Are low-activity comets intrinsically different from more active comets?

Cochran, A. L.; Green, Jacklyn R.; Barker, E. S.

doi:10.1016/0019-1035(89)90112-7

Cited by 10 publications

(10 citation statements)

References 10 publications

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“…This is not the first study of its kind. In addition to the papers by AH95, F09 and LS11 listed in the introduction, smaller studies were carried out by A'Hearn and Millis (1980), Newburn and Spinrad (1984), Fink and Hicks (1996) and by our group (Cochran 1987;Cochran et al 1987Cochran et al , 1989Cochran et al , 1992Cochran and Barker 1987). Thus, it has already been discovered that, while the spectra of most comets are very similar, some comets show much weaker C 2 and C 3 relative to other species.…”

Section: Trends In the Datamentioning

confidence: 96%

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Thirty years of cometary spectroscopy from McDonald Observatory

Cochran

Barker

Gray

2012

Icarus

101

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We report on the results of a spectroscopic survey of 130 comets that was conducted at McDonald observatory from 1980 through 2008. Some of the comets were observed on only one night, while others were observed repeatedly. For 20 of these comets, no molecules were detected. For the remaining 110 comets, some emission from CN, OH, NH, C 3 , C 2 , CH, and NH 2 molecules were observed on at least one occasion. We converted the observed molecular column densities to production rates using a Haser (1957) model. We defined a restricted data set of comets that had at least 3 nights of observations. The restricted data set consists of 59 comets. We used ratios of production rates to study the trends in the data. We find two classes of comets: typical and carbon-chain depleted comets. Using a very strict definition of depleted comets, requiring C 2 and C 3 to both be depleted, we find 9% of our restricted data set comets to be depleted. Using a more relaxed definition that requires only C 2 to be below a threshold (similar to other researchers), we find 25% of the comets are depleted. Two-thirds of the depleted comets are Jupiter Family comets, while one-third are Long Period comets. 37% of the Jupiter Family comets are depleted, while 18.5% of the Long Period comets are depleted. We compare our results with other studies and find good agreement. marked difference being the amount of continuum present. This simple observation leads to the question of whether all comets share the same composition or if there are comets with fundamentally different compositions. If differences are seen, then an additional question of the origin of the differences would be raised: are differences the result of different formational scenarios or different evolutionary scenarios? These

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Section: Trends In the Datamentioning

confidence: 96%

“…Some of the comets described in this present paper were already discussed in prior papers (e.g. Cochran et al 1987Cochran et al , 1989Cochran et al , 1992Cochran et al , 2009Cochran and Barker 1987). They are included again for completeness so that all the observations can be found in the same place.…”

Section: Introductionmentioning

confidence: 95%

Thirty years of cometary spectroscopy from McDonald Observatory

Cochran

Barker

Gray

2012

Icarus

101

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“…Despite this, there is consensus that C 2 is depleted with respect to CN by both Cochran et al (1989) and Fink et al (1999) on the basis of upper limits for C 2 detections and by Schulz et al (2003) from a single observational set. We note that our success in acquiring detections of the C 2 emission throughout the apparitions is due to the much larger aperture sizes we typically use as compared with aperture or long-slit spectroscopy, greatly improving the overall contrast of the emission bands to the underlying continuum, since the radial profile of the continuum generally drops off much more rapidly than the observed gas species.…”

Section: Compositionmentioning

confidence: 99%

Physical and compositional studies of Comet 81P/Wild 2 at multiple apparitions

Farnham

Schleicher

2005

Icarus

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“…The ongoing McDonald Observatory Faint Comet Survey by Cochran (1987) and colleagues has observed approximately 100 comets since its inception in 1979. Cochran, Green, and Barker (1989) analyzed 29 "low activity" comets, and Cochran (1990) briefly summarized results for the CN, C2, and C3 abundances of a larger sample of 48 comets. These studies concluded that only one comet -Ρ/Giacobini-Zinner -stood out as having substantially different relative abundances; however, many of the comets have only "uninteresting" upper limits for C2 and C3.…”

Section: Data Bases For Compositional Studies Of Cometsmentioning

confidence: 99%

Comet Taxonomy and Evolution

Schleicher¹

1994

Symp. - Int. Astron. Union

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Abstract.Measurements of physical and dynamical properties of comets have yielded considerable evidence for variations in the origin and evolution of these primordial objects. Given these findings, one might reasonably expect to observe differences in the chemical composition as well. This paper reviews our current state of knowledge of the similarities and differences in the composition of comets, and summarizes the recent findings by A'Hearn et al. (1994) for two taxonomic classes of comets and evidence of compositional variation due to origin and/or evolution.

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Are low-activity comets intrinsically different from more active comets?

Cited by 10 publications

References 10 publications

Thirty years of cometary spectroscopy from McDonald Observatory

Thirty years of cometary spectroscopy from McDonald Observatory

Physical and compositional studies of Comet 81P/Wild 2 at multiple apparitions

Comet Taxonomy and Evolution

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