planets around evolved stars, few key questions that could be tackled with gaia lopez bruno obs. de...
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Planet detections : Discovery and understanding of Earth and Solar System : 5 bodies (Mercury, Venus, Mars, Jupiter, Saturn) at first sight distinguishable from the other stars because changing their place on the sky were discovered very early, Anaxagore ( , Eclipse mechanism), Aristote ( , Earth’s sphericity), Erastothènes ( , mesure of Earth’s diameter), Hipparque (-130, precession of Earth axis), Ptolémée (middle of 2snd century A.D., a model of Solar System), …, Copernic ( , Heliocentrisme), Kepler (1609, elliptical orbits). Discovery and understanding of Extrasolar planetary Systems : has started in with the discovery of planets around pulsars (2 cases apparently confirmed) and has continued with the discovery (since 1994) of giant planets around ‘normal stars’.TRANSCRIPT
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Planets around evolved stars,few key questions that could be tackled with GAIA
Lopez Bruno Obs. De la Côte d’Azur, Dpt. Fresnel UMR 6528, BP 4229 06304 Nice Cedex4, France.
Content : Introduction – few key questions. On the dynamical evolution of planets ? On the formation of planets ? On the possibility for life to develop around Red Giants ? The potential of GAIA.
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Planet detections :
Discovery and understanding of Earth and Solar System : 5 bodies (Mercury, Venus, Mars, Jupiter, Saturn) at first sight distinguishable from the other stars because changing their place on the sky were discovered very early, Anaxagore (-499-427, Eclipse mechanism), Aristote (-384-322, Earth’s sphericity), Erastothènes (-276-195, mesure of Earth’s diameter), Hipparque (-130, precession of Earth axis), Ptolémée (middle of 2snd century A.D., a model of Solar System), …, Copernic (1473 1543, Heliocentrisme), Kepler (1609, elliptical orbits).
Discovery and understanding of Extrasolar planetary Systems : has started in 1990-91 with the discovery of planets around pulsars (2 cases apparently confirmed) and has continued with the discovery (since 1994) of giant planets around ‘normal stars’.
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On the dynamical evolution of planets ?
1) Mass loss phenomenom and tidal dissipations between planets and the Red Giant star (Rasio et al. 1996) : no remaining planets inside 1 AU around a 1 solar massstar in evolution, Earth’s fate ?, other planets of our Solar System should survive.
2) Resonances in planetary systems like our own should lead to the ejection of planetsinside 5 AU.
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On the formation of planets ?
Since the discovery of planets around pulsar (Wolszczan and Frail 1992) with Msini of2.8 and 3.4 Earth’s masses and respectively at 0.47 and 0.36 AU, a second generationplanet formation is suggested around pulsars that may result from the merging of 2 dwarf starsfor instance (Livio et al 1992).
More generaly planets may form at different stages of the stellar evolution.
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Stingray nebula
In about 1000 years …
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On the possibility for life to develop around Red Giant stars ?
Terrestrial planets, around Reg Giants, in ‘Habitable zone’ offering possibility for life to develop can be discovered by GAIA (Lopez and Schneider 2002 submitted).
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Earth’formation-4.550 Gyrs
No trace of fossils
Résidus carbonés-3.850 Gyrs
700 Myrs at mostFor life occurence
-3.600 Gyrs
Oldest fossils known (cyanobacteries)-3.550 Gyrs
Heavy meterotic bombardementduring the first Gyr
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The potential of GAIA.
1) Red giants are bright and numerous but expected problems for planet detectionwith GAIA related to surface features linked to convection in the stellar atmosphere.
2) A problem probably relaxed for Sub-Giant stars around which searchingFor Earth’s like planets in habitable zones transiting long enough for life toDevelop is of strong interest.
3) A search of planets around White Dwarfs is very adapted to the potential of GAIA.A SIMBAD/CDS search show that nearly 400 WD of mv less than 15 exist. Type DO, DA,DB.
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In a sphere of 20 pc around the Sun (from AQ, Allen) :
Jupiter like planets produce well measurableReflex motion of the star, larger than 10 micro-arcsecs. Hundred of potential sources for such a detection.
A 10 Earth’s mass planet produces a reflex motionof the star of the order of 5 micro-arcsecs. Assuming theWD at 10 pc and of 0.6 solar mass and the planet at 1 AU.A few sources.
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Interferometry and circumstellar environments
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Compagnons stars as a sub-product of this search of planets