Where Could It Be?
Astronomers estimate that Planet Nine could be orbiting anywhere between 400 and 800 astronomical units (AU) from the Sun. One AU is the average distance between the Earth and the Sun. For comparison, Neptune is about 30 AU away. That means Planet Nine could be more than 13 times farther away than Neptune.
If it is really out there, it might be located in a region of the sky that is hard to study. The area it could be hiding in is huge. Because it would be faint and moving slowly, pinpointing it is like finding a cosmic needle in a haystack. However, telescopes such as Subaru in Hawaii are being used to scan likely locations. Scientists are using computer simulations to predict the best spots to look.
They are also looking in both visible and infrared light. Even if the planet does not reflect much sunlight, it might give off a small amount of heat that infrared telescopes could detect. So far, it has not shown up in any survey, but astronomers continue to search.