Hunting Planet Nine: Graduate students use novel search technique

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In 2016, Caltech researchers Michael Brown and Konstantin Batygin proposed evidence for the existence of a new planet, and a search for Planet Nine ensued. In February, campus graduate students Michael Medford and Danny Goldstein introduced a novel search technique.

Planet Nine has little in common with Pluto, the planet Brown is often accused of “killing,” because his research led to its declassification.

According to Batygin, Planet Nine is about 10 times “more massive” than Earth, takes 10,000 to 20,000 years to orbit the sun and — unlike other planets in the solar system — has an elliptical rather than circular orbit.

“We haven’t seen Planet Nine directly. … We do, however, know that it’s there based on the gravitational influence it exerts upon the field of debris beyond Neptune, called the Kuiper belt,” Batygin said.

Objects in our solar system with distant orbits — more than 400 years — appear clustered together in space, Batygin said. The only “viable explanation” for this “anomalous” physical clustering is a distant planet’s existence, according to Batygin.

The problem for researchers now lies in locating Planet Nine.

“It’s much, much harder than finding a needle in a haystack — it’s like finding a needle in a billion haystacks but with the advantage that you’re allowed to use computers to help you search,” said Yale professor of astronomy Greg Laughlin, who with graduate student Sarah Millholland used simulations to further define Planet Nine’s orbital parameters.

Brown, Batygin and other astronomers’ search for Planet Nine often involves meticulously scanning the night sky with a telescope, the direct method used to locate Uranus and Neptune.

Rather than capturing new images, Medford and Goldstein are repurposing past data through a new software developed with their faculty advisor, adjunct professor of astronomy Peter Nugent.

Looking at about a million images previously collected from a San Diego-based telescope, software overlaps the images and subtracts known objects such as stars: locating objects that change from night to night in a specific section of the sky.

Their system then guesses the direction of the planet’s orbit, shifts the millions of images along the possible ellipses and adds them together.

“In doing so, you hope to bring out from the background signals or planets that would otherwise be invisible in any one single image,” Medford said.

According to Medford, around 10 billion ways to combine the images exist. Even if the methodology doesn’t locate Planet Nine, it could narrow the search area or help locate new objects.

“I think it’d be the absolute coolest way to discover Planet Nine because they’re looking within existing data,” Batygin said.

Laughlin places the odds of finding Planet Nine around fifty-fifty. He believes locating Planet Nine — “a discovery that’d be just about the biggest thing that could happen in astronomy, and maybe all of science in the near term” — may lie in the combination of different researchers’ theoretical, simulation and data-mining approaches.

According to Medford, finding Planet Nine could indicate the solar system is “much bigger than we think.”

“If something that big formed that far out, then our idea of the early conditions of the early solar system is maybe missing some pieces,” Goldstein said.

Christine Giuliano at [email protected] and follow her on Twitter at @christinegiul.