Exoplanets Flashcards
Define the habitable zone
Distance from the star so that these planets have liquid water on the surface
Why are exoplanets difficult to find?
•very faint as intrinsically and relative to their parent star
•very close to their parent star
What is the closest star to the sun?
Proxima Centauri a red dwarf
What is our closest planet?
Proxima Centauri b
Describe Proxima Centauri b
•orbits with habitable zone
•might be tidally locked
•star has solar flares which can increase luminosity by factor of 10000
•4.2 light years from earth
What does the amount of Doppler shift depend on?
Inclination of orbit
What are eccentricities?
Deviations from sinusodial light curve indicate elliptical orbits
How do transits detect exoplanets?
If a planet moves between us and its parent stars it will block some starlight. With this method we can detect planets which orbit directly in front of the star.
How many planets have been discovered through transit method?
7
Describe planet J1407b
•super Saturn
•orbits brown dwarf j1407
•200 times larger than Saturns rings
•detected through transit method
Describe kepler 16b
•Saturn-mass planet orbiting binary star
•transits of both stars been observed
•Whitburn habitable zone but gas giant
What is gravitational lensing?
Light bending around a massive object causing us to see multiple images of a single real object
What can cause anomalies in light curves?
If lens star has an orbiting planet ( can be used to detect low mass planets)
What do objects in multi planet system orbit?
Their common centre of mass
Describe direct imaging
•one use of adaptive optic
•light of star is blocked out
•only possible for planets with large orbits
How many exoplanets have been detected?
Over 5000
What do extrasolar planets often have?
Eccentric orbits
What are hot jupiters?
Exo planets that have masses and radii similar to Jupiter but periods of few days
Why have we discovered so many hot Jupiters?
Strong selection effect, since such planets easier to find for most detection methods
How do hot Jupiters differ from our solar system?
•cannot form in situ and within frost line so unable to build from ices
•possibly formed further out and migrate inwards
What type of planets require long monitoring to seee orbits?
Earth like planets
How many planets did the Kepler space telescope detect?
Over 2500 planets through transit technique
What is good evidence for the disk formation model of planets?
Kepler detecting number of multiple planet systems that tells us that orbital planes of planets must be very. Loosely aligned or wouldn’t all transit
Describe transmission spectroscopy
•planet appears larger within an absorption line
•atmosphere helps to absorb light of star
•outside absorption feature the light can go through the atmosphere
What do spectral lines do to appearance of planets?
Make them look bigger
What is the main purpose of the TESS mission?
To find close by planets for characterisation via transit method
Describe pulsar planets
•most likely formed from debris of explosion
•unlikely life is possible due to very high radiation
Why did no one expect pulsars to have planets?
Pulsars result of supernovae explosions
