Methods for the detection of exosolar planets Astronomical Seminar January 2004 Erik Butz.
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Transcript of Methods for the detection of exosolar planets Astronomical Seminar January 2004 Erik Butz.
![Page 1: Methods for the detection of exosolar planets Astronomical Seminar January 2004 Erik Butz.](https://reader035.fdocuments.net/reader035/viewer/2022070412/56649ecf5503460f94bdc2f2/html5/thumbnails/1.jpg)
Methods for the detection of exosolar planets
Astronomical Seminar
January 2004
Erik Butz
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Overview Introduction Today‘s methods Future prospects Summary
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Introduction Big question of mankind:
Are we alone in the universe?
Many speculations: Mars, Venus and other planets in the solar system
Search for exosolar planets was hopeless for several centuries because of insufficient sensitivity of instrumentation and because of enormous distances
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Introduction 2 Key technique for first discoveries
developed by Christian Doppler in 1842:
c
v
Through shift in spectral lines, velocity of an object can be determined
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Introduction 3
1992 first planet around pulsar found (OBS! Not using radial velocity method!)
Pulsar timing: Systematic variation in arrival of pulsar pulses
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Introduction 4
1995 first planet around Main Sequence(MS) Star (51 Peg)
Since then: More than 110 planets found!
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Today‘s methods Several searches ongoing using
Radial Veclocity technique
Measurement of Doppler shift in the spectrum of the star due to gravitational influence of the planet.
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Planetary Doppler Shift 1
Source: www.Extrasolar.net
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Planetary Doppler Shift 2
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Planetary Doppler Shift 3
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Planetary Doppler Shift 4
Long struggle to reach sufficient sensitivities
Jupiter causes shift of 15 m/s
Compare to line-width ~km/s
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Planetary Doppler Shift 5
Breakthrough hoped for at 10 m/s
First groups were unlucky: Did not find planet with sensitivity
of 10 m/s 51 Peg: 50 m/s => would not have
been a problem
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Planetary Doppler Shift 6
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Planetary Doppler Shift 7 Todays precision: ~2 m/s
Compare to: Earth: 0.1 m/s
No Earth finder with present doppler methods!
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Planetary Doppler Shift 8 Advantages:
Enables finding of planet with comparably low effort
Can be used on smaller telescopes as well
Disadvantages: Deviation is ~MP => easier to find
larger planets and smaller periods =>shorter observation times
Due to orbital inclination no direct determination of MP
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Planetary Doppler Shift 9
Only determination of MP sin i
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Todays methods 2 Complementary searches using
astrometric measurements
Measurement of systematic variations of star position also because of gravitational influence of planet
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Astrometry 1 Star‘s apperent path due to planet
is ellipse with major half axis :
d
a
M
M P *
Effect is larger for nearby stars
If M*, a and d known: Determination of MP
Deviation for Jupiter in d ~ 10 pc is of order of milliarcsec or lower
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Astrometry 2
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Astrometry 3
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Astrometry 4 Problem: milliarcsec precision only
reached in radio
Hipparcos: ~1 milliarcsec
VLTI(not yet available): 10-100µarcsec
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Astrometry 5 Future: µarcsec astrometry possible,
but:
Earth moves sun about 500 km 0,03 %
Sunspots and other dynamic instabilities
0.5 %
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Today‘s methods 3
Luminosity variation during Transits of planets
Problems: Situation is highly improbableEffect is small:
Sun/Jupiter in 10 pc: ~2% (0.02m)
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Transits 1 Advantages:
Feasible with low effortCan be done with many stars in short time
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Transits 2
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Transits 3
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Future prospects
Imaging of planets in IR and VIS
Problems:
!!10~ 9
*
L
LP
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Interferometric imaging 1
Ratio in IR (i.e. at maxPlanet) 105 better
Furthermore: interferometry to further reduce starlight
Nulling interferometry: destructive interference at star position but not at planet position
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Summary Several methods
for discovery of exosolar planets
More then 110 planets found
Future methods will enable more discoveries and deeper investigation
With Transits:
Atmosphere‘s=>signatures of life
With extremely large(150 mirrors of 1 m 150 km baseline) space telescope
imaging on exosolar planets