(planet not in the solar system)
An extra-solar planet (or exoplanet) is a
planet outside the solar system, e.g.,
orbiting another star.
The first confirmed detection of
an exoplanet was in 1992 and the
first around a main sequence star
(51 Pegasi) in 1995.
As of 2/2019, 3900+ planets around 2800+ stars are known.
A number of methods have been contemplated for future technology:
- detecting the effects of magnetism, e.g., the planet's field affecting the star's field.
The RV method reveals the relative density of the host star and planet,
and a transit reveals their relative radius, so the density of
a planet can be estimated if the planet can be observed by both
methods, limited by the accuracy of these estimates for the star.
For this reason, follow-ups are carried out to get both if that
possibility looks promising, and leads to attempts to predict
transit times from RV data, especially if the orbit is long
(i.e., transits are infrequent) and available telescope time
Some terms used to indicate planets of various characteristics,
particularly their rough size:
- Earths - roughly the size of Earth, rocky.
- super-Earths - noticeably larger than Earth, to 10-or-so Earth masses, sometimes confined to rocky planets.
- mega-Earths - more than 10 times the mass of Earth, yet rocky.
- mini Neptunes - noticeably smaller than Neptune, sometimes confined to gas planets.
- Neptunes - roughly the size of Neptune, gas.
- gas giants - gas planet roughly Saturn size or larger.
- Jupiters - roughly the size of Jupiter, gas.
- super Jupiters or super giants - up to 80-or-so Jupiter masses.
- hot Jupiters - Jupiter-like, in tight orbits around the star, e.g., a fraction of a day.
- hot Neptunes - similar for Neptune-sized planets.
Larger than super Jupiters are brown dwarves. Terms like super Neptune
are also used to indicate a Neptune-like composition.
(These terms present a style issue: whether Jupiter, Earth, and
Neptune should be capitalized, e.g., in hot Jupiter or in
Jupiters. I find no rules, and only partial consistency, and
have elected to follow the style I find most common.)
The spacecraft Kepler surveyed
a portion of the sky for exoplanets,
detecting (including K2) 5500 not-yet-eliminated candidates,
of which 2700 have been confirmed to be planets as of 2/2019.
Projected population statistics based upon surveys:
- Half of star systems have super Earths.
- 1/6 have Earths.
- 5% have gas giants
- 1% have hot Jupiters.
The commonly used method of referring to exoplanets is somewhat-modeled
after the system for individual members of binary stars. The
first planet discovered is specified by the star's name followed
by "b", the next, "c". For example HD 80606 b is a planet
orbiting the star HD 80606.
If two or more are discovered simultaneously,
they are lettered outward from the innermost.
Automated Planet Finder (APF)
atmospheric temperature profile
Black Widow Pulsar (B1957+20)
bulk silicate earth (BSE)
California-Kepler Survey (CKS)
carbon dioxide (CO2)
Carl Sagan Institute (CSI)
double-line spectroscopic binary
exoplanet eclipse light curve
European Southern Observatory Very Large Telescope (ESO VLT)
extreme adaptive optics (ExAO)
F-type star (F)
51 Pegasi b (51 Peg b)
47 Tucanae (47 Tuc)
general circulation model (GCM)
Gliese-Jahreiss Catalog (GJ)
GJ 1132 b
GJ 1214 b
Gemini Planet Imager (GPI)
hot Jupiter (HJ)
internal gravity wave
intertropical convergence zone (ITCZ)
K-type star (K)
Keck Planet Finder (KPF)
Keck Planet Imager and Characterizer (KPIC)
maximum iron fraction
New Worlds Mission
numerical weather prediction (NWP)
one dimensional climate model
Origins Space Telescope (OST)
Qatar Exoplanet Survey (QES)
radial velocity (RV)
Rossiter-McLaughlin effect (RM effect)
Sloan Digital Sky Survey (SDSS)
stellar radius determination
Sagittarius Window Eclipsing Extrasolar Planet Search (SWEEPS)
Transiting Exoplanet Survey Satellite (TESS)
Terrestrial Planet Finder (TPF)
Trans-Atlantic Exoplanet Survey (TrES)
transit timing variations (TTV)
Ultimate Spitzer Phase Curve Survey (USPCS)
vegetation red edge (VRE)
water vapor planet
James Webb Space Telescope (JWST)