February 24, 2020

15.03.11: A Borderline Brown Dwarf.

Oh Be A Fine Girl/Guy Kiss Me Now… the mnemonic for stellar classification running from hottest to coldest has been long overdue overhaul, as brown dwarf classes L, T, and now Y have been placed on the cool end of the scale. And in the past month, a paper by Kevin Luhman and colleges at Pennsylvania State University have reported what may be the coolest brown dwarf known.

At 19.2 parsecs distant, the dim dwarf simmers in the infrared at about 300 Kelvins, or about +80° degrees Fahrenheit, a nice Florida day. The dwarf orbits a white dwarf companion, and has an apparent separation of 130” which would compute to an orbital radius of about 2500 A.U. Observations of this dwarf named  WD 0806-661 B were completed using NASA’s Spitzer Space Telescope and the twin 6.5 meter Magellan telescopes located in Chile. At an estimated 8 Jupiter masses, this brown dwarf represents one of the very few Y dwarfs discovered in the widl and challenges the blurry line between planet and proto-star.

So, just what is such a bizarre star like? Such a realm is methane rich, powered by Lithium-7 into Helium-4 fusion, and possesses such strange spectral indicators as an iron rain. Curiously, since most brown dwarfs are governed by a force known as electron degeneracy pressure, most have a volume similar to Jupiter. Spitzer and NEOWISE continue to survey the skies for such elusive objects, and the idea that an extremely cool brown dwarf may be our closest stellar neighbor could be in the realm of possibility as surveys are completed in 2011.

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