C / 1969 Y1 (Bennett)

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C / 1969 Y1 (Bennett) [i]
Comet Bennett.jpg
Properties of the orbit ( animation )
Epoch:  April 4th 1970 ( JD 2,440,680.5)
Orbit type long-period
Numerical eccentricity 0.9962
Perihelion 0.538 AU
Aphelion 282 AU
Major semi-axis 141 AU
Sidereal period ~ 1678 a
Inclination of the orbit plane 90.0 °
Perihelion March 20, 1970
Orbital velocity in the perihelion 57.4 km / s
history
Explorer JC Bennett
Date of discovery December 28, 1969
Older name 1970 II, 1969i
Source: Unless otherwise stated, the data comes from JPL Small-Body Database Browser . Please also note the note on comet articles .

C / 1969 Y1 (Bennett) is a comet that could be seen with the naked eye in 1970 . Due to its extraordinary brightness, it is counted among the " Great Comets ". It was the second comet that was also observed from orbiting satellites .

Discovery and observation

The comet was on the evening of 28 December 1969 by the South African amateur astronomer John C. Bennett with a 125 mm - refractor in Pretoria discovered. The discovery came just 15 minutes after he began his regular comet search program, which he had carried out for many years and had searched in vain for 333 hours in the past three years. Bennett estimated the comet's magnitude 8.5 mag and described it as small, diffuse, and with no discernible tail . He reported his discovery to the official authorities and was able to repeat his observation of the comet the following evening.

Further independent discoveries were made in South Africa and Australia over the following days. In the first days of January 1970, the comet was observed by many observers in the southern hemisphere , while its brightness initially changed little. At the end of January it had reached about 7 mag and for the first time a tail 1 ° long could be detected. Until the end of February, the comet could also be observed with the naked eye, the tail had reached 5 ° length.

In March the comet's brightness increased rapidly and it could also be seen for the first time in the morning sky by observers in southern regions of the northern hemisphere . By the middle of the month the brightness reached values ​​of 0 mag and the length of the tail 10 °, which was curved with many thread-like structures and an unusually large amount of dust. On March 22nd, the comet came closest to the Sun for observers on Earth, and in the course of a few days it ceased to be visible to observers in the southern hemisphere as it moved to the northern sky. Its brightness slowly decreased again. The shape and shape of the tail changed from night to night, it showed fan-shaped rays and an opposing tail could also be observed. Towards the end of the month the comet was a circumpolar object and thus visible all night, the brightness was still 1.5 mag, while the length of the gas tail was 10 ° and that of the dust tail at least 20 °.

Although the comet continued to lose its brightness, the longest tail lengths of over 20 ° were observed in the first half of April. Both the gas tail and the dust tail showed rapid changes, kinks and compression. The last observations with the naked eye were made in May, by the end of the month the brightness had dropped to 7 mag and the length of the tail had decreased to 2.5 °.

From August on, the tail was no longer visible and the brightness was around 11–12 mag in mid-September and had fallen to around 13 mag by mid-November. The last photographic observation was made on February 27, 1971 by Elizabeth Roemer at Catalina Station in Arizona . An attempt to find the comet again at the end of June was unsuccessful.

The comet reached a maximum brightness of 0.5 mag, making it the seventh brightest comet since 1935.

Scientific evaluation

Soon after the first orbital elements could be calculated, it was assumed that the comet would become “a bright object for observation with the naked eye”. It turned out that it combined three favorable properties that made it an extraordinary comet for observation: a short perihelion distance to the sun, a short distance to the earth and a high level of brightness. Numerous research projects were therefore initiated, so that Comet Bennett became the most photographed and most thoroughly researched comet of its time.

Ultraviolet

A few years earlier it was suspected that comets were surrounded by a gas envelope made of hydrogen , which could be detected by observations in the ultraviolet light of the Lyman α line at 121.5 nm. This observation is not possible from the ground, however, because the ultraviolet light does not penetrate the atmosphere . The first observation of a comet in the ultraviolet came in January 1970, when the Orbiting Astronomical Observatory (OAO-2) recorded the spectrum of comet C / 1969 T1 (Tago-Sato-Kosaka) and detected the predicted gas envelope. When comet Bennett reached a favorable position for observation from space in February of the same year, it was also systematically observed with OAO-2 from mid-March to mid-April because of this discovery in order to follow the temporal and spatial changes in the comet's coma . In addition to the Lyman α line, the emission lines of OH, NH and CN could also be measured.

