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Solar System

Minor Planets & Near Earth Objects

During the course of its mission, Gaia will map all sources brighter than visual magnitude ~20. Among these will be thousands of Solar System objects, primarily main belt asteroids circling the Sun between the orbits of Mars and Jupiter. With its ability to detect faint and fast-moving objects, it is expected that Gaia will also detect several thousand Near-Earth Objects (NEOs), which are thought to be comets and asteroids that have been nudged by the gravitational attraction of nearby planets into orbits that allow them to enter the Earth's neighbourhood.

Favourable observing conditions

Gaia will operate from the second Lagrange point L2 of the Sun-Earth system and will be able to observe down to an angular distance of 45° from the Sun. This allows for observations of objects in the asteroid blind spot between the Sun and Earth and to discover small bodies orbiting the Sun inside the Earth's orbit - a region that is virtually unobservable from the Earth. Objects that are in more exotic orbits are also potentially discovered by Gaia, during observations of the sky regions far from the ecliptic.

Science Goals

Orbit determination
Gaia will accurately measure the positions and velocities of asteroids over the five years of the mission, leading to a determination of their orbits with an unprecedented precision.

Mass determination
The tiny gravitational pull experienced by asteroids during close approaches between two bodies alters their path. This small deviation will be recorded in the Gaia astrometric measurements, from which the object's mass can be derived. The expected number of asteroid masses to be determined this way is ~100, as compared to the approximately 20 known today.

Gaia will perform multi-epoch photometric observations of the Solar System's minor bodies. These observations will reveal their surface properties and composition by the amount of light that the minor bodies reflect at particular wavelengths.

A refined classification of the population of minor bodies will emerge from the giant data base, revealing the kinship between asteroids, NEOs, and meteorites. In addition, the variation of physical parameters with the distance to the Sun will also be studied.

Last Update: 19 June 2007

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