Eddington

1. Eddington Stellar evolution Habitable planets

2. Two Major Science Goals Reliable tested theory Detection of habitable of stellar evolution to be Earth-like planets - their used in astrophysics frequency and properties Ages of stars, structure, Other planets properties chemical evolution and planetary systems Stellar oscillations Planetary Transits Asteroseismology High precision long duration relative photometry

4. Asteroseismology 1. Observations Power spectrum of flux gives oscillation frequencies 2. Theory Calculate oscillation frequencies of stellar model 3. Testing Compare model predictions with observations 4. Inversion Determine model that fits the observed frequencies - pressure, density, core mass, rotation, age,... Techniques tried and tested on SoHO

5. Serious problems in stellar modeling • Effects of rotation • age determination • chemical evolution of massive stars • Effects of overshoot from convective cores • late evolution, supernovae explosions • evolution of abundances • Settling of helium and heavier elements • age determination of low-mass stars Eddington will make fundamental contributions to solving these problems

6. Stellar Evolution Central to Astronomy Ages of stars, clusters, origin of elements Dating galactic structure (discs, bulge, halo) Chemical evolution of our galaxy and other galaxies Light element abundances (He, Li) and the early Universe History and future of the Sun - solar terrestrial relations

7. Solar frequency spectrum from VIRGO on SoHO

8. Results from helioseismology • Inversion for solar sound speed • evidence for mixing • test of equation of state • Inversion for solar rotation • convection-zone dynamics (not available in stars) • rotation of the deep interior; stellar rotational evolution

9. Relative difference in sound speed between Sun and model Effect of mixing

10. Inferred solar internal rotation Base of convection zone Near solid-body rotation of interior

11. But the Sun is just one simple star • No convective core • Slow rotation • Relatively unevolved • Comparatively simple material physics Proper investigations of stellar structure and evolution require study of a broad range of stars Eddington will provide this

12. Red Giant 1 M • • 10 M Variety of stellar internal structure Convective envelope Convective core

13. Eddington’s capabilities for asteroseismology • Study oscillations corresponding to those of the Sun in stars down to magnitude V = 12 • Very high duty cycle (95 %) leads to simple interpretation of frequency spectrum • Very extended observations of single field during planet-finding phase will give excellent frequency resolution of slow pulsators • Open clusters with massive pulsating stars, to study pre-supernova evolution • Open clusters with solar-like pulsators • Old, metal-poor stars as samples of the early evolution of the Galaxy

14. COROT’s limit The Praesepe Cluster Eddington’s limit

15. Results of inversion for a 1.45 Msun star Edge of convective core

16. Uncertainties of key parameters for a cluster with moderate-mass stars Ages Y Z Pre-Eddington >20% >10% >10% With separations 1.3% 0.3% 3% With frequencies <0.1% <0.1% 0.1%

17. Planet search Detection of habitable Earth-like planets 0.8 < R/REarth < 2.5, 0oC < T < 100oC How frequent are they? Masses, radii, orbits Properties of parent stars Major step in search for life elsewhere in the Universe Target selection strategy for Darwin Properties of other planets and planetary systems Formation of planetary systems Detected by transits of planets across stellar disc

18. The Habitable Zone From Kastings1996

19. Detection of other Earths Are there other worlds? and how many? Discovery of habitable planets with sizes and temperatures similar to Earth: R~ 0.8 - 2.5 REarth T= 0 - 100ºC -> Estimation of abundance of habitable worlds A necessary step in the detection of bio-activity loss of atmosphere, no plate tectonics Will develop into gas giant

20. The Formation and Evolution of Planets

21. Planetary Systems Origin Discovery of Extrasolar Planets has upset conventional theories on Solar System Origin Distribution of Solar System planets not compatible with positions of Hot Giant planets - migration? Eddington survey for low-mass planets will lead to generalisation of planetary system origin theories "Current Theories about Solar-System Origin are observationally driven by Exoplanets"

22. Earth like Photometry of Jupiter-like transit by HST HD 209458 precision: 6x10-5 Data: Charbonneau, Brown, Gilliland, 2000

23. Results from Transit Observations • reflected light: • non-transiting hot giant planets • amplitude of transit: • size of planet • time between transits: • orbital period, distance, temperature • duration of transit: • orbital inclination • shape of transit: • planetary rings, stellar surface • variations in arrival times of transits: • detection of massive planetary moons habitable sites around Gas Giants? time of transit of our Earth varies by5 mins due to presence of Moon

24. Eddington´s Detection Capabilities for Planets around Solar-type (G2V) star stellarbrightness 3.5 V=18 3 Complete coverage of habitable zone for G,K,M stars 2.5 2 V=16 R/REarth 1.5 Hab. zone V=14 + 1 Earth 0.5 V=12 0 50 100 150 200 250 300 350 400 Period

25. Comparison with other missions For a solar-type star Eddington and COROT are for three transits at V=14 SIM is for a star at 5 pc Radial velocity is for 1 m/s rad vel SIM (astrometry) COROT Planet mass (Earths) Hab. zone Eddington Orbital radius (AU)

26. Payload Requirements • High photometric precision: • 1 ppm for V = 11 in 30 d (  0.3 Hz). •  = 2-3 x 10-5 magnitude in 1 h for V = 13. • High precision long duration relative photometry • 1.2m telescope - 3o field of view - tiled CCDs • Large field of view: • ~50,000 stars for asteroseismology (1ppm V < 12). 2 years (1-2 months per field). Cover H-R diagram (masses, ages, abundances, clusters) • ~500,000 MS stars for planet search (10 ppm V < 17). 3 years on 1 field (20,000 planets with R<15 Rearth, dozens of Earth-like planets in habitable zone) • High duty cycle: • 95% (L2 orbit)