From the photometric data obtained with OAO-2, the production rate of OH and H, as well as their dependence on the distance from the sun of the comet, could be derived. The results confirmed the assumption that gas production by comets at short distances from the Sun is determined by the evaporation of water from the nucleus . The total loss of water during its passage through the inner solar system has been estimated to be around 200 million tons .

On April 1 and 2, the comet was also observed for the first time by the Orbiting Geophysical Observatory (OGO-5). With a more sensitive photometer than with OAO-2, the emissions of hydrogen atoms could be detected up to a distance of several million km from the comet's core. The mass of this hydrogen could be derived from the measurements at around 2 million t . After these first successful measurements, it was decided to continue observing the comet with the instruments on board OGO-5, and a total of twelve intensity maps of the comet's Lyman-α emission were obtained by April 30th. The maps show the development of the hydrogen envelope over the course of a month. On April 1, when the comet was about 0.6  AU from the Sun, the hydrogen envelope had an area of ​​20 million km × 15 million km, after which it slowly became smaller. The inferred production rate of hydrogen atoms was comparable to the value obtained from the OAO-2 observations. In further investigations, attempts were made to theoretically underlay the measurement results with greater agreement and to provide refined models for the formation of the hydrogen shells.

Visible light

At the Goddard Space Flight Center in Maryland from March 28 to April 18, 1970, images of the comet were made with interference filters at various wavelengths in the purple, blue, green and yellow regions of the spectrum. In particular, the emission lines of CN, C 2 , CO + and Na were evaluated. Maps of the comet's coma with lines of equal brightness (isophotes) up to a distance of 150,000 km from the nucleus were created from these and other recordings, which were taken on April 8th and 9th at the Hamburg observatory in white light . Similar research was also conducted from March 31 to April 27 at the University of Western Ontario's Hume Cronyn Memorial Observatory in Canada . There, too, pictures of the comet were made with interference filters at different wavelengths in the violet, blue and green regions of the spectrum. In particular, the emission lines of CN and C 2 were measured and their intensity profiles in parallel and perpendicular directions to the comet's tail were evaluated and displayed in the form of isophotes.

From March 30 to May 7, 1970, spectrographic examinations of the comet were carried out at the University of Toledo Observatory in Ohio . In this way, brightness profiles of the emission lines of C 2 and CN up to distances of 100,000 km from the comet's nucleus were obtained. A brightness profile of the “forbidden” emission line of the oxygen atom at 630 nm was also created from images taken on April 18 . It has been suggested that these atoms stem from the decay of CO 2 and that Comet Bennett's CO 2 was more abundant than water. The same recordings were also used to create a brightness profile of the H 2 O + ion up to a distance of about 100,000 km from the core and to determine its production rate. The results could be revised later by improving the preparation of the data. However, the exact formation process of the radicals in the comet's coma remains unclear. B. the amount of OH radical cannot be explained solely by the decay of water evaporating from the core.

From March 7th to 18th, pictures of the comet were taken at the Cerro Tololo Inter-American Observatory in Chile , in which the comet's tail showed no noticeable disturbances, only pronounced lateral rays could be observed. This indicates that relatively calm interactions between the solar wind and the associated magnetic fields and the comet took place during this period .

Recordings made from the end of March to the end of May at the Osservatorio Astrofisico di Asiago in Italy could be evaluated with regard to the distribution of gas and dust in the tail of comet Bennett. On the 3rd / 4th April it could be observed that the gas tail of the comet was torn from the coma. Spectra of the neutral gas envelope showed the emission lines of CN, C 2 , C 3 , CH, NH 2 and Na. The gas tail showed a daily fluctuating intensity and structure, which indicated a very irregular production of CO + . In particular, attempts were made to correlate a noticeable kink observed in the comet's gas tail on April 4 with simultaneous measurements of solar activity and solar wind. For this purpose, measurement data were used that were supplied at the same time by the space probes OGO-5, Vela 5 , HEOS-1 and Pioneer 8 , as well as by the ALSEP experiment installed by Apollo 12 on the lunar surface . In an initial investigation, no events were found in the measured dynamics of the solar wind that could explain the deformations of the comet's tail. However, further investigation concluded that, first, the dynamics of the solar wind measured near Earth were likely to be different from those near the comet, and second, the monitoring of the solar wind was patchy in location and time, so that the deformations of the comet's tail can still be traced back to events in the solar wind.

