[extropy-chat] stardust discovery
amara at amara.com
Sat Mar 18 18:30:01 UTC 2006
A follow-up comment regarding the crystalline silicate in the dust
particle from the Stardust mission. Since it seems that the silicate
can cycle from crystalline to amorphous, other new research confirms
nicely that cycle. My colleague told me that Max-Planck Institute for
Astronomy in Heidelberg had a press release where they found a
sequence of brown dwarf dust changing from amorphous to crystalline.
They compared it with comet Hale-Bopp which has the strongest signals
for crystalline dust. See here:
>Stardust's discovery of crystalline silicates in the dust of comet
>Wild 2 implies either: (1)
>1) that the dust formed above glass temperature (>>1000K) in the inner
>disk region around a hot young star, and was radially mixed in the
>solar nebula from the inner regions a larger distance from the star
>2) the dust particles condensed in the outflow of evolved red giants or
>supergiants stars (for example AGB stars eject 15% of their silicates in
>Discovering which tells us alot of the early formation of the solar
>system. Another complication is that crystalline silicates are rapidly
>converted into amorphous silicates in the interstellar medium and
>back to crystalline silicates in protoplanetary disks.
>Next question: does it match solar?
>Also, wasn't crystalline silicates was found in the spectra of
>comet Hale-Bopp? Then Stardust's discovery shouldn't be a surprise.
>Also, I read that calcium-aluminum-inclusions (CAI) were found,
>which are probably from the extremely early part of solar-system
>formation (or from the molecular cloud before), which are known
>to form quickly by a high temperature event (lightning, for example),
>cooling in an hour or a few hours.
>So the stardust comet samples indeed have 'hot' embedded in 'cold'...
>Xander Tielens: Interstellar and Circumstellar Dust
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