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Trojan asteroid detected in Neptune's 'dead zone'

Trojan asteroid 2008 LC18 is orbiting in a fixed spot in Neptune's orbit where the gravitational pull of Neptune and the sun balance out. Its discovery may help shed light on questions about planetary formation.


Astronomers have discovered a so-called Trojan asteroid orbiting Neptune – shown here in this 1989 photo taken by Voyager 2. The asteroid is located in the gas giant's gravitational 'dead zone,' where no previous object was known to exist.


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Astronomers have discovered a new asteroid in a region of Neptune's orbit where no previous object was known to exist -- a so-called gravitational "dead zone."


The asteroid, classified as a Trojan, was found in a difficult-to-detect area near Neptune, known as the Lagrangian point L5. Lagrangian points are five areas in space where the gravitational tugs from two relatively massive bodies -- such as Neptune and the sun -- balance out. This allows smaller bodies, like asteroids, to remain stable and fixed in synch with the planet's orbit, as they orbit the sun.

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"We believe Neptune Trojans outnumber the Jupiter Trojans and the main-belt asteroids between Mars and Jupiter," Scott Sheppard of the Carnegie Institution in Washington, D.C., told SPACE.com. "If Neptune was where the main-belt was, we'd know thousands of these objects."

He added that thousands of Trojan asteroids are associated with Jupiter.

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Stable regions

At Neptune, the L4 and L5 regions are 60 degrees along the planetâ€™s 360-degree orbital path, ahead and behind the planet respectively. In this configuration, dust grains and other small bodies are able to collect and remain there.

Neptune Trojans are very faint because they are so far away from the Earth and the sun, making them difficult to detect. Astronomers Scott Sheppard of the Carnegie Institution in Washington, D.C., and Chad Trujillo of the Gemini Observatory in Hilo, Hawaii, discovered the Trojan asteroid, 2008 LC18, through an innovative observational strategy.







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The research from this study will be published in the Aug. 13 issue of the journal Science.

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