Astronomers Use ALMA to Investigate DeeDee Planetary Body

Posted on April 18, 2017

Astronomers are using ALMA (Atacama Large Millimeter/submillimeter Array) to investigate DeeDee, a recently discovered planetary body in our solar system. It is about three times the current distance of Pluto from the Sun. It is the second most distant known trans-Neptunian object (TNO) with a confirmed orbit. It is also known as planetary body 2014 UZ224.

The ALMA data revealed that DeeDee is 635 kilometers across. This is about two-thirds the diameter of the dwarf planet Ceres. It is not yet known if DeeDee is a dwarf planet. Astronomers say that at this size it should have enough mass to be spherical and meet dwarf planet criteria.

David Gerdes, a scientist with the University of Michigan and lead author of the paper published in Astrophysical Journal Letters, says in the announcement, "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. 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."

ALMA can detect the heat (in the form of millimeter-wavelength light) emitted naturally by cold objects in space. The astronomers say the heat signature from a distant solar system object would be directly proportional to its size. The reflected visible light from DeeDee is only about as bright as a candle seen halfway the distance to the moon. However, ALMA was able to home in on the planetary body's heat signature and measure its brightness in millimeter-wavelength light. This information enabled astronomers to determine that it reflects about 13% of the sunlight that hits it. By comparing these ALMA observations to the earlier optical data, the astronomers had the information needed to calculate its size.

DeeDee was first discovered in late 2016 using data from the Dark Energy Survey. Light from DeeDee takes nearly 13 hours to reach Earth. The informal name DeeDee was given to it by astronomers. It is short for "Distant Dwarf." The ALMA image of the faint millimeter-wavelength glow from DeeDee is pictured below. An artist's concept image is pictured above.

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