MID-INFRARED OBSERVATIONS OF THE NUCLEUS AND DUST OF COMET P/SWIFT-TUTTLE

NASA-CR-204995FINAL TECHNICAL REPORTNAGW 3127 Fund 23343AJune 1997 Barbara JonesMid-Infrared Observational and Theoretical Studies ofStar Formation and Early Solar SystemsThe first 2 years of this program were used to make mid-IR observations of regions of star for-mation in the Orion nebula with the UCSD mid-IR camera at the UCSDAJniversity of Minnesotatelescope at Mt. Lemmon. These observations attempted to make the first systematic study of anextended region, known to have newly forming stars, and expected to have complex mid-IR emis-sion. We discovered, to our surprise, that most of the thermal emission originated from extendedsources rather than from point sources. This interesting observation made the analysis of the datamuch more complex, since the chop/nod procedures used at these wavelengths produce a differ-ential measurement of the emission in one region compared to that in the adjacent region. Disen-tangling complex extended emission in such a situation is very difficult.In parallel with this work we were also observing comets in the thermal infrared, the othercomponent of the original proposal. Some spectacular data on the comet Swift-Tuttle wasacquired and published (Fomenkova, Jones et al., Astron. J., 1995, 110, 1866). This paperdescribes a changing jet structure observed over a 2 week period. The rotation period of the cometcan be measured at 66 hours. The size of the nucleus can also be estimated (at 30 km) from theobserved excess flux from the nucleus. These data have lead to the development of modelsdescribing the action of dust particles of differing sizes and composition leaving the nucleus. Thespatial distribution of the predicted IR emission has been compared to the observed jet structures,leading to estimates of both particles sizes, relative amounts of silicate vs organic grains, and theamounts of dust emitted in the jets vs isotopic emission. This work forms the basis for the PhDthesis of James Sarmecanic.