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Mar 24 2015

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Why don’t we have Super-Earths here?

Every other discovered Solar System seems to have them: large planets that orbit very close to their star. Our Solar System seems to be the exception, not the rule. A new research paper claims that Our Solar System May Have Once Harbored Super-Earths.

They postulate that Jupiter’s orbit changed over time in the early Solar System, and in an inward sweep, it acted like a wrecking ball and cleared out all of the early Super-Earths, knocking them into the Sun. Saturn’s formation, however, pulled Jupiter out to its current orbit, which allowed the terrestrial planets, including Earth, to form.

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This snapshot from a new simulation depicts a time early in the solar system’s history when Jupiter likely made a grand inward migration (here, Jupiter’s orbit is the thick white circle). As it moved inward, Jupiter picked up primitive planetary building blocks, or planetesimals, and drove them into eccentric orbits (turquoise) that overlapped the unperturbed part of the planetary disk (yellow), setting off a cascade of collisions that would have ushered any interior planets into the sun.

This model solves several puzzles, like

  • Why don’t we have Super-Earths
  • Why are the terrestrial planets so much different from the rest of our planets?
  • Why doesn’t Earth show any evidence of significant Hydrogen in its primordial atmosphere, when it was clearly present in abundance (witness the gas giants).

Key conclusion:

And that sets us apart in another way from the majority of exoplanets. Batygin expects that most exoplanets – which are mostly super-Earths – have substantial hydrogen atmospheres, because they formed at a point in the evolution of their planetary disk when the gas would have still been abundant. “Ultimately, what this means is that planets truly like Earth are intrinsically not very common,” he says.

Which may also explain why SETI hasn’t found anything. Maybe the chances of an Earth developing in the habitable zone of a planet are actually pretty small.

Permanent link to this article: http://www.newspaceraces.com/2015/03/24/why-dont-we-have-super-earths-here/

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