Our outer solar system is home to numerous rocky worlds, but these are typically not large enough to be considered planets. Take Pluto, for instance, which is no longer classified as a planet due to its smaller size and the fact that it lives in a region of the solar system occupied by many other similar rocky planetoids.

But now an astounding new discovery could, quite literally, rock the world of astronomy in a way not seen since the discovery of Neptune. Astronomers using data from the Atacama Large Millimeter Array (ALMA) may have spotted a whole new planet floating in the cold outer reaches of our solar system, and it's possible this new object is a "super-Earth" world, reports Forbes.

The object has been spotted twice now in the direction of Alpha Centauri, which is the closest star system to our own at just over 4 light-years away. Two observations are enough to confirm its existence, but not quite enough to know much about it. For instance, it's not enough to determine the object's orbit and distance, and that means we don't yet know exactly how big it is. Astronomers have narrowed down the options, however.

Perhaps the most exciting possibility (which is also the theory favored by the object's discoverers) is that it orbits about 300 AU away, which would make it about 1.5 times the size of Earth. If true, this would make the object the first "super-Earth" found in our solar system. It would also be our solar system's most distant object. (By comparison, Pluto is only about 40 AU away.)

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There are some reasons to be skeptical of this possibility, however. To exist at this proposed distance, the object would have to have an extremely inclined orbit, which would be rather odd for a super-Earth planet, to say the least. Even so, that doesn't make it impossible.

Another possibility is that the object is a cool brown dwarf drifting at about 20,000 AU away. A brown dwarf should be visible in the infrared, however, which is unlikely to be the case with this object, as it wasn't detected by earlier infrared sky surveys.

Yet a third scenario, and perhaps the least ground-breaking possibility of them all, is that this object represents an extreme trans-Neptunian object about 100 AU away from the sun. That's pretty far out there — it would still be the most distant object ever discovered in our solar system — but at that distance the object would be smaller than Pluto. So it would just be another far-out planetoid drifting in the outer solar system, like many others. That's still neat, but not quite so radical.

Interestingly, previous observations of the orbits of known trans-Neptunian objects have led some astronomers to speculate that one or two super-Earth’s could very well be lurking in the outer solar system. So if this new object does turn out to be a super-Earth, it would provide vindication for those theories.

For now, we'll just have to wait for more observations to take place to know for sure. Whatever the results, it's exciting to know that our solar system still harbors secrets waiting to be discovered. Who knows how many rocky worlds are scouring through the icy friction of our outer solar system? This new object may be the latest discovery, but it is unlikely to be the last.

Bryan Nelson ( @@brynelson ) writes about everything from environmental problems here on Earth to big questions in space.

Object discovered in our outer solar system could be a new planet
Another rocky world in our solar system? Some astronomers believe that this distant object could be a super-Earth planet.