Why Don't Super-Earths and Hot-Jupiters Like Each Other?
Astronomers have looked at a lot of other star systems in recent years. They've found ample evidence of "hot Jupiters," those gas giants that are close to their parent star, and "super-Earths," those probably rocky worlds, larger than Earth but smaller than Neptune. But in all their searching, all their discoveries, there is only one star system that has them both.
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The system is called WASP-47 and actually has three planets close in to the star: a hot Jupiter, a hot super-Earth and a hot Neptune. Meanwhile, the other 100-or-so hot Jupiters found don't have any (detected, at least) super-Earth companions. What is up with that?
A new study proposes that it's very hard to find both in the same system because super-Earths get very easily destroyed.
"I argue that the lack of super-Earth companions to hot Jupiters is evidence that most of these planets have experienced strong gravitational effects from other planets or stars in the past: they are sent onto highly eccentric orbits like those of comets, and then their orbits circularize over time," said lead author Alexander James Mustill, a senior astronomy and physics research fellow at Lund University in Sweden, in an email to Discovery News.
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"During the phase of high eccentricity, they destroy any super-Earths orbiting close to the star, usually by forcing them to collide with the star or with the planet itself."