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Weather Patterns on a Brown Dwarf

The largest variations in brightness ever seen on a cool brown dwarf have turned up on the brown dwarf 2MASS 2139 (known as 2MASS J21392676+0220226 to its friends). The findings, reported at the Extreme Solar Systems II conference in Jackson Hole, Wyoming, show a remarkable 30 percent change in brightness in a period of just under eight hours. The assumption is that brighter and darker patches of atmosphere are periodically moving into view as the brown dwarf rotates.

In fact, Ray Jayawardhana (University of Toronto), co-author of the paper on this work, thinks one possibility is something similar to what we see in our own Solar System. “We might be looking at a gigantic storm raging on this brown dwarf, perhaps a grander version of the Great Red Spot on Jupiter in our own solar system,” says Jayawardhana, “or we may be seeing the hotter, deeper layers of its atmosphere through big holes in the cloud deck.”

Image: Astronomers have observed extreme brightness changes on a nearby brown dwarf that may indicate a storm grander than any seen yet on a planet. This finding could new shed light on the atmospheres and weather on extra-solar planets. Credit: Art by Jon Lomberg.

Whatever the case, this is helpful stuff. Older brown dwarfs have atmospheres not unlike giant planets, so we may be able to use this brown dwarf work to make inferences about exoplanet atmospheres. That will involve studying the brightness variations on 2MASS 2139 over time as we watch weather patterns evolve. The work should allow us to calculate wind speeds in the atmosphere and help us understand how winds are generated in this extreme environment.

Weather is poorly enough understood even on nearby planets, but brown dwarfs simplify the picture. The paper has this to say on the subject:

BDs represent a simplified case where atmospheric dynamics result primarily as a consequence of rapid rotation and internal heat, without the complication of external forcing due to irradiation from a parent star. In addition, the observation of weather on BDs extends the study of cloud meteorology to a higher gravity regime, never before probed.

L and T-class brown dwarfs offer up temperatures in the range of 2200 to 500 Kelvin, with atmospheres cool enough that we can consider them precursors to the study of giant planet atmospheres. How dust grains of silicates and metals condense to form clouds is an ongoing study:

Our current understanding of ultracool atmospheres, including the formation and sedimentation of condensate clouds has developed based on comparisons of detailed atmosphere models to observations of hundreds of L and T dwarfs identified in the solar neighborhood… Nonetheless, fundamental questions remain concerning the most basic properties of condensates including their vertical and horizontal distributions, and how these evolve as a function of effective temperature, as well as the role of secondary parameters such as gravity, metallicity, convection, and rotation.

And the authors go on to point out the need for long-term monitoring both photometrically and spectroscopically over a wide range of wavelengths to reveal the true nature of the brown dwarf’s variability. It’s interesting to see that the researchers looked into the possibility that 2MASS 2139 might be an interacting binary (which is exactly what I wondered when I first read this), but they concluded that the scenario was highly implausible. The study is based on data from the 2.5-meter telescope at Las Campanas Observatory in Chile.

The paper is Radigan et al., “High Amplitude, Periodic Variability of a Cool Brown Dwarf: Evidence for Patchy, High-Contrast Cloud Features,” submitted to the Astrophysical Journal and available online.

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Comments on this entry are closed.

  • Martin J Sallberg September 15, 2011, 13:18

    How can you be so sure that old brown dwarfs have atmospheres similar to giant gas planets? They may as well have unique features, due to high gravity, permanent chaos-theroretical change caused by their deuterium-fusing past, or something completely else. And what can the difference between “free” brown dwarfs and brown dwarfs orbiting stars be, and do any, and if so which, of those differences apply to free-floating gas giants?

  • Gregory Benford September 15, 2011, 13:38

    Paul, any new work on finding brown dwarfs within a few light years? A stepping stone to the bright stars would spur much exploration.

  • Enzo September 15, 2011, 23:09

    Gregory,

    WISE has found one at only 9 light years and also the coldest so far only 25 C :
    http://www.newscientist.com/blogs/shortsharpscience/2011/08/coolest-brown-dwarf-discovered.html

    More, closer ones are hopefully still in WISE’s data.

  • Paul Gilster September 16, 2011, 8:25

    Greg, still waiting on WISE, as Enzo says. but wouldn’t it be a wonderful inducement for interstellar probe ideas if we did find a brown dwarf a couple of light years out? Talk about changing the landscape…

  • jkittle September 16, 2011, 8:57

    So… we have a range of brown dwarf sizes, activities, ages and temperatures, some with apparent surface temperatures as low as 25C, and with more discoveries sure to follow the scope is should to expand further. Can we discuss the types of life forms that may survive in these objects ( PS. one man’s Dwarf star is another man’s Giant Gas planet- one of the the few places in our language where the larger object is a Dwarf.) . Perhaps we could engineer living organisms to INTRODUCE into these warm and violent gas balls. There should be plenty of energy available from the chemical composition differences in the plumes of rising gas. ( we might call them CHEMO-AEROTROPHS, in relation to chemolithotrophs).

