Arnaud Cassan ( ARI / ZAH Heidelberg ) 4th Planet Formation Workshop MPIA, 1 st March 2006 Discovery of a cool 5.5 Earth-mass planet through gravitational.

Präsentation zum Thema: "Arnaud Cassan ( ARI / ZAH Heidelberg ) 4th Planet Formation Workshop MPIA, 1 st March 2006 Discovery of a cool 5.5 Earth-mass planet through gravitational."—  Präsentation transkript:

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

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

3 Arnaud Cassan ( ARI / ZAH Heidelberg ) 4th Planet Formation Workshop MPIA, 1 st March 2006 Magnification: u Magnification curves Einstein ring radius: (t-t 0 )/t E The single lens case

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

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

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

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

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

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

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

11 Arnaud Cassan ( ARI / ZAH Heidelberg ) 4th Planet Formation Workshop MPIA, 1 st March 2006 What we know from the unique modeling Planet/star mass ratio : q = m p / M * = (7.6 ± 0.7) x 10 -5 Instantaneous separation/Re : d = r phys / R E = 1.61 ± 0.01 Source star distance : D S = 8.5 kpc Einstein ring crossing time : t E = 11.0 ± 0.1 days R E = v t t E = 1/c [ 4GM * D L (1-D L /D S ) ] 1/2

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

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

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

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

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

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