View source for Comet Bennett

{{Short description|Great Comet of 1970}}
{{About|the "Great Comet of 1970"|the 1974 comet of the same name|C/1974 V2 (Bennett)}}
{{Infobox comet
| name            = C/1969 Y1 (Bennett)<br>(Great Comet of 1970)
| image           = Comet Bennett 30.5 March 1970.jpg
| caption         = Comet Bennett photographed by S. M. Larson and R. B. Minton on 30 March 1970
| discovery_ref   = {{r|IAUC_2196}}
| discoverer      = [[John Caister Bennett]]
| discovery_site  = [[Pretoria]], South Africa
| discovery_date  = 28 December 1969
| designations    = 1970 II, 1969i{{r|ICQ1}}
| orbit_ref       = {{r|jpl1}}
| epoch           = 12 April 1970 ([[Julian day|JD]] 2440688.5)
| observation_arc = 301 days
| obs             = 529
| semimajor       = 145 [[Astronomical Unit|AU]]
| perihelion      = 0.538 AU
| aphelion        = 289.54 AU
| eccentricity    = 0.99629
| period          = 1,747 [[Julian year (astronomy)|a]]
| inclination     = 90.04°
| asc_node        = 224.7°
| arg_peri        = 354.1°
| tjup            = 0.035
| Earth_moid      = 0.4690 AU
| Jupiter_moid    = 2.6681 AU
| physical_ref    = {{r|Delsemme_1973a}}
| mean_radius     = {{val|3.76|0.46}} km
| albedo          = {{val|0.66|0.13}}
| M1              = 4.6
| M2              = 
| magnitude       = 0.0<br>{{small|(1970 apparition)}}
| last_p          = 20 March 1970
| next_p          = ~3600 <!-- Calculated from future 1/a value from http://www.oaa.gr.jp/~oaacs/nk/nk837.htm because Solar System is n-body system. -->
}}

'''Comet Bennett''', formally known as '''C/1969 Y1''' (old style '''1970 II''' and '''1969i'''), was one of the two bright comets observed in the 1970s, along with [[Comet West]] and is considered a [[great comet]].{{r|jpl2}} The name is also borne by an altogether different comet, [[C/1974 V2]]. Discovered by [[John Caister Bennett]] on December 28, 1969, while still almost two [[astronomical unit|AUs]] from the [[Sun]], it reached [[perihelion]] on March 20, passing closest to Earth on 26 March 1970, as it receded, peaking at magnitude 0.{{r|cometography}} It was last observed on 27 February 1971.{{r|cometography}}

== Observational history ==
The comet was discovered by [[John Caister Bennett]] on 28 December 1969 from [[Pretoria]], South Africa, during his comet seeking routine. The comet was located in the constellation [[Tucana]], in 65° south declination, and had an estimated magnitude of 8.5.{{r|Hendrie_1999}} At that time the comet was about 1.7 AU both from the Sun and the Earth.{{r|cometography}} The orbit was computed by M. P. Candy of the [[Perth Observatory]] and it became apparent that the comet could become a bright object by the end of March, during its perihelion at a distance of 0.54 AU, as it moved northwards.{{r|Hendrie_1999|cometography}}

The comet became visible to the naked eye in February, and the first week of that month it had a magnitude of 5 and its tail measured about one degree in length. By the end of February the comet had brightened to a magnitude of 3.5 while its tail was about two degrees long.{{r|ICQ2}} The comet continued to brighten during March, as it approached both the Sun and Earth. By the middle of the month it was a first magnitude object with a prominent curved tail about 10 degrees long.{{r|cometography|ICQ2}}

The comet reached perihelion on 20 March and crossed the equator on 25 March, becoming better visible in the morning sky of the north hemisphere,{{r|Hendrie_1999}} staying at an [[Elongation (astronomy)|elongation]] greater than 32 degrees.{{r|Marsden_1971}} On 26 March was the perigee of the comet, when it approached Earth at a distance of {{convert|0.69|AU|e6km|abbr=unit}}.{{r|cometography}} The comet was then at the square of the [[Pegasus (constellation)|Pegasus]] and continued moving northwards until it reached its maximum north declination of 83° in August, when the comet was in the constellation of [[Camelopardalis]].{{r|Hendrie_1999}} The comet at the start of April had a magnitude of 1, but as it receded both from the Sun and Earth,{{r|cometography}} it had dimmed to a magnitude of 3-4 by the end of April, when it was circumpolar, located in [[Cassiopeia (constellation)|Cassiopeia]]. The comet had in April two tails, with the longest being 20-25 degrees long.{{r|cometography|ICQ2}} Although by the start of May the comet head had faded to magnitude 5, its tail was still 10-15 degrees long, but by the end of the month it was only 2.5 degrees long. It was last seen by [[naked eye]] around mid May.{{r|cometography|Hendrie_1999|ICQ2}}

