Extrasolar%20Planets

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Extrasolar Planets
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Some prehistory

• Absence of evidence clearly was not evidence of
  absence planets dim and situated next to
  brilliant stars
• Laplace and Kant ideas had vastly different
  implications
• (Dont fixate yet on possible habitats!)

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History

• 1952 Struve proposes radial-velocity search
• 1963-9 van de Kamp, Barnards Star astrometry
• 1990- HST FGS astrometry
• 1994 Wolszczan first pulsar planets!
• 1995 Queloz/Meyor 51 Peg hot Jupiter
• 1995- Marcy/Butler/Fisher team
• Now 155 planets from radial velocities
• Neptunes and smaller

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Otto Struve, The Observatory, Oct 1952
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40 years of devilish details

• Mechanical stability of spectrographs need
  measurement series of parts per billion accuracy
  spanning years
• Software to unravel subtle atmospheric and
  instrumental effects
• Who knew there would be planets a hundred times
  easier to find than Jupiter?

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155 worlds and counting
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More heavy elements more planets
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What we know and dont

• Metal-rich stars have more planets
• Many orbits are very eccentric
• Multiplanet systems exist
• Some binary/triple stars keep close planets
• Just now getting to Neptune-mass planets
• Terrestrial extrasolar planets still only inferred

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More techniques

• Transit photometry
• Dynamics of dusty rings (exo-Kuiper belts)
• Gravitational lensing
• Interferometry imaging and astrometry
• Coronagraphy

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Transit detections

• Edge-on orbits
• Favors large and close-orbiting planets
• Can survey large numbers of stars at once
• Statistics if not targeted stars systems
• Followup of Doppler planets sizes, rings,
  evaporating atmospheres, temperatures

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Transit variations
Doppler shift
Brightness
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Sizes of giant planets
(ESO)
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Hubble and the evaporating atmosphere of HD
209458b
Vidal-Madjar et al. 2004
We see H,C,O,Na on the way out (its hot)
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Spitzer and planet temperatures
TrES-1, Charbonneau et al. AstrophysJ 2005
Do this at multiple wavelengths and get a crude
planetary spectrum
HD 209458, Deming et al. Nature 2004
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Places we dont see transits
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More transits

• STARE/Sleuth/Sherlock
• OGLE, other microelensing surveys
• MOST? (CSA)
• Kepler (NASA)
• COROT (CNES)
• Eddington (ESA)

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Planets decenter and warp rings
b Pictoris
a PsA Fomalhaut
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Gravitational lensing

• General relativity a distant mass can
  concentrate light
• Star-star microlensing is seen if we watch enough
  stars (millions)
• Planets at the right place have a distinct
  signature, now seen
• Existing data precise enough to have shown
  terrestrial-mass planets

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Star-star microlensing
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Now add a planet
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Lensing planet around OGLE-2005-BLG-71
Udalski et al., OGLEMOA teams, June 2005. Note
need for rapid response!
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Enter Interferometry

• Classic problems stellar glare, atmospheric blur
• Even HST doesnt quite (yet?) separate planets
  reflected light from stars
• Combining separated telescopes can help, both in
  resolution and by nulling out most of the
  starlight.
• Optical-wavelength interferometry is technically
  challenging. For real.

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Interferometers

• CHARA, COAST, NPOI (mostly stellar)
• Palomar testbed
• Keck
• ESO VLT
• Into space SIM, TPF-I, Darwin
• What Goldin had in mind that would be tears

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Palomar Testbed Interferometer
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Terrestrial Planet Finder (TPF)aka Planetquest
Just like the name says
One element or many? Yes
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ESAs Darwin breaks the chains
Interferometer of free-flying 3m telescopes
(2015?) Identify and characterize nearby
terrestrial worlds.
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TPF-I

• Look in IR, where contrast is best
• Need some spectral resolution anyway same
  detectors would see atmospheric absorption from
  free oxygen (O2 and O3), CO2
• Amount of exo-zodiacal dust is crucial
• May need to be at Jupiters distance, plus
  cryogenically cool 4x1.5m telescopes

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Looking far ahead TPI

• Terrestrial Planet Imager
• Multiple free-flying telescopes, precisely
  controlled for beam combination
• Example five four-telescope interferometers (8m
  each), hundreds of km apart
• Goal many resolution elements across disk of
  planets found by TPF

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Amateurs get into the game!

• t Bootis planet detected spectroscopically with
  16 telescope and fiber-optic spectrograph (Tom
  Kaye et al., www.spectrashift.com)
• Key lensing observations of star/planet system by
  two New Zealand amateurs (Grant Christie, Jennie
  McCormick) with 10-14 telescopes

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Even multiple-star systems

• 55 Cancri, 16 Cygni, g Cephei (hints from 1992
  data!) have planets, are in wide binaries
  (compared to planet orbits, anyway)
• Simulations planets within 3 AU of a Centauri
  components would still be stable
• Formation?!?

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Multiple-planet systems
How many ways can giant planets form?
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SuperJovians or brown dwarfs?
ESO VLT HST
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History of planetary systems

• Dynamics, TNOs imply early evolution of orbits in
  solar system
• Disk interactions predicted hot Jupiters!
• Resonances imply ongoing interaction in other
  systems
• Not particularly aligned with Milky Way
• Pulsar planets may be reborn systems

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Implications for exobiology bioastronomy
astrobiology life-bearing planets

• Many sunlike stars have giant planets the more
  metal-rich the better
• Many of these are in places hostile to
  terrestrial planets
• Moons may offer rich pickings, opening up faint,
  cool stars for habitable zones
• Interstellar probes can start with significant
  knowledge of the target systems

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p.s. we still apparently dont know all the solar
planets