National Geographic News
An illustration of a distant planetary system.

The Gliese system is one of several newfound solar systems, including GJ676A (not pictured).

Illustration by Dana Berry, National Geographic

Rachel Kaufman

for National Geographic News

Published July 6, 2012

Astronomers have detected our "grotesque" twin: A planetary system arranged much like our own solar system, a new study says.

Dubbed GJ676A, the system has two rocky planets orbiting close to its host star, and two gas giants orbiting far away. This means the system is arranged like our system—though in GJ676A, everything is much larger.

For instance, the smallest rocky planet in GJ676A is at least four times the mass of Earth, while the largest gas giant is five times the size of Jupiter.

Other multiple-planet systems have been discovered, such as HD10180, which has been called the richest exoplanetary find ever because of the seven to nine planets orbiting its host star. (Also see "Our Solar System May Have Millions of 'Twins.'")

But HD10180's planets are all gas giants in relatively close orbits, while GJ676A has both rocky and gas planets—and its "Neptune-like" planet takes 4,000 days to make one orbit, said study leader Guillem Anglada Escudé, a postdoctoral researcher at the University of Gottingen in Germany.

The long orbits of GJ676A's gas giants and the short orbits of its close-in, extremely hot super Earths are what led the astronomers to dub GJ676A our solar system's twin.

"Hidden" Planets Detected Via New Technique

Anglada Escudé and team used a new data-analysis technique to detect smaller planets around the star, which had already been known to host one gas giant.

"This means that it's likely that other systems have hidden companions," he said. "We just need to apply the new techniques to find them."

(See "Light From a 'Super Earth' Seen—A First.")

The finding also may refine planetary-formation models, he added. According to one popular explanation for super Earths so close to a host star, the planets form farther out and migrate inward.

"But your planet that moves picks up all the mass with it," Anglada Escudé said.

"That didn't happen here, because you still had mass to form the gas giants. It's possible that the gas giants formed first in long-period orbits—they didn't migrate—and then a few million years later, you start forming super-Earths with the leftovers."

The grotesque-twin research appears in ArXiv.



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