Exoplanets Flashcards
How were exoplanets first discovered?
Timing variations caused by changes in light travel time and motion of the pulsar in orbit.
How can we see exoplanets from direct imaging?
Planets are faint at optical wavelengths, more favourable at IR wavelengths.
How can we used the movement of a star to detect exoplanets?
Large exoplanets cause the star to move noticeably due to gravity. We can look at this movement to estimate the planets mass etc.
What is the transit method of detecting exoplanets?
If orbital plane is aligned conveniently, planet will pass in front of the star, causing a dip in the light curve of the star.
What can we witness when the planet passes behind the star?
Another dip in light curve due to star blocking out light from planet: loss of photons from planet.
What can we learn from direct imaging?
Atmospheric composition
What can we learn from radial velocity?
Orbits (periods etc)
What can we learn from transits?
Radius but when combined with RV get mass, hence density. But probability of transit rapidly diminishes with increasing period.
What are the two mechanisms from which planets could have migrated from more distant parts of their systems to get to their host stars?
- Interactions in the solar disk
- Planet-planet scattering
What is the Rossiter-McLaughlin effect?
Measures alignment between spin axis of star and orbital plane of planet by looking at different parts of the absorption lines being blocked out.
What is the equation for the amount of energy absorbed by a planet?
E(abs) = (1-A)πR^2*F
What is the equation for the amount of energy emitted from the planet?
E(emit) = 4πR^2*σT^4
How do we get an equation for the equilibrium temperature of a star?
Set E(abs) = E(emit) and rearrange for T.
What is the habitable zone?
The zone around a star at which a planet is the right Teq to enable water to exist.
What is Trappist-1 and some of its properties?
Low luminosity and HZ at a period of a few days. 7 planet system
