Welcome to the TROY project

Welcome to the main website of the TROY project. In this page you will find all the information related to the project, some basic ideas about trojan planets in the "Background for beginners" section, more advanced information in the "Background for experts" section, the researchers involved in the project in "The Team", and a section of "Publications" about our current knowledge of trojan planets, both from our team and from other studies.


The TROY project is a multi-technique observational and theoretical effort to understand the formation and evolution of planetary systems from the detection and characterization of the first exo-trojan planets (see Background section). The analysis of the gravitational forces in the well-known two body problem yields to the existence of five stable locations (or Lagrangian points) where such forces compensate to each other. Two of them (L4 and L5) are very stable and can host smaller bodies librating around them, as in the case of Jupiter in the Solar System. Since these bodies are outgrowths of the planet formation process, the detection of the first exotrojans will open a new scientific window to investigate the clues of planet formation and migration in outer planetary systems.

The main aim of the TROY project is to find the first trojan bodies co-orbiting with known extrasolar planets and measure their occurrence rate (eta-Trojan). More particularily, we would like to answer the following questions:

  • What is the maximum mass of unique body that a planet+star system can host in the Lagrangian points keeping the stability of the system?
  • How this mass depends on the properties of the planet and/or star?
  • Is there a maximum size for a trojan?
  • How trojan planets are formed? Are they captured during the planet migration or do the form in situ by collisions of minor bodies?
  • In the case of the capture scenario, what is the maximum mass that can be trapped in the gravity wells of the two-body system keeping the stability of the system?
  • In the case of the in situ formation scenario, what is the maximum mass that can be accreted in the gravity wells of the two-body system keeping the stability of the system?
  • How common is the existence of trojan planets in extrsolar systems? Is the small size of the Jupiter's trojans a rule or an exeption?
  • What can the properties of the trojan orbits around the Lagrangian points tell us about the history of the planetary system?