12. Exoplanets 1 Flashcards
Why are exoplanets difficult to find?
Very faint, very far away ,very close to parent star
How can we use astrometry to find exo planets? (Look up its limits and add to question)
All objects in a planetary system orbit there common centre of mass, so can track movement ans angular resolutions, could identify the presence and distances of planets orbiting stars
Doppler technique for finding exoplanets?
-as star orbits centre of mass wavelength shifts alternately towards blue and read as it gets further and closer allowing us to determine radial velocity from curve
-using planet mass and orbital period (found from keplers third law) can determine planets semi major axis
-we use radial velocity curve, star mass, and planet period and apply conservation of momentum to find mass of planet
How we use transits to find exoplanets composition?
-planet moves between us and parent star and amount of star light blocked tells us planet radius using size of host star
-can combine planet radius with radial velocity info (used to find planet mass) to find density (mass/volume)
-allows us to investigate planet composition
What is semi major axis?
Average Distance between planet and star
What is transit method and what can we find about exoplanets from it?
-planet moves between us and parent star and amount of star light blocked tells us planet radius because we know size of host star and how much ought it usually emits
What is micro lensing?
When a Foreground star passes a background star the gravitational field of foreground star can create a gravitational lens that magnifies the background stars light
-if background star has an orbiting planet may produce an anomaly in magnification so can detects low mass planets
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What is direct imaging and what are its limits?
-if host star isnt very bright its possible to directly image the planet
