1. DARWIN The InfraRed Space Interferometer

2. Status of exo-planet search Stars (Solar type) observed: +3000 Planets detected: ~ 86 Radial velocity measurement precision –1-2 m/s intrinsic limit? –Earth requires 0.1 m/s Occultation: Planet orbiting HD209458 P = 3.5 days m = 0.7 M jup R p = 1.4 R jup

3. Status of exo-planet search

4. Search For Extrasolar Planets Search For Extrasolar Planets COROT COROT has two main scientific programs working simultaneously on adjacent regions of the sky: ASTEROSEISMOLOGY SEARCH FOR EXTRASOLAR PLANETS (“Super- Earths”- if they exist!)

5. Search For Extrasolar Planets Search For Extrasolar Planets EDDINGTON Habitable Planets Jupiter /Sun =1 % Earth/ Sun = 8.4*10 -5 Mars/Sun = 3*10 -5 Photometric precision require space mission >EDDINGTON determines minimum size of DARWIN

6. Direct detection of nearby Earths Two major difficulties: 1. Contrast: 10 7 in the infrared for a Sun-Earth system 2. Angular Separation: 0.1 arcsec for a Sun-Earth system at 10pc 7 10 6 Dynamic range and resolution

7. Searching for nearby Earths Candle light 0.3m from lighthouse at a distance of 1000km Light is drenched in radiation from the star

8. interferometer Recomb. Tele- scope 1 Tele- scope 2 Dsin  Nulling

9. Principle of a Bracewell nulling interferometer Pupil plane recombination  no image (the only thing we detect is an integrated flux) bright output dark output 20 m 500 milli-arcsec Transmission map NULLING INTERFEROMETRY  0

10. The InfraRed Space Interferometer DARWIN 6 telescopes (1.5m) Hexagonal configuration Beam combiner Passive cooling (40 K)

11. Concept Infrared interferometer –Multi-aperture : 1.5 m telescopes baselined –Laurance class configuration –Wide band spectroscopy Free-flyer –Micropropulsion –Laser & RF metrology Wavefront filtering –Enabling technology – relaxes requirement on WF qualitiy

12. The InfraRed Space Interferometer DARWIN The Solar system as viewed from 10 pc on the 1:st of January 2001 with the Darwin baseline system Venus Mars Earth Nulled Sun

13. Characterizing nearby Earth’s We thus not only want to detect planets similar to ours but also characterize them from the light they produce

14. Characterizing Earths Calculated atmospheric spectra (  = 200) Photon m -2 s -1 300K BB 6 8 10 15 20  m Observed spectra H 2 O O 3 CO 2 6 8 10 15 20  m

15. Search for exo-life What is life? contains information can self-replicate can evolve Life on Earth as a reference: Carbon (organic) chemistry in water solution Goal 2: Astrobiology

16. Search for exo-life Attempt to detect life by remote sensing. Probably one of the most difficult problems in observational astronomy… Most likely criterion is simultaneous presence of liquid H 2 O together with presence of O 2 1. O 2 produced by life 2. O 2 very reactive gas / rocks… if not continuously produced it vanishes in  <  million yrs 3. O 3 better than O 2. It is logaritmically dependant on amount of O 2 + spectral lines in the IR Presence of O 3 = signature of life unless non-biotic production

17. Search for exo-life - for > 20 yrs, no abiotic production of O 3 found when: O 3 with liquid H 2 O atmosphere at T ~ 270 K (Habitable Zone) Qualifying the H 2 O / O 3 criterion: If criterion stands, organic life can be searched for

18. NASA’s Terrestrial Planet Finder Four 3.5m telescopes Identical objectives to Darwin Good basis for future collaboration