Earth as seen from the International Space Station.
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Earth as seen from the International Space Station.NASA
March 5, 2019
Research Highlight

Earth's Trojan Asteroids

In a recent comment article for Nature: Astronomy, Renu Malhotra of the Lunar and Planetary Laboratory at The University of Arizona discusses the need for further study of Earth’s Trojan asteroids, which are small bodies trapped in Earth’s orbital path at the L4 and L5 regions. These regions are what are known as Lagrangian points; locations in space created by the gravitational pull of two large objects (such as the Sun and the Earth). Gravitational forces create stable points in space where objects can become trapped. The L4 point leads Earth’s orbit and the L5 point follows. Both L4 and L5 sit at 60 degrees off of the Earth-Sun axis.

Lagrangian points of the Earth-Sun system (not to scale). Objects at the Lagrangian points (purple dots) remain in the same relative position to one another as the Earth orbits the Sun.
Lagrangian points of the Earth-Sun system (not to scale). Objects at the Lagrangian points (purple dots) remain in the same relative position to one another as the Earth orbits the Sun.Image credit: NASA Astrobiology.

The L4 and L5 points are important because they are relatively near the Earth and the objects trapped at these points are not well understood. The recent paper discusses current knowledge of the near-Earth Trojan asteroid population, and outlines the steps and technology needed for further assessment of these important regions of space.

The study, “The case for a deep search for Earth’s Trojan asteroids,” was published in Nature: Astronomy. The work was supported by the Nexus for Exoplanet System Science (NExSS).  NExSS is a NASA  research coordination network supported in part by the  NASA Astrobiology Program. This program element is shared between NASA’s Planetary Science Division (PSD) and the Astrophysics Division.