Extra-terrestrial life:Extra-terrestrial life:Is there anybody out there?Is there anybody out there?……

SaturdaySept 24th

2005

Dr Martin HendryUniversity of Glasgow

“It’s life, Jim, and just as we know it…”

Water

Oxygen

CarbonDioxide

Mars 2004:Mars 2004: Mars Express ( + Beagle 2)

Spirit + Opportunity

SpectroscopySpectroscopy

Electron orbiting nucleus of atom absorbs light of the precise energy needed to make it jump to higher energy level.

Absorption Spectrum

Electron orbiting nucleus of atom absorbs light of the precise energy needed to make it jump to higher energy level.

Absorption Spectrum

Electron orbiting nucleus of atom absorbs light of the precise energy needed to make it jump to higher energy level.

Absorption Spectrum

Electron orbiting nucleus of atom absorbs light of the precise energy needed to make it jump to higher energy level.

Absorption Spectrum

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

Wavelength (microns)

Stre

ngth

of

abso

rpti

on

2004:

Mars Express Orbiter detects frozen water and carbon dioxide at the South Pole of Mars.

H2O CO2 Visible light

2mm

The moons of The moons of JupiterJupiter

Inside Europa

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

Exoplanets are ‘drowned out’ by their parent star. Impossible to image directly with current telescopes (~10m mirrors)…

Keck telescopeson Mauna Kea,Hawaii

1. How can we detect extra-solar planets?

They cause their parent star to ‘wobble’, as they orbit their common centre of gravity

1. How can we detect extra-solar planets?

They cause their parent star to ‘wobble’, as they orbit their common centre of gravity

Star + planet in circular orbit about centre of mass

Star + planet in circular orbit about centre of mass

Star + planet in circular orbit about centre of mass

Can see star ‘wobble’, even when planet is unseen.

But how large is the wobble?…

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 !!!

Suppose line of sight is in orbital plane

Direction to Earth

Direction to Earth

Suppose line of sight is in orbital plane

Star has a periodic motion towards and away from Earth

Star

Laboratory

51 Peg – the first new planetDiscovered in 1995

Doppler wobble

-1sm55v

What have we learned about exoplanets?Highly active, and rapidly changing, field

2000: 29 exoplanets

What have we learned about exoplanets?Highly active, and rapidly changing, field

2000: 29 exoplanets

2005: 136 exoplanets

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

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

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

The Search for Extra-Solar Planets

What (or who) will we find?…

This leads us to an interesting question:

This leads us to an interesting question:

Fermi’s Paradox:

“Where is Everybody?……”

“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

They are here and are meddling in Human affairsThey are here and are meddling in Human affairs

They were here, and left evidence of their presenceThey were here, and left evidence of their presence

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

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

They exist but have not yet communicatedThey exist but have not yet communicated

They stay at home…

They exist but have not yet communicatedThey exist but have not yet communicated

They stay at home…

…and surf the net

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