Chapter 7 The Nature Of Exoplanetary Systems Flashcards
What are the two prominent methods of detecting exoplanets?
Doppler spectroscopy was initially used to discover exoplanets.
Transit photometry then proved to be a more fruitful method for discovering exoplanets.
How are exoplanets named?
The planet takes on the name of the star plus a letter starting with the letter ‘b’ for the first planet discovered then the letters C, D etc.
If multiple planets are discovered at the same time the naming starts with the closest planet to the star and works out.
Why are M dwarf stars not initially targeted in exoplanet searches?
They have more complex spectral lines and low luminosities, both of which hamper radial velocity studies.
What is type 1 migration?
The spiral structure of the circumstellar disc external to a kernel experts a gravitational influence that pushes the kernel inwards. this force overcomes the outward pressure caused by the circumstellar disc internal to the kernel.
The inward migration is proportional to the mass of the disc and the mass of the kernel.
as the kernel grows in size the inward migration rate increases into the colonel has grown a sufficient mass to open up a gap in the disk causing migration to slow.
What is type 2 migration?
This is where disc contraction and migration slow down to the same rate. Although most of the gas around the kernel has been captured the kernel will still continue to slowly gain mass and so slowly continue to migrate inwards.
A few factors, including density, thickness, viscosity, and temperature of the disc can affect the continued rate of migration.
What can prevent a migrating gas giant from falling into the star?
-Title interactions between the planet and the star.
-Magnetic interactions between the star and the disk.
-Evaporation by Stella radiation of a narrow zone in the disc a few AU from the star creating a migration barrier.
-Interactions with other planets forming within the disc.
How do planets end up with high eccentricities?
- when two planets are in orbital resonances.
-The close encounter of two gas giants can cause one to be flung into interstellar space and the other to maintain a highly eccentric orbit.
If a planet has a highly eccentric orbit and a small periastron distance then title effects from the star and potentially aided by disc gas will reduce eccentricity creating a small low eccentricity orbit.
