Subaru Planet searchextrasolar planets
extrasolar planets
12:00 July 23, 2004, Planetary science seminar University College London
12:00 July 23, 2004, Planetary science seminar University College London
Department of Physics, University of Tokyo Yasushi Suto
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Search for Search for extrasolarextrasolar planets planets the goal: the goal: Are we alone ?Are we alone ?
origin of the earthorigin of the earth origin of the Solar Systemorigin of the Solar System habitablehabitable planets planets ⇒⇒ origin of life origin of life signature of signature of extraextra--terrestrial lifeterrestrial life ?? extraextra--terrestrial intelligence ?terrestrial intelligence ?
P. Ulmschenider: “Intelligent Life in the Universe” (Springer 2003)
“Where are they ?” E.Fermi (1950)
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Why Why extrasolarextrasolar planets planets nownow ?? directly related to directly related to one of the most one of the most fundamental questionsfundamental questions
origin of lifeorigin of life Just startedJust started
first discovery in 1995 ! first discovery in 1995 ! easier to convince taxpayerseasier to convince taxpayers
other sciences became too detailed or too other sciences became too detailed or too matured to achieve really fundamental matured to achieve really fundamental contributioncontribution
Very few experts in this field, and quite Very few experts in this field, and quite interdisciplinaryinterdisciplinary
whatever experts in physics, planetary science, whatever experts in physics, planetary science, astronomy, geology, climate, and biology are astronomy, geology, climate, and biology are welcome to join in many respectswelcome to join in many respects
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Direct imaging ?Direct imaging ? Jupiter at a distance of 10 pc Jupiter at a distance of 10 pc
visual magnitude: 27mag angular distance from the star
0.5arcsec ×10-9
0.5 arcsec
X10-9-10
need to detect a 10-9 times darker object than the main star which locates within a typical seeing scale of the ground observation !
⇒ Just impossible⇒ Just impossible
Gliese229 b: angular
separation 7 arcsec
luminosity ratio 5000
(T.Nakajima)
Jupiter seen at a distance of 10pc : Jupiter seen at a distance of 10pc : 14 times closer to the star !14 times closer to the star !
1/200,000 darker !1/200,000 darker !
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Radial velocity of a star perturbed by a planetRadial velocity of a star perturbed by a planet
Even if a planet is not directly observable, its presence can be inferred dynamically
velocity modulation of the Sun:
12.5 m/s Jupiter 0.1 m/s Earth
an accuracy of 3m/s achieved from the ground observation ⇒ the current major method in search for Jupiter-sized planets
an accuracy of 3m/s achieved from the ground observation ⇒ the current major method in search for Jupiter-sized planets
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radial velocity measurement with I2-cell Absorption lines of IAbsorption lines of I22 as as accurate standard rulersaccurate standard rulers Accuracy Accuracy 3m/s3m/s achievedachieved
I2-cell HD209458
HD209458+I2cell
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http://hubblesite.org/newscenter/archive/2001/38/
Variation: 1%(Rplanet/RJupiter)2(RSun/Rstar)2
from the ground: 0.1% OK for Jupiter, but not for Earth
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planet searchplanet search
Precise mass since inclination angle is determined (only observable for edge-on system: inclination ~ 90 deg.) size of the planet can be estimated complementary to the radial velocity method Low probability:
10% (0.05AU/aorbit)(Rstar/RSun
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A brief history of the discovery A brief history of the discovery of of extrasolarextrasolar planetsplanets
1995 : the first extrasolar planet around the main sequence star 51 Pegasi (Mayor & Quelos) 1999 : transit of a known planet around HD209458 (Charbonneau et al., Henry et al.) 2001 : discovery of Na in the atmosphere of HD209458b 2003 first discovery of a planet by transit method alone (1.2 day orbital period: OGLE) 123 extrasolar planets are reported (July 8, 2004)
http://exoplanets.org/
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51 51 PegasiPegasi b: the first discovered b: the first discovered planet around a mainplanet around a main--sequence starsequence star
discovered from the periodic change of the radial discovered from the periodic change of the radial velocity of the central star (Mayor & velocity of the central star (Mayor & QuelozQueloz 1995)1995)
P=4.2 days !P=4.2 days !
