Dozens of young scientists from all over Europe have gathered this week at
Les Houches in Savoie, France, for intensive briefings on ESA’s next star-
mapping satellite, Gaia. As the successor to the very successful Hipparcos
space astrometry project, Gaia was approved last year as an ESA Cornerstone
mission to be launched around 2012. Engaging the interest and participation
of the next generation of astronomers will be vital for the project’s success.

The Hipparcos satellite (1989-93) revolutionized astrometry, the science of
star measurement, by fixing the positions, brightnesses, colours and
variations of millions of stars in our vicinity far more accurately than ever
before. Astrometry was previously a difficult, backwater subject of interest
to only a few specialists. Hipparcos changed all that, with results that are
still impacting on every branch of astronomy, from comets to cosmology.

Gaia will be 100 times better than Hipparcos. By charting a billion stars, to
much greater distances than Hipparcos, it will give an unprecedented picture
of the positions and motions of stars across most of the Milky Way Galaxy.
Besides transforming the science of stars and galaxies, Gaia will be a top
discoverer of asteroids and alien planets.

“Gaia will deliver its first results more than ten years from now,” notes
Michael Perryman, Gaia’s project scientist. “Key individuals have already
devoted half their working lives to conceiving and accomplishing Hipparcos,
and to inventing Gaia. Who’ll pick up the baton when they retire? That’s the


* Les Houches Summer School 2001
* Gaia home page

* Gaia home page (astrophysics division, SSD)

Gaia — an ambitious space observatory in astronomy. Gaia was adopted within
the scientific programme of the European Space Agency (ESA) in October 2000.
It aims to measure the positions of an extremely large number of stars with
unprecedented accuracy. As a result, the distances and motions of the stars
in our Galaxy will be determined with extraordinary precision, allowing
astronomers to determine our Galaxy’s three-dimensional structure, space
velocities of its constituent stars and, from these data, further our
understanding of our Galaxy’s origin and evolution.