2008 LC18 - Neptune Trojan Asteroid Discovered

"Asteroid Near Neptune Found in Gravitational Dead Zone"
Space.com (August 12, 2010)

"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, which follows Neptune's orbit around the sun, may help shed light on fundamental questions about planetary formation and migration.

"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. ..."

The article gives a pretty good look at what may be the start of a new wave of observations.

That phrase, "dead zone," in the title and first paragraph? It sounds cool, and probably encourages folks to read the article - but I think it's a bit more accurate to visualize the Lagrange points as invisible 'dips' in space-time where debris tends to collect.

Reading that, I think I see why the Space.com editors decided to go with "dead zone." It sounds much cooler.

I think the new asteroid is more intriguing than informative - at least for now. Astronomers think they'll be able to get a better idea of what happened as the Solar system developed, after studying this object. It's called 2008 LC18, by the way.

And others like it.

"...'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.'..."

I'd like to know why Scott Sheppard thinks there are that many Neptune Trojans: but I won't make snide cracks about his estimate. My guess is that the estimated count derives from what little astronomers have been able to learn of

"...'We estimate that the new Neptune Trojan has a diameter of about 62 miles (100 km), and that there are about 150 Neptune Trojans of similar size at L5,' Sheppard said. 'It matches the population estimates for the L4 Neptune stability regions.'..."

2008 LC18 is so far away - and, more to the point, so dim - that it's hard-to-impossible to tell what it's made of. Today. A few years from now? My guess is that it'll be a sort of race, to see whether someone gets a robot probe to 2008 LC18 before near-Earth telescopes get a clear look at the thing, and start analyzing its surface.