Investigation of Coma Morphology of Long and Short Period Comets

Comets are icy bodies known to contain dust, ice, carbon dioxide, ammonia, methane and other similar gases. They contain dust, ice, carbon dioxide, ammonia, methane and such similar gases. They are the carriers of the most primitive, volatile-rich materials in the Solar System. They are divided into two groups: long period comets (LPCs) and short period comets (SPCs). The LPCs have orbital periods of 200 years or more, while those of the SPCs are less. The orbits of SPCs are distributed along the ecliptic, whereas the LPC orbits are nearly isotropic (1). The physical differences between the two kinds are not well understood. It is generally assumed that the LPCs lack a mantle, therefore their comae should be largely homogenous. The SPCs, on the other hand, are thought to have formed with a mantle which may cause jet-like features in the coma. The presence of such a mantle is inferred rather than directly observed. It is modelled to be a dust layer covering the surface of the nucleus which thermally insulates it and hence reduces sublimation rate, but does not stop the escape of the sublimating molecules completely (2,3) In this project, I conducted CCD (charged coupled device) reduction on images of comets from the WIYN 0.9 m telescope with the HDI camera at Kitt Peak National Observatory. With these images, I analyzed the comets’ physical characteristics by performing aperture photometry to obtain their apparent and absolute magnitudes and creating a compilation of the morphologies of the SPC and LPC comae in order to compare their appearances and determine the implications on the formation of their nuclei in the early solar system.

Figure 1. Sample single image of 65P taken with the HDI camera of WIYN 0.9 m telescope at Kitt Peak National Observatory, Arizona with a 60 second exposure on March 27, 2017. It is a short period comet with period of 7.66 years. The pixel scale is 0.43 arcseconds.

1. A’Hearn, M. F., Millis, R. C., Schleicher, D. O., Osip, D. J., & Birch, P. V. The ensemble properties of comets. Icarus, 118, 223-270, 1995

2. Mendis, D.A., & Brin, G.D. Monochromatic brightness variations of comets, The Moon, 17, 359 , 1977

3. Brin, G.D., & Mendis, D.A, Dust release and mantle development in comets, Astrophysical Journal, 229, 402, 1979