MISSING a huge cloud of rocks? Try looking in Neptune鈥檚 orbit. There seem to be plenty there, if the tilt of an asteroid discovered in the planet鈥檚 orbit is anything to go by. The asteroids in the unseen cloud might even outnumber those in the main asteroid belt between Mars and Jupiter.
The asteroid was discovered by Scott Sheppard of the Carnegie Institution of Washington DC and Chadwick Trujillo of the Gemini Observatory in Hawaii. They used Carnegie鈥檚 Magellan-Baade 6.5-metre telescope in Chile and the 8.2-metre Gemini telescope. It is one of four 鈥淭rojan鈥� asteroids, which orbit in lockstep with the planet.
The Trojans orbit about 5 billion kilometres ahead of Neptune on its circular journey around the sun. What makes the latest Trojan unique is its orbit, which is tilted 25掳 relative to the plane of the solar system.
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Because asteroids with such tilts are difficult to spot, the sighting means observers can make a statistical inference that there must be many more (Science, DOI: 10.1126/science.1127173).
