The tragic fate of the "double" of the earth

Two groups of researchers for the first time managed to measure the mass of exoplanets the size of the Earth [1, 2]. We are talking about the planet Kepler-78b, the diameter of which is only not much more earthly, and the mass assessment ranges from 1.69 to 1.86 mass of the Earth. She turns near the star in the constellation Swan at a distance of 400 light years from us. It turns out that the density of this planet is similar to the earthly, and this, in turn, involves a similar composition of rocks and the presence of an iron core.

On this, however, all the similarities ends. After all, the Kepler-78B orbit is about 40 times less than that of our Mercury, the year there lasts only 8.5 hours, and the temperature on the surface is believed to reaches 2300-3100 degrees Kelvin. It is unclear why the Kepler-78b was so close to her star, because she could not form at such a distance from the luminaries, but her further fate would most likely be very unenviable-sooner or later the powerful tidal forces of the hostess stars will be torn.

What is noteworthy is this news besides the tragic fate of the planet the size of the Earth? The fact is that the mass of exoplanets is usually evaluated on the basis of the influence that its gravity on the parent star exerts it (this is judged by the Doppler shift in the star spectrum). The mass of exoplanets with the size of the Earth is usually difficult to evaluate, because they do not have such a powerful effect on their stars as gas giants (they are recorded according to mini-stampers when they find themselves between their star and earthly observers). However, the Kepler-78B, the diameter and orbit of which was first calculated by the Astronomer group, analyzing the data of the NASA Kepler space observatory (the corresponding publication was in August [3]) is close enough to its star to cause measurable fluctuations in its movement.

Maxim Borisov