Have astronomers spotted Planet Nine?
Scientific American · Phil Plait ·
Archived observations appear to show a moving object in the far-distant outer solar system, but its reality is unclear
The outer solar system is getting crowded with theoretical planets.
Well, it’s not crowded, exactly. Billions of small rocky, icy bodies orbit the Sun out past Neptune. But space is so vast that they rarely pass within a million kilometers of one another. There’s lots of room out there.
In fact, that’s part of the problem for planet hunters right now: this volume of space is so unimaginably huge and so far away that searching it for even relatively large objects is tricky.
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