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 suspectedthere 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.

['Have you SEEN Pluto?' - New Horizons scientist still rallying for planetary status] 

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.

Quelle: The Washington Post

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Right now 2014 UZ224 lies nearly 14 billion kilometers away, ranking it third among the most distant objects known in the Kuiper Belt.

Early today the IAU's Minor Planet Center announced that astronomers in Chile have discovered a Kuiper Belt object, designated 2014 UZ224, that's currently 91.6 astronomical units from the Sun. This corresponds to 13.7 billion kilometers (8.5 billion miles), nearly three times farther out than Pluto is at the moment. Only two other known KBOs are more distant: Eris (96.2 a.u.) and V774104 (103 a.u.) to

Based on observations over the past three years, astronomers know that the Kuiper Belt object known as 2014 UZ224 has a highly elliptical, 1,140-year-long orbit that stretches nearly four times farther from the Sun than Pluto can ever be.
NASA / JPL / Horizons

In fact, 2014 UZ224is closer to the Sun than average right now and headed inbound. Its 1,140-year-long orbit is quite eccentric, swinging as close as 38 a.u. (think "Pluto's orbit") and as far away as 179.8 a.u. Technically, astronomers don't consider it part of the classical Kuiper Belt but instead a "scattered disk object" whose orbits have been perturbed outward due to encounters with Neptune.

A team led by David Gerdes (University of Michigan) first spotted this object in August 2014, and then several times again in 2015 and 2016, using the 4-m Victor Blanco reflector at Cerro Tololo Inter-American Observatory in Chile. Thanks to CTIO's Dark Energy Camera, which Gerdes helped develop for the Dark Energy Survey (DES), 2014 UZ224 stood out clearly in images despite its apparent magnitude of only 23½.

"The same combination of survey area and depth that makes DES a state-of-the-art cosmological survey also makes it a great tool for making discoveries in our own cosmic backyard," Gerdes explains. "Our search for trans-Neptunian objects is a serendipitous by-product of the survey data." The effort has yielded dozens of Kuiper Belt objects so far, even though the team has examined only a fraction of the amassed observations. "I hope 2014 UZ224 is not the most interesting thing we eventually find!" Gerdes adds.

For now, his team knows little more about their distant discovery other than its orbit and apparent brightness. Given its distance, however, the object should be sizable — anywhere from 400 km across (if its surface is bright and 50% reflective) to 1,200 km (if very dark and 5% reflective). If its true size edges toward the larger end of this range, then 2014 UZ224 would likely qualify for dwarf-planet status.

Fortunately, we should have a much better estimate of the object's size very soon. Gerdes has used the ALMA radio-telescope array to measure the heat radiating from 2014 UZ224, which can be combined with the optical measurements to yield its size and albedo.

"The Blanco telescope is decades old, but DECam is a state-of-the-art instrument that has revitalized it in several ways," Gerdes explains. "First, the focal plane is huge, so the telescope now has a 3°-square field of view. And second, the DECam's CCDs are extremely sensitive in the red and near-infrared light, which makes it particularly good at detecting high-redshift objects."

. . . and apparently also good at spotting bodies at the fringes of the observable solar system.

Quelle: Sky&Telescope