so, in the hunt for exoplanets, the biggest surprise is few of them look like the earth.
the most common type of planet around other stars is what is known as “super-earth.” a super-earth is a planet i=with a crushing atmosphere and masses 3-10 times the mass of earth.so, why does our planet, with it’s exposed continents & relatively thin atmosphere, appear to be so rare? a “new”(2016) theory (well, it’s new to me. don’t judge.) suggests that earth is a “second generation planet, built from the remnants of a demolition derby, from giant planets that (once) dominated the inner solar system. imagine, 4.6 billion years ago, the planets in the solar system began to form from a vast disc of dust and debris. giant Jupiter formed first and settles into a faraway orbit. where the earth is today, a band of super earths form. the gravity of these planets dominated the inner solar system, preventing anything else from forming.
…until Jupiter joins the party. after a few million years, the gravity of the protoplanetary disk slows Jupiter down, spiraling it into the inner solar system. this inward motion also pushes asteroids towards the super-earth, changing and disturbing their orbits. some would be kicked out of the solar system, and others will crash into the sun, while still others will collide with each other and smash each other to pieces. then, after all the super-earth are gone, Jupiter is tugged back out by a newly formed planet, Saturn. the planetary building continues in the inner solar system, but these planets are building on scraps, with thinner atmospheres. among these is earth, a second jeneration planet capable of life.
cool!
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