Science! By Jan. 19, 2015 1:32 pm
Astronomers suspect super-Earths lurk at the edge of our solar system | Science! |

There might be something unexpected lurking out there in the outer solar system. In fact, there could be two somethings. A new report from astronomers at the Complutense University of Madrid presents evidence that points to at least two large planets out past the orbit of Neptune, somewhere beyond the icy Kuiper Belt. If true, this would be one of the biggest discoveries in the history of astronomy.

The researchers came to this conclusion by analyzing the orbits of 13 extreme trans-Neptunian objects (ETNOs). Based on what we know about orbital dynamics and the nature of the outer solar system, these objects should have certain properties. For example, they should have an average distance (known as semi-major axis) from the sun of about 150 AU (1 AU is the distance from Earth to the sun). They should also have an orbital inclination very close to the plane of the solar system. Real life, it turns out, does not match the predictions. The 13 objects have average distances ranging anywhere from 150 to 525 AU and inclinations of about 20 degrees.

Based on this, the researchers suspect there are massive objects in the outer solar system that are causing these unexpected orbital parameters. Most ETNOs are quite small, but it would still take fairly massive objects to disrupt their orbits in this way. These theoretical planets would also be much farther out than most Kuiper Belt objects like Pluto — about 200 AU distant. The Kuiper Belt only stretches to about 50 AU with the Oort cloud beyond it. That would make these mysterious planets difficult or impossible to spot with current technology, even though the team also says they could be more massive than Earth. Imagine, a super-Earth in our own solar system.

Astronomers suspect super-Earths lurk at the edge of our solar system | Science! |

This isn’t the first time astronomers have mused about the possible existence of large bodies at the edges of the solar system. A 2014 study from Chadwick Trujillo and Scott Sheppard announced the discovery of 2012 VP113, an ETNO with semi-major axis of 80 AU. This study suggests the highly eccentric orbits of these objects (like Sedna) is also consistent with a massive thing further out in the solar system.

There are still other explanations for the unusual orbital mechanics we see at the edges of the solar system. ETNOs could be captured from other solar systems, or perhaps they are just reacting to the gravity of nearby stars from past close encounters.We could also be mistaken about the orbits of some ETNOs. They take thousands of years to make a single orbit, so it’s possible their paths have been altered relatively recently. Note, there is a fringe theory that a brown dwarf star (basically a failed star) lurks out there. This is a fun idea, but it’s not compatible with the observations. Modern telescopes would be able to spot that.

Astronomers suspect super-Earths lurk at the edge of our solar system | Science! |

If there are super-Earths out there, it would take years for a space probe to get there to study them, but you can be sure we’d try. For now, we await more data.

Now read: Kepler Rising: NASA resurrects its planet hunter to great effect

Astronomers suspect super-Earths lurk at the edge of our solar system | Science! |


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