Pluto lovers, I have excellent news. Back in 2014, the dwarf planet gained a new friend in the outer reaches of the solar system: A far-flung object known informally as DeeDee. In fact, it's so distant that astronomers have been trying to figure out what DeeDee is for the past few years to no avail. Recently, however, the discovery team used a powerful radio telescope in Chile to study the faint object more closely, and they were able to determine more about DeeDee — beginning with the fact that like Pluto, it's a dwarf planet.
DeeDee, also known by the less adorable name of 2014 UZ224, was discovered in 2014 by a team of astronomers led by a researcher from the University of Michigan. Using the Blanco telescope in Chile's Cerro Tololo Inter-American Observatory, they were able to determine a few of the object's characteristics. Located in the Kuiper Belt, a region of the solar system beyond Neptune, DeeDee is the second-furthest trans-Neptunian object that we know of (right behind a fellow dwarf planet called Eris). Its orbit is highly elliptical, taking a whopping 1,100 years to complete. At its closest, it's 38 astronomical units (AU) from the sun, and at its furthest, the dwarf planet is 180 AU away.
To give you an idea of how far away DeeDee winds up, one AU is the average distance between the Earth and the sun, and Pluto's orbit takes it an average of about 40 AU away from the sun.
However, researchers weren't able to determine much else about DeeDee. They were relatively certain that the object was big enough to be a dwarf planet; in fact, the nickname DeeDee is short for "Distant Dwarf." But it wasn't until they studied it through a more powerful telescope — the Atacama Large Millimeter/submillimeter Array (ALMA) — that they were able to classify it that way for sure. According to Space.com, ALMA registered DeeDee's heat signature, which astronomers could use to determine the planet's size.
According to their calculations, published in mid-April, DeeDee is about 394 miles across, and it should have enough mass to make it spherical. In short, it meets all the criteria to be considered a dwarf planet, although it hasn't been officially classified as one just yet. At the moment, DeeDee is about 92 AU from the Sun; according to a news release, light from the dwarf planet takes 13 hours to reach Earth.
In a statement, lead astronomer David Gerdes noted that, like its neighbor Pluto, DeeDee is also freezing. "We calculated that this object would be incredibly cold, only about 30 degrees Kelvin, just a little above absolute zero," he explained.
Although there are currently only eight designated planets in our solar system, there are many more dwarf planets than you may realize. Aside from Pluto, NASA recognizes four other dwarves: Ceres, Haumea, Makemake, and Eris. According to the agency, the primary difference between a regular planet like Earth or Mercury and a dwarf planet lies in their orbits. "Planets have cleared the path around the sun while dwarf planets tend to orbit in zones of similar objects that can cross their path around the sun," NASA explains on its website.
So what does all this mean for you? Aside from making for interesting dinner conversation, DeeDee is a reminder how just how little we know about our solar system. Who knows how many worlds are waiting to be discovered? Pluto might not be such a lonely planet after all.