If you have a computer and patience, you can help Nasa look for the mysterious ‘Planet Nine’

PUBLISHED : Wednesday, 01 March, 2017, 1:22pm
UPDATED : Wednesday, 01 March, 2017, 9:21pm

The hunt for “Planet Nine” is intensifying, and anyone can join in.

All you need is a computer with an Internet connection, plenty of patience, and the determination to hunt for something that would be very dim and might not actually exist.

Planet Nine, sometimes referred to as Planet X, is the hypothetical planet beyond Pluto that astronomers have been buzzing about for a couple of years. If it’s there, it’s probably big - larger than Earth, perhaps a “mini-Neptune.”

A new initiative by Nasa and the University of California at Berkeley, called Backyard Worlds: Planet 9, is crowdsourcing the hunt for Planet Nine. It will use archived observations from Nasa’s Wide-field Infrared Survey Explorer (WISE) mission, which scanned the skies for asteroids and other faint objects. It’s possible that Planet Nine - or perhaps a “brown dwarf” star or two - is lurking in its speckled images of space.

I’m just going to tell you: It’s there
CalTech astronomer Mike Brown

This planet could be 500 times as far from the sun as Earth is, but it would still be part of our solar system, with a highly elliptical orbit that never takes it anywhere close to the sun. Planet Nine should not be confused with the many “exoplanets” discovered orbiting distant stars. Nor is it the planet known as Nibiru, which exists only in the imagination of people peddling pseudoscience and apocalyptic narratives about worlds in collision.

The mystery planet’s existence is inferred from the orbits of many smaller bodies in the outer solar system. They orbit the sun and cluster in a manner that suggests the possible gravitational influence of an unseen, large planet. The evidence for its existence has been getting stronger, Caltech astronomer Mike Brown said.

“I’m just going to tell you: It’s there,” Brown said.

Not everyone is persuaded.

“The evidence is very intriguing, but I don’t think I can put a high likelihood on it yet,” said Renu Malhotra, a University of Arizona professor of planetary science. “I see the evidence as being quite soft, still.”

Even the name is iffy. Planet Nine? Planet X? Planet 10? It’s confusing. There used to be nine officially recognised planets in our solar system - the ninth being little Pluto, discovered in 1930. But after Brown and other astronomers began discovering small planetlike objects in the outer solar system, a debate erupted over the definition of a “planet.” In 2006, the International Astronomical Union decided that Pluto was a member of a class of objects to be known as “dwarf planets.”

In 2014, astronomers Scott Sheppard of the Carnegie Institution and Chad Trujillo of the Gemini Observatory in Hawaii published a paper suggesting that there may be a massive “perturber” in the outer solar system that affects the orbits of smaller objects. Sheppard and Trujillo said those smaller objects orbit the sun at an angle as if avoiding the hidden, larger planet. “It would resemble a giant frozen snowball,” Sheppard said in 2015.

Brown set out to debunk Sheppard and Trujillo’s conjecture, but instead he wound up providing supporting evidence. Last year, Brown and Caltech colleague Konstantin Batygin published a paper in the Astronomical Journal that offered a possible orbit for the hidden planet, which a news release from Caltech referred to as “Planet Nine.”

Brown said last week that additional observations of distant, small objects and ensuing calculations and modelling suggest that Planet Nine is roughly eight times as massive as Earth and slightly closer to the sun than previously thought. He said it is probably the core of a giant planet that was ejected from the inner solar system long ago. He said it’s likely to have an atmosphere, which would make it warmer and easier to detect. If it’s a dense, rocky planet, it’ll be smaller, colder, darker and harder to find.

Sheppard said he has also become more optimistic about the existence of the planet.

“We still see a clustering trend. That brings me to about 90 per cent sure that this planet exists beyond Pluto,” he said this week. “I don’t think there’s a credible alternative hypothesis right now.”