Rsum

1
Planets around evolved stars, few key questions
that could be tackled with GAIA



Lopez Bruno


Obs. De la Côte dAzur, 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.
2
(No Transcript)
3
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, Earths
sphericity), Erastothènes (-276-195, mesure of
Earths 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.
4
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, Earths
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.
5
On the formation of planets ?
Since the discovery of planets around pulsar
(Wolszczan and Frail 1992) with Msini of 2.8 and
3.4 Earths 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.
6
(No Transcript)
7
In about 1000 years
Stingray nebula
8
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).
9
Earthformation -4.550 Gyrs
-3.600 Gyrs
No trace of fossils
Heavy meterotic bombardement during the first Gyr
Oldest fossils known (cyanobacteries) -3.550 Gyrs
700 Myrs at most For life occurence
Résidus carbonés -3.850 Gyrs
10
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 Earths 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.
11
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 Earths 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.
12
Interferometry and circumstellar environments
13
Compagnons stars as a sub-product of this search
of planets