Studying moving objects is the same technique that was used to discover Pluto in 1930. But unlike Pluto or the other planets in the Solar System, these objects are too far away from the Sun to be spotted using reflected visible light.
“There are just over four light-years between Neptune, the farthest known planet in our solar system, and Proxima Centauri, the nearest star, and much of this vast territory is unexplored,” said Kuchner. “Because there’s so little sunlight, even large objects in that region barely shine in visible light.”
And this is where WISE comes in. The objects, likely brown dwarfs but maybe Planet 9, glow in infrared, which means the NASA observatory can catch their light.
“We’ve pre-processed the WISE data we’re presenting to citizen scientists in such a way that even the faintest moving objects can be detected, giving us an advantage over all previous searches,” Meisner stated.
Planet 9 was first proposed at the beginning of 2016 to explain the curious orbits of many trans-Neptunian objects. Its alleged orbit lies at least 200 times farther than the Earth from the Sun, and while there’s a lot of enthusiasm for this potential new planet, until we see it, it remains a hypothesis.