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Gonggong and its moon Xiangliu (red circle) seen by the Hubble Space Telescope in 2010

While idly scanning trans-Neptunian objects & suchlike miscellaneous dwarf planets of the outer solar system, Ferrebeekeeper was stunned to see a familiar name–GongGong, the dark water dragon who messed up Chinese cosmology and nearly destroyed the world. In Chinese mythology, GongGong’s reign of chaos was stopped by the gentle creator goddess Nuwa. However, in order to repair the damage wrought by the naughty dragon, Nuwa was forced to jerryrig creation back together with turtle legs and river rocks (and the end result is decidedly more rickety than the original).

The dwarf world Gonggong was discovered by astronomers waaaaaaay back in 2007. Although it is not the most famous dwarf planet in the solar system, it is not inconsequential in size and has a diameter of 1,230 km (760 mi). Gonggong’s eccentric ecliptic orbit takes 550 Earth years and the planetoid rotates very slowly as well. At its perehelion (when it is closest to the sun) it is 55 AUs from Earth, however at its apehelion it is 101.2 AUs (1.514×1010 km) away from the gentle sun. Brrrr! Gonggong was last at perehelion fairly recently, in 1857, and now it is moving farther and farther away–so if you left your wallet there in 1857, you may just want to get a new one. The orbital diagram below shows the orbit of Gonggong (in yellow) contrasted with that of Eris.

Like the lozenge-world Haumea, Gonggong is a strange reddish pink color because of organic compounds known as tholins which cover its ancient ice. In some stories, the evil water dragon Gonggong had a copper head, so maybe the name suits it. Oh, also, in Chinese mythology GongGong has a sidekick, a wicked nine-headed demon named Xiangliu. Gonggong the planetoid has a tiny moon which bears this name. Finally, Chinese mythology is weirdly ambiguous about whether Nuwa and Zhu Rong finished off GongGong or whether he escaped to cause trouble another day. If I were hiding out from a bunch of quasi omnipotent Earth deities for thousands of years, I know where I would go!

Artist's Interpretation of Sedna (Credit: Gemini artwork by Jon Lomberg)

After the discovery of Pluto in 1930, there was a long hiatus in discovering objects of comparable size. Then in 2003, a team of astronomers led by Mike Brown of Caltech discovered a distant icy sphere which was quickly heralded as “the tenth planet.”  Mike Brown announced the discovery on his website along with his team’s rationale for naming the object.  He wrote “Our newly discovered object is the coldest most distant place known in the Solar System, so we feel it is appropriate to name it in honor of Sedna, the Inuit goddess of the sea, who is thought to live at the bottom of the frigid Arctic Ocean.

It turns out that Sedna is only one of many similar snowball-like planetoids beyond Neptune.  In fact, Ferrebeekeeper has already described the dwarf planet Eris (named after the Greek goddess of Strife) which is the largest currently known Kuiper belt object.  Sedna was the first to be discovered since Pluto and it sparked a debate about such objects which ultimately resulted in Pluto’s downgrade to dwarf planet.  Sedna also has some unique features which make it remarkable in its own right.

The orbit of Sedna (red) set against the orbits of Jupiter (orange), Saturn (yellow), Uranus (green), Neptune (blue), and Pluto (purple)

Sedna takes 11,400 years to complete its orbit around the sun and its bizarre highly elliptical orbit has given rise to much conjecture among astronomers.  Although some astronomers believe it was scattered into a skewed orbit by the gravitational influence of Neptune, other astronomers believe it originated in the inner Oort cloud and was never close enough to Neptune to be affected by the giant’s gravity.  Some scientists speculate that its lengthy orbit may have been caused by a passing star (perhaps from the sun’s birth cluster).  A few theorists have gone one step further and conjectured that Sedna is from a different solar system and was captured by our Sun billions of years ago.  A final school contends that Sedna is evidence of an unknown giant planet somewhere in the depths of space (!).

A photo of Sedna taken from a powerful telescope on Earth

We don’t know much about Sedna except that is probably 1,200–1,600 km in diameter and that its surface is extremely red.  After Mars, Sedna is one of the reddest astronomical objects in our solar system.  This color comes from the profusion of tholins covering the methane and nitrogen ice of which the little world is formed.  Tholins are large, complex organic molecules created by the interaction of ultraviolet light on methane and other simple hydrocarbons.  It is believed that early Earth (prior to obtaining an oxidizing atmosphere) was rich in Tholins and they are one of the precursors to the rise of life.

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