First signs of Planet Nine may have been finally detected

Scientists may have made a breakthrough in their search for Planet Nine, identifying a faint object whose brightness and slow motion are exactly what is expected of a cosmic body at that distance from Earth and the Sun. Scanning through infrared observations gathered decades ago, they found an object that was at a particular place in one survey and had moved across in the second survey done 23 years later.

The study by researchers from National Tsing Hua University in Taiwan was published in the Publications of the Astronomical Society of Australia. The authors said the object emerged as the single best candidate after the analysis of millions of infrared sources. However, they asserted that this is not confirmation of a ninth planet, and only gives them a new target to focus on in the hunt for this elusive body, which may or may not exist.

Why do we think Planet Nine is real?

Planet Nine remains a hypothetical object, but astronomers are confident that it exists, even though it has never been seen. The signs point to this body being real. Several objects in that region seem to have huddled around an unknown body, as reflected in their unusually tilted orbits. This suggests that a larger body's gravity could be pulling them.

This planet would be lurking beyond Neptune, hundreds of astronomical units away, in a cold and dark region where sunlight barely reaches. This makes finding Planet Nine extremely difficult since barely any light would bounce towards Earth. But planets release heat, and so astronomers started using spacecraft that can detect infrared radiation.

Surveys from 1983 and 2006 were studied

Terry Long Phan and his team studied data from two such missions - RAS, the Infrared Astronomical Satellite from 1983 and Japan’s AKARI spacecraft, which did an infrared survey in 2006 and 2007. This long gap gave them a window into how a distant planet might have shifted its place. They looked for objects that appeared in both the surveys and were consistent with a slow movement.

They searched for a planet located between 500 and 700 astronomical units and around 7 to 17 times Earth’s mass by checking for brightness, location and infrared characteristics. They found 22 possible pairings; the number then reduced to 13 before they were left with just one candidate. This object had moved by 47.46 arcminutes between the IRAS and AKARI observations.

Why has it not been declared Planet Nine?

While scientists may have detected a possible Planet Nine candidate, they are not rushing to confirm it. It still needs to fit into the parameters of an object that would cause the unusual trajectories of objects in the outer Solar System. For this to happen, it must move on the right path.

Phan says further research should utilise the Dark Energy Camera on the 4-meter Blanco Telescope in Chile to see if this object is moving on the right orbit to qualify as Planet Nine.