Mini neptune

from Wikipedia, the free encyclopedia

A mini-Neptune - in contrast to the gas giant, also called a gas dwarf - is an extrasolar planet smaller than Uranus and Neptune with up to ten Earth masses . Such planets have dense hydrogen - helium atmospheres, possibly with deep layers of ice, rocks, or liquid oceans of water , ammonia , a mixture of both, or heavier volatiles. Mini-Neptunes have small cores made of volatile materials with a low density. Theoretical studies of such planets are loosely based on knowledge of Uranus and Neptune. Without their dense atmosphere, they would be classified as ocean planets . The dividing line between a rock planet and a gas planet is estimated to be around two earth radii .

In fact, empirical observations have shown that planets with a radius greater than 1.6 Earth radii (more massive than about 6 Earth masses ) contain significant amounts of volatile matter or hydrogen / helium gas, and such planets apparently have a diverse composition that is not simply due to mass -Radius relationship as can be explained with rock planets. Other studies came to the same conclusion. The lower mass limit for Mini-Neptune can vary widely for different planets, depending on their composition, from just one to twenty Earth masses.

Various discovered exoplanets may be mini-neptunes based on their known masses and densities. For example, Kepler-11f has a mass of 2.3 Earth masses, but its density is the same as that of Saturn , suggesting that it is a mini-Neptune with a liquid ocean enveloped in a thick hydrogen-helium atmosphere and only with a small rocky core. The even smaller planet Kepler-138d with only about one earth mass is possibly also a gas planet because of its relatively large diameter (~ 20500 km) and the associated low density. Such planets, however, do not orbit their parent stars in too narrow orbits, because otherwise their thick atmospheres would evaporate from the heat or be blown away by the stellar wind . The inner planets in the Kepler-11 system have a higher density than those further away from the star.

See also

Web links

Individual evidence

  1. ↑ ... also written “gas dwarf” (see also Neptune-like gas planets could become life-friendly , at Grenzwissenschaft-aktuell , on March 9, 2015) and also in English “ gas dwarf ” (see also Bill Andrews: Two New Classes of Exoplanets Discovered. June 2, 2014, accessed on September 14, 2019 (English). ) ...
  2. ↑ EJW de Mooij, M. Brogi, RJ de Kok, J. Koppenhoefer, SV Nefs, IAG Snellen, J. Greiner, J. Hanse, RC Heinsbroek, CH Lee, PP van der Werf: Optical to near-infrared transit observations of super-Earth GJ1214b: water-world or mini-Neptune? arxiv : 1111.2628 .
  3. ↑ Daniel C. Fabrycky, Jack J. Lissauer, Darin Ragozzine, Jason F. Rowe, Jason H. Steffen, Eric Agol, Thomas Barclay, Natalie Batalha, William Borucki, David R. Ciardi, Eric B. Ford, John C. Geary , Matthew J. Holman, Jon M. Jenkins, Jie Li, Robert C. Morehead, Avi Shporer, Jeffrey C. Smith, Martin Still: Architecture of Kepler's Multi-transiting Systems: II. New investigations with twice as many candidates . arxiv : 1202.6328 .
  4. ^ Johan Matson: When Does an Exoplanet's Surface Become Earth-Like? Retrieved March 28, 2015 .
  5. ^ Courtney D. Dressing et al .: The Mass of Kepler-93b and The Composition of Terrestrial Planets . arxiv : 1412.8687 .
  6. ^ Leslie A. Rogers: Most 1.6 Earth-Radius Planets are not Rocky . arxiv : 1407.4457 .
  7. ↑ Lauren M. Weiss, Geoffrey W. Marcy: The Mass-Radius Relation for 65 Exoplanets Smaller than 4 Earth Radii . arxiv : 1312.0936 .
  8. ↑ Geoffrey W. Marcy, Lauren M. Weiss, Erik A. Petigura, Howard Isaacson, Andrew W. Howard, Lars A. Buchhave: Occurrence and core-envelope structure of 1-4x Earth-size planets around Sun-like stars . arxiv : 1404.2960 .
  9. ↑ Geoffrey W. Marcy, Lauren M. Weiss, Erik A. Petigura, Howard Isaacson, Andrew W. Howard, Lars A. Buchhave: Masses, Radii, and Orbits of Small Kepler Planets: The Transition from Gaseous to Rocky Planets . arxiv : 1401.4195 .
  10. ↑ Ron Cowen: Earth-mass exoplanet is no Earth twin. Retrieved March 28, 2015 .