Scientists Say Something May Have Visited the Solar System and Rearranged the Planets

And it was *big.*

Disorder of the Day

The Sun is an incandescent but benevolent dictator. For billions of years, it's kept our star system well organized through the influence of its powerful gravity. All the planets revolve around it on roughly the same plane, and they also move in the same direction.

Even so, there are slight anomalies in the architecture of our stellar neighborhood that can't be fully explained by the Sun's governance, some astronomers argue, because it appears that the orbits of the planets were altered at some point in the distant past.

Now, a new yet-to-be-peer-reviewed study suggests that an enormous interstellar object up to fifty times the mass of Jupiter may have been responsible for stirring the planets out of their original orbits — showing that perhaps not even the Sun can protect us from the chaos caused by foreign intruders.

The work joins other studies that have proposed interstellar flybys to explain eccentricities in the orbits of certain objects in the solar system.

Ebb and Flow

The solar system is approximately 4.6 billion years old. Astronomers believe that roughly 100 million years into its existence, the planets first began to form in a rotating, flat cloud of gas around the nascent Sun known as a protoplanetary disk. This explains why all the planets are in a coplanar orbit with each other and revolve in the same direction.

They didn't stay put, though, and a phenomenon called planetary migrations was put forth by astronomers to account for how certain planets ended up in unlikely places. Uranus and Neptune, for example, are thought to have formed closer to the Sun than where their orbits currently reside, while other planets in the process of being formed were ejected out of the system entirely.

Until now, the prevailing theory for these disturbances was that they were caused by gravitational interactions between the planets, which may push and pull each other out of their original positions, and also the influence of the protoplanetary disk itself, which could sweep up the inchoate worlds and drop them off somewhere else.

Space Invader

Still, a few wrinkles remain. The orbits of gas giants — Jupiter, Saturn, Uranus, and Neptune — exhibit puzzling eccentricities that the researchers argue aren't satisfyingly explained by current migration theories.

So perhaps it wasn't just internal mechanisms that caused today's configuration, but something big blowing through our star system. The researchers calculated that if an object between two to 50 times the mass of Jupiter flew within 20 astronomical units — that's 20 times the distance between the Sun and the Earth — of the solar system's center, it could explain the bizarre orbits we see today.

Through computer simulations, the researchers estimate that the probability of this happening is 1 in 100 — which are pretty good odds in this field.

What the object could've been, however, is anyone's guess. Maybe it was a rogue gas giant that was ejected from its own star system, come to wreak havoc on ours. Wouldn't that be poetic?

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