Extra-terrestrial life: Is there anybody out there?… Saturday Sept 24 th 2005 Dr Martin Hendry University of Glasgow
“It’s life, Jim, and just as we know it…”
Water Oxygen Carbon Dioxide
Mars 2004: Mars Express ( + Beagle 2) Spirit + Opportunity
Spectroscopy
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) Strength of absorption
2004: Mars Express Orbiter detects frozen water and carbon dioxide at the South Pole of Mars. H2OH2O CO 2 Visible light
2mm
The moons of Jupiter
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 planets
Exoplanets are ‘drowned out’ by their parent star. Impossible to image directly with current telescopes (~10m mirrors)… Keck telescopes on 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
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
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 planet Discovered in 1995 Doppler wobble
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 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, water carbon 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:
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 affairs
They were here, and left evidence of their presence
Voyager 1 would take ~75000 years to reach Proxima Centauri…… They 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 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 100,000 th of the age of the Galaxy
They exist but have not yet communicated They stay at home…
They exist but have not yet communicated They stay at home… …and surf the net
They 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