Possibility of Intelligent
Extraterrestrial Life?

What is Meant By Intelligent
Extra-terrestrial Life?
• Capable of thinking
• Making conscious Decisions
• Purposeful activity

Adaptability of Life
We know from Earth that life can survive and thrive in extreme conditions o Extreme Temperatures: -15c – +60c o Extreme Dryness, or underwater o With light, without light o Extreme altitudes o Extreme pressure
This shows that the range at which life can survive is vast.

Necessary Conditions For Planet
To Support Life
• Comfortable distance from its star (habitable zone)
• Strong enough gravity to hold a protective atmosphere.
• Magnetic Field – to protect the planet from radiation from the star.
• Solid/liquid Surface – it is unlikely a gas planet would be able to harbour life.

Habitable Zones
• The region around a star within which planetary-mass objects with sufficient atmospheric pressure can support liquid water at their surfaces.
• Larger the star, larger the habitable zone and the further away it is from the star.
• Habitable zones for other solar systems have been based around the
Earths biosphere.
• On November 4, 2013, astronomers reported, based on Kepler space mission data, that there could be as many as 40 billion Earth-sized planets orbiting in the habitable zones of sun-like stars and red dwarf stars within the Milky Way Galaxy.

The Sun compared to other stars
• The sun is a g2 star meaning it is between 5000 – 6000 (k)
• Our sun is a very average star in terms of size mass and temperature
• Different types of stars can range quite highly in size and temperature
• For example some stars can reach up to 50000(k)
• This would dramatically change a habitable zone for planets within a stars orbit
• This enables us to locate planets in the habitable zone in different stars solar systems

Spectral features
• The spectral type of a star is not only the differences in heat and size it also mean stars have different features.
• Our sun is made up of metals and ionized metals such as ionized calcium. • Having this make up creates an atmosphere with the correct composition to support our life.
• Different stars will create different atmospheres for their solar systems
• However this doesn’t mean life cannot exist, as other life could depend on elements other than oxygen ect.

The Drake Equation

R* = Average rate of star formation fs = Fraction of good stars with planetary systems ne = Number of planets around these stars with an
‘ecoshell’
fl = Fraction of those planets where life develops fi = Fraction of living species that develop intelligence fe = Fraction of intelligent species with communications technology
L = Lifetime of the communicative phase

Use of the Drake Equation
• By inserts all the estimates for each value into the equation we get a range of N from as low as 2 to as high as 280,000,000 planets with extra-terrestrial civilisations.
• The range is so high because the estimates of some values are complete guesses
• At the moment the Drake Equation is limited in its usefulness, although if we knew more of its values it could give us a more accurate estimate in the future.

Candidates Potentially
Harbouring Life
• Kepler-22b
• Gliese 667Cc
• HD 85512b
• Europa – moon of