archive: SETI Brown dwarf stars may have weather!

SETI Brown dwarf stars may have weather!

Larry Klaes ( )
Fri, 07 May 1999 13:00:56 -0400

>X-Authentication-Warning: majordom set sender
to owner-astro using -f
>Date: Fri, 7 May 1999 15:45:30 GMT
>From: Ron Baalke <>
>Subject: [ASTRO] Weather Out Of This World
>Reply-To: Ron Baalke <>
>Anglo-Australian Observatory
>PO Box 296
>Epping NSW 1710
>Weather out of this world
>Astronomers have found the first hints that failed stars known as 'brown
>may have weather patterns with winds, clouds and storms. This was announced
>today by Dr Chris Tinney at ScienceNOW! in Melbourne.
>Dr Tinney of the Anglo-Australian Observatory and Mr Andrew Tolley, a
student at
>the University of Oxford, recently observed a brown dwarf and noted
changes in
>its surface chemistry as it rotated. They made their observations with
>Australia's largest optical telescope, the Anglo-Australian Telescope (AAT),
>located at Siding Spring outside Coonabarabran NSW.
>Brown dwarfs are failed stars with masses in between that of Jupiter-like
>planets and normal stars. For decades, scientists have suspected that brown
>dwarfs exist but the first confirmed detection came only a few years ago.
>after 30 years of searching, less than 50 brown dwarfs have been
discovered. Of
>these, only a handful are bright enough and close enough to be studied for
>Tinney's team is leading Southern Hemisphere attempts to learn more about
>dwarfs. They are very faint, and extremely difficult to detect, and for
>and Tolley to have noted surface changes is remarkable.
>Brown dwarfs never made it as stars, being too small to light up their
>furnaces. Instead, they just smoulder away in space at temperatures below
>degrees -- less than a third that of a typical star like the sun. 'Proper'
>are so hot that their surfaces are a completely smooth mix of vapourised
>material. But the outer layers of brown dwarfs are cool enough for
chemicals to
>'rain' out as smoke-like particles.
>Tinney said, "Brown dwarfs are too small and far away to see the clouds. We
>detected them indirectly through the effects they have on the brown dwarf's
>atmosphere. We looked for a changing pattern of chemistry in the
atmosphere of
>one brown dwarf, called LP944-20, as it rotated."
>With a special instrument developed by the AAT, called the Taurus Tuneable
>Filter, Tinney and Tolley were able to 'tune into' a very narrow
wavelength band
>and accurately measure tiny fluctuations. The narrow band chosen matched
that of
>a tracer molecule called titanium oxide. The strength of this tracer allowed
>astronomers to track the formation of cloud particles.
>Now that the technique has been honed, the astronomers are looking to other
>brown dwarfs. "We plan to study at least two more brown dwarfs in the next
>months," Tinney concluded.
>Background material on brown dwarfs,
>Background material on titanium oxide,
>Information and photos are also available on the ScienceNOW! website,
>For further information contact:
>Roger Bell,
>Public Relations Officer
>Anglo-Australian Observatory
>(02) 9372 4865
>Dr Chris Tinney
>(02) 9372 4849 (Office), May 3-5, May 6 (9am-2pm),May 11-14
>0416 092117 (Mobile), May 6 (4pm) - May 10
>[Image caption:]
>The left panel shows the weather patterns we might expect on a brown dwarf
if it
>looked like Jupiter. The right panel shows observed variations seen as the
>dwarf LP944-20 rotates. The arrows highlight strong episodes of cloud passage
>where very different signals are seen in the two colours observed.