100-Kilometer-Sized Trojan Asteroid Found in Neptune’s Dead Zone

Image020 Astronomers have found a scary object near Neptune: a 100-kilometer diameter Trojan asteroid -a type of asteroid found in graveyards of space junk "frozen in time" since the formation of the Solar System.. Scientists believe up to 150 similar objects could await discovery in the same dead zone. The asteroid, 2008LC18, occurs in an area of the sky where the Milky Way, our own galaxy, is especially bright.

The new asteroid was discovered by Dr Scott Sheppard of the Carnegie Institution and Dr Chadwick Trujillo of the Gemini Observatory, Hawaii. They orbit in the same plane as a planet, but don't collide with it. This is because they occur in "dead zones" where gravitational forces allow the asteroid to orbit at precisely the same speed as the planet.These Lagrangian points, as the dead zones are called, occur 60 degrees ahead and behind the planet. 

Almost all of the 200,000 Trojan asteroids larger than 1kilometer found to date orbit with Jupiter. However, the newly discovered Trojan is one of only six associated with Neptune. Eventually, the Trojan cloud associated with Neptune could prove to be as big as that orbiting with Jupiter.

Dr Sheppard said that his team had to devise a "a unique observing strategy" to spot the asteroid against this bright star field. They used interstellar dust to mask the star light so the 100km asteroid became clearly visible.The breakthrough was made using the 8.2m Japanese Subaru telescope in Hawaii.

Professor Alan Fitzsimmons of Queens University Belfast, an expert on asteroids, said that it was "an incredibly exciting discovery. It's another important clue for unravelling the early evolution of the Solar System".

Casey Kazan via http://www.bbc.co.uk/news/science-environment-10954453

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