Beyond Pluto

What's out beyond the orbit of Pluto and still within our solar system? Well, more than enough strange objects to keep astronomers busy at their telescope eyepieces for decades to come. For astronomers Mike Brown and Chad Trujillo of the California Institute of Technology, it was an exciting moment of discovery. Looking at photographic plates of the sky back in 2002, Brown and Trujillo were the first observers to identify a new, large denizen of our solar system, a planetoid they named Quaoar (pronounced KWAH-o-ar, after the god of creation of the Tongva, a California Indian tribe). The ball-shaped planetoid, approximately half the size of Pluto, is the largest object found in the solar system since Clyde Tombaugh discovered Pluto in 1930. Quaoar, technically named 50000 Quaoar, is 4 billion miles (6.4 billion kilometers) from the Sun in a region known as the Kuiper Belt (named after the late astronomer Gerard Kuiper). The K Belt is a distant place where thousands of ancient icy, rocky fragments orbit the Sun beyond the planets. It is believed that Kuiper objects such as Quaoar date back to the birth of our solar system. &emsp;&emsp; Slightly oblate in shape, Quaoar isn't as tiny as you might think—it's approximately 800 miles (1,300 kilometers) in diameter. A calendar year on Quaoar is 288 years long because it takes the planetoid almost 300 years to orbit the Sun. Surprisingly, the orbit of this new world is stable and circular in comparison to Pluto. It is likely that more Quaoar-sized Kuiper Belt planetoids will be discovered in the near future. But many astronomers believe Pluto will remain safe as the solar system's ninth planet; it probably won't be dethroned for a variety of reasons that include its size, priority of discovery, and astronomical tradition. A visit to frozen Quaoar and its tiny moon Weywot, would be an exotic travel experience. Even with a fast, high-tech nuclear-powered spacecraft, the 4-billion-mile-long trip to Quaoar would take a year or more; solar-power panels would be useless for generating onboard electricity during such a voyage. Out there, in the dark frontiers of the solar system, the Sun appears as just another star. Much like the planet Pluto (or "dwarf planet" if you prefer the official term), Quaoar is probably cratered and composed of rock, water ice, and organic compounds—methane, carbon dioxide, and carbon monoxide. The surface, slowly pummeled over millions and millions of years by solar and cosmic particles, is likely to be dark as pitch. In fact, Brown and Trujillo think the surface of the frozen planetoid has a consistency similar to asphalt. It is possible that organic chemicals on Quaoar's surface may have formed gooey pools of a tar-like material. The suggestion of extraterrestrial, abiogenic asphalt makes this writer think of the famous downtown Los Angeles tar pits. The only warnings to a visitor to distant Quaoar: Bring plenty of oxygen, dress warmly and watch where you step. Lou Varricchio is a former NASA science writer.

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Beyond Pluto

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