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the first discovery of the transit the first discovery of the transit of a planet: HD209458of a planet: HD209458
detected the light curve detected the light curve change at the phase change at the phase consistent with the radial consistent with the radial velocity velocity (Charbonneau et al. (Charbonneau et al. 2000, Henry et al. 2000) HST 4 orbits2000, Henry et al. 2000)
Ground observation (2000)
Estimated parameters of HD209458bEstimated parameters of HD209458b
First ever convincing evidence for the case First ever convincing evidence for the case of an of an extrasolarextrasolar planet !planet ! MMpp=0.63 M=0.63 MJJ, , RRpp=1.3 R=1.3 RJ J
ρρ=0.4 g/cm=0.4 g/cm33 < < SaturnSaturn’’s densitys density Gas planet ! (not black hole, rock Gas planet ! (not black hole, rock ……)) =970 cm/s=970 cm/s22
HD209458 G0V V=7.58 (d=47pc) HD209458b Orbital Period 3.52474 ± 0.00004 days
viewing angle 86.68±0.14 deg Mass 0.63 MJupiter Size 1.347±0.060 RJupiter
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First detection First detection of atmospheric of atmospheric absorption of absorption of HD209458bHD209458b with HSTwith HST
http://hubblesite.org/ newscenter/archive/
Nov. 2001: additional sodium absorption during the transiting phase (Charbonneau et al. 2002)
The first detection of atmosphere of an extrasolar planet
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G eocoron
Unexpectedly large amount of Lyαabsorption (15%)
⇒ evaporating neutral hydrogen cloud
“Spectro-photometric search for scattered light from HD209458b”
S02B-16 on October 24 and 26, 2002 Yasushi Suto, Norio Narita (Univ. of Tokyo) Toru Yamada, Wako Aoki (National Ast. Obs. Japan) Bun-ei Sato (Kobe Univ.)
Edwin L. Turner , Brenda Frye (Princeton Univ.) Josh Winn (Harvard Univ.)
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Search for the planetary atmosphere from the ground observation
HHαα absorption analysis completed; upper limit absorption analysis completed; upper limit 0.1%0.1% Winn et al. Winn et al. 20042004 PASJ, in pressPASJ, in press (astro(astro--ph/0404469)ph/0404469) Analysis of other lines in progress (Narita et al. 2004)Analysis of other lines in progress (Narita et al. 2004)
Constraining the stellar spin and the planetary orbital axes from the Rossiter-McLaughlin effect
New analytic formulae (New analytic formulae (OhtaOhta, , TaruyaTaruya & & SutoSuto 2004)2004) Analysis in preparation (Narita et al. 2004)Analysis in preparation (Narita et al. 2004)
Search for reflected light from planets Just started collaboration with a group in UK ! Just started collaboration with a group in UK ! St. Andrews University (A. Cameron, C. Leigh)St. Andrews University (A. Cameron, C. Leigh)
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Orbital phase and radial velocity of HD209458b in our observing run
Subaru/HDS
Winn et al. (2004) PASJ, in press. astro-ph/0404469
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HD209458b
4861.344861.34HHββ
6562.816562.81HHαα
4340.484340.48HHγγ
Hα
2020
The most stringent upper limit on the Hα absorption in the atmosphere of HD209458b
Hα fractional absorption
HHαα absorption <0.1% (Winn et al. 2004)absorption <0.1% (Winn et al. 2004) LLαα absorption=15% (Vidalabsorption=15% (Vidal--Madjar et al. 2003)Madjar et al. 2003)
TTexcitationexcitation< (0.6< (0.6--1.3)eV (1.3)eV (heavilyheavily modelmodel--dependent)dependent)
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The Rossiter-McLaughlin effect During a transit of a planet, flux from a part of stellar surface is blocked which induces a time- dependent asymmetry in the stellar Doppler broadened line profile. This produces an apparent anomaly of the stellar radial velocity.