27. Payload Design • Telescope: Collecting area + Field of view. • 3º FOV, planar, unvignetted, and fully corrected. • Symmetric PSF,  1 arcsec anywhere in the FOV. • 1.5 x 106 photo-electrons/s for V = 11 • 1.2 m compact TRT with no refractive component. • Heritage from well-studied design • EddiCam: • Array of 20 CCDs covering the 3º FOV ( 19 cm). • Full-frame mode for planet search (7.4 sq.deg.) • Frame-store buffer shields on 16 CCDs for astero-seismology (3.25 sq.deg.). • One camera with sequential priority observing modes. • CCD detectors:20 x 80 mm in size • 740 x 2900, 27  (1.5 arcsec), pixels. Full-well capacity: 1.6 x 106 e-/pix. Operation at -90o (passive cooling) in L2 orbit.

28. Telescope’s layout riveted Al rings payload / spacecraft I/F

29. High-Precision Photometry • Photon-noise limited differential photometry (other sources of noise kept well < 8 x 10-4 s-1 on relevant time scales): • Satellite jitter (0.1 arcsec 1 ) • Thermal stability (0.1 K/hr) • Read-out noise (<20 e- per pixel) • Periodic perturbations (< 8 x 10-7 peak-to-peak) • Defocusing and dynamical range (precision and range versus source confusion and read-out noise): • Asteroseismology: 12 arcsec (8 pix.), 6 < V < 14. • Planet finding: 9 arcsec (6 pix.), 11 < V < 18.

30. Focal Plane CCD Array

31. Noise sources • Target star plus “trailing” and neighbouring stars. • Background; residual stray and zodiacal light. • Flat field structure, including sub-pixel variations. • Spacecraft pointing jitter. • Telescope’s point spread function. • Variations induced by stellar activity. • Dark current (including “telegraphic” noise). • Radiation-induced traps (CTE degradation). • Hot pixels due to high-energy particles. • Cosmic ray hit events. • Integration and read-out procedures. • Algorithms for on-board data processing.

32. Performance (asteroseismology))

33. Performance (planet finding)

34. Baseline assumptions 1) Soyuz-Fregat launcher baselined, launch from Baikonur. 2) Two approaches studied: Mars Express-based platform. European standard platforms (e.g. Prima) 3) Assumed launch date is 2008, with 2 years lifetime for design and 6 years for consumables (XMM approach). Earliest technical feasible launch date is on 2006. 4) ESA responsible for the complete programme, including launch, telescope, spacecraft operations and Science Operation Centre. 5) CCD camera and the Science Data Centre(s) PI supplied. 6) Mars Express programmatic approach baselined, with all S/C units & assemblies considered in principle off-the-shelf, with 2003 technology maturity. 7) One 15 m ground station (Kourou). One shift, 5 yr operations.

36. Deployed Satellite

37. Satellite exploded view

38. Spacecraft design approach • Operational Mission Lifetime 5 years • Solar Aspect Angle  35 ° • Spacecraft stabilised 3-axis • Observation Duration 1-2 months per star field • 3 years for planet-finding • Lift-off Mass (20% sys. marg.) 940 kg • Power (10% system margin) 520 W, 6 yr end-of-life • Average data rate 64 kbps (science) + 2 for HK • Pointing Accuracy (rms): • Absolute ± 3 arcmin • Relative ± 0.1 arcsec/15 min • (telescope error signal used for attitude information)

39. A.S. Eddington 1882-1944 Pioneer in stellar structure, oscillating stars, relativity, cosmology, outreach “... it is reasonable to hope that in a not too distant future we shall be competent to understand so simple a thing as a star.” Internal Constitution of the Stars (1926) “It would indeed be rash to assume that nowhere else in the Universe has nature repeated the strange experiment which she has performed on the Earth.” Nature of the Physical World (1933)

40. Eddington Science A reliable tested theory of stellar evolution Asteroseismology - stellar oscillations probe the interior Test models of stellar structure and evolution Determine key parameters (eg convective overshoot) Determine the internal structure (pressure, density, rotation) Physics of stellar interiors: mixing, diffusion, ... Chemical evolution of stars Determine the age of stars and stellar systems Dating machine for components of galactic structure

41. Eddington Science Extrasolar planets Detection of » 20,000 planets R < 15 RE Detection of » 500 in the habitable zone (dozens of Earths) First reliable statistics on the abundance of planets Earth-like planets for stars as faint as V » 17 Coverage of habitable zone for G, K, M stars Detection of massive satellites around planets Detection of hot giant planets by reflected light Major step in search for habitats for life Input to Darwin (target selection strategy and statistics)

42. Eddington Proposal Timeline • Oct 99: Call for F mission proposals. • Jan 00: 49 proposals received, 6 selected for assessment studies. • Jul 00: Assessment studies finished. • Sep 00: Presentations made followed by selection of 2 F-missions (NGST and SOLO) and a “reserve” F-mission (Eddington). Reserve to be implemented depending on NGST and LISA schedules or provision of further resources. • Oct 00: Selected mission package approved at SPC for 2007-2013.

43. ESA Planning • Eddington Science Team established in January 01. • ITT for telescope design to be issued in April. • Issue of a “Letter of Interest” for PI provided payload camera and data centers. • A study of CCD characterization and evaluation of noise sources to start in April. • First Eddington Workshop to be held in June in Córdoba (Spain). • ITT for the spacecraft design to start next year. • Final decision on project implementation by the end of 2002.