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Pluto gets a buddy: A new dwarf planet is discovered in our solar system

An exaggerated color photo shows the varied terrain of Pluto, the most well-known dwarf planet. (NASA/JHUAPL/SwRI)

Out beyond Neptune, past Pluto, through the chaos of the Kuiper belt to a point some 8.5 billion miles from the sun, a new dwarf planet has just joined our solar system.

The Iowa-sized object, which is about half as big as Pluto and twice as distant, was described Tuesday in the International Astronomical Union's Minor Planet Electronic Circulator. It joins a growing list of dwarf planets known to populate the solar system: Ceres, Haumea, Makemake, Eris and — most famous of all — Pluto. It's suspected there could be at least 100 more.

The “trans-Neptunian object,” known for now as 2014 UZ224, was discovered by University of Michigan astrophysicist David Gerdes with the help of a team of undergraduate researchers.

Gerdes is part of an international team of scientists working on the Dark Energy Survey — an effort to map the universe and elucidate some of its mysteries, particularly, why the expansion of the universe is accelerating. To do a dark energy survey, you need a dark energy camera, so the DES built a wide-angle camera in Cerro Tololo, Chile, that's capable of snapping images of the whole sky.

A few years ago Gerdes was supervising some undergraduate researchers he wanted to give them a challenge. He handed them one of the camera's maps of the entire galaxy and asked whether they could pinpoint which objects were in our own solar system.

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The secret was to identify the ones that moved. Viewed against the vast backdrop of the Milky Way, close-by planets and other bodies appear to move more quickly in relation to everything else. Working with Gerdes, the students helped develop software that could pick out those subtly moving objects. They identified about a half dozen new bodies in those first few months.

This July, Gerdes was using that same software when he came across UZ224.

It took some careful tracking to confirm the discovery and map out 2014 UZ224's orbit. Its exact path is still unclear, because the planet takes more than 1,000 years to complete a single loop of the sun. But it's believed that 2014 UZ224 is the third most-distant object in the solar system.

Gerdes said it's possible some astronomers might dispute 2014 UZ224's dwarf planet designation. The distant body is pretty small, even for a dwarf planet.

But the term applies for now. Meanwhile, he and his colleagues are on to (literally) bigger things: looking for the mysterious Planet Nine, whose existence was speculated about in the Astronomical Journal earlier this year.

"The fact that we can find a very distant, very slow-moving object like this in our survey," he said, "is a promising sign that if there's more things like this out there, we have a good shot at finding them."

Correction: An earlier version of this post inaccurately described the role of Gerdes’ students in this research. They helped write the software that allowed him to identify 2014 UZ224 this summer.

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