originally discussed in eclipsing binary systems (Rossiter 1924; McLaughlin 1924)
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Origin of angular momentum
out of transit
Stellar rotation and planetary orbit Queloz et al. (2000) A&A 359, L13
ELODIE on 193cm telescope
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Analytic templates for the velocity anomaly due to the Rossiter -McLaughlin effect
ε=0.64
Subaru/HDS error-bar
ε=0
Subaru/HDS error-bar
Limb darkening: B= 1- ε (1-cos θ) (Semi)-analytic template curves (Ohta, Taruya & Suto 2004)
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Search for scattered light from HD209458bSearch for scattered light from HD209458b
Statistical search Statistical search for the scattered for the scattered components components DopplerDoppler--shifted at shifted at vvpp(t) from the (t) from the stellar absorption stellar absorption lines.lines. The spectral The spectral resolution of HDS resolution of HDS ((λ /λλ /λ=50000) is =50000) is 10 times better 10 times better than that of STIS, than that of STIS, HST (HST (λ /λλ /λ=5540).=5540).
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A possible roadmap of A possible roadmap of sciences of sciences of extrasolarextrasolar planetplanet
Discovery phase of gas giant planetsDiscovery phase of gas giant planets Discovery phase of planetary atmosphereDiscovery phase of planetary atmosphere Detailed spectroscopic study of planetsDetailed spectroscopic study of planets Discovery of terrestrial planetsDiscovery of terrestrial planets Identifying BiomarkerIdentifying Biomarker
RedRed--edge of edge of extrasolarextrasolar plant ?plant ? Discovery of Habitable planetDiscovery of Habitable planet Discovery of Extraterrestrial lifeDiscovery of Extraterrestrial life
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Astrobiology ? Not yetAstrobiology ? Not yet Discovery of Discovery of extrasolarextrasolar planets is a wonderful planets is a wonderful breakthrough in astronomy (and philosophy, maybe)breakthrough in astronomy (and philosophy, maybe)
But mere discovery has no biological informationBut mere discovery has no biological information
How can we identify the signature of life ? How can we identify the signature of life ? BiomarkerBiomarker
Suppose our earth is Suppose our earth is located at 10pc away. Can located at 10pc away. Can we identify any signature we identify any signature of life from photometric of life from photometric and spectroscopic data and spectroscopic data alone ?alone ?
EarthEarth--shineshine http://modarch.gsfc.nasa.gov/ http://www.nasa.gov/home/index.html
Red edgeRed edge of ((extrasolarextrasolar) plants: ) plants: a biomarker in extrasolarextrasolar planetsplanets
Significant reflectivity Significant reflectivity of leaves of terrestrial of leaves of terrestrial planets for planets for λλ>7000>7000
An interesting (maybe An interesting (maybe unique) candidate for unique) candidate for a biomarker ?a biomarker ?
extrasolarextrasolar plantsplants as as a biomarker in a biomarker in extrasolar planets Seager, Ford & Turner
Reflection spectrum of leaves
Chlorophyll A Chlorophyll B
Discovered redshifts of “spiral nebulae” now known as galaxies Essential contribution for Hubble’s discovery of expanding universe
“Observations of Mars in 1924 made at the Lowell Observatory: II
spectrum observations of Mars’’ PASP 36(1924)261
Red-edge as a biomarker (at least) in 1924 !
Astrobiology indeed in 1924 ! Astrobiology indeed in 1924 !
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Expected daily change of the reflected light from the earth
Ford, Seager & Turner: Nature 412 (2001) 885
Assume that the earth’s reflected light is completely separated from the Sun’s flux !
TPF (Terrestrial Planet Finder) in (1020) years from now ?
Periodic change of 10% level due to different reflectivity of land, ocean, forest, and so on Cloud is the most uncertain factor: weather forecast !