The comet was observed to fade during summer, autumn and winter. By the start of July it was around magnitude 10 and by the September it was magnitude 12.{{r|Hendrie_1999}} In January 1971 it was photographed as an 18.9 magnitude object. It was last photographed by [[Elizabeth Roemer]] on 27 February 1971, when the comet was 4.9 AU from the Sun and 5.3 AU from Earth.{{r|cometography}}

== Scientific results ==
Soon after the first orbital elements could be calculated, it was suggested that the comet would become "a bright object, that could be observed with [[unaided eye]]." It was found to combine three favorable characteristics that made it an exceptional comet for observation: a short perihelion distance, a short distance from Earth, and high intrinsic brightness.{{r|Mobberley_2011}} Numerous research projects were therefore initiated, so that Comet Bennett became the most photographed and most thoroughly researched comet at the time of its appearance.{{r|Marsden_1971}}

=== Ultraviolet observations ===
A few years earlier it had been suggested that comets are surrounded by a shell of [[hydrogen]] gas, which could be detected by observing in the [[ultraviolet]] the [[Lyman-alpha line|Lyman α line]] at 121.5&nbsp;nm. However, this observation is not possible from the ground 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 2]] (OAO-2) acquired the spectrum of comet [[C/1969 T1 (Tago-Sato-Kosaka)]] and verified the predicted hydrogen envelope. In February of the same year, Comet Bennett reached a favorable observation position for observation from space and was systematically observed with OAO-2 and OGO-5 on the basis of this discovery from mid-March to mid-April in order to track the temporal and spatial changes in the comet's coma.{{r|Code_1972}}

From the photometric data obtained with OAO-2, the production rates of OH and H and their dependence on the comet's distance from the sun could be derived. The results confirmed the assumption that the gas production of comets at small solar distances 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 at 200 million tonnes.{{r|Lillie_1976|Keller_1974}}

The comet was also observed for the first time by the [[Orbiting Geophysical Observatory]] (OGO-5) on April 1 and 2. With a more sensitive [[photometer]] than with OAO-2, emissions from hydrogen atoms could be detected up to a distance of several million km from the comet's nucleus. From the measurements, the mass of this hydrogen could be derived at about 2 million tones.{{r|Bertaux_1970}} After these first successful measurements, it was decided to continue observing the comet with the instruments on board OGO-5 and thus a total of twelve intensity maps of the comet's Lyman-α emission were obtained by April 30. The maps show the evolution 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 was 20 million km × 15 million km in size, after which it slowly began to shrink. The derived hydrogen atom production rate was comparable to the value obtained from the OAO-2 observations.{{r|Bertaux_1973|Keller_1973}} In further investigations, attempts were then made to theoretically underpin the measurement results with greater agreement and to provide refined models for the formation of the hydrogen shells.{{r|Keller_1975|Lillie_1976}}

=== Visible light ===
At the [[Goddard Space Flight Center]] in Maryland, images of the comet were taken from March 28 to April 18, 1970, with interference filters at different wavelengths in the violet, blue, green, and yellow regions of the spectrum. In particular, the emission lines of [[cyanide|CN]], [[diatomic carbon|C<sub>2</sub>]], [[Carbon monoxide|CO+]] and [[Sodium|Na]] were evaluated. Maps of the comet's coma with lines of the same brightness ([[isophote]]s) up to a distance of 150,000&nbsp;km from the nucleus were created from these and other images taken on April 8 and 9 at the [[Hamburg Observatory]] in white light.{{r|Rahe_1976}} Similar surveys were also conducted from March 31 to April 27 at the University of Western Ontario's [[Hume Cronyn Memorial Observatory]] in Canada. There, too, images of the comet were taken 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<sub>2</sub> were measured and their intensity profiles evaluated in parallel and perpendicular directions to the comet's tail{{r|Borra_1971}} and presented in the form of isophotes.{{r|Borra_1973}}

