Sub-Brown Dwarf

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Size comparison: Sun , Cha 110913-773444 and Jupiter .

A sub-Brown Dwarf , even brown dwarf planetary mass (ger .: planetary-mass brown dwarf ), a is the object of planetary mass that does not like a planet from a protoplanetary disk has developed, but like a star or a brown dwarf by Contraction of a stellar gas cloud , but remained below the minimum mass of a brown dwarf of approx. 13  Jupiter masses .

There is still no established German term for these objects.

properties

These "failed stars", which resemble gas planets , do not have enough mass for nuclear fusion and are therefore cold and dark. They can have surface temperatures of around 180 to 330 ° C, around 0 ° C or even below. Although they do not shine in visible light, they can be detected with infrared telescopes such as the Spitzer Space Telescope . Sub-Brown Dwarfs are found in the galactic halo and interstellar space .

Since these objects are not assigned to stars or star systems , they are viewed by some astronomers as "vagabond planets", while others reject the term planet for these objects because they did not arise in orbit a star system and did not break out of it.

The lower mass limit for Sub-Brown Dwarfs is approximately one mass of Jupiter or between 0.001 and 0.01  solar masses . It arises from the fact that when the object collapses, it has to radiate the resulting thermal energy again, and this depends on the opacity of the gas. The upper mass limit is like that for all objects of planetary mass at about 13 Jupiter masses. Above this mass, the nuclear fusion of deuterium begins , and one speaks of brown dwarfs.

Y-dwarfs

The term Sub-Brown Dwarf overlaps with the term Y-dwarf . This comes from the classification of stars according to spectral classes . The term is not congruent, however, since Y dwarfs with 9 to 25 Jupiter masses can be about twice as heavy as brown dwarfs of planetary mass. Thus only the lighter Y-dwarfs are also objects of planetary mass, the heavier ones, however, are real brown dwarfs.

Examples

Individual evidence

  1. ↑ Telescope discovers 14 extremely cool brown dwarfs . In: krone.at . July 5, 2010 ( online version [accessed December 11, 2016]).
  2. ↑ Charles Q. Choi: How Cold Is a Y Dwarf Star? Even You Are Warmer . space.com. August 25, 2011. Retrieved December 12, 2016.
  3. ↑ a b Kevin Luhman: Discovery of a ~ 250 K Brown Dwarf at 2 pc from the Sun . arxiv : 1404.6501 .
  4. ↑ P. Delorme et al .: CFBDSIR2149-0403: a 4–7 Jupiter-mass free-floating planet in the young moving group AB Doradus? . In: Astronomy & Astrophysics . December 2012. arxiv : 1210.0305 . bibcode : 2012A & A ... 548A..26D . doi : 10.1051 / 0004-6361 / 201219984 .
  5. ↑ Alan P. Boss, Gibor Basri, Shiv S. Kumar, James Liebert, Eduardo L. Martín, Bo Reipurth, Hans Zinnecker: Nomenclature: Brown Dwarfs, Gas Giant Planets, and? tape 211 , June 1, 2003, p. 529 .
  6. ↑ Scholz, Alexander; Geers, Vincent; Jayawardhana, Ray; Fissel, Laura; Lee, Eve; Lafreniere, David; Tamura, Motohide: Substellar Objects in Nearby Young Clusters (Sonyc): The Bottom of the Initial Mass Function in Ngc 1333 . The Astrophysical Journal. July 13, 2009. Retrieved January 18, 2017.
  7. ^ Position statement on the definition of a "planet" . Working Group on Extrasolar Planets. February 28, 2003.
  8. ^ A b Michael C. Cushing: 50 Years of Brown Dwarfs - From Prediction to Discovery to Forefront of Research . In: Viki Joergens (Ed.): Astrophysics and Space Science Library . tape 401 . Springer, 2014, ISBN 978-3-319-01162-2 , Ultracool Objects: L, T, and Y Dwarfs, S. 113-140 ( online ).