Cool Observations of Exotic Exoplanet

As predicted, results from Rosetta are pouring out, far faster than I can possibly keep up with. Last week saw a special issue of Astronomy & Astrophysics (October 30 2015), filled with reports from the Rosetta mission. Fifty articles! Hundreds of authors! Obsessive detail! Help! I can’t possibly read all this!

Instead, I focused my own humble attention on the splashy news from Endinburgh, where astronomers have systematically investigated the strange “extrasolar object”, PSO J318.5-22. Discovered in 2013, this thing is a largish planetish object, traveling alone—no sun, just a lonely planet.  Very unusual.

The report this week describes painstaking telescopic observations which detected variability in the object—the “the first detection of variability in such a cool, low-surface gravity object”. I don’t pretend that I can follow the technical details (I’m not an astronomer, you could fill encyclopedias with what I don’t know about light curves.) The report suggests that this PSO rotates with a period greater than 5 hours. The variability also suggests changing cloud cover—“weather”. If confirmed, this would be “the first detection of weather on an extrasolar planetary mass object.”

As the commentary indicates, this “weather” is acid dust clouds and molten Iron rain. Not exactly Earth-like, but certainly interesting.

If nothing else, this object reminds us that stars and planets (and comets and dust and everything) are all part of a spectrum of ways that matter clumps in space. Not quite as poetic as Sun versus Moon, or Mars versus Venus, but very elegant.

Very nice work.


  1. Beth A. Biller, Johanna Vos, Mariangela Bonavita, Esther Buenzli, Claire Baxter, Ian J.M. Crossfield, Katelyn Allers, Michael C. Liu, Mickaël Bonnefoy, Niall Deacon, Wolfgang Brandner, Joshua E. Schlieder, Trent Dupuy, Taisiya Kopytova, Elena Manjavacas, France Allard, Derek Homeier, and Thomas Henning, Variability in a Young, L/T Transition Planetary-Mass Object (accpted). ApJ letters, October 2015.


Space Saturday

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