Max Planck Institute for Astronomy - Annual Report 2005

98 IV. Instrumental Development
IV.3 DARWIN
DARWIN is an ambitious European Space Agency (Esa)
mission with the explicit goal of finding Earth-like planets,
characterizing their atmospheres, and searching
for life. Darwin is being developed in a rich context
of exo-planetary and exo-biological investigation. For
example, the discovery over the last decade of close to
200 planets orbiting other stars has energized a renewed
focus on the fundamental question of whether life exists
on other planets in the universe.
Answering this question is a complex and difficult
task, since planets like our own are typically 10 billion
Fig. IV.3.1: The flotilla of Darwin spacecraft searching for evidence
of life in the Universe.
times fainter than their parent star. At the distances of
even the most nearby stars, such worlds would also be
very close to the intense glare of their suns. The combination
of small angular separation and huge brightness
ratio strongly restricts the ways in which astronomers can
look for such planets.
Nulling interferometry, a technique in which the light of
the host star is blanked out by superimposing phase-shifted
images, offers a real prospect of overcoming these challenges.
Earths are relatively bright and suns are relatively dim
at mid-infrared wavelengths (6–20 µm). There are also a
number of powerful »biomarkers«, spectral signatures of
the presence of life in the mid-infrared regime. The improved
contrast ratio and useful tracers, coupled with the
easier task of aligning and controlling an interferometer at
longer wavelengths, have led to the concept of the Darwin
mission: a mid-infrared free-flying space interferometer.