Elusive Planet Nine Lurks In The Shadows, Here's Why It's 'Invisible'

Astronomers are still on the lookout for the elusive Planet Nine. Unfortunately, the missing planet might be invisible, which is why it's notoriously difficult to catch.

The ninth planet in the solar system has been lurking in the shadows for a long time now. Scientists hunting for it have found plenty of clues that it's out there, such as one cosmic object's peculiar orbit.

However, a proper glimpse of Planet Nine has yet to be achieved. One reason? It might be invisible.

The Many Challenges Plaguing The Search For Planet Nine

Michael Brown, an astronomer at the California Institute of Technology, explains to Washington Post that while he is optimistic that Planet Nine will eventually be found, there's a reason why it's essentially invisible to current observatories and astronomers.

The location is a major obstacle in spotting this planet. According to calculations by Brown and his colleague Konstantin Batygin in 2016, Planet Nine likely weighs from five to 20 Earth masses and travel along an orbit that's hundreds or 1,000 times farther from the sun than Earth.

At this distance, space is very, very dark. At 600 astronomical units away, Planet Nine would appear 160,000 times dimmer than Neptune. If it hits 1,000 astronomical units, it would be a million times fainter than the farthest known planet from the sun.

The endlessly wide expanse of the solar system is also a considerable challenge for scientists who have to sweep the area for hints of Planet Nine. There are a limited number of instruments that are capable — and too many missions to count.

Furthermore, elements in outer space could conspire to keep the elusive object shrouded from view: the light pollution from Milky Way or the glare of a particularly bright star. If Planet Nine is currently at a distant point in its orbit, it could take thousands of years for it to circle back to a point where it's visible from Earth.

The Future Of Planet Nine

To cope with the many challenges involved in seeing the hidden planet of the solar system, scientists are exploring other methods to detect it such as searching for its heat glow.

Despite the setbacks and seemingly insurmountable challenges, scientists are still expecting for the discovery to come through at one point.

"Every time we take a picture, there is this possibility that Planet Nine exists in the shot," Surhud More, an astronomer at the University of Tokyo, says.