E
SA’s Gaia is destined to
create the most accurate
map yet of the Milky Way. By
making accurate measurements of
the positions and motions of 1% of
the total population of roughly 100
billion stars, it will answer questions
about the origin and evolution of
our home Galaxy.
The Gaia mission blasted off the
morning of Dec. 19, 2013 on a Soyuz
rocket from Europe’s Spaceport
in Kourou, French Guiana, on its
exciting mission to study a billion
suns.
Gaia will settle into orbit around
a gravitationally-stable virtual point
in space called L2, some 1.5 million
kilometres beyond Earth as seen
from the Sun.
After a four-month commissioning
phase – during which all of the
systems and instruments will be
turned on, checked and calibrated
– Gaia will be ready to begin its fiveyear science mission.
Gaia’s sunshield will block heat
and light from the Sun and Earth,
providing the stable environment
needed
by
its
sophisticated
instruments
to
make
an
extraordinarily sensitive and precise
census of the Milky Way’s stars.
“Gaia promises to build on the
legacy of ESA’s first star-mapping
mission, Hipparcos, launched in
1989, to reveal the history of the
galaxy in which we live,” says JeanJacques Dordain, ESA’s Director
General. “It is down to the expertise
of Europe’s space industry and
scientific community that this nextgeneration mission is now well and
truly on its way to making groundbreaking discoveries about our
Milky Way.”
Repeatedly scanning the sky,
Gaia will observe each of the billion
stars an average of 70 times each
over the five years. It will measure
the position and key physical
properties of each star, including
its brightness, temperature and
chemical composition.
By taking advantage of the slight
change in perspective that occurs
as Gaia orbits the Sun during a year,
it will measure the stars’ distances
and, by watching them patiently
ESA’s Gaia mission will produce an unprecedented 3D map of our galaxy by mapping the
Image: ESA/ATG Medialab/ESO/S. Brunier
position and motion of a billion stars.
over the whole mission, their motions
across the sky.
The
position,
motion
and
properties of each star provide
clues about its history, and Gaia’s
huge census will allow scientists to
piece together a ‘family tree’ for
our home Galaxy.
The motions of the stars can be
put into ‘rewind’ to learn more
about where they came from and
how the Milky Way was assembled
over billions of years from the
merging of smaller galaxies, and
into ‘fast forward’ to learn more
about its ultimate fate.
“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,” says 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.”
By comparing its repeated scans
of the sky, Gaia will also discover
tens of thousands of supernovas,
the death cries of stars as they reach
the end of their lives and explode.
And slight periodic wobbles in the
positions of some stars should reveal
the presence of planets in orbit
around them, as they tug the stars
from side to side.
Gaia will also uncover new
asteroids in our Solar System and
refine the orbits of those already
known, and will make precise
tests of Einstein’s famous theory of
General Relativity.
After five years, the data archive
will exceed 1 Petabyte or 1 million
Gigabytes, equivalent to about
200,000 DVD’s worth of data. The
task of processing and analysing
this mountain of data will fall to the
Gaia Data Processing and Analysis
Consortium, comprising more than
400 individuals at scientific institutes
across Europe.
“Where Hipparcos catalogued
120,000 stars, Gaia will survey almost
10,000 times as many and at roughly
40 times higher precision,” says Timo
Prusti, ESA’s Gaia project scientist.
“Along with tens of thousands
of other celestial and planetary
objects, this vast treasure trove
will give us a new view of our
cosmic neighbourhood and its
history, allowing us to explore the
fundamental properties of our Solar
System and the Milky Way, and our
place in the wider Universe.”
The spacecraft was designed
and built by Astrium, with a core
team 6