1 Extrasolar Planets and the Search for Other Earths A drought of planetary discovery (until recently) Why should we expect to find other worlds? How we found the thousands of worlds we now “know” Why we haven't yet seen another of these worlds (maybe one or two) How we WILL see them soon? How UVa is involved? Can we find other Earth-like worlds? Will we be able to detect life elsewhere?
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Extrasolar Planets and the Search for Other Earths · Extrasolar Planets and the Search for Other Earths A drought of planetary discovery (until recently) Why should we expect to
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Extrasolar Planets and the Search for Other Earths
A drought of planetary discovery (until recently)
Why should we expect to find other worlds?
How we found the thousands of worlds we now “know”
Why we haven't yet seen another of these worlds
(maybe one or two)
How we WILL see them soon?
How UVa is involved?
Can we find other Earth-like worlds?
Will we be able to detect life elsewhere?
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A Legacy of Extrasolar Planetary Expectations
35+ years ago in a Galaxy close to home....
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Why Should We Expect to Find Other Planets?
Planetary system formation is a natural by-product of star formation
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Why Should We Expect to Find Other Planets?
The planets grew via “accretion” - a process common to all forming stars.
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Why Should We Expect to Find Other Planets?
We see stars forming elsewhere.
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Why Should We Expect to Find Other Planets?
These forming stars are surrounded by flattened disks of dust and gas.... just what we expect!
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So Where Are All of These Planets?
We live in a Galaxy, the Milky Way, that contains ~100 billion stars.
Until 1995 there was no direct evidence for planets outside of the Solar System!
Since we've been using telescopes since the early 1600's you would think it should have been easier.
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Hide and Seek?
Stellar “glare” hides the planets (which are more than a billion times fainter than their star) from view.
– - This unwanted light is a consequence of the starlight being diffracted by and scattering within the telescope.
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Hide and Seek?
Stellar “glare” hides the planets (which are more than a billion times fainter than their star) from view.
– - This unwanted light is a consequence of the starlight being diffracted by and scattering within the telescope.
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Two Indirect Detection Techniques
1) Doppler Wobble
The planet swings the star around as it orbits.
We measure the velocity of the star using the Doppler shift.
» Jupiter's motion displaces the Sun roughly by the Sun's diameter (once every 12 years - a Jupiter year)
» If viewed from a nearby star this motion is equivalent to reading the date on a dime held at a distance of 10 miles.
» This motion shifts the Sun's velocity by about 20 meters per second (the equivalent of the shift in the pitch of sound produced by an object moving at one inch every hour)
» This technique works best if
– - the planet is quite massive (super-Jupiters)
– - the planet is quite close to its star
• - big velocity shift and very short orbital period
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Two Indirect Detection Techniques
1) Doppler Wobble
The planet swings the star around as it orbits.
We measure the velocity of the star using the Doppler shift.