Exoplanet Discovery

Oxford 20120316
Suzanne: purpose of this talk is “refutable comments”
In actual fact I think only a crazy person would attempt
to predict the ESP future…
What is the aim of exoplanet
 Our aims may be quite different from that of our
funding bodies.
 Do we see the “big picture”?
 While doing the STFC roadmap I originally thought
about aims that were, I though, important and in my
career horizon eg terrestrial planets and their
atmospheres. This was loosely rewritten above me to
something like the “Star Trek Boldly go” phase
“Seek out new life and civilizations…”
So is the life question what its all about?
Maybe its not so far away from where we are moving
towards – habitability and HZ planets
Before you move forward its time to reflect – that way
you can take stock of where you actually are
Landmark events
1992 – the pulsar planets (Wolszczan & Frail0)
1995 – first hot jupiter, 51 Peg (Mayor & Queloz)
start of RV surveys (continuing)
1999 – first transit detection (Charbonneau et al, Tony
et al)
start of transit surveys (continuing)
(worth pointing out that at this time there was
barely a UK ESP community)
2001 – Na in HD209458b (Charbonneau et al, Brown et
2005 – first detection of thermal emission with spitzer
(Charbonneau et al, Deeming et al)
2007 – (water vapour in ESP atmospheres, Tinneti et al)
2008 – first unambiguous direct images (Kalas et al,
Marois et al) (probably other object a few years earlier)
2009 – launch of Kepler, 2 big esp results:
size distribution
multiple planet systems
(>50 HZ planets)
(but Kepler is transformational for stellar science)
2010 – first direct spectrum (Janson et al)
2011 – K22b?
Kepler is addressing important question – its prime science
driver is hÅ
But Kepler has raised many questions
for example:
1) Are planets with R~2RE terrestrial or ice/gas composition
2) Multiple planets eg Why are these systems so flat?
3) Small planets
Kepler has given an opportunity to look at architectures in a
new way - a field day for evolution and dynamics
New thinking/themes…
 Comparative planetology – tentative steps but
probably not for a few years for a more thorough
investigation. Diversity amongst small planets – Corot7b/K10 (Mercury like) and quite different to many of
the K11 components and GJ1214b
 Planet-star interactions and tidal interactions – the
Kepler data has made this a viable subject
 Planetary atmospheres – Kepler doesn’t help much,
but in the future we can imagine looking at ages of
planets (astroseismology) and atmospheric
composition – what will we find?
 Planets in different environments especially binary
systems and evolved stars
sampling long period
(relatively high mass) planets
 Exoplanet science is young – still in a
discovery/characterisation phase. Fundamental
discoveries are still being made – knowledge of ESP
atmospheres is at best rudimentary. Theorists need
more constraints.
 Exoplanet science, perhaps not unsurprisingly, driven
by technology developments (be it hardware or
sometime software (data analysis techniques)).
 But also creative thinking (which can happen at any
An Easy Way out – EPRAT 2010
Post 2020
Ambitious plans don’t last their
first clash with reality…
Big questions over this timescale
 What is the diversity and architecture of exoplanetary
systems as a function of stellar parameters and birth
What is the diversity of the internal structure of
What is the diversity of exoplanetary atmospheres?
What is the origin of the diversity and how do planets
What are the conditions for planet habitability, how
common is exo-life and can we detect the
Missing science
 Activity – we need to be much smarter in the way we
deal with this – it is vital to getting the most out of our
esp observations. This has implications – we have little
information about planets and early type stars, some
sketchy info on evolved stars. We need as many
“clocks” as we can get hold of.
 Formation – still missing an understanding of
conglomerates – maybe ALMA?
Looking forward
Discovery/Characterisation potential technology driven
2012-16 Kepler extended mission?
Kepler – looking forward
 Devils advocate: What more is Kepler going to deliver?
We already know ~ the frequency of terrestrial HZ
planets (or rather that’s hidden in the data), so why
bother? Is it really all about
 No matter what you think of the ESP future the stellar
astrophysics results will be transformational….
(no one has mentioned the heatbeat binaries – its so
Looking forward
Discovery/Characterisation potential technology driven
2012-16 Kepler extended mission?
2012-13 The start of “routine” direct imaging
Direct Imaging
 Planets are visible due to scattered starlight or because they are self
luminous. The planetary cross-section is small so that scattered
starlight is faint compared to host star (table in delta mags):
Ratio more favourable at IR wavelengths where planets can be self-luminous
(depending on temperature). Need to block light from host star (coronagraph).
