ESA's Gaia star surveying satellite launches

The European Space Agency launched its star-surveying satellite Gaia into space Thursday, hoping to produce the most accurate three-dimensional map of the Milky Way and to better understand the evolution of our galaxy.

The satellite was lifted into space from French Guiana at 6:12 a.m. (4:12 a.m. ET) aboard a Russian-made Soyuz rocket, the agency said.

Soon after the launch, Gaia unfurled its 10-metrecircular sun shield a crucial moment in the mission. The shield protects the spacecraft's sensitive instruments from the rays of the sun while simultaneously collecting solar energy to power the spacecraft.

"Everything was super smooth," said Paolo Ferri, head of mission operations at the Paris-based European Space Agency.

Gaia is now heading for a stable orbit around a point known as Lagrange 2 some 1.5 million kilometresaway on the opposite side of the Earth from the sun. Once it gets there next month, the satellite's instruments will be switched on and it will follow what Ferri described as "a very peculiar pattern" designed to keep its back always turned to the sun.

Timo Prusti, ESA's project scientist, likened the mission's goal to the switch from two-dimensional movies to 3D. At the moment, he said scientists are working with a largely "flat" map of the galaxy.

"We want to have depth," he said.

Using its twin telescopes, Gaia will study the position, distance, movement, chemical composition and brightness of a billion stars in the galaxy, or roughly oneper cent of the Milky Way's 100 billion stars.

The data will help scientists determine the Milky Way's origin and evolution, according to Jos de Bruijne, deputy project scientist for the Gaia program.

Galactic archaeology

"The prime importance of this mission is to do galactic archaeology," he said in a phone interview from French Guiana. "It will reveal the real history of our galaxy."

The project is the successor to ESA's Hipparcos satellite, which was launched in 1989 and measured the position of 100,000 stars in the Milky Way.

Gaia, which is named after an ancient Greek deity, will go far beyond that. Scientists have compared its measuring accuracy to measuring the diameter of a human hair from 1,000 kilometresaway.

"There is still a lot that we don't understand about the Milky Way," said Andrew Fox, an astronomer with the Space Telescope Science Institute in Baltimore, Maryland. He is not involved in the project, but his position at the science center is funded by the European Space Agency.