Transcript Planet detections

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.
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’.
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 mass
star 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 planets
inside 5 AU.
On the formation of planets ?
Since the discovery of planets around pulsar (Wolszczan and Frail 1992) with Msini of
2.8 and 3.4 Earth’s masses and respectively at 0.47 and 0.36 AU, a second generation
planet formation is suggested around pulsars that may result from the merging of 2 dwarf stars
for instance (Livio et al 1992).
More generaly planets may form at different stages of the stellar evolution.
In about 1000 years …
Stingray nebula
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).
Earth’formation
-4.550 Gyrs
-3.600 Gyrs
No trace of fossils
700 Myrs at most
For life occurence
Heavy meterotic bombardement
during the first Gyr
Oldest fossils known (cyanobacteries)
-3.550 Gyrs
Résidus carbonés
-3.850 Gyrs
The potential of GAIA.
1) Red giants are bright and numerous but expected problems for planet detection
with GAIA related to surface features linked to convection in the stellar atmosphere.
2) A problem probably relaxed for Sub-Giant stars around which searching
For Earth’s like planets in habitable zones transiting long enough for life to
Develop 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.
In a sphere of 20 pc around the Sun (from AQ, Allen) :
Jupiter like planets produce well measurable
Reflex 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 motion
of the star of the order of 5 micro-arcsecs. Assuming the
WD at 10 pc and of 0.6 solar mass and the planet at 1 AU.
A few sources.
Interferometry and circumstellar environments
Compagnons stars as a sub-product of this search of planets