Scientists have analyzed two recently discovered exoplanets that have similar sizes but very different densities, and can offer a unique view of how worlds are formed.
Kepler-107b and Kepler-107c have almost identical radii of 1.5 and 1.6 terrestrial radii, but their densities are twice as different, according to the researchers.
Scientists from the National Institute of Astrophysics (INAF) of Italy and the University of Bristol in the United Kingdom spent three years observing the exoplanetary system Kepler-107 through the Telescopio Nazionale Galileo in La Palma.
They collected more than one hundred spectroscopic measurements of the four planets of subneptic masses at Kepler-107, the name of NASA’s Kepler space telescope, which discovered the exoplanetary system five years ago.
Unlike the relationship of the Earth with the Sun, the planets in the Kelper-107 system are much closer to each other and to their host star (its equivalent to our sun). All planets have an orbital period of days instead of years.
It is not uncommon for the planet closest to the host star to be the densest due to warming and interaction with the host star, which can cause the loss of the atmosphere.
However, in the case of Kepler-107, the second planet, 107c, is denser than the first, 107b, according to a study published in the journal Nature Astronomy.
So much so that 107c contains at its core a fraction of iron mass at least twice that of 107b, which indicates that at some point, 107c had a giant collision of high speed with a protoplaneta of the same mass or more collisions With multiple planets of a lower mass.
These impacts would have ripped part of Kepler-107c’s mantle of rock and silicate, suggesting that it is now denser than it was originally.
“It is believed that giant impacts played a fundamental role in shaping our current solar system,” said Zoe Leinhardt, computational astrophysicist at the University of Bristol.
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“The moon is probably the result of such an impact, the high density of Mercury is also, and Pluto’s great satellite, Charon, was probably captured after a giant impact, but until now, we had not found any evidence of gigantic impacts in planetary systems outside ours, “said Leinhardt.
“If our hypothesis is correct, it would connect the general model we have for the formation of our solar system with a planetary system that is very different from ours,” he said.
“With this discovery, we have added another piece in the understanding of the origin of the extraordinary diversity in the composition of small exoplanets,” said Aldo Bonomo, INAF researcher.