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Extra-terrestrial life:Extra-terrestrial life:Is there anybody out there?Is there anybody out there?……
SaturdaySept 24th
2005
Dr Martin HendryUniversity of Glasgow
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“It’s life, Jim, and just as we know it…”
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Water
Oxygen
CarbonDioxide
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Mars 2004:Mars 2004: Mars Express ( + Beagle 2)
Spirit + Opportunity
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SpectroscopySpectroscopy
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Electron orbiting nucleus of atom absorbs light of the precise energy needed to make it jump to higher energy level.
Absorption Spectrum
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Electron orbiting nucleus of atom absorbs light of the precise energy needed to make it jump to higher energy level.
Absorption Spectrum
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Electron orbiting nucleus of atom absorbs light of the precise energy needed to make it jump to higher energy level.
Absorption Spectrum
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Electron orbiting nucleus of atom absorbs light of the precise energy needed to make it jump to higher energy level.
Absorption Spectrum
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Electron orbiting nucleus of atom absorbs light of the precise energy needed to make it jump to higher energy level.
Absorption Spectrum
This energy is now missing from the spectrum of light:
Dark Absorption Line
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Wavelength (microns)
Stre
ngth
of
abso
rpti
on
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2004:
Mars Express Orbiter detects frozen water and carbon dioxide at the South Pole of Mars.
H2O CO2 Visible light
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2mm
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The moons of The moons of JupiterJupiter
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Inside Europa
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The stars are VERY far away. The nearest star (after the Sun) is about 40 million million km from the Earth. It takes light more than 4 years to travel this distance..
If the distance from the Earth to the Sun were the width of this screen, the nearest star would be in Nashville !!!!
The search for extra-solar planetsThe search for extra-solar planets
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Exoplanets are ‘drowned out’ by their parent star. Impossible to image directly with current telescopes (~10m mirrors)…
Keck telescopeson Mauna Kea,Hawaii
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1. How can we detect extra-solar planets?
They cause their parent star to ‘wobble’, as they orbit their common centre of gravity
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1. How can we detect extra-solar planets?
They cause their parent star to ‘wobble’, as they orbit their common centre of gravity
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Star + planet in circular orbit about centre of mass
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Star + planet in circular orbit about centre of mass
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Star + planet in circular orbit about centre of mass
Can see star ‘wobble’, even when planet is unseen.
But how large is the wobble?…
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Star + planet in circular orbit about centre of mass
Can see star ‘wobble’, even when planet is unseen.
But how large is the wobble?…
e.g. ‘Jupiter’ at 30 l.y.
= one three millionth of the width of the Full Moon !!!
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Suppose line of sight is in orbital plane
Direction to Earth
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Direction to Earth
Suppose line of sight is in orbital plane
Star has a periodic motion towards and away from Earth
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Star
Laboratory
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51 Peg – the first new planetDiscovered in 1995
Doppler wobble
-1sm55v
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What have we learned about exoplanets?Highly active, and rapidly changing, field
2000: 29 exoplanets
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What have we learned about exoplanets?Highly active, and rapidly changing, field
2000: 29 exoplanets
2005: 136 exoplanets
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What have we learned about exoplanets?Highly active, and rapidly changing, field
2000: 29 exoplanets
Up-to-date summary at
http://www.exoplanets.org
Now finding less massive planets further from their parent star
2005: 136 exoplanets
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4. NASA: Terrestrial Planet Finder ESA: Darwin
Looking to the Future
}~ 2015 launch
These missions plan to use interferometry to ‘blot out’ the light of the parent star, revealing Earth-mass planets
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4. NASA: Terrestrial Planet Finder ESA: Darwin
Looking to the Future
}~ 2015 launch
Spectroscopy will search for signatures of life:-
Spectral lines of oxygen, watercarbon dioxide in atmosphere?
Simulated ‘Earth’ from 30 light years
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The Search for Extra-Solar Planets
What (or who) will we find?…
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This leads us to an interesting question:
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This leads us to an interesting question:
Fermi’s Paradox:
“Where is Everybody?……”
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“Where is Everybody?”
by Stephen Webb(Praxis, 2002)
Fifty solutions to the Fermi Paradox and the problem of extraterrestrial life:
o They are here
o They exist but have not yet communicated
o They do not exist
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They are here and are meddling in Human affairsThey are here and are meddling in Human affairs
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They were here, and left evidence of their presenceThey were here, and left evidence of their presence
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Voyager 1 would take ~75000 years to reach Proxima Centauri……
They exist but have not yet communicatedThey exist but have not yet communicated
The stars are very far away / they have not had time to reach us
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They exist but have not yet communicatedThey exist but have not yet communicated
The stars are very far away / they have not had time to reach us
Voyager 1 would take ~75000 years to reach Proxima Centauri……
……but this is less than 100,000th of the age of the Galaxy
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They exist but have not yet communicatedThey exist but have not yet communicated
They stay at home…
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They exist but have not yet communicatedThey exist but have not yet communicated
They stay at home…
…and surf the net
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They exist but have not yet communicatedThey exist but have not yet communicated
They are signalling but we don’t know how to listen
The ‘Waterhole’: strong H and OH emission between 1.42 GHz and 1.64 GHz
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