lecture 1: introduction & methods 1.introduction 2.techniques for discovery & study 3.the...
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Lecture 1: Introduction & Methods
1. Introduction2. Techniques for discovery & study3. The NASA Kepler mission
Planetary Systems Orbiting Diverse Stars
Where do we stand today?
• Total: 330+ ( 31 systems) discovered to-date
• Statistics:• Gas giant planets, like Jupiter & Saturn,
exist around >12% of stars (Marcy et al.);
• Lower-mass planets (Super-Earths, ~12 known to-date)
are more common (Mayor et al.);
• No Earth-like planets yet …
Planets Known to Orbit Other Stars:
Small stars, Brown dwarfs, & planets
Bur
row
s 20
00)
Evolution of luminosity with time for different masses
Properties of planets & small stars
Models: Baraffe et al. four different ages: 0.5, 1, 3, & 5 Gyr
Red: Pont et al. (2005) OGLE-TR-122
The Planets of our Solar System
New types ofplanets:
Hot Jupiters
Super-Earths
(Sasselov 2008)
Super-Earths
Mass range:~1 - 10 Earth mass
“Confusion region”
The super-Earths M-R diagram
Fix one ratio: Earth-like
Fe/Si
max radius
min
radius
H2O
Valencia, Sasselov, O’Connell (2007)
Super-Earths:excellent homesfor life
(Sasselov 2008)
Imag
e: S
.Cun
diff
Techniques for discovery: Star-to-planet inequalities
• In light: 1010 (optical) to 107 (infrared)
• In mass: 105 to 103
• In size: 102 to 10.
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Exoplanet discovery space:2007 & looking forward
Planned Kepler space mission:may detect Earth-like planets,
but measure only size, not mass
Pla
net
Mas
s
Direct Detection of Planets
• Direct detection is challenging because of the technicallimits oftelescopicobservations
Direct Detection of Planets
• Three planetsorbiting HR8799
…if star’s ageis < 300 Myr
(Marois et al. 2008)
Direct Detection of Planets
• There maybe more planets,but more obs neededto confirm even thisone.
(Kalas et al. 2008)
Radial Velocities (Doppler method): Discovery & Mass measurement
Radial velocities seenin star HD 209458 -the variation is dueto a planet that is lessmassive than Jupiter.
(Mazeh et al. 1999;Marcy et al. 2000)
HD 209458b: a Hot Jupiter
The HARPS planet-search program ESO 3.6 – La Silla- Geneva Observatory
- Physikalisches Institut, Bern- Haute-Provence Observatory- Service d’Aeronomie, Paris- ESO
1 m/s
(from C. Lovis)
HD 40307
HARPS-N Spectrometer on WHT
HARPS-NEF: Harvard Origins Initiativewith Obs. Geneve on the William Herscheltelescope (WHT), Canary Islands
A HARPS clone,but for severalimprovements…
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Summer 07: Ti:sapphire femtosecond laser comb
Fall 2007: characterize with astro spectrograph
2008: develop high-rep ratecomb for astro applicationsand demo on mountain-top
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2009: Optimized system for1 cm/s Doppler shift precision
Harvard/Smithsonian/MIT astro-comb project
Li et al. (2008, Nature, April)
Transits: A Method for Planet Discovery & Study
Transit Measurements
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Transit & eclipse of HD189733b
Heather Knutson & Dave Charbonneau (2007)
OGLE-TR-113b
Transit Light Curve
Doppler Shift
Konacki, Torres,Sasselov, Jha (2004)
The HAT Network: FLWO Mt.Hopkins Arizona… and Hawaii Mauna Kea
(Bakos et al. 2009)
We have discovered >11 new planets with it in 2 years.
What can we learn from transiting extrasolar planets
HD 209458b: Dimming of light due to transit, observed with HST.
Brown, Charbonneau, Gilliland, Noyes, Burrows (2001)
Tells usDIRECTLY:Planet radius,
INDIRECTLY:Planet densityPlanet composition
Illustration of high precision: (RP)~3%
Transits of exoplanets from Hubble:
Brown et al. (2006)
Lig
ht
Flu
x
Time
TrES-1
HD 209458Spot
Mass-RadiusDiagram:
Hot Jupiters
Super-Earths
(Sasselov 2008)
A New super-Neptune: HAT-P-11b
Bak
os, N
oyes
, Pal
, Lat
ham
, Sas
selo
v et
al.
(200
9)
Transit & eclipse of HD189733b
Heather Knutson & Dave Charbonneau (2007)
Spectrum for HD 189733bObtained by transit transmission & eclipse emission
Wavelength
Inve
rse
Res
idua
l Flu
x
New 2 m Spectrum for HD 189733b
(Sw
ain
et a
l. 2
008)
NASA Kepler mission: transit search for planets
Cygnus / Lyra
(RA=19h23m, Dec=44.5d)
Completing the Copernican Revolution:the discovery of “New Earth”
NASA Mission - Mar. 2009
Kepler is ready to launch:
Mar. 5, 2009
Assembly at Ball Aerospace
Kepler expected yields: ~ 500 super-Earths, ~ 50 Earth analogs;
(5-10% good radii)
The “PROBLEM” with KEPLER:
not able to get data on masses forsmall planets - reflex amplitudes will be less than 30 cm /sec.
SOLUTION: build a novel Doppler instrument to fit on a large telescope. Use it to measure masses, and hence mean densities for KEPLER’s best candidate Earths & super-Earths!
HARPS-N Spectrometer
Synergy with Kepler:
Provide ability to reach RV amplitudes of about 10 cm /sec.
Given Porb and phase from transit,this can translate to 10% massesin the Super-Earth and Earthsregime.
HARPS-N by Harvard - Geneva on the William Herschel telescope (WHT), Canary Isl.
HARPS-N Spectrometer on WHT
HARPS-NEF: Harvard Origins Initiativewith Obs. Geneve on the William Herscheltelescope (WHT), Canary Islands
A HARPS clone,but for severalimprovements…
QuickTime™ and a decompressor
are needed to see this picture.
Some Conclusions:
1. Extrasolar Earths - a worthy (and historic) goal: • help us understand planet formation in general• help us constrain pre-biotic chem / pathways to life
2. We now have the tools - to discover & study: • Transits (Kepler), spectrograph (astro-comb)
Super-Earths
Mass range:~1 - 10 Earth mass
“Confusion region”
Super-Earths as proxies for EarthHow to distinguish mini-Neptune from super-Earth:
< Three types of atmospheres
(Miller-Ricci, Seager,Sasselov 2008)
Super-Earths as proxies for EarthHow to distinguish mini-Neptune from super-Earth:
(Mill
er-R
icci
, Sea
ger,
Sas
selo
v 2
008)