Distant dwarf planet confirmed by ALMA

The newest observations from ALMA have confirmed that the Solar System object 2014 UZ224 is a dwarf planet.

ALMA detected the infrared glow of the body nicknamed DeeDee, confirming that it is large enough to be considered a dwarf planet.
Credit: Alexandra Angelich (NRAO/AUI/NSF)

Researchers are getting better acquainted with one of the most distant known members of our Solar System. New observations by the Atacama Large Millimetre/submillimetre Array (ALMA) of the distant object 2014 UZ224 have apparently confirmed it is large enough to be considered a dwarf planet.

The planet has been nicknamed DeeDee, short for Distant Dwarf, and is three times further out than even Pluto, making it the second most distant known trans-Neptunian object after Eris.

“Far beyond Pluto is a region surprisingly rich with planetary bodies. Some are quite small but others have sizes to rival Pluto, and could possibly be much larger,” says David Gerdes, an astronomer at the University of Michigan who authored the study. “Because these objects are so distant and dim, it’s incredibly difficult to even detect them, let alone study them in any detail. ALMA, however, has unique capabilities that enabled us to learn exciting details about these distant worlds.”

DeeDee is currently 92 times the distance between the Earth and Sun away, but its orbit could take it even further away.
Credit: Alexandra Angelich (NRAO/AUI/NSF)

At first DeeDee’s size was uncertain, as it is difficult to tell the difference between a large planet and a highly reflective one when observing at visible wavelengths. The submillimetre wavelengths ALMA looks at, however, gauge a planet’s heat output which is much more closely tied to a planet’s size. This allowed researchers to confirm the planet is roughly 635km across, large enough that it should be spherical and meet the criteria necessary to be considered a dwarf planet.

DeeDee was first announced in autumn 2016, having been discovered in data taken as part of the Dark Energy Survey. The survey aims to understand the mysterious dark energy that is driving our Universe apart, but has proved useful for Solar System science. More than 1.1 billion candidate Solar System bodies have been found in the survey's nearly 15,000 images, but most of these turned out to be background stars or galaxies.

Read more about the Solar System's dwarf planet's on BBC Sky at Night Magazine:

Several, however, were found to be slowly drifting across the field of view, suggesting they may lie within our Solar System. DeeDee was identified in 12 different images and found to be moving so slowly that it would take 1,100 years to make one orbit of the Sun.

The same techniques could be used to find other distant and slow moving objects in our Solar System, including the hypothesised Planet Nine that may reside far beyond DeeDee and even Eris.

“There are still new worlds to discover in our own cosmic backyard. The Solar System is a rich and complicated place,” says Gerdes.


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