kepler-36b, the rocky planet, is probably the ones that pays the price with high tectonic activity and if it ever had an atmosphere that’s been stripped away by Kepler-36c. Consequently, it’s unlikely that on Kepler-36b there are any life forms.
The close proximity of the two orbits is something never seen. Astronomers speculate that they’re the result of some movements of the planets within their star system until they reached their current configuration. Surely, this exceptional situation will be studied further.
