Wikipedia:Notability (extrasolar planets)

The following notability guideline covers the astronomical-objects notability policy as it applies to extrasolar planets and astronomical objects in systems containing them. Extrasolar planets include, for the purpose of this policy, any planets, confirmed or unconfirmed, orbiting stars or brown dwarfs other than the Sun, as well as sub-brown dwarfs and rogue planets. This policy only considers extrasolar planets, as well as other large objects in exoplanetary systems that have achieved hydrostatic equilibrium, and does not cover mere trends in astrophysical data that do not rise to the level of candidate planets. Protoplanetary disks and other circumstellar disks are specifically excluded from the purview of this policy, and fall under the more general astronomical objects notability criteria.

Extrasolar planets

Inherent and inherited notability

As with any astronomical object, extrasolar planets and other planet-like bodies are not considered notable simply for being discovered or being listed in a large database like the Extrasolar Planets Encyclopaedia, but must rather have significant coverage in reliable sources as prescribed by the general notability guideline. There is no exception to this rule made for potential habitability, distance to Earth, or other similar milestones; any extrasolar planet or planet-type object with an article must have in-depth treatment beyond the listing of statistics such as mass, radius, semimajor axis, or Earth Similarity Index. As with any astronomical object, though, this section should not be construed as excluding the construction of lists of extrasolar planets that may or may not be notable by themselves.

Lacking inherent notability, extrasolar planets do not inherit notability from their parent stars, either, even if the star has a traditional name like Castor or Sirius. If a star has notability while planetary-mass bodies in the system do not, then the information for the planet should be merged into a separate section in the article for the star. The reverse situation is similar; stars that are notable primarily by virtue of their possessing a planetary system should have their information presented along with the planetary-system information under an article named for the star.

Criteria

There are several criteria in determining whether or not an extrasolar planet deserves an article of its own, whether its information should be merged into another article, whether the extrasolar planet should lack coverage entirely outside of lists, or whether some other option should prevail. In keeping with the spirit of the general notability guideline, the key determinant of these factors is the level of coverage in reliable sources and the consequent potential length of an article.

• If an extrasolar planet is covered comprehensively in several reliable sources, containing collectively enough information to write an article that could be substantially longer than a stub article and which could not be reasonably incorporated into a more general article in summary style, then the planet can have a dedicated article.
• If an extrasolar planet could have all information about it reasonably contained within a level-2 heading, without subsections, under summary style, and an appropriate infobox, the information about the planet should be inserted in an article about the star or star system.
  • A planet orbiting a star that is notable and well-characterized enough in its own right to allow for extensive coverage of the star itself in an article should be covered in an article about the planetary system of that star as a whole.
  • In the case of a single-planet system, the information should be inserted into a level-2 section within the article about the star or star system itself, whether or not the star is well-characterized.
• An exoplanet that has not received characterization beyond the presentation of a few statistics in a larger database should not have its own article, and should instead be covered in a larger list.

There are several caveats to the above list, as it does not work for all bodies defined as extrasolar planets for the purpose of this policy:

• All articles about free-floating planetary-mass bodies function by the simple pass-or-fail system prescribed in astronomical objects notability.
• Potential exomoons follow the above criteria, with the change that all references to are replaced with references to host planets. If the host planet does not have an article (and the exomoon is not otherwise notable) its information is contained in the article about the star its host planet orbits.

Exoplanetary host stars

There is a simple test to determine what level of coverage exoplanetary host stars should have:

• Exoplanetary host stars in multiple-star systems that have been well-characterized independently of the system as a whole (e.g. Alpha Centauri A) may have their own articles.
• Host stars in single-star systems that meet the standards of astronomical object notability, or which have extrasolar planets with at least as much notability to be covered in a subsection of the star's article, may have their own articles.
• Exoplanetary host stars or systems that are neither themselves notable, nor have extrasolar planets rising to a level of notability allowing greater than list coverage, should be covered in list form.