13-04 Extrasolar Planets

Is the solar system formation model described in the previous section a correct one?
 

Extrasolar planets are very dim and very close to their parent stars. Direct imaging is difficult.

The method of determining masses in a single-line spectroscopic binary was exploited to find the first extrasolar planet orbiting 51 Pegasi in 1995 by Michel Mayor and Didier Queloz, who were awarded the 2019 Nobel Prize in Physics "for the discovery of an exoplanet orbiting a solar-type star".



The mass function:
m₂³sin³θ  /  (m₁+m₂)²  =  v₁³P  /  (2πG)
 

The number of detected extrasolar planets is increasing rapidly!



(For updated information, check NASA Exoplanet Archive, Catalog and more individual information.)
 

The 4 methods to detect exoplanets:
Radial velocity, transit, microlensing, and direct imaging

But, challenges to the model of planet formation: many of them have large masses and small orbital radii - the so-called Hot Jupiters.
 

Extrasolar planets vs brown dwarfs
Red dwarfs (0.08 -- 0.8 M_⊙)
Brown dwarfs (0.013 -- 0.08 M_⊙) (2M1207 in the previous figure is a brown dwarf with a planet 2M1207b)
Planets are those objects of mass lower than 0.013 M_⊙, i.e., 13 M_J.

The Kepler mission (2009 - 2018) used the transit method. Exoplanet candidates in habitable zones have been found. Check also the on-going TESS mission.