  • jkittle September 16, 2011, 15:06

    Gregory B
    The other game in town is run by the Panstarrs team out in Hawaii. They are looking for objects on the distant edges of the solar system , probing the visible wavelengths out to about 1000 nm (very near infrared) they can cover about 3/4 ths of the sky form their location. In theory they could see a Jupiter sized object out to the inner part of the Oort cloud based on reflected light ( Which drops off very quickly due to the inverse square law). heavier objects stay about the same diameter as Jupiter and just gain in density as the mass increase, up to the point were they start hydrogen fusion and become red dwarfs.. The large brown dwarf objects may be darker in color and harder to see in visible light than Jupiter.
    With the still functional WISE telescope turned off, we only have the present data to sift though and we need to have more, in part because these brown dwarfs are very noisy : they tend to fluctuate in thermal output a lot. this in turn may make it harder to spot them in the noisy background, a problem similar to that seen in Kepler, though the observations are aimed at a different method of planet detection. The result is that it will take about three years to get the full story from Panstarrrs ( the method requires multiple earth orbits to get a measure of proper motion) and a long time will also be needed to sort though the best WISE candidates using ground based scopes to follow up and confirm.
    the JWST will not be helpful in FINDING brown dwarfs due to its very small Field of View, but it would be superb to characterize the ones we have located. WFIRST in its present planning is not set for the right wavelengths to see the cool objects, though there is talk of having its wavelengths extended downward to ~3000 nm, , then it would be a superb instrument for finding warm objects. finally the LSST is a much more powerful version of PanStarrs and would help with solar system objects. Observation takes time , money and instruments!

  • jan September 17, 2011, 12:26

    Is this brown dwarf orbiting a star? Maybe we just happened to see it when it had recently collided with a fairly large object, and this is the resulting maelstrom. Or one of its moons arrived at the Roche limit and has recently
    broken up.

    Or is that too much of a coincidence?

    Could brown dwarfs have something similar to solar flares?

  • Steven Rappolee September 17, 2011, 13:55

    could solar voltaic orbiting platforms harvest infrared photons from these objects?
    enough to power a laser power system to slow down and speed up passing world ships?
    these objects could be gravity sling shots for navigation purposes for passing world ships
    would these objects form planets? ice worlds for world ship replenishment, a large world ship could simply stay awhile, say to build the first laser stations there
    and an idea, a large world ship in flight has a large ocean at its zero gee center for aquaculture, during acceleration this ocean becomes a sea at the bottom of the world ship, during deceleration it becomes an ocean at the top of our world ship.
    and what kind of weather would form at a ocean at the center of a rotating world ship?
    take the story, “flight of the dragon fly” and you can imagine the physics of a weightless world ocean inside a world ship, as acceleration stopped the bottom ocean would form a bulge or funnel at its center and part of the ocean would flow onto the spinning walls of the world ship, but I am not how much of which :):)

  • Steven Rappolee September 17, 2011, 18:15

    a further thought for our brown dwarf bound world ship,
    a rotating world ship with an ocean at its ‘bottom” would once acceleration stopped experiencing micro gravity at the center of that sea, this portion of the sea would bow “upwards” but still be rotating, its this that causes our funnel.

    I am thinking this funnel would break into giant drops in the micro gravity center of our world ship, and that these drops would tend to coalesce and break apart (?) if the spherical ocean grew to large however the outer surface of the ocean would start to feel centrifugal force as it nears the rotating floor below, would the ocean then look like a cough drop?
    worse would it rain down on the people below? a deep space accident to rival Noah ! So I have a science fiction story here, but I need a co author! help!
    our world ship in this story is heading for a brown dwarf by the way…………………………:):):) so I need a brown dwarf close to the ecliptic so our world ship can dive over its north pole on a southerly ecliptic trajectory towards alpha Centauri, all good story’s need a sequel!
    by the way our world ship has been in flight so long that the inhabitants may have lost the wisdom as to why the builders put in a micro gravity world ocean in the first place ( aquaculture :) )

  • jkittle September 17, 2011, 23:42

    if he drown dwarf was cool enough, you coudl perhaps use some form of atmospheric braking against the thin envelop of solar wind, perhaps wiht a large sail. not suref the phycial parameters… you may be entering the system at 0-5% to 5 % of C

  • spaceman September 19, 2011, 4:45

    I was under the impression that the recently reported WISE discovery of a brown dwarf only 9 light years away was part of a data release that is still just a modest fraction of the total data taken by WISE; therefore, there is still a good chance that even more brown dwarfs–including one perhaps closer than 9 light years– will show up in future data releases. Is this assessment correct?

  • jkittle September 19, 2011, 8:26

    Spaceman
    that is correct- Data from only a fraction of the sky has been released, and even for this data there is great potential for having missed these faint objects. Each potential BD identified so far has been checked by other telescopes, and the list of BD candidates for further inspection has not been nearly exhausted. One can anticipate many more Dwarfs from the survey, probably out to about 50 to 100 light years. As the paper started, these first finds will be used to help refine the search patterns. WISE data will be cited in hundreds if not thousands of publications over the next decade- including asteroid studies, looking at other low mass stars, investigating dark matter and dark energy, Survey of galaxies, stellar nurseries, and who knows maybe a gas giant in the far reaches of the solar system… time will tell. combine the dagta with Panstarrs and LSST when it comes on line- WOW! we will have laid out the “Genome” of near space out to about 50 light years.