Three images of the comet in red light, which were taken from May 5th to 8th at the Thuringian State Observatory Tautenburg , when the earth was almost in the plane of the comet's orbit, showed two anomalous structures in the comet's tail: one radial structure and one short tip directed towards the sun, probably caused by the dust of the comet. The later evaluation of these observations provided evidence for the peculiarity of a "neck line structure" (NLS) in the dust tail of a comet, which was theoretically derived only in 1977.

Infrared

Observations of the brightness development of the comet in the infrared were made at the Lunar and Planetary Laboratory in Arizona from late March to mid-April 1970 . In addition, on March 31, 1970, observations with an infrared telescope were made on board a Learjet .

On April 4, 1970, Comet Bennett was photometrically measured at the O'Brien Observatory of the University of Minnesota in the near and mid- infrared at 2–20 µm wavelength. In addition to the continuum of a black body of around 500 K at short wavelengths, an emission line was also found at 10 µm , which was attributed to silicate grains in the comet's dust. The measurement result was confirmed by another measurement on April 21 at the Kitt Peak National Observatory in Arizona.

Microwaves

An attempt was made to detect the emission of formaldehyde at 4.83 GHz on six days in mid-March 1970 with the radio telescope of the Green Bank Observatory in West Virginia . An attempt was also made on four days at the end of March 1970 with the radio telescope of the United States Naval Research Laboratory in Maryland to detect the emission of water molecules at 22.2 GHz. In both cases, no such emissions could be detected.

Others

Comet Bennett had also been placed on the astronaut observation program aboard Apollo 13 . After the comet could already be photographed on April 13, 1970, it was supposed to be recorded again on April 14, after the daily television broadcast was complete. During the maneuver with which the spaceship was to be aligned for these recordings, one of the oxygen tanks exploded and the subsequent rescue measures prevented all further scientific programs.

In 1973, Delsemme and Rud first attempted to determine the radius and albedo of several comets, including comet Bennett, from measurements of brightness during large distances from the Sun and from the observed gas production at short distances from the Sun. Assuming that the comet's nucleus consists essentially of water ice and that the entire surface is completely covered with snow , which sublimates on approaching the sun , an albedo of about 0.66 could be derived for the comet's nucleus. This value is significantly higher than the values ​​that were later found for comet surfaces, which was probably due to impermissible assumptions and incorrect measurements of the comet's brightness. Nevertheless, their calculation method was groundbreaking for later research.

Orbit

Favored by the mutual positions of comet and earth ( elongation always greater than 32 °) it could be observed continuously from its discovery in the southern sky to its sightings in the middle of September 1970 near the celestial north pole . For the comet, von Marsden was able to determine an elliptical orbit that is inclined by about 90 ° to the ecliptic from 391 observation data over a period of about 10 months . Its orbit is thus perpendicular to the orbits of the planets . At the point of the orbit closest to the sun ( perihelion ), which the comet last traversed on March 20, 1970, it was a little further from the sun than the innermost planet Mercury at a distance of about 80.4 million km . On March 26th, it came close to Earth to about 0.69 AU / 103.0 million km.

As early as 1973 had Marsden, Sekanina shown and Yeomans that the orbit of the comet can best be described as out of the gravitational well as non-gravitational be taken into account when calculating forces. For the comet's original orbit before it approached the inner solar system, they determined an ellipse with a value for the semi-major axis of around 135 AU, which corresponds to an orbital period of around 1570 years. In a more recent study from 1978 Marsden, Sekanina and Everhart then gave new values ​​for the original and the future semiaxis. However, this calculation only took into account gravitational forces.

According to the latest research by Królikowska, in which 548 observations over a period of about 10 months and also non-gravitational forces were taken into account, the following applies: The comet moves on an extremely elongated elliptical orbit around the sun. According to the orbital elements afflicted with a certain uncertainty and taking into account non-gravitational forces, some time before the passage of the inner solar system in 1970, its orbit had an eccentricity of about 0.9960 and a semiaxial major axis of about 135.5 AU, so that its Orbit period was around 1575 years. The comet could therefore last have appeared in antiquity around the year 395. The orbital eccentricity became due to the gravitational pull of the planets, in particular by passing Saturn on August 24, 1968 in about 5 AU and on November 2, 1971 in about 6 ¼ AU, and on Jupiter on March 23, 1970 in about 5 AU slightly enlarged to around 0.9962 and the semi-major axis to around 140 AU, so that its orbital period increased to around 1660 years. When it reaches the point of its orbit furthest from the sun ( aphelion ) around the year 2800 , it will be 41.8 billion km from the sun, almost 280 times as far as the earth and over 9 times as far as Neptune . Its orbit speed in the aphelion is only about 0.11 km / s. The comet's next perihelion is expected to occur around the year 3630.

In a study by Hasegawa , comet Bennett was given as a candidate for a possible match with a comet observed in China and Europe from September 363, but this assumption could not be specifically confirmed.

See also

Web links

Individual evidence

  1. ^ BG Marsden: Comets. In: Quarterly Journal of the Royal Astronomical Society. Vol. 11, 1970, pp. 221-235 ( bibcode : 1970QJRAS..11..221M ).
  2. ^ Peter Grego: Blazing a Ghostly Trail: ISON and Great Comets of the Past and Future . Springer, Cham 2013, ISBN 978-3-319-01774-7 , pp. 135-136.
  3. ^ John E. Bortle: International Comet Quarterly - The Bright-Comet Chronicles. Retrieved April 26, 2016 .
  4. ^ GW Kronk, M. Meyer: Cometography - A Catalog of Comets. Volume 5: 1960-1982 . Cambridge University Press, Cambridge 2010, ISBN 978-0-521-87226-3 , pp. 252-259.
  5. ^ A b B. G. Marsden: Comets in 1970. In: Quarterly Journal of the Royal Astronomical Society. Vol. 12, 1971, pp. 244-273 ( bibcode : 1971QJRAS..12..244M ).
  6. ^ BG Marsden: Comets in 1971. In: Quarterly Journal of the Royal Astronomical Society. Vol. 13, 1972, pp. 415-435 ( bibcode : 1972QJRAS..13..415M ).
  7. ^ Ch. Bertaud: Observations de la comète Bennett (1969i). In: L'Astronomie. Vol. 84, 1970, pp. 361-374 ( bibcode : 1970LAstr..84..361B ).
  8. ↑ M. Beyer: Physical observations of comets. XVII. In: Astronomical News. Vol. 293, 1972, pp. 241-257 ( bibcode : 1972AN .... 293..241B ).
  9. ↑ a b M. J. Hendrie: Comet Bennett 1969i. In: Journal of the British Astronomical Association. Vol. 109, 1999, pp. 14-21 ( bibcode : 1999JBAA..109 ... 14H ).
  10. ^ P. Moore, R. Rees: Patrick Moore's Data Book of Astronomy . Cambridge University Press, Cambridge 2011, ISBN 978-0-521-89935-2 , p. 271.
  11. ↑ International Comet Quarterly - Brightest comets seen since 1935. Retrieved April 12, 2016 (English).
  12. ↑ M. Mobberley: Hunting and Imaging Comets. Springer, New York 2011, ISBN 978-1-4419-6904-0 , pp. 64-66 doi: 10.1007 / 978-1-4419-6905-7 .
  13. ^ AD Code, TE Houck, CF Lillie: Ultraviolet Observations of Comets. In: AD Code (Ed.): The Scientific Results from the Orbiting Astronomical Observatory (OAO-2). NASA Scientific and Technical Information Office, Washington DC 1972, NASA SP-310, pp. 109-114 ( PDF; 196.6 MB ).
  14. ^ CF Lillie, HU Keller: The Gas Production Rate of Comet Bennett. In: BD Donn, M. Mumma, W. Jackson, M. A'Hearn, R. Harrington (Ed.): The Study of Comets. Part 1. The Proceedings of IAU Colloquium No. 25. NASA Scientific and Technical Information Office, Washington DC 1976, NASA SP-393, pp. 323-329 ( bibcode : 1976NASSP.393..323L ).
  15. ^ HU Keller, CF Lillie: The Scale Length of OH and the Production Rates of H and OH in Comet Bennett (1970 II). In: Astronomy & Astrophysics. Vol. 34, 1974, pp. 187-196 ( bibcode : 1974A & A .... 34..187K ).
  16. ↑ J.-L. Bertaux, J. Blamont: Observation de l'émission d'hydrogène atomique de la comète Bennett. In: Comptes rendus hebdomadaires des séances de l'Académie des sciences. T. 270, Série B, 1970, pp. 1580–1584 ( link to archive )
  17. ↑ J.-L. Bertaux, JE Blamont, M. Festou: Interpretation of Hydrogen Lyman-Alpha Observations of Comets Bennett and Encke. In: Astronomy & Astrophysics. Vol. 25, 1973, pp. 415-430 ( bibcode : 1973A & A .... 25..415B ).
  18. ^ HU Keller: Hydrogen Production Rates of Comet Bennett (1969i) in the First Half of April 1970. In: Astronomy & Astrophysics. Vol. 27, 1973, pp. 51-57 ( bibcode : 1973A & A .... 27 ... 51K ).
  19. ^ HU Keller, GE Thomas: A Cometary Hydrogen Model: Comparison with OGO-5 Measurements of Comet Bennett (1970 II). In: Astronomy & Astrophysics. Vol. 39, 1975, pp. 7-19 ( bibcode : 1975A & A .... 39 .... 7K ).
  20. ^ HU Keller, GE Thomas: A High-Velocity Component of Atomic Hydrogen in Comet Bennett (1970 II). In: BD Donn, M. Mumma, W. Jackson, M. A'Hearn, R. Harrington (Ed.): The Study of Comets. Part 1. The Proceedings of IAU Colloquium No. 25. NASA Scientific and Technical Information Office, Washington DC 1976, NASA SP-393, pp. 316-321 ( bibcode : 1976NASSP.393..316K ).
  21. ^ J. Rahe, CW McCracken, BD Donn: Monochromatic and White-Light Observations of Comet Bennett 1969i (1970 II). In: Astronomy & Astrophysics Supplement Series. Vol. 23, 1976, pp. 13-35 ( bibcode : 1976A & AS ... 23 ... 13R ).
  22. ^ EF Borra, WH Wehlau: Narrow-Band Photometry of Comet Bennett (1969i). In: Publications of the Astronomical Society of the Pacific. Vol. 83, 1971, pp. 184-191 doi: 10.1086 / 129098 ( bibcode : 1971PASP ... 83..184B ).
  23. ^ EF Borra, WH Wehlau: Narrow-Band Isophotes of Comets Tago-Sato-Kosaka and Bennett. In: Publications of the Astronomical Society of the Pacific. Vol. 85, 1973, pp. 670-673 doi: 10.1086 / 129525 ( bibcode : 1973PASP ... 85..670B ).
  24. ^ AH Delsemme, JL Moreau: Brightness Profiles in the Neutral Coma of Comet Bennett (1970 II). In: Astrophysical Letters. Vol. 14, 1973, pp. 181-185 ( bibcode : 1973ApL .... 14..181D ).
  25. ^ AH Delsemme, MR Combi: The Production Rate and Possible Origin of O ( 1 D) in Comet Bennett 1970 II. In: The Astrophysical Journal. Vol. 209, 1976, pp. L149-L151 doi: 10.1086 / 182286 ( bibcode : 1976ApJ ... 209L.149D ).
  26. ↑ AH Delsemme, MR Combi: Production Rate and Origin of H 2 O + in Comet Bennett 1970 II. In: The Astrophysical Journal. Vol. 209, 1976, pp. L153-L156 doi: 10.1086 / 182287 ( bibcode : 1976ApJ ... 209L.153D ).
  27. ^ AH Delsemme, MR Combi: O ( 1 D) and H 2 O + in Comet Bennett 1970. II. In: The Astrophysical Journal. Vol. 228, 1979, pp. 330-337 doi: 10.1086 / 156850 ( bibcode : 1979ApJ ... 228..330D ).
  28. ^ M. Oppenheimer: An Analysis of the Coma of Comet Bennett 1970 II. In: The Astrophysical Journal. Vol. 225, 1978, pp. 1083-1089 doi: 10.1086 / 156577 ( bibcode : 1978ApJ ... 225.1083O ).
  29. ^ FD Miller: The Side-Ray Systems of Comet Bennett, 1970 March 7-18. In: The Astronomical Journal. Vol. 104, 1992, pp. 1207-1215 doi: 10.1086 / 116309 ( bibcode : 1992AJ .... 104.1207M ).
  30. ↑ K. Wurm, A. Mammano: Contributions to the Kinematics of Type I Tails of Comets. In: Astrophysics and Space Science. Vol. 18, 1972, pp. 273-286 doi: 10.1007 / BF00645393 ( bibcode : 1972Ap & SS..18..273W ).
  31. ↑ K. Wurm, A. Mammano: The Motion of Dust and Gas in the Heads of Comets with Type II tails. In: Astrophysics and Space Science. Vol. 18, 1972, pp. 491-503 doi: 10.1007 / BF00645412 ( bibcode : 1972Ap & SS..18..491W ).
