Although the image below isn’t particularly striking, do focus in on it for a moment. You’re looking at what astronomers now consider the coldest brown dwarf yet to be found. Look just down from the top of the image and just left of center for the unusually red pinpoint. This is CFBDS J005910.83-011401.3, thankfully abbreviated CFBDS0059. A science fiction writer with brown dwarf credentials (Karl Schroeder is just the guy) could think of a more poetic name and set up a story around such a place.
Image: Three-color image of the star field in which the brown dwarf has been discovered. The brown dwarf is the very red object seen at the top left of the image. This image illustrates how very different is the color of this object compared to the other cold stars around. Image copyright Canada-France-Brown-Dwarf-Survey 2008.
As interesting stars go, CFBDS0059 isn’t all that far away, some forty light years. Massing between 15-30 Jupiter masses, it’s typical of brown dwarfs in at least one sense, not being able to sustain thermonuclear reactions. It’s also unusually like a giant planet, more so than other known classes of brown dwarfs, not only because of temperatures in the range of 350 degrees Celsius but also because of the presence of ammonia, hitherto undetected in brown dwarf near-infrared spectra.
By contrast, L dwarfs have temperatures in the range of 1200 to 2000 degrees Celsius, while the cooler T dwarfs (both of these are considered brown dwarf classes) come in at under 1200 Celsius. Are we looking at a new class of brown dwarfs in CFBDS0059? They would offer an unusual chance to fill in the gap between giant planets and stars. The most significant aspect of a find like this one is the chance to study a cold brown dwarf in relation to exoplanets we cannot directly observe. This ‘almost planet,’ not swamped by light from a parent star, may help us tune up our models for working with distant planetary atmospheres.
And other cool brown dwarfs fitting the proposed spectral class Y are likely to be found. The same team points to ULAS0034 as an example, and the paper on this work notes “We therefore expect to ﬁnd another few similarly cool objects, and hopefully one signiﬁcantly cooler…” The paper is Delorme et al., “CFBDS J005910.90-011401.3: reaching the T-Y Brown Dwarf transition?” accepted by Astronomy & Astrophysics and available online.