On 7 October 2002, Michael Brown and Chadwick Trujillo of the California Institute of Technology announced the discovery of a large object in the solar system at the meeting of the Division for Planetary Sciences of the American Astronomical Society. The new object, dubbed "Quaoar" by the two astronomers after a creation god of the Tongva native American tribe, was provisionally designated as "2002 LM 60" by the International Astronomical Union.
This new frozen world is about 1,250 km in diameter, roughly one tenth of that of Earth, and was made up of equal portions of rocks and ice. It dwells in the Kuiper Belt at about 42 AU away and moves around the Sun every 288 years (1 Astronomical Unit = the distance between the Earth and the Sun, about 150 million kilometers). In fact, Professor YI Zhaohua of the Nanjing University, while discussing the gravitational field of solar system in his book "Basis of Celestial Mechanics", has pointed out that it was not a surprise to have planets beyond Pluto.
Astronomers have confirmed that apart from the asteroid belt, there is a Kuiper Belt region composed of a vast population of small bodies extending 30 to 100 AU away from the Sun. Gerard Kuiper, from whom the region was named, was a Dutch-born American astronomer who focused his study on the solar system in 1940's. The first Kuiper Belt Object (KBO) was discovered by astronomers at Hawaii in 1992. It was 10 times smaller and 10,000 times fainter than Pluto. Since then, observers from various parts of the world discovered over 600 KBOs with diameters ranging from 50 km to 1,000 km.
Brown and Trujillo predicted that eventually more KBOs even larger than Quaoar would be found with follow-up observations and analysis. By then, Pluto will likely be kicked out of the nine planets. Pluto's position as the ninth planet has long been questioned since its discovery in 1930, for its relative size was far too small to be able to contribute to the orbital irregularities that Uranus and Neptune are having. If Pluto is likened to a small butterfly weighing 10 g, then Uranus and Neptune are like pigs weighing 70 kg. With such a great difference in size Pluto's effect on the two planets is minimal and is not the culprit for their orbital problem. Who can that be then?
Perhaps the best way to understand Quaoar was to flyby it with a spaceship. But in the meantime, we can explore the object by using the "Micro Space Telescope" similar to that proposed by the National Observatory of the Chinese Academy of Science. The telescope can carry out prolonged observations of a single object at different wavelengths from multi-angles. The results could be valuable supplements to the Hubble Space Telescope.
The discovery of Quaoar might enable us to have a better understanding of the formation of the solar system. Or at least it has inspired the writer to think that we could have one more choice when christening a cruise. In the near future, we may have the "Quaoar" on which we will get together to look for other planets.
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