Comet C/2012 S1 (ISON): Observations of the Dust Grains from SOFIA and of the Atomic Gas from NSO Dunn and McMath-Pierce Solar Telescopes (Invited)

D. H. Wooden, C. E. Woodward, D. E. Harker, M. S. Kelley, M. Sitko, W. T. Reach, I. De Pater, R. D. Gehrz, L. Kolokolova, A. L. Cochran, A. J. McKay, K. Reardon, G. Cauzzi, G. Tozzi, D. J. Christian, D. B. Jess, M. Mathioudakis, C. M. Lisse, J. P. Morgenthaler, M. M. Knight

Research output: Contribution to conferenceAbstract

Abstract

Comet C/2012 S1 (ISON) is unique in that it is a dynamically new cometderived from the Oort cloud reservoir of comets with a sun-grazingorbit. Infrared (IR) and visible wavelength observing campaigns wereplanned on NASA's Stratospheric Observatory For Infrared Astronomy(SOFIA) and on National Solar Observatory Dunn (DST) and McMath-PierceSolar Telescopes, respectively. We highlight our early results. SOFIA(+FORCAST [1]) mid- to far-IR images and spectroscopy (~5-35 μm) ofthe dust in the coma of ISON are to be obtained by the ISON-SOFIA Teamduring a flight window 2013 Oct 21-23 UT (r_h≈1.18 AU). Dustcharacteristics, identified through the 10 μm silicate emissionfeature and its strength [2], as well as spectral features from cometarycrystalline silicates (Forsterite) at 11.05-11.2 μm, and near 16, 19,23.5, 27.5, and 33 μm are compared with other Oort cloud comets thatspan the range of small and/or highly porous grains (e.g., C/1995 O1(Hale-Bopp) [3,4,5] and C/2001 Q4 (NEAT) [6]) to large and/or compactgrains (e.g., C/2007 N4 (Lulin) [7] and C/2006 P1 (McNaught) [8]).Measurement of the crystalline peaks in contrast to the broad 10 and 20μm amorphous silicate features yields the cometary silicatecrystalline mass fraction [9], which is a benchmark for radial transportin our protoplanetary disk [10]. The central wavelength positions,relative intensities, and feature asymmetries for the crystalline peaksmay constrain the shapes of the crystals [11]. Only SOFIA can look forcometary organics in the 5-8 μm region. Spatially resolvedmeasurements of atoms and simple molecules from when comet ISON is nearthe Sun (r_h<0.4 AU, near Nov-20--Dec-03 UT) were proposed for bythe ISON-DST Team. Comet ISON is the first comet since comet Ikeya-Seki(1965f) [12,13] suitable for studying the alkalai metals Na and K andthe atoms specifically attributed to dust grains including Mg, Si, Fe,as well as Ca. DST's Horizontal Grating Spectrometer (HGS) measures 4settings: Na I, K, C2 to sample cometary organics (along with Mg I), and[O I] as a proxy for activity from water [14] (along with Si I and FeI). State-of-the-art instruments that will also be employed include IBIS[15], which is a Fabry-Perot spectral imaging system that concurrentlymeasures lines of Na, K, Ca II, or Fe, and ROSA (CSUN/QUB) [16], whichis a rapid imager that simultaneously monitors Ca II or CN. FromMcMath-Pierce, the Solar-Stellar Spectrograph also will target ISON(320-900 nm, R~21,000, r_h
Original languageEnglish
Pages7
Publication statusPublished - 01 Dec 2013

Keywords

  • 6015 PLANETARY SCIENCES: COMETS AND SMALL BODIES Dust
  • 6023 PLANETARY SCIENCES: COMETS AND SMALL BODIES Comets: dust tails and trails
  • 6005 PLANETARY SCIENCES: COMETS AND SMALL BODIES Atmospheres
  • 6008 PLANETARY SCIENCES: COMETS AND SMALL BODIES Composition

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    Wooden, D. H., Woodward, C. E., Harker, D. E., Kelley, M. S., Sitko, M., Reach, W. T., De Pater, I., Gehrz, R. D., Kolokolova, L., Cochran, A. L., McKay, A. J., Reardon, K., Cauzzi, G., Tozzi, G., Christian, D. J., Jess, D. B., Mathioudakis, M., Lisse, C. M., Morgenthaler, J. P., & Knight, M. M. (2013). Comet C/2012 S1 (ISON): Observations of the Dust Grains from SOFIA and of the Atomic Gas from NSO Dunn and McMath-Pierce Solar Telescopes (Invited). 7. http://abstractsearch.agu.org/meetings/2013/FM/P24A-07.html