From March 30 to May 7, 1970, spectrographic studies of the comet were made at the [[Ritter Observatory|Observatory]] of the [[University of Toledo]] in Ohio. In this way, brightness profiles of the emission lines of {{chem|C|2}} and CN were obtained up to a distance of 100,000 km from the comet's nucleus.{{r|Delsemme_1973b}} A brightness profile of the [[Forbidden mechanism|"forbidden" emission line]] of the oxygen atom at 630 nm was also created from images from April 18. It has been suggested that these atoms result from the decay of {{CO2}} and that comet Bennett contained {{CO2}} in excess of water.{{r|Delsemme_1976a}} The same images were also used to create a brightness profile of the {{H2O-nl}}+ ion up to a distance of about 100,000 km from the nucleus and to determine its production rate.{{r|Delsemme_1976b}} The results could later be revised through improved processing of the data.{{r|Delsemme_1979}}

From March 7 to 18, images of the comet were taken at the [[Cerro Tololo Inter-American Observatory]] in Chile. The comet's tail showed no noticeable disturbances, only pronounced side rays could be observed. This indicates that relatively quiet interactions between the [[solar wind]] and associated magnetic fields and the comet were occurring during this period.{{r|Miller_1992}}

Images taken from late March to late May at the [[Osservatorio Astrofisico di Asiago]] in Italy were evaluated for the distribution of gas and dust in Comet Bennett's tail. On the 3/4 April, it was observed that the comet's gas tail had been torn off the coma.{{r|Wurm_1972a}} Spectra of the neutral gas envelope showed the emission lines of CN, C<sub>2</sub>, [[triatomic carbon|{{C3}}]], [[methylidyne radical|CH]], [[amino radical|{{chem2|NH2}}]] and Na. The gas tail showed a diurnal variation in intensity and structure, indicating a very erratic production of CO+.{{r|Wurm_1972b}} In particular, attempts were also made to correlate a prominent kink observed in the comet's gas tail on April 4 with simultaneous measurements of solar activity and solar wind. This was done using measurement data provided around the same time by the OGO-5, Vela 5, HEOS-1 and [[Pioneer 8]] spacecraft, as well as by the ALSEP experiment installed on the lunar surface by [[Apollo 12]]. In a first investigation, no events were found in the measured dynamics of the solar wind that could explain the deformations of the comet's tail.{{r|Burlaga_1973}} However, further investigation concluded that, first, the dynamics of the solar wind measured near Earth were probably different from those near the comet, and second, the monitoring of the solar wind was patchy in terms of location and time, so that the deformations of the comet's tail can probably still be traced back to events in the solar wind.{{r|Jockers_1973}}

Three images of the comet in red light, taken May 5–8 at the [[Karl Schwarzschild Observatory|Thuringian State Observatory in Tautenburg]], when the Earth was almost in the comet's orbital plane, showed two anomalous structures in the comet's tail: a radial structure and a short sunward spikes, probably caused by the comet's dust. The later evaluation of these observations provided evidence for the peculiarity of a "neckline structure" (NLS) in the dust tail of a comet, which was only theoretically derived in 1977.{{r|Pansecchi_1987}}

=== Infrared ===
Observations of the comet's brightness evolution in the [[infrared]] were made in late March to mid-April 1970 at the [[Lunar and Planetary Laboratory]] in Arizona. In addition, on March 31, 1970, observations were made with an infrared telescope on board a [[Learjet]].{{r|Kleinmann_1971}}

On 4 April 1970, Comet Bennett was photometrically measured at the [[O'Brien Observatory]] of the [[University of Minnesota]] in the [[near infrared|near]] and [[mid-infrared]] at 2-20&nbsp;μm wavelength. In addition to the continuum of a [[black body]] of about 500 K at short wavelengths, an emission line could also be detected at 10&nbsp;μm, which was traced back to [[silicate]] grains in the dust of the comet.{{r|Maas_1970}} The measurement result was confirmed by another measurement on April 21 at [[Kitt Peak National Observatory]] in Arizona.{{r|Hackwell_1971}}

=== Microwaves ===
With the [[radio telescope]] of the [[Green Bank Observatory]] in West Virginia, an attempt was made over six days in mid-March 1970 to detect the emission of [[formaldehyde]] at 4.83&nbsp;GHz.{{r|Huebner_1970}} Likewise, the radio telescope at the [[United States Naval Research Laboratory]] in Maryland attempