The activities of comets related to their aging and origin
- Fred L. Whipple
- … show all 1 hide
Rent the article at a discountRent now
* Final gross prices may vary according to local VAT.Get Access
Two indices have been developed for the purpose of comparing the natures of various classes of comets. The first is the Activity Index (AI), measuring the inherent magnitude increase in brightness from great solar distances to maximum near perihelion. The second, or Volatility Index (VI), measures the variation in magnitude near perihelion. Tentative determinations of these two indices are derived from observations by Max Beyer over more than 30 years for long-period (L-P) and short-period (S-P) comets near perihelion and from other homogeneous sources. AI determinations are made for 32 long-period (L-P) comets and for 14 short-period (S-P). The range of values of AI is of the order of 3 to 10 magnitudes with a median about 6. An expected strong correlation with perihelion distance q, is found to vary as ∼ q −2.3. Residuals from a least-square solution (ΔAI) are used for comparing comets of different orbital classes, the standard deviation of a single value of ΔAI is only ±1m.1 for L-P comets and ±1m.2 for S-P comets.
Among the L-P comets, 19 of period P larger than 104 years yield 〈ΔAI〉 = 0m.27 ± 0m.25 compared to 0m.39 ± 0m.26 for 13 of period between 102 years and 104 years. This denies any fading with aging among the L-P comets. Also no systematic change with period occurs for the VI index, leading to the same conclusions. Weak correlations are found with the Gas/Dust ratio of comets. No correlations are found between the two indices, nor of either index with near-perihelion magnitudes or orbital inclination.
The various data are consistent with a uniform origin for all types of comets, the nuclei being homogeneous on the large scale but quite diverse on a small scale (the order of a fraction of kilometer in extent). Small comets thus may sublimate away entirely, leaving no solid core, while huge comets may develop a less volatile core by radioactive heating and possibly become inactive like asteroids after many S-P revolutions about the Sun. When relatively new, huge comets may be quite active at great solar distances because of volatiles from the core that have refrozen in the outer layers.
- Bayer, M.: 1969, “Nachweis und Ergebnisse von Kometen-Beobachtungen aus den Jahren 1921–1968”, Astron. Nach., 291, 257–264.
- Beyer, M.: 1972, “Physische Beobachtungen von Kometen XVII”, Astron. Nach., 293, 241–257.
- Bobrovnikoff, N. T.: 1941, “Investigations of the Brightness of Comets, Part I”, Contr. of the Perkins Observatory, No. 15.
- Bobrovnikoff, N. T.: 1942, “Investigations of the Brightness of Comets, Part II”, Contr. of the Perkins observatory, No. 16.
- Bortle, J. E. 1991, “Post-perihelion Survival of Comets with Small q”, Inter. Comet Quart., 13, 89–91.
- Cochran, A. L. 1990, “Are all Comets Created Equal ?”, Asteroids, Comets, Meteors III, ed. C. I. Lagerkvist et al, Uppsala Univ., 281–284.
- Goldreich, P. and Ward, W. R.: 1973, “The Formation of Planetesimals”, Astrophys. J., 183, 1051–1061.
- Duncan, M., Quinn, T., and Tremaine, S.: 1987, “The Formation and Extent of the Solar System Comet Cloud”, Astrophys. J., 94, 1330–1338.
- Duncan, M., Quinn, T., and Tremaine, S.: 1988, “The Origin of Short-period Comets”, Astrophys. J., 328, L-69–73.
- Fernandez, J. A.: 1980, “On the Existence of a Comet Belt Beyond Neptune”, Mon. Not. Roy. Astr. Soc., 192, 481–491.
- Green, S. F., Meadows, A. J., and Davies, J. K.: 1985, “Infrared Observations of the Extinct cometary Candidate Minor Planet (3200) 1983TB”, Mon. Not. R. A. S., 214, 29p–36p.
- Halliday, I.: 1988, “Geminid Fireballs and the Peculiar Asteroid 3200 Phaethon”, Icarus, 76, 279–294.
- Hartmann, W. K., Tholen, D. J., and Cruikshank, D. P.: 1987, “The Relationship of Active Comets, ‘Extinct’ Comets, and Dark Asteroids”, Icarus,69, 33–50.
- Hills, J.G.: 1981, “Comet showers and the Steady-State Infall of Comets From the Oort Clouds”, Astron. J., 86, 1730–1740.
- Hills, J. G.: 1982, “The Formation of Comets by Radiation Pressure in the Outer Protosun”, Astron. J., 87, 906–910.
- Joss, P. C.: 1973, “On the origin of short-period Comets”, Astron. Astrophys., 25, 271–273.
- Kresák, L.: 1979, “Dynamical Interrelations Among Comets and Asteroids”, Asteroids, ed. T. Gehrels, Univ. Arizona Press, 289–309.
- Kuiper, G. P.: 1951, “On theOrigin of the Solar System”, Astrophysics, Ed. J. A. Hynek, McGraw-Hill, NY, 357–424.
- Meech, K. J. and Belton, M. J. S.: 1989, “(2060) Chiron”, Bur. Ast. Telegrams, IAU, No. 4770.
- Meech, K. J.: 1991, “Physical Aging in Comets”, Comets in The Post-Halley Era”, IA U colloquium 116, ed. R. L. Newburn, Jr., M. Neugebuer and J. Rahe, Kluwer Acad. Pub., 625.
- Oort, J.: 1950, “The Structure of the Cloud of Comets Surrounding the Solar System and a Hypothesis Concerning its Origin”, Bull. Astron. Netherlands, 11, 91.
- Opik, E. J.: 1963, “The Stray Bodies in the Solar System. Part 1. Survival of Cometary Nuclei and the Asteroids”, Advan. Astron. Astrophys., 2, 219–262.
- Rickman, H.: 1991, “The Thermal History and Structure of Cometary Nuclei”, Comets in to Post-Halley Era, Ed. R. L. Newburn, Jr., M. Neugebauer, J. Rahe, Kluwer Acad. Pub., 733–760.
- Sekanina, Z.: 1982, “The problem of split Comets in Review”, Comets, ed. L. L. Wilkening, Univ. Arizona, Tucson, 251–287.
- Sekanina, Z.: 1991. “Cometary Activity, Discrete Outgassing Areas, and Dust-Jet Formation”, Comets in the Post-Halley Era, Eds. R. L. Newburn, Jr., M. Neugebauer, J. Rahe, Kluwer Acad. Pub., 769–823.
- Strazzula, G. and Johnson, R. E.: 1991, “Irradiation Effects on Comets and Cometary Debris”, Comets in the Post-Halley Era, Ed. R. L. Newburn, Jr., M. Neugebauer, J. Rahe, Kluwer Acad. Pub., 243–275.
- Vsekhsvyatskii, S. K.: 1964, Physical Characteristics of Comets, Israel Prog. Sci. Translations”, Jerusalem, p20.
- Whipple, F. L.: 1950, “A comet Model. I. The Acceleration of comet Encke”, Astrophy. J., 111, 374–394.
- Whipple, F. L.: 1991, “A new Activity Index for Comets”, International Conference on Asteroids, Cornets, Meteors, in press.
- Whipple, F. L.: 1992, “A Volatility Index for Comets”, Icarus, submitted.
- Whipple, F. L. and Stefanik, R. P.: 1966, “On the Physics and Splitting of Cometary Nuclei”, Nature et Origine des Comètes, Soc. Royale des Sci. de Liege, Ser. 5, Vol. 5, 33–52.
- Yabushita, S. and Wada, K.: 1988, “Radioactive Heating and Layered Structure of Cometary Nuclei”, Earth, Moon, and Planets, 40, 303–313.
- Yamamoto, T. and Kozasa, T.: 1988, “The Cometary Nucleus as an Aggregate of Planetesimals”, Icarus, 75, 540–551.
- The activities of comets related to their aging and origin
Celestial Mechanics and Dynamical Astronomy
Volume 54, Issue 1-3 , pp 1-11
- Cover Date
- Print ISSN
- Online ISSN
- Kluwer Academic Publishers
- Additional Links
- aging of comets
- activity of comets
- Industry Sectors
- Fred L. Whipple (1)
- Author Affiliations
- 1. Smithsonian Astrophysical Observatory, 60 Garden Street, 02138, Cambridge, Massachusetts, U.S.A.