2.4 Exoplanets Flashcards
What is an exoplanet
A planet orbiting s star other than our own - outside the solar system
Why are exoplanets difficult to find
They are so far away we need very advanced technology to see them or find them
Why are the 3 main techniques for finding an exoplanet indirect
They rely on observing the effect on their host star
What is astrometry
As massive exoplanets orbit their parent star their gravitational pull can cause the star to wobble/ change position
These wobbles can be detected - we measure the precise position of the star relative to eachother to see if they move over time
What limits the accuracy of astrometry
The turbulence of our atmosphere
What’s the transit method
If an exoplanet moves across its star in their orbit they cause a typically 1% drop in brightness
- by measuring amount of light received by a star over a period of time
What’s the problem with the transit method
It has to be On the same plane as we are in order to see it moving across
What’s radial velocity (using Doppler shifts) method
The wobbling of a star did to exoplanets gravity can also cause wavelengths to be slightly red-shifted and blue-shifted on a regular time scale as a star moved away from us and towards us
Spectroscopy is able to reveal small shifts in wavelength and has been proved the most successful
Why does the atmosphere have a negative affect on discovering exoplanets
Small rocky exoplanets like earth can’t be discover due to atmospheric turbulence
Why can we find earth like planets
They need to be:
Not to big - likely a gas giant
Medium- earth like relatively small mass so little effect on host star
Too small - not enough gravity to hold onto atmosphere
What are the 2 essential chemical ingredients for life
Carbon - element had ability to make compass and form basis of more complex molecules (chemical building blocks of life)
Liquid water - excellent solvent and transport mechanism for nutrients
Need for photosynthesis and to break down large molecules (hydrolysis)
What are the 2 principal origins of water on earth
Our gassing of hydrogen and oxygen from volcanoes to produce steam and condense to water
Deposited by comets containing ice striking earth
Where must a planet be to sustain life
Habitable Zone
Or
Goldilocks zone
What’s the habitable / Goldilocks zone
A narrow range of distances from the star which the temperature allows liquid water to exist - neither to hold or cold
What did frank drake do in 1961
Made the Drake equation
What is the Drake equation
Combine estimated probabilities of a number of factors That as a result estimate number of civilisations in our galaxy that could communicate with us
Where in our solar system could life exist
Jupiters moon Europa
Mars
How do we use space probes to search for signs of life
Test for microbes or bi-products
How does spectral analysis of planetary atmospheres test for life
Search for gases such as oxygen and methane that are produced by living organisms
How does the analysis of radio waves help search for life
Try to detect signals that could have originated from extra terrestrial intelligent forms of life in Galaxy
What are the ethical problems of finding life
Would it be wiser to transfer organisms from one environment into a totally different one where they could become extinct or adapt too well and flourish
Could life on Earth be threatened we don’t know their capabilities
Do we really want to discover that we aren’t alone?
Name some factors of the Drake equation
L= length of time signals released into space
Fp= fraction of those stars that have planets
R*= average rate of star formation per year in our galaxy
Fi= fraction of that life that goes on to develop intelligence
