Editing Planetary core (section)

===Extrasolar===
As the field of exoplanets grows as new techniques allow for the discovery of both diverse exoplanets, the cores of exoplanets are being modeled. These depend on initial compositions of the exoplanets, which is inferred using the absorption spectra of individual exoplanets in combination with the emission spectra of their star.

====Chthonian planets====
A [[chthonian planet]] results when a gas giant has its outer atmosphere stripped away by its parent star, likely due to the planet's inward migration. All that remains from the encounter is the original core.

====Planets derived from stellar cores and diamond planets====
[[Carbon planet]]s, previously stars, are formed alongside the formation of a [[millisecond pulsar]]. The first such planet discovered was 18 times the density of water, and five times the size of Earth. Thus the planet cannot be gaseous, and must be composed of heavier elements that are also cosmically abundant like carbon and oxygen; making it likely crystalline like a diamond.<ref name="National Geographic Society 2011">{{cite journal |publisher=National Geographic Society |title="Diamond" Planet Found; May be Stripped Star |journal=National Geographic |date=2011-08-25 |url=http://news.nationalgeographic.com/news/2011/08/110825-new-planet-diamond-pulsar-dwarf-star-space-science/ |archive-url=https://web.archive.org/web/20111016203105/http://news.nationalgeographic.com/news/2011/08/110825-new-planet-diamond-pulsar-dwarf-star-space-science |url-status=dead |archive-date=October 16, 2011 }}</ref>

[[PSR J1719-1438]] is a 5.7 millisecond pulsar found to have a companion with a mass similar to Jupiter but a density of 23&nbsp;g/cm<sup>3</sup>, suggesting that the companion is an ultralow mass carbon [[white dwarf]], likely the core of an ancient star.<ref name="Bailes, et al. 2011">{{cite journal |last=Bailes |first=M. |display-authors=etal |title=Transformation of a Star into a Planet in a Millisecond Pulsar Binary |journal=Science |volume=333 |date=September 2011 |pages=1717–1720 |doi=10.1126/science.1208890 |pmid=21868629 |issue=6050|arxiv = 1108.5201 |bibcode = 2011Sci...333.1717B |s2cid=206535504 }}</ref>

====Hot ice planets====
Exoplanets with moderate densities (more dense than Jovian planets, but less dense than terrestrial planets) suggests that such planets like [[GJ1214b]] and [[GJ436]] are composed of primarily water. Internal pressures of such water-worlds would result in exotic phases of [[water]] forming on the surface and within their cores.<ref name="MessageToEagle.com 2012">{{cite web |publisher=MessageToEagle |title=Hot Ice Planets |date=2012-04-09 |url=http://www.messagetoeagle.com/hoticeplanets.php |access-date=2014-04-13 |archive-date=2016-03-04 |archive-url=https://web.archive.org/web/20160304233856/http://www.messagetoeagle.com/hoticeplanets.php |url-status=dead }}</ref>