MID-INFRARED SPECTROPHOTOMETRIC OBSERVATIONS OF FRAGMENTS B AND C OF COMET 73P/SCHWASSMANN-WACHMANN 3

Journal Article · Sat Jan 15 00:00:00 EST 2011 · Astronomical Journal (New York, N.Y. Online)

DOI:https://doi.org/10.1088/0004-6256/141/1/26· OSTI ID:21583269

Harker, David E ^[1]; Woodward, Charles E ^[2]; Kelley, Michael S ^[3]; Sitko, Michael L ^[4]; Wooden, Diane H ^[5]; Lynch, David K ^[6]

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1. Center for Astrophysics and Space Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0424 (United States)
2. Department of Astronomy, School of Physics and Astronomy, University of Minnesota, 116 Church Street, S. E., Minneapolis, MN 55455 (United States)
3. Department of Astronomy, University of Maryland, College Park, MD 20742-2421 (United States)
4. Space Science Institute, Boulder, CO 80301 (United States)
5. NASA Ames Research Center, Space Science Division, MS 245-1, Moffett Field, CA 94035-1000 (United States)
6. Thule Scientific, P.O. Box 953, Topanga, CA 90290 (United States)

We present mid-infrared spectra and images from the Gemini-N (+ Michelle) observations of fragments SW3-[B] and SW3-[C] of the ecliptic (Jupiter family) comet 73P/Schwassmann-Wachmann 3 pre-perihelion. We observed fragment B soon after an outburst event (between 2006 April 16-26 UT) and detected crystalline silicates. The mineralogy of both fragments was dominated by amorphous carbon and amorphous pyroxene. The grain size distribution (assuming a Hanner-modified power law) for fragment SW3-[B] has a peak grain radius of a{sub p} {approx} 0.5 {mu}m, and for fragment SW3-[C], a{sub p} {approx} 0.3 {mu}m; both values are larger than the peak grain radius of the size distribution for the dust ejected from ecliptic comet 9P/Tempel 1 during the Deep Impact event (a{sub p} = 0.2 {mu}m). The silicate-to-carbon ratio and the silicate crystalline mass fraction for the submicron to micron-sized portion of the grain size distribution on the nucleus of fragment SW3-[B] were 1.341{sup +0.250}{sub -0.253} and 0.335{sup +0.089}{sub -0.112}, respectively, while on the nucleus of fragment SW3-[C] they were 0.671{sup +0.076}{sub -0.076} and 0.257{sup +0.039}{sub -0.043}, respectively. The similarity in mineralogy and grain properties between the two fragments implies that 73P/Schwassmann-Wachmann 3 is homogeneous in composition. The slight differences in grain size distribution and silicate-to-carbon ratio between the two fragments likely arise because SW3-[B] was actively fragmenting throughout its passage while the activity in SW3-[C] was primarily driven by jets. The lack of diverse mineralogy in the fragments SW3-[B] and SW3-[C] of 73P/Schwassmann-Wachmann 3 along with the relatively larger peak in the coma grain size distribution suggests that the parent body of this comet may have formed in a region of the solar nebula with different environmental properties than the natal sites where comet C/1995 O1 (Hale-Bopp) and 9P/Tempel 1 nuclei aggregated.

• OSTI ID: 21583269
• Journal Information: Astronomical Journal (New York, N.Y. Online), Vol. 141, Issue 1; Other Information: DOI: 10.1088/0004-6256/141/1/26; ISSN 1538-3881
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ASTROPHYSICS
CARBON
COMETS
DATA ANALYSIS
DUSTS
GRAIN SIZE
INFRARED SPECTRA
MINERALOGY
SILICATE MINERALS
SILICATES
SOLAR NEBULA
SPECTROPHOTOMETRY
ELEMENTS
MICROSTRUCTURE
MINERALS
NEBULAE
NONMETALS
OXYGEN COMPOUNDS
PHYSICS
SILICON COMPOUNDS
SIZE
SPECTRA