THE SEARCH FOR EXTRA-TERRESTRIAL LIFE

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OVERVIEW

• Why we search
• Celestial bodies
• How we define life
• Requirements for life
• The drake equation

WHY WE SEARCH

• Curiosity
• Survival
• Population
• Resources

CELESTIAL BODIES

• Stars
• Black holes
• Planets

STARS

BLACK HOLES

PLANETS

how we define life

• No simple answer
• Any molecular structure that can contain the information and means for reproduction

Requirements for life

• Stellar system requirements
• Planetary requirements

Stellar system requirements

• A suitable planet
• A suitable star

A Suitable planet

• Right size (too big = strong gravity = thick atmosphere = hot temperature and vice versa)
• Stable orbit to maintain consistent conditions throughout the year
• Located in the habitable zone

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A Suitable star

• The right spectral class
• Spectral classes are sorted from the most massive, brightest and hottest O-class stars to the lightest/dimmest/coldest M-class stars

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Planetary requirements

• Energy
• Temperature
• Liquid water
• Essential chemicals
• An atmosphere

Energy

• Fuels chemical reactions
• Comes in the form of light & chemical energy

Temperature

• Required to allow liqiud water to be present
• Range -15C to 115C

Liquid water

• Medium that allows molecules to dissolve and move between cells

Essential chemicals

• Carbon (in combination with nitrogen, oxygen and hydrogen among others
• All life as we know it is carbon based because of the wide variety of chemical bonds it can make, the stability of its molecule chains and its ability to easily make and break bonds with oxygen

An Atmosphere

• A suitable atmosphere consists of mostly nitrogen and oxygen
• Traps heat
• Protects against radiation

The drake equation

• Allows us to estimate the amount of intelligent civilizations in our galaxy
• N = R*·Fp·Ne·Fl·Fi·Fc·L

N = R*·Fp·Ne·Fl·Fi·Fc·L

• N = number of civilizations
• R* = Amount of suitable stars formed per year in our galaxy
• Fp = Fraction of those stars that forms planets
• Ne = Average number of habitable planets per star that forms planets

N = R*·Fp·Ne·Fl·Fi·Fc·L

• Fl = The fraction of those habitable planets where life emerges
• Fi = ^ where intelligence evolves
• Fc = ^ that is capable of interstellar communication
• L = The amount of years a civilization remains detectable

The problem?

• We only know 3 of the variables
• R* = 1
• Fp = 1
• Ne = 0.25~
• The rest is currently unknown

Conclusion