An article accepted for publication in the “Astrophysical Journal Letters” describes the research that followed the discovery of a possible dwarf planet called 2014 UZ224 and nicknamed DeeDee, as in Distant Dwarf. A team led by David Gerdes of the University of Michigan announced its discovery in October 2016 and thanks to a further observation carried out by the ALMA radio telescope they estimated other features.
DeeDee is one of many celestial bodies that exist beyond the orbit of Neptune, in this case at a distance from the Sun that currenlty is more or less three times Pluto’s. The research in that vast frontier of the solar system has increased recently also because according to some theoretical interpretations of anomalies in the orbits of some trans-Neptunian objects there could be a full-fledged planet. However, DeeDee was discovered thanks to a stroke of luck in an investigation called Dark Energy Survey which aimed to observe galaxies and supernovae.
The DECam, the instrument that identified it, allowed to obtain limited information at visible light about DeeDee so observations with other instruments were needed. The ALMA radio telescope, inaugurated in March 2013, is generally used to observe other solar systems and galaxies but in some cases it can also be used to study objects that are in the neighborhood in comparison and are relatively small.
In DeeDee’s case, observing it with ALMA was useful because this extraordinary radio telescope can pick up the heat emissions at millimeter wavelengths that are dim to say the least from a cold body in space. DeeDee has a surface temperature of just 30 Kelvin, meaning 30 degrees above absolute zero, and yet that’s enough heat to be picked up by ALMA. This allowed the astronomers to determine that it reflects only about 13% of the sunlight that hits it.
ALMA provided the information needed to complete those collected previously at visible light and to estimate some other characteristic of DeeDee. In particular, David Gerdes and his team estimated with a good degree of accuracy that its diameter is about 635 kilometers (about 395 miles). This means that it’s significantly smaller than Ceres but a little bigger than the giant asteroid Vesta. Its size may be enough to have an approximately spherical shape while Vesta is an oblate spheroid.
DeeDee’s shape is important to establish if it can be classified as a dwarf planet. That’s the bureaucratic part of the research even if Pluto’s story teaches how many controversies can arise from this type of decision. DeeDee’s study is important because it provides new information on an area of the solar system where there may be tens of thousands of objects including the theoretical ninth planet.
So far we have observed above all an area that seems huge but is actually only a part of the solar system but to complete the reconstruction of its history and its evolution we need to have a clear idea of what lies in its outer areas. The ALMA radio telescope proved a valuable instrument for this type of study and David Gerdes hopes that it can be used to find other objects out there and expand our knowledge of that area of the solar system.