Brown Dwarf HWYL 04 021

2024-01-06T00:00:00Z

Brown Dwarf "Curiously, since the Na D lines [i.e., sodium spectral absorption lines] can be prominent in brown dwarf spectra and will suppress the green wavelengths and since the color 'brown' is two parts red, one part green, and very little blue, brown dwarfs should not be brown. In fact, recent calculations suggest that they are red to purple, depending upon the exact shape of the line wings of Na D, the abundance of the alkalis, the presence of high-altitude clouds, and the role of water clouds at lower T effS (≳ 500 K). A mixture of red and the complementary color to the yellow of the Na D line makes physical sense. It is the complementary color, not the color , of the Na D line(s) because Na D is seen in absorption, not emission. Indeed, the recent measurement of the spectrum of the L5 dwarf 2MASSW J1507 from 0.4 μ m to 1.0 μ m (Fig. 21; Reid et al. 2000a) indicates that this L dwarf is magenta in (optical) color. This is easily shown with a program that generates the RGB equivalent of a given optical spectrum (in this instance, R:G:B::1.0:0.3:0.42, depending upon the video 'gamma'). Hence, after a quarter century of speculation and ignorance, we now have a handle on the true color of a brown dwarf — and it is not brown" (p. 13). Burrows, Adam, W.B. Hubbard, J.I. Lunine, and James Liebert. "The Theory of Brown Dwarfs and Extrasolar Giant Planets." arXiv . arXiv:astro-ph/0103383v1, 22 March 2001. https://arxiv.org/pdf/astro-ph/0103383.pdf