• Resolution: as viewed from 10pc the Earth would be 0.1 arcsec and Jupiter
0.5 arcsec from the Sun. At 100 pc the separations are 10 and 50 milli-arcsec
respectively. Telescope resolution (in milli-arcsec) dependant on aperture and
10m Keck
42m ELT
Optical – resolution ok, contrast bad, IR – resolution worse, contrast better
Direct Ground based imaging
 Coronagraphic
 Large, young,
planets at 5AU
Drivers: high contrast 14-16 mags,
high angular resolution 0.1-3
arcsec, sensitivity down to V=10,
companions to H~24, spectral
resolution R~30
Looking forward
Discovery/Characterisation potential technology driven
2012-16 Kepler extended mission?
2012-13 The start of “routine” direct imaging
2013-18 Astrometry begins
Astrometric detection
Astrometric techniques aim to measure the transverse
component of the photocentric displacement. ‘Astrometric
Signature’ given by:
M* d
a PL Semi-major axis (AU),
d distance (pc)
Note – signature scales linearly with semi-major axis (ie better for
long period objects), compliments RV technique/transits which have
bigger signals at short periods.
Astrometric limit given by the non-uniformity of illumination over the stellar disk
eg in the case of the sun - a spot covering 1% of disk would cause the apparent
centre of the sun to shift by up to 0.005RSun (the wobble induced in the sun by
the Earth is has a maximum amplitude ~0.0003RSun).
Astrometric First Detections
VB10 (Pravdo & Shaklin 2009). Host star is
an extremely cool M dwarf
10yr of ground based measurements => 6
MJ companion in 0.74yr orbit
Not confirmed by recent results
Upcoming experiments
PRIMA/VLT (soon), ~30as
GAIA (launch 2012/3), ~10as
Maybe Sim(-lite) (2020? but not yet funded), 4as
Astrometric signal + RV => orbital plane etc 10as would enable the detection of
Jupiter’s to 240pc, Uranus’s to 44pc, Earth’s to 1.5pc
Looking forward
Discovery/Characterisation potential technology driven
2012-16 Kepler extended mission?
2012-13 The start of “routine” direct imaging
2013-18 Astrometry begins
2019 or 2024 EUCLID/WFIRST micrlensing
 First thing – I don’t believe EUCLID or WFIRST will
have a microlens programme. Its already not in the
EUCLID baseline, and I doubt WFIRST will even be
build. But there is good reason for a microlens survey:
it’s the easiest way to measure the frequency of
terrestrial sized bodies at large orbital periods. There
are many problems but this fact stands – there is a case
for a mission – we cannot sample this parameter space
by any other means
Looking forward
Discovery/Characterisation potential technology driven
2012-16 Kepler extended mission?
2012-13 The start of “routine” direct imaging
2013-18 Astrometry begins
2019 or 2024 EUCLID/WFIRST micrlensing
2019 JWST
Will be transformational
in many areas in
particular planet
formation and
coronagraphic imaging
Longer term
 Space Missions:
These are actively being studied and in competitions
TESS 2017 Explorer class. Bright star transit survey
(but the devil or rather the correlated noise is in the detail…)
FINESSE 2017 Explorer class. Hot-jupiter spectra
PLATO 2024? ESA M3? Bright star transit survey
ECHO 2024 ESA M3. Hot-jupiter, ice-giant, and
maybe a HZ planet spectra.
Whats happened to all the other
Darwin - interferometer
Sim(lite) – astrometry
TPF-C - coronagraph
TPF-I - interferometer
SEE-COAST – coronagraph
There are loads more – too many to list. Why have they fallen away?
Answ: mixture of immature technology and community infighting… <this is our biggest danger and stems from our diversity.
Is there one mission/concept addressing top level science that the ESP
community can gather behind?
Lets not forget ground based work
 RV surveys – ESPRESSO will be built and available
from 2015, HARPS-N in the next few weeks (primarily
Kepler followup)
 NGTS (I could ignore it)
 E-ELT? CODEX/AO Imaging
Lessons for young astronomers
 You need an angle – get attached to a project that will produce.
 Work on a significant problem.
 Look forward – try and gauge where the fun will be – right now
all the Kepler small planets are in Harvard…
 The next few years look to be difficult for PDRA positions – go
where the job is (WASP/UK students and PDRA’s are involved in
Kepler and other projects).
This is a fast moving, dynamic subject!
Stand backWe live at an extremely privileged time where the
dreams/thoughts from our ancestors are, for the first
time in reach.

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