German astronomers have confirmed the size of the object orbiting the sun outside Pluto’s orbit, estimating its size to be about 3000 km (1860 mi) across. They are now debating whether to call the object, informally known as Xena and formally catalogued as object 2003 UB313, a planet or something else.
For the record, Xena, which was discovered last year, is about 700 km (440 mi) wider than Pluto, the puniest planet in our solar system, and about 370 km (230 mi) smaller than the Moon. So, as planets go, Xena is not much to speak of.
Astronomers of late have tended to classify objects like Pluto and Xena as planetesimals, inhabitants of the Kuiper Belt, a cloudlike band of relatively small chunks of rock, ice and dust encircling the solar system.
Complicating matters is that both Pluto and Xena have moons, as do all the planets save Venus and Mercury. Pluto’s moon, Charon, is large enough for the two to be called a binary planet system. (The size of Xena’s satellite, named (naturally) Gabrielle*, has yet to be measured.) Another complication is that Pluto has been considered a planet since its discovery in 1930.
Xena and Gabrielle’s mutual orbital period around the sun is 558 earth years. With a very elongated orbit resembling that of a comet, the pair may approach close enough to the sun for Xena to outgas an atmosphere. Otherwise, they are very cold (-250 C) and dark.
The news of Xena’s size may disappoint, but not discourage those folks fearmongering about Planet X or Nibiru, celestial bodies that are reputed to cause calamities of cosmic proportions on Earth. I have included links to rational discussions of Planet X and Nibiru. Googling either term will bring up thousands of fringe-science sites linking them to ancient Sumeria, aliens, the Christian Apocalypse, the dawning of the Age of Aquarius, and maybe even Elvis — I haven’t checked that last one yet.
* Both names are from the TV series, “Xena: Warrior Princess.” Xena, played by Kiwi Lucy Lawless, is a bad girl turned good during the days of Greek mythos. Gabrielle, played by Texan Renée O’Connor, is her faithful sidekick. Unfortunately, if the object 2003 UB313 and its moon get names, the names will come from the real Greek and Roman pantheons, not the television versions. Personally, my vote is for Xena and Gabrielle.
You can catch up the new Greek mythology with these items from Amazon.com (how fitting!):