London

On the same day that Venus was observed as a black disk traversing the Sun, the European Space Agency (ESA) was advised to resurrect a mission based around such mini-eclipses. If built, the Eddington space-based observatory will use similar events to search for planets in other solar systems.

The €210-million (US$250-million) project would consist of three telescopes arranged to track the light intensities of many stars over several years. The plan is to place the structure beyond the Moon to allow uninterrupted observation of thousands of stars.

When, as viewed from Earth, Venus crossed the path of the Sun on 8 June, the silhouette of the planet reduced the star's brightness by a tenth of a per cent. Eddington is designed to detect changes a thousand times smaller than that, and will use dips in star brightness to deduce the existence of distant planets.

Eddington will also investigate what the insides of stars are made of, by measuring the frequency of emitted light and deducing information about their chemical and physical properties. This may illuminate star evolution: “Studying younger and older stars will help us understand the Sun,” says Ian Roxburgh, an astronomer at Queen Mary, University of London, and a coordinator in the mission's design team.

The project was approved in 2002 for launch in 2008, but was shelved last November after its design phase, because the ESA budget would not stretch to cover its cost.

On 8 June, ESA's Space Science Advisory Committee (SSAC) recommended that the project be given precedence after receiving advice from several other committees. “The SSAC strongly endorsed Eddington,” says Giovanni Bignami, who is chairman of the committee and director of the CESR, the laboratory of space astrophysics in Toulouse, France. “It is our first priority.”

Eddington now tops the space agency's list of unfunded science missions. “If ESA receives more money, Eddington would be the priority,” says Roxburgh.

Jean-Jacques Dordain, director-general of ESA, is currently seeking an extra €700 million in funding for the agency from its member states. Eddington should be built if a fraction of that comes through.