ESA's billion-star surveyor Gaia is
slowly being brought into focus. This test image shows a dense cluster
of stars in the Large Magellanic Cloud, a satellite galaxy of our Milky
Way.
Once Gaia starts making routine measurements, it will generate truly
enormous amounts of data. To maximise the key science of the mission,
only small 'cut-outs' centred on each of the stars it detects will be
sent back to Earth for analysis.
This test picture, taken as part of commissioning the mission to 'fine
tune' the behaviour of the instruments, is one of the first proper
'images' to be seen from Gaia, but ironically, it will also be one of
the last, as Gaia's main scientific operational mode does not involve
sending full images back to Earth.
NGC 1818 - part of a test image taken during commissioning of the Gaia payload. Copyright: ESA/DPAC/Airbus DS
Gaia was launched on 19 December 2013, and is orbiting around a virtual point in space called L2, 1.5 million kilometres from Earth.
Gaia's goal is to create the most accurate map yet of the Milky Way. It
will make precise measurements of the positions and motions of about
1per cent of the total population of roughly 100 billion stars in our
home Galaxy to help answer questions about its origin and evolution.
Repeatedly scanning the sky, Gaia will observe each of its billion
stars an average of 70 times each over five years. In addition to
positions and motions, Gaia will also measure key physical properties of
each star, including its brightness, temperature and chemical
composition.
To achieve its goal, Gaia will spin slowly, sweeping its two telescopes
across the entire sky and focusing the light from their separate fields
simultaneously onto a single digital camera – the largest ever flown in
space, with nearly a billion pixels.
But first, the telescopes must be aligned and focused, along with
precise calibration of the instruments, a painstaking procedure that
will take several months before Gaia is ready to enter its five-year
operational phase.
As part of that process, the Gaia team have been using a test mode to
download sections of data from the camera, including this image of
NGC1818, a young star cluster in the Large Magellanic Cloud. The image
covers an area less than 1per cent of the full Gaia field of view.
The team is making good progress, but there is still work to be done to
understand the full behaviour and performance of the instruments.
While all one billion of Gaia’s target stars will have been observed
during the first six months of operations, repeated observations over
five years will be needed to measure their tiny movements to allow
astronomers to determine their distances and motions through space.
As a result, Gaia’s final catalogue will not be released until three
years after the end of the nominal five-year mission. Intermediate data
releases will be made, however, and if rapidly changing objects such as
supernovae are detected, alerts will be released within hours of data
processing.
Eventually, the Gaia data archive will exceed a million Gigabytes,
equivalent to about 200 000 DVDs of data. The task of producing this
colossal treasure trove of data for the scientific community lies with
the Gaia Data Processing and Analysis Consortium, comprising more than
400 individuals at institutes across Europe.
For more information, please contact:
Markus BauerESA Science and Robotic Exploration Communication Officer
Tel: +31 71 565 6799
Mob: +31 61 594 3 954
Giuseppe Sarri
Gaia Project Manager
Email: giuseppe.sarri@esa.int
Timo Prusti
Gaia Project Scientist
Email: timo.prusti@esa.int
Source: ESA/Gaia