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Earthshine observationEarthshine observation Spectroscopic observation of dark side of the Spectroscopic observation of dark side of the MoonMoon the red edge in the scattered light from the earth the red edge in the scattered light from the earth can be identified ?can be identified ? Simulated spectroscopic observation of the earth Simulated spectroscopic observation of the earth at several pc awayat several pc away
Sunlight
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a previous attempt of earthshine spectroscopy: red-edge in a pale blue dot ?
refectivity
Woolf & Smith ApJ 574 (2002) 430
“The spectrum of earthshine: A Pale Blue Dot Observed from the Ground”
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http://www.kepler.arc.nasa.gov/
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infra-red space interferometry: imaging and spectroscopy
http://ast.star.rl.ac.uk/darwin/
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Gas planets: from discovery phase to “characterization” phase
Understand origin, formation and evolution
Discovery of terrestrial planets Discovery of habitable planets
Liquid water
Ultra-precise spectroscopy Separate the planetary emission/reflection/absorption spectra from those of stars
How to convince ourselves of the presence of life simply from remote
observations ? Biomarker !!!
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Thanks !
This presentation PDF file is located atThis presentation PDF file is located at
http://wwwhttp://www--utap.phys.s.uutap.phys.s.u--tokyo.ac.jptokyo.ac.jp /~suto/mypresentation_2004e.html/~suto/mypresentation_2004e.html
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CCD: 4.1k x 2k x 2 13.5µm/pixel, 0.12”/pixel
Gain: 1.7e-/ADU Readout time: 70sec Saturation level: 50000e-
λ /λ=50000
Hα
Wavelength []
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Deep Transit Search with Subaru Deep Transit Search with Subaru SuprimeSuprime CamCam The first attempt of deep transit planet search with The first attempt of deep transit planet search with Subaru 8m telescope + wideSubaru 8m telescope + wide--field camera (field camera (SuprimeSuprime-- Cam) on September 27 and 28, 2002Cam) on September 27 and 28, 2002 T.Yamada (P.I: NAOJ), T.Yamada (P.I: NAOJ), Y.SutoY.Suto (co.I.: U.Tokyo), (co.I.: U.Tokyo), E.L.Turner (co.I: Princeton U.), et al.E.L.Turner (co.I: Princeton U.), et al.
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dadRdRmTtP a RRaRPRNN porbitTvisppp *
probability that stars with radius R* have
planets with radius Rp and semi-major axis a
geometrical probability
for the transit
visibility of transit for a system with orbital period Torbit, transit
duration tT, transit depth dm=2.5log(1+Rp
2/R* 2)
Expect to have ~10 transit candidates Expect to have ~10 transit candidates by monitoring 10000 stars (per night , by monitoring 10000 stars (per night , most optimistically) !most optimistically) !
Photometric followPhotometric follow--up with APO 3.5mup with APO 3.5m Spectroscopic followSpectroscopic follow--up with Subaru HDS up with Subaru HDS
Searching for the atmospheric signature of transiting extrasolar planets
Search for extrasolar planets
Why extrasolar planets now ?
Radial velocity of a star perturbed by a planet
radial velocity measurement with I2-cell
Stellar light curve variation due to planetary transit
Transit method for the extrasolar planet search
A brief history of the discovery of extrasolar planets
51 Pegasi b: the first discovered planet around a main-sequence star
the first discovery of the transit of a planet: HD209458
Estimated parameters of HD209458b
HD209458bevaporating planet ?
On-going three projects with HDS
Orbital phase and radial velocity of HD209458b in our observing run
search for Hα absorption due to the atmosphere of HD209458b
The most stringent upper limit on the Hα absorption in the atmosphere of HD209458b
The Rossiter-McLaughlin effect
Spectroscopic transit signature: the Rossiter-McLaughlin effect
Analytic templates for the velocity anomaly due to the Rossiter -McLaughlin effect
Search for scattered light from HD209458b
A possible roadmap of sciences of extrasolar planet
Astrobiology ? Not yet
Red edge of (extrasolar) plants: a biomarker in extrasolar planets
Vesto Melvin Slipher (1875-1969)
Expected daily change of the reflected light from the earth
Earthshine observation
a previous attempt of earthshine spectroscopy: red-edge in a pale blue dot ?
Kepler (NASA: launch 2008?)
Prospects in the 21st century: from astronomy to astrobiology
Thanks !
HD209458 Subaru/HDS spectrum
expected number of transits