  32. ↑ LF Burlaga, J. Rahe, B. Donn, M. Neugebauer: Solar Wind Interaction with Comet Bennett (1969i). In: Solar Physics. Vol. 30, 1973, pp. 211-222 doi: 10.1007 / BF00156190 ( bibcode : 1973SoPh ... 30..211B ).
  33. ↑ K. Jockers, Rh. Lüst: Tail Peculiarities in Comet Bennett Caused by Solar Wind Disturbances. In: Astronomy & Astrophysics. Vol. 16, 1973, pp. 113-121 ( bibcode : 1973A & A .... 26..113J ).
  34. ↑ L. Pansecchi, M. Fulle, G. Sedmak: The nature of two anomalous structures observed in the dust tail of Comet Bennett 1970 II: a possible Neck-Line Structure. In: Astronomy & Astrophysics. Vol. 176, 1987, pp. 358-366 ( bibcode : 1987A & A ... 176..358P ).
  35. ^ DE Kleinmann, T. Lee, FJ Low, CR O'Dell: Infrared Observations of Comets 1969g and 1969i. In: The Astrophysical Journal. Vol. 165, 1971, pp. 633-636 doi: 10.1086 / 150927 ( bibcode : 1971ApJ ... 165..633K ).
  36. ^ RW Maas, NP Ney, NJ Woolf: The 10-Micron Emission Peak of Comet Bennett 1969i. In: The Astrophysical Journal. Vol. 160, 1970, pp. L101-L104 doi: 10.1086 / 180537 ( bibcode : 1970ApJ ... 160L.101M ).
  37. ↑ JA Hackwell: 10µ Emission Spectrum of Comet Bennett. In: The Observatory. Vol. 91, 1971, pp. 33-34 ( bibcode : 1971Obs .... 91 ... 33H ).
  38. ^ WF Huebner, LE Snyder: Radio Search for Formaldehyde in Comet Bennett (1969i). In: The Astronomical Journal. Vol. 75, 1970, pp. 759-761 doi: 10.1086 / 111021 ( bibcode : 1970AJ ..... 75..759H ).
  39. ^ TA Clark, B. Donn, WM Jackson, WT Sullivan III, N. Vandenberg: Search for Microwave H 2 O Emission in Comet Bennett (1969i). In: The Astronomical Journal. Vol. 76, 1971, pp. 614-616 doi: 10.1086 / 111171 ( bibcode : 1971AJ ..... 76..614C ).
  40. ^ RW Orloff: Apollo By The Numbers: A Statistical Reference - Apollo 13 Timeline. NASA History Division, accessed May 18, 2016 .
  41. ↑ AH Delsemme, DA Rud: Albedos and Cross-sections for the Nuclei of Comets 1969 IX, 1970 II and 1971 I. In: Astronomy & Astrophysics. Vol. 28, 1973, pp. 1-6 ( bibcode : 1973A & A .... 28 .... 1D ).
  42. ↑ NASA JPL Small-Body Database Browser: C / 1969 Y1 (Bennett). Retrieved March 29, 2016 .
  43. ↑ A. Vitagliano: SOLEX 11.0. Archived from the original on September 18, 2015 ; accessed on May 2, 2014 .
  44. ^ BG Marsden, Z. Sekanina, DK Yeomans: Comets and nongravitational forces. V. In: The Astronomical Journal. Vol. 78, 1973, pp. 211-225 doi: 10.1086 / 111402 ( bibcode : 1973AJ ..... 78..211M ).
  45. ^ BG Marsden, E. Roemer: Comets in 1974. In: Quarterly Journal of the Royal Astronomical Society. Vol. 19, 1978, pp. 38-58 ( bibcode : 1978QJRAS..19 ... 38M ).
  46. ^ BG Marsden, Z. Sekanina, E. Everhart: New osculating orbits for 110 comets and analysis of original orbits for 200 comets. In: The Astronomical Journal. Vol. 83, 1978, pp. 64-71 doi: 10.1086 / 112177 ( bibcode : 1978AJ ..... 83 ... 64M ).
  47. ^ M. Królikowska: Long-period comets with non-gravitational effects. In: Astronomy & Astrophysics. Vol. 427, 2004, pp. 1117-1126 doi: 10.1051 / 0004-6361: 20041339 ( PDF; 283 kB ).
  48. ^ I. Hasegawa: Orbits of Ancient and Medieval Comets. In: Publications of the Astronomical Society of Japan. Vol. 31, 1979, pp. 257-270 ( bibcode : 1979PASJ ... 31..257H ).