The Gaia space telescope blasted off into clear skies over South America on Thursday morning on an ambitious mission to map one billion stars in the Milky Way.

Engineers and scientists on the £625m mission celebrated a perfect launch from the European Space Agency's facility in Kourou, French Guiana at 6.12am local time (9.12am GMT).

The rocket thundered into the heavens, shed its boosters and slipped out of sight as it powered towards its destination, the L2 Lagrangian point, which lies 1.5 million kilometres from Earth.

The spacecraft will take a week or so to reach its orbit around the sun. Once there, the telescope will start to turn gently and map the precise locations of all the stars and other celestial bodies that fall within its gaze.

"It is an emotional moment and one of the wow moments in life," Timo Prusti, Gaia project scientist, told the Guardian from the launch site. "A perfect launch and deployment of the sunshield. We are ready to observe the stars."

Mission officials will run tests on the telescope's instruments when it arrives at the L2 Lagrangian point in the new year before it starts its first observations of stars, and planets in other solar systems. The mission is expected to last five years.

Peter Allan, a scientist on the Gaia project at the Rutherford Appleton Laboratory in Oxfordshire, said the launch was flawless. "In the buildup to take-off, you could see whole banks of green lights in the control room. It took off exactly on time. Before it disappeared, you could see the boosters separate and fall away. It's up in space and on its way."

Gaia's star map will account for 1% of the stars in the Milky Way, information that will help scientists answer questions about the origin and evolution of the galaxy. "We have built Gaia primarily to understand the detailed structure of the galaxy we live in, the Milky Way. Until now, that has not been possible," said Allan.

On Friday, engineers will command Gaia to perform the first of two critical thruster firings to make sure the rocket is on the right course to reach its destination. The second firing, due in around 20 days, will send the spacecraft into its operational orbit around the sun.

Instruments aboard the space telescope will be switched on, checked and calibrated during a four-month commissioning phase before Gaia begins its five years of observations.

By watching the stars from different positions, Gaia can build up a picture of the exact distances of stars and how they move. The measurements can be used to "rewind time" to look at where the stars came from and how the galaxy came to look the way it does today.

Scientists on the mission say the telescope will discover tens of thousands of dying stars that explode in spectacular supernovae. By watching for subtle movements of stars, they also hope to learn of previously unknown planets that tug on their parent stars as they circle round them.

"Gaia represents a dream of astronomers throughout history, right back to the pioneering observations of the ancient Greek astronomer Hipparchus, who catalogued the relative positions of around a thousand stars with only naked-eye observations and simple geometry," said Alvaro Giménez, Esa's director of science and robotic exploration.

"Over 2,000 years later, Gaia will not only produce an unrivalled stellar census, but along the way has the potential to uncover new asteroids, planets and dying stars," he added.