(Proposal ID) S10A-101

(PI) Sheppard, Scott

(Proposal Title)
A Neptune Trojan Survey for the New Horizons Spacecraft

(Abstract)
Trojan asteroids share a planet's semi-major axis but lead (L4) or follow 
(L5) the planet by about 60 degrees near the two triangular Lagrangian points 
of equilibrium. These minor planets were likely captured in these locations 
around the planet formation epoch and thus their current dynamical and physical
 properties will help constrain the formation, evolution and migration of the 
planets. The Neptune Trojans currently consist of only six known objects, all 
in the leading L4 cloud. Three of these were discovered in our initial survey 
of the L4 region allowing us to determine that Neptune was likely on a much 
more eccentric orbit in the distant past. We propose to continue a survey for 
Neptune Trojans in the trailing L5 region and to recover promising candidates 
found in 2009A with Subaru. Only with knowledge of the Trojan numbers and 
orbits in both the L4 and L5 clouds will we be able to understand their 
formation and evolution and further constrain planet accretion and migration. 
In addition, the New Horizons spacecraft will pass through the Neptune L5 
region in 2013 on its way to Pluto. It is important that we understand the 
possible dust production produced by collisions of the Trojans as well as find 
suitable Trojans that New Horizons will observe as it passes through the area.