In the News this month... the puzzle of crystalline silicates in comets
The image shows a young sun-like star encircled by its planet-forming disk of gas and dust. The silicate that makes up most of the dust would have begun as non-crystallized, amorphous particles. CREDIT: NASA/JPL-Caltech
When they compared their results to similar spectra of EX Lupi taken between outbursts, they found that the older observatories only showed the presence of amorphous silicates rather than the crystalline form. In the newer observations taken during the star's outburst, a broad peak corresponding to amorphous silicates was present, but an additional narrow peakat a wavelength of 10 microns was also visible. This narrow feature is likely caused by the presence of forsterite, the magnesium-rich crystalline form of the mineral olivine.
The appearance of this additional feature in the spectrum during the star's outburst suggests that crystal formation was happening in the star's disk during the outburst. The researchers think that this is the first time ongoing crystal formation has been observed. They say that the crystals were probably formed on the surface layer of the star's inner disk by heat from the outburst, in a process known as thermal annealing where a substance is heated to a temperature where some some of its bonds break and then re-form altering the material's structure and physical properties. The forsterite crystals detected are just like those found in comets in the solar system which could have been produced by similar outbursts from out own Sun when it was much younger.
Posted by Megan on Saturday 30th May 2009 (13:06 UTC) | Add a comment | Permalink
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