
PLATO
in the context of the
extrasolar planet research
Giusi Micela (INAF-OAPa)
G. Micela – Bologna 5/03/2009
Outline
• Cosmic Vision context
• Relevance of transits for extrasolar planet
search
• PLATO contribution
• Beyond PLATO
G. Micela – Bologna 5/03/2009
Cosmic Vision
• On 18 October 2007, ESA selected for an
Assessment Study 6 M-class and 3 L-class
candidate mission concepts resulting from the
first Call for Mission for the Cosmic Vision plan.
• These mission concepts are competing for
launch opportunities in 2017/2018.
• down-selection for definition phase for M-class
missions in fall 2009
• final selection for flight of M-class mission in
2011
G. Micela – Bologna 5/03/2009
M-class missions
• Solar mission
• Space Plasmas
• NEO
• Dark energy
(Dune + Space)
• Infrared (Japan)
• Extrasolar planets
G. Micela – Bologna 5/03/2009
Known
exoplanets
• 316 planets in 270
systems, Oct 1995 Feb 2009 from RV
searches. 33 multiple
systems.
• 57 Transiting planets
• 7 from microlensing
surveys.
+ a few others
G. Micela – Bologna 5/03/2009
ESP population synthesis
Left panel: Core accretion+migration simulations by Ida & Lin (2004),
showing gas giants, ice giants, rocky planets. around solar-like stars
Right panel: Radial-velocity discovered planets.
G. Micela – Bologna 5/03/2009
Planetary search methods domains
• Transits due to
Earth-like
planets can be
detected with
accurate (10-4)
photometric
searches. 
only from space
G. Micela – Bologna 5/03/2009
New planets are
continuously
discovered.
The number of new
discovered transits
is quickly increasing
(~2/3 in the last two
years)
G. Micela – Bologna 5/03/2009
Transits
• For an edge-on orbit, transit duration is:
 Dt ≈ (PR*) / (pa)
• P=period, a=semi-major axis of orbit
• Probability of transit
– Ptransit ≈ R* / a
– For Earth (P=1yr, a=1AU), Ptransit=0.5%
– But for close, “hot” Jupiters, Ptransit=10%
– Of course, to detect Earths at 1 AU we need
to monitor the star for up to 1 year
G. Micela – Bologna 5/03/2009
Transits
• Advantages
– Easy. Can be done with small, cheap telescopes
– Possible to detect low mass planets, including
“Earths”, especially from space
• Disadvantages
– Probability of seeing a transit is low
• Need to observe many stars simultaneously
– Easy to confuse with starspots, binary/triple systems
– Needs radial velocity measurements for confirmation,
masses
G. Micela – Bologna 5/03/2009
Transits
Radial velocity + Transits
Porb, dist, mass, radius, density, inclination
Transits from ground  Jupiters
Transits from space  Earths
G. Micela – Bologna 5/03/2009
• Radial velocity follow up are needed to
determine the properties of transit
discovered planets
• Critical point. Transits from space may
now detect earth-size planets  bottle
neck due to limiting vrad measurement
capabilities. We need to measure ~cm/sec
• Very stable spectroscopes,
new generation telescopes
G. Micela – Bologna 5/03/2009
• We need also to know very well the host
properties
 Rpl = f(R*)
 Mpl = f(M*)
age = age*
Bright stars!!
G. Micela – Bologna 5/03/2009
Observational properties
• Mass distribution
for vrad-discovered
planet (upper) and
transiting planets
(lower)
G. Micela – Bologna 5/03/2009
Observational properties
Orbital distance
distribution for vraddiscovered planet
(upper) and
transiting planets
(lower)
G. Micela – Bologna 5/03/2009
The first space transit mission:
CoRoT
•
•
•
French mission with ESA contribution
Launch Dec. 2006 , extension of 3 years
more
Extrasolar planets and asteroseismology
Six planets already discovered
Many candidates
Very long follow up phase
G. Micela – Bologna 5/03/2009
Convection Rotation and
planetary Transits - CoRoT
Wide field
telescope (27cm
aperture) with 4
deg field. Most
stars from 1115Mag.
6 planets
• EXO-2 orbiting a young active
star
• EXO-3 high mass, compact object
• EXO-7 – rocky (2xR(Earth)) with
P~0.85d
G. Micela – Bologna 5/03/2009
A&A Cover
Convection Rotation and
planetary Transits - CoRoT
Wide field
Planetary transits
G. Micela – Bologna 5/03/2009
A&A Cover

PLATO
PLAnetary Transits & Oscillations of stars
Next generation mission for ultra-high precision stellar photometry
beyond CoRoT & Kepler
Search for and characterisation of exoplanets + asteroseismology
http://www.lesia.obspm.fr/cosmicvision/plato
http://www.oact.inaf.it/plato/PPLC/Home.html
Class-M mission under assessment study at ESA in the framework of « Cosmic Vision » programme
G. Micela – Bologna 5/03/2009
The science objectives of PLATO
PLAnetary Transits & Oscillations of stars
main objective : evolution of exoplanetary systems (= planets + host stars)
- the evolution of planets and that of their host stars are intimately linked
- a complete & precise characterisation of host stars is necessary to
measure exoplanet properties: mass, radius, age
1. compare planetary systems at various stages of evolution
2. correlation of planet evolution with that of their host stars
= comparative exoplanetology
Three kinds of observables :
1. detection & characterisation of planetary transits
2. seismic analysis of exoplanet host stars
3. complementary ground based follow-up (spectroscopy)
transit detection
- Porb, Rp/R*, R*/a
G. Micela – Bologna 5/03/2009
seismic analysis
- R*, M*, age
- interior
spectrum, RV, photometry, imaging,…
- exoplanet confirmation
- chemical composition of host stars
- … and of exoplanet atmospheres
Scientific Requirements
main science objectives
- detection and study of Earth-analog systems
- exoplanets around the brightest stars, all sizes, all orbital periods
- full characterisation of planet host stars, via seismic analysis
high level science requirements
-P1: > 20,000 bright (~ mV≤11) cool
dwarfs (>F5V) with precise and reliable
characterization including seismic analysis . We expect ~ 20 Earths
-P2: > 80,000 bright cool dwarfs; detection of planets in the long runs and seismic
analysis during step & stare phase
- P3: ~ 1000 very bright stars (4 ≤mV≤ 8): targets for future instruments
- P4: ~ 3000 very bright stars (4 ≤mV≤ 8): asteroseismology along the HR diagram
-P5: > 250,000 cool dwarfs; planets without stellar seismic analysis
G. Micela – Bologna 5/03/2009
Scientific Requirements
high level science requirements
-P1: > 20,000 bright (~ mV≤11) cool
dwarfs (>F5V);
noise < 27 ppm in 1hr
= 1 ppm in 30 d
= req. seismic analysis
- P2: > 80,000 bright cool dwarfs; noise < 80 ppm in 1hr during long pointing
but < 27 ppm in 1 hr during step & stare phase
= req. for 1Rearth
- P3: ~ 1000 very bright stars (4 ≤mV≤ 8) for 3 years: asteroseismology of specific targets
- P4: ~ 3000 very bright stars (4 ≤mV≤ 8) for > 5 months: asteroseismology + planet search
- P5: > 250,000 cool dwarfs; noise < 80 ppm in 1 hr for 3 years
- very long monitoring ≥ 3 years
G. Micela – Bologna 5/03/2009
- very high duty cycle ≥ 95%
Main Instrument Requirements
- very wide field: > 550 deg2 (CoRoT: 4 deg2; Kepler: 100 deg2)
- 2 successive fields (2 x 3y) + step & stare phase (1y: e.g. 4 fields x 3 months)
- large collecting area
- very low instrumental noise, in particular satellite jitter ≤ 0.2 arcsec
requirements for ground- and space-based follow-up
- high precision radial velocity measurements: false-alarm elimination, masses
- high resolution spectroscopy: chemical composition
- differential spectroscopy: exoplanet atmosphere composition
G. Micela – Bologna 5/03/2009
The PLATO study organization
ESA
study scientist, study manager, payload manager
M. Fridlund
R. Lindberg
D. Lumb
2 industrial
contractors
ESA
PSST
PLATO Consortium Council
Payload + SVM
PPLC =
PLATO Payload Consortium
PI: C. Catala
Co-Pi: M. Deleuil
study of payload
system
telescopes/optics
Focal Plane
onboard data processing
ground data centre
G. Micela – Bologna 5/03/2009
PSC =
PLATO Science Consortium
PI: D. Pollacco
Co-Pis: G. Piotto
H. Rauer
S. Udry
science case
scientific preparation
field characterisation and choice
follow-up observations
The PPLC Payload concept
- fully dioptric design
- 11cm pupil, 28°x28° field
- FPA: 4 CCDs 35842, 18
- 40 normal telescopes:
full frame CCDs
cadence 25s
8 ≤ mV ≤ 14
- 2 « fast » telescopes:
frame transfer CCDs
cadence 2.5s
4 ≤ mV ≤ 8
- overlapping line-of-sight concept
- 2 long pointings (3 yrs)
- 1 yr step & stare
G. Micela –
Bologna 5/03/2009
continuous
observation,
field rotation every 3 months
Performance of PPLC baseline design
magnitude for noise 27 ppm in 1 hr
highest priority requirement: > 20,000 cool dwarfs with noise < 27 ppm in 1 hr
26500
61000
303000
performance of initial industrial design, now being improved
G. Micela – Bologna 5/03/2009
P1 sample
P2 sample
P5 sample
Performance of PPLC baseline design
G. Micela – Bologna 5/03/2009
Performances
planets down to 0.6 Rearth
around G-type stars with mV=9.6-11.1
with seismic analysis
(26,500 stars)
P1
transit depth
detected at 3 
if duration = 10h
G. Micela – Bologna 5/03/2009
planets down to 1 Rearth
around late-type stars with mV≤12-13
(>300,000 stars; incl. 60,000 with
potential seismic analysis )
P2 P5
telluric planets
around stars up to A-type with mV=9.6-11.1
PLATO outcome (1)
•
PLATO will search planets orbiting bright stars.
It will therefore possible to follow up the exo-planetary
system with ground based and space telescopes (e.g.,
ELT, JWST, etc. ) to obtain a complete characterization
of the planet, its atmosphere, and the whole planetary
system
PLATO is the only instrument with this capability!
G. Micela – Bologna 5/03/2009
PLATO outcome (2)
PLATO will detect Earth-like planets
Small size planets orbiting solar-type stars with about 1 year period
The exo-planets discovered by PLATO can be fully
characterized
The same data that PLATO acquires for the planet search, are
used to derive the internal structure of the hosting stars (by
asteroseismology). This is mandatory to:
-
Precisely measure properties of exoplanets: mass, radius, age
-
Comparatively study planetary systems of different age
-
Correlate the planet and hosting star evolution.
G. Micela – Bologna 5/03/2009
PLATO outcome (3)
PLATO will provide:
a complete and unbiased database
to understand the evolution of stars and their planets
PLATO will bring us:
-complete characterization of large number of exoplanets
(size, mass, age,density)
- improvement of exoplanet statistics
- correlation planetary versus stellar evolution
- decisive progress in stellar and planetary evolution
modelling
G. Micela – Bologna 5/03/2009
• Date: March 6 *
Mission: Kepler
Launch Vehicle: United Launch Alliance Delta II
Launch Site: Cape Canaveral Air Force Station Launch Complex 17 - Pad 17-B
Launch Time: 10:49:57 p.m. EST
Description: The Kepler Mission, a NASA Discovery
mission, is specifically designed to survey our region of
the Milky Way galaxy to detect and characterize
hundreds of Earth-size and smaller planets in or near the
habitable zone.
G. Micela – Bologna 5/03/2009
Kepler Results (!)
Time will tell but:
35 hot Jupiters bright enough
for RV confirmation (14th
mag) - HARPS-N WHT.
Superearths? Yes - probably
many
Terrestrial planets?
Probably…
Earth analogs??
but difficult to be confirmed
through follow up
\ G. Micela – Bologna 5/03/2009
Next steps
After characterizing the star-planet systems
• Substantial progress in theories of planet
formation for giant and terrestrial planets
• Atmospheric properties (giants soon,
earths ?) Albedo, clouds, dynamics, temperature,
composition
• Habitability conditions (environment)
• Biosignatures, identification and
observations
G. Micela – Bologna 5/03/2009
Next steps
• Technical issues
• The `best’ technology  interferometry or
coronography from space
• Ids of the best target samples: nearby
solar type very quiet stars with planet(s) in
habitable zone  PLATO could furnish
some
G. Micela – Bologna 5/03/2009
Next steps
• Significant effort of the community to prepare a roadmap
for extrasolar planetary science
• ESA EPR-AT (Exo-Planet Roadmap Advisory Team): will
deliver a document next year (spring) – meeting open to
the community Jan-Feb 2010 (http://sci.esa.int/sciencee/www/object/index.cfm?fobjectid=42830)
• BLUE DOTS: Initiative of the community to prepare a
roadmap for detection and characterization of habitable
exoplanets. Conference in Barcelona (Sept. 2009)
(http://www.blue-dots.net)
G. Micela – Bologna 5/03/2009
Just to conclude
• Extrasolar planet science is growing very quickly
• A fluorishing of new projects and instruments
from ground and from the space
• with PLATO we will know, on solid statistical
bases, which kind of planetary systems exist and
their properties
• PLATO is part of a roadmap that will bring us in
some decades (?) to biosignature detection in
extrasolar planet atmospheres
G. Micela – Bologna 5/03/2009