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Biology Articles » Astrobiology » Constraints on nebular dynamics and chemistry based on observations of annealed magnesium silicate grains in comets and in disks surrounding Herbig Ae/Be stars » Figures

Figures
- Constraints on nebular dynamics and chemistry based on observations of annealed magnesium silicate grains in comets and in disks surrounding Herbig Ae/Be stars

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Fig. 1.   UV spectra obtained with the IUE of the Herbig Be star HD 100546 at two epochs (thin and thick lines). The spectra illustrate variability in the red-shifted infall features and variability in the strength of blue-shifted absorption associated with the stellar wind. The wind can be traced to approx200 km/s. The electronic transitions involved are the Si+ UV multiplet 2 and the resonance doublet of C+3.

figure 1

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Fig. 2.   Three IR spectra (Upper) of amorphous Mg silicate smoke annealed in the laboratory for 6, 48, and 196 h at 1,027 K, fit by using seven gausian peaks and compared with the spectrum of dust in comet Halley, fit by using five of these same peaks.

figure 2

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Fig. 3.   Schematic drawing of a protostellar nebula (distance on a log scale) centered on the protoSun. The region of dust processing is shown (5 AU), infalling envelope, bipolar outflow, and less collimated wind. Comet formation is expected to occur from approx5 to beyond 40 AU.

figure 3

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Fig. 4.   Calculated and empirical vapor pressures in the range 15-200 K (68, 69). Compounds include interstellar grain mantle (N2, CO, CO2) and hydrogenated nebular species (CH4, C2H4, C2H6, C3H6, C3H8, NH3). C2H6, C3H8, and NH3 are enlarged for clarity.

figure 4

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