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Discovery of a cool 5.5 Earth-mass planet through gravitational microlensing

Discovery of a cool 5.5 Earth-mass planet through gravitational microlensing. Arnaud Cassan Astronomisches Rechen-Institut (ARI), Zentrum für Astronomie der Universität Heidelberg (ZAH). The microlensing effect. lens plane. source plane. Image. < mas. Source. Observer. u.

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Discovery of a cool 5.5 Earth-mass planet through gravitational microlensing

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  1. Discoveryof a cool 5.5 Earth-mass planet throughgravitational microlensing Arnaud Cassan Astronomisches Rechen-Institut (ARI),Zentrum für Astronomie der Universität Heidelberg (ZAH) Arnaud Cassan ( ARI / ZAH Heidelberg ) 4th Planet Formation Workshop MPIA, 1st March 2006

  2. The microlensing effect lens plane source plane Image < mas Source Observer Arnaud Cassan ( ARI / ZAH Heidelberg ) 4th Planet Formation Workshop MPIA, 1st March 2006

  3. u Magnification: The single lens case Magnification curves Einstein ring radius: (t-t0)/tE Arnaud Cassan ( ARI / ZAH Heidelberg ) 4th Planet Formation Workshop MPIA, 1st March 2006

  4. Image separation : • Einstein radius crossing time : • Maximum amplification : • unresolved images ! • Flux magnification monitoring Arnaud Cassan ( ARI / ZAH Heidelberg ) 4th Planet Formation Workshop MPIA, 1st March 2006

  5. Why a network of telescopes ? Ongoing microlensing events alerted byOGLE, MOA (EROS, MACHO) Follow-up network : PLANET collaboration Days Arnaud Cassan ( ARI / ZAH Heidelberg ) 4th Planet Formation Workshop MPIA, 1st March 2006

  6. Observational strategy Observatories Raw data Data reduction pipeline ( on-line reduction ) ”Homebase” :- light curves modeling- observational strategy- public alerts- anomaly predictions Arnaud Cassan ( ARI / ZAH Heidelberg ) 4th Planet Formation Workshop MPIA, 1st March 2006

  7. Arnaud Cassan ( ARI / ZAH Heidelberg ) 4th Planet Formation Workshop MPIA, 1st March 2006

  8. OGLE 2005-BLG-390Lb : a cool 5.5 Earth-mass planet 10.8.05 31.7.05 Beaulieu et al., 2006, Nature 439, 437 Arnaud Cassan ( ARI / ZAH Heidelberg ) 4th Planet Formation Workshop MPIA, 1st March 2006

  9. OGLE-2005-BLG-390 Arnaud Cassan ( ARI / ZAH Heidelberg ) 4th Planet Formation Workshop MPIA, 1st March 2006

  10. Arnaud Cassan ( ARI / ZAH Heidelberg ) 4th Planet Formation Workshop MPIA, 1st March 2006

  11. What we know from the unique modeling • Planet/star mass ratio : q = mp / M*= (7.6 ± 0.7) x 10-5 • Instantaneous separation/Re : d = rphys / RE= 1.61 ± 0.01 • Source star distance : DS= 8.5 kpc • Einstein ring crossing time : tE= 11.0 ± 0.1 days • RE = vttE = 1/c [ 4GM*DL(1-DL/DS) ]1/2 Arnaud Cassan ( ARI / ZAH Heidelberg ) 4th Planet Formation Workshop MPIA, 1st March 2006

  12. The mass of OGLE 2005-BLG-390Lb Arnaud Cassan ( ARI / ZAH Heidelberg ) 4th Planet Formation Workshop MPIA, 1st March 2006

  13. Arnaud Cassan ( ARI / ZAH Heidelberg ) 4th Planet Formation Workshop MPIA, 1st March 2006

  14. Deriving physical parameters • Planet mass & orbit : mp = 5.5 +5.5-2.7 Earth-mass • ap = 2.6+1.5-0.6 AU • Host star :M* = 0.2 +0.2-0.1 Msol • Lens distance : DL = 6.6 ± 1 kpc Arnaud Cassan ( ARI / ZAH Heidelberg ) 4th Planet Formation Workshop MPIA, 1st March 2006

  15. Arnaud Cassan ( ARI / ZAH Heidelberg ) 4th Planet Formation Workshop MPIA, 1st March 2006

  16. Microlensing event OGLE 2005-BLG-390:A cool and distant planet of 5.5 Earth masses • third planet discovered through microlensing • lowest-mass extra-solar planet so far, with large separation • support of core-accretion theory of planet formation : • discovery despite low sensitivity  such low mass extra-solar planets are most likely very common • microlensing searches will be able to measure the frequency of extra-solar planets ultimately (especially around M-dwarfs) Arnaud Cassan ( ARI / ZAH Heidelberg ) 4th Planet Formation Workshop MPIA, 1st March 2006

  17. Arnaud Cassan ( ARI / ZAH Heidelberg ) 4th Planet Formation Workshop MPIA, 1st March 2006

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