"It is exciting to have quadrupled the known population of Neptune Trojans," said lead researcher Scott Sheppard. "In the process, we have learned a lot both about how these asteroids become locked into their stable orbits, as well as what they might be made of, which makes the discovery especially rewarding."

The recently discovered Neptune Trojans are only the fourth stable group of asteroids observed around the Sun. The others are the Kuiper Belt just beyond Neptune, the Jupiter Trojans, and the main asteroid belt between Mars and Jupiter.

Evidence suggests the Neptune Trojans are more numerous than either the main asteroid belt or the Jupiter Trojans, but they are difficult to observe because they are so far away from the Sun. Astronomers therefore require the largest telescopes in the world equipped with sensitive digital cameras to detect them.

Reporting in the June 15 online issue of Science Express, the team said the Trojan asteroids cluster around one of two points that lead or trail the planet by about 60 degrees in its orbit, known as Lagrange points.

In these areas, the gravitational pull of the planet and the Sun combine to lock the asteroids into stable orbits synchronized with the planet.

German Astronomer Max Wolf identified the first Jupiter Trojan in 1906, and since then, more than 1800 such asteroids have been identified marching along that planet's orbit. Because Trojan asteroids share a planet's orbit, they can help astronomers understand how planets form, and how the solar system evolved.

Researchers hypothesized that Trojans might also flank other planets, but evidence for this has surfaced only recently. In 2001, the first Neptune Trojan was spotted in the planet's leading Lagrangian point.

In 2004, Sheppard and Chadwick Trujillo of the Gemini Observatory, a co-author of the current study, found the second Neptune Trojan using Carnegie's Magellan-Baade 6.5 meter telescope in Las Campanas, Chile.

They found two more in 2005, bringing the total to four, and observed them again using the 8.2 meter Gemini Telescope in Hawaii in order to accurately determine their orbits. All four of the known Neptune Trojans reside in the planet's leading Lagrange point.

One of the new Trojans has an orbit that is more steeply tilted to the plane of the solar system than the other three. Although only this one has such a steep orbit, the methods used to observe the asteroids are not sensitive to objects so far out of tilt with the rest of the solar system.

The very existence of this Trojan suggests that there are many more like it, and that Neptune's Trojans as a whole occupy thick clouds with complex, interlaced orbits.

"We were really surprised to find a Neptune Trojan with such a large orbital inclination," Trujillo said. "The discovery of the one tilted Neptune Trojan implies that there may be many more far from the solar system plane than near the plane, and that the Trojans are really a "cloud" or "swarm" of objects co-orbiting with Neptune."

A large population of high-inclination Neptune Trojans would rule out the possibility that they are left over from early in the solar system's history, since unaltered primordial asteroid groups should be closely aligned with the plane of the solar system.

These clouds probably formed much like Jupiter's Trojan clouds did: once the giant planets settled into their paths around the Sun, any asteroid that happened to be in the Trojan region "froze" into its orbit.

Sheppard and Trujillo also compared, for the first time, the colors of all four known Neptune Trojans. They are all about the same shade of pale red, suggesting that they share a similar origin and history.

Though it is hard to tell for sure with only four on the books, the researchers think the Neptune Trojans might share a common origin with the Jupiter Trojans and outer irregular satellites of the giant planets.

These objects might be the last remnants of the countless small bodies that formed in the giant planet region, most of which eventually became part of the planets or were tossed out of the solar system.

Project X

The Aurora programme kicked off at Lockheed's Skunkworks in 1987. It was intended as a replacement for the SR-71. The first flight occuring in 1989. It became operational in 1995. The UK's knowledge of it was based on the fact that the US used RAF airbase at Machrihanish, Strathclyde* - with its three-mile-long runway - as a staging post for Mach 4, 200,000ft high dashes home across the North Pole.

In August 1989, it was positively identified by "Chris Gibson, a Scottish oil-exploration engineer and, at the time, a member of the British Royal Observer Corps (ROC), was working on the oil rig Galveston Key in the North Sea when he noticed an aircraft in the shape of a pure isoceles triangle refuelling from a KC-135 Stratotanker alongside two F-111s."

The aircraft has also been spotted across the US, in Norway and the Netherlands, often to the accompaniment of a deafening sonic boom and its characteristic "donuts on a string" con trail - caused by its revolutionary scramjet propulsion plant...

And so on and so forth. Regular readers will by now be reminded of our recent analysis of the black-helicopter-scrambling Blackstar project, a "two-stage-to-orbit system that could place a small military spaceplane in orbit" which was pretty well shot down in flames by this analysis of the available data.

Aurora, too, has been subjected to a fair amount of sceptical scrutiny. According to the doubters, an alleged 1985 $455m budget allocation for the project was in fact for a range of black aircraft projects, under the umbrella title "Aurora". Furthermore, the former head of Lockheed's Skunkworks division, Ben Rich, claims in his book Skunk Works that Aurora was nothing more than a budgetary codename for the stealth project which eventually led to the B-2 Spirit.

There are, of course, no pictures of Aurora, no definitive video footage and no real concrete specifications, leading to widespread, and often wild, speculation about the beast's performance and appearance. Those of you who like your secret projects blacker than black are directed to this entertaining Aurora picfest, while there's plenty more background on the project here.

Whether Aurora ever existed or not as an individual aircraft, we may never know. The project was allegedly cancelled in 1992 by the then Department of Defense supremo Dick Cheney, so it seems unlikely that the excised black projects in the MOD's 2000 report refer to it.

In which case, what are they? F-117A? B-2?. Or something more sinister perhaps: anyone fancy taking the X-22 anti-gravity disc craft for a spin?®
Bootnote

*Highly improbable, since the base is right next to the Scottish town of Campbeltown and an enormous golf course and boasts no major facilities for advanced aircraft projects. It ceased military operations in 1995, but still acts as the local airport.

Back in 2000, a Chinook helicopter crash 10 miles from Machrihanish was attributed by some to "a massive jet wake into which the helicopter flew, causing the crew to lose control". The cause? Aurora, naturally.