* Astronomy

Neptune's 4 outermost unnamed satellites have now been given official names by the IAU.

S/ 2002 N 1 has been named Halimede
 S/ 2002 N 2 has been  named  Sao
 S/ 2002 N 3 has been  named Laomedeia
S/ 2002 N 4  has been  named Neso.

A Thick Cloud of Neptune Trojans and Their Colours
The dynamical and physical properties of asteroids offer one of the few constraints on the formation, evolution and migration of the giant planets. Trojan asteroids share a planet's semi-major axis but lead or follow it by about 60 degrees near the two triangular Lagrangian points of gravitational equilibrium. Here we report the discovery of a high inclination Neptune Trojan, 2005 TN53. This demonstrates that the Neptune Trojan population occupies a thick disk which is indicative of ``freeze-in'' capture instead of in-situ or collisional formation. The Neptune Trojans appear to have a population several times larger than the Jupiter Trojans. Our colour measurements show that Neptune Trojans have statistically indistinguishable slightly red colours suggesting they had a common formation and evolutionary history and are distinct from the classical Kuiper Belt objects.

Read more (PDF)

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 that the Neptune Trojans are more numerous than either the asteroids in the main belt or the Jupiter Trojans, but they are hard 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.

Read more