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Substellar object
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<h2 id="classification">Classification</h2> <p><a href="/facts/William_Duncan_MacMillan/ohmGYobq">William Duncan MacMillan</a> proposed in 1918 the classification of substellar objects into three categories based on their density and phase state: solid, transitional and dark (non-stellar) gaseous.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> Solid objects include Earth, smaller <a href="/facts/Terrestrial_planet/jpMC1ULt">terrestrial planets</a> and moons; with Uranus and Neptune (as well as later <a href="/facts/Mini-Neptune/vV0xt7bD">mini-Neptune</a> and <a href="/facts/Super_Earth/C8xrtn2w">Super Earth</a> planets) as transitional objects between solid and gaseous. Saturn, Jupiter and large gas giant planets are in a fully "gaseous" state. </p> <h2 id="substellar-companion">Substellar companion</h2> <p>A substellar object may be a companion of a star,<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> such as an <a href="/facts/Exoplanet/zjfmqfUf">exoplanet</a> or <a href="/facts/Brown_dwarf/fa7kr9lH">brown dwarf</a> that is orbiting a star.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> Objects as low as 8–23 Jupiter masses have been called substellar companions.<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> </p><p>Objects orbiting a star are often called planets below 13 <a href="/facts/Jupiter_mass/EtLUmeEN">Jupiter masses</a> and brown dwarves above that.<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> Companions at that planet-brown dwarf borderline have been called <a href="/facts/Super-Jupiter/E2V1wmfX">Super-Jupiters</a>, such as that around the star <a href="/facts/Kappa_Andromedae/CAl67Y2r">Kappa Andromedae</a>.<a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a> Nevertheless, objects as small as 8 Jupiter masses have been called brown dwarfs.<a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a> </p> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Brown_dwarf/fa7kr9lH">Brown dwarf</a></li> <li><a href="/facts/List_of_planet_types/gmnHgTcy">List of planet types</a></li> <li><a href="/facts/Planet/rbPjE6Bx">Planet</a></li> <li><a href="/facts/Red_dwarf/56CMQcF0">Red dwarf</a></li> <li><a href="/facts/Sub-brown_dwarf/KBdlnxo1">Sub-brown dwarf</a></li></ul> <ul><li>Quoted as Chabrier and Baraffe: Chabrier, Gilles; Baraffe, Isabelle (September 2000). "Theory of Low-Mass Stars and Substellar Objects". <i>Annual Review of Astronomy and Astrophysics</i>. 38: 337–377. <a href="/facts/ArXiv_(identifier)/H6EtgnBe">arXiv</a>:<a href="https://arxiv.org/abs/astro-ph/0006383">astro-ph/0006383</a>. <a href="/facts/Bibcode_(identifier)/9HtdQSGB">Bibcode</a>:<a href="https://ui.adsabs.harvard.edu/abs/2000ARA&A..38..337C">2000ARA&A..38..337C</a>. <a href="/facts/Doi_(identifier)/muM9Etpq">doi</a>:<a href="https://doi.org/10.1146%2Fannurev.astro.38.1.337">10.1146/annurev.astro.38.1.337</a>. <a href="/facts/S2CID_(identifier)/ldJsHa2Y">S2CID</a> <a href="https://api.semanticscholar.org/CorpusID:59325115">59325115</a>.</li></ul> <h2 id="external-links">External links</h2> <ul><li> Media related to Substellar objects at Wikimedia Commons</li> <li><a href="https://web.archive.org/web/20200520091343/https://www.astrobio.net/meteoritescomets-and-asteroids/a-guide-to-exoplanet-hunting/">Keck views star and companion</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>§3, What Is a Planet?, Steven Soter, Astronomical Journal, 132, #6 (December 2006), pp. 2513–2519. <a href="http://adsabs.harvard.edu/abs/2006AJ....132.2513S" target="_blank">http://adsabs.harvard.edu/abs/2006AJ....132.2513S</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Chabrier and Baraffe, pp. 337–338 <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Alula Australis Archived 2006-08-24 at the Wayback Machine, Jim Kaler, in Stars, a collection of web pages. Accessed on line September 17, 2007. <a href="http://www.astro.uiuc.edu/~kaler/sow/alulaaus.html" target="_blank">http://www.astro.uiuc.edu/~kaler/sow/alulaaus.html</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>A search for substellar members in the Praesepe and σ Orionis clusters, B. M. González-García, M. R. Zapatero Osorio, V. J. S. Béjar, G. Bihain, D. Barrado Y Navascués, J. A. Caballero, and M. Morales-Calderón, Astronomy and Astrophysics 460, #3 (December 2006), pp. 799–810. <a href="http://adsabs.harvard.edu/abs/2006A%26A...460..799G" target="_blank">http://adsabs.harvard.edu/abs/2006A%26A...460..799G</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Chabrier and Baraffe, §2.1.1, 3.1, Figure 3 <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Chabrier and Baraffe, §4.1, Figures 6–8 <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>Hille, Karl (2018-01-11). "Hubble Finds Substellar Objects in the Orion Nebula". NASA. Retrieved 2018-01-30. <a href="https://www.nasa.gov/feature/goddard/2018/hubble-finds-substellar-objects-in-the-orion-nebula" target="_blank">https://www.nasa.gov/feature/goddard/2018/hubble-finds-substellar-objects-in-the-orion-nebula</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>MacMillan, W. D. (July 1918). "On stellar evolution". Astrophysical Journal. 48: 35–49. Bibcode:1918ApJ....48...35M. doi:10.1086/142412. <a href="/wiki/William_Duncan_MacMillan" target="_blank">/wiki/William_Duncan_MacMillan</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>STScI-1995-48 <a href="http://hubblesite.org/newscenter/archive/releases/1995/48/" target="_blank">http://hubblesite.org/newscenter/archive/releases/1995/48/</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>Mugrauer, M., et al - Direct detection of a substellar companion to the young nearby star PZ Telescopii (2010) <a href="https://ui.adsabs.harvard.edu/abs/2010A%26A...523L...1M/abstract" target="_blank">https://ui.adsabs.harvard.edu/abs/2010A%26A...523L...1M/abstract</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>S. Geier, et al - Discovery of a Close Substellar Companion to the Hot Subdwarf Star HD 149382 (2009) <a href="http://iopscience.iop.org/1538-4357/702/1/L96/" target="_blank">http://iopscience.iop.org/1538-4357/702/1/L96/</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>Boss, A. P.; Basri, Gibor; Kumar, Shiv S.; Liebert, James; Martín, Eduardo L.; Reipurth, B.; "Nomenclature: Brown Dwarfs, Gas Giant Planets, and ?", in Brown Dwarfs, Proceedings of IAU Symposium #211, held 20–24 May 2002 at University of Hawaii, Honolulu <a href="http://adsabs.harvard.edu/full/2003IAUS..211..529B" target="_blank">http://adsabs.harvard.edu/full/2003IAUS..211..529B</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> <li id="fn:13"><p>Astronomers Directly Image Massive Star's 'Super-Jupiter'11.19.12 <a href="https://www.nasa.gov/topics/universe/features/super-jupiter.html" target="_blank">https://www.nasa.gov/topics/universe/features/super-jupiter.html</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></p></li> <li id="fn:14"><p>Discovery of a Planetary-Mass Brown Dwarf with a Circumstellar Disk, Luhman, et al., 2005 <a href="http://iopscience.iop.org/1538-4357/635/1/L93/" target="_blank">http://iopscience.iop.org/1538-4357/635/1/L93/</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></p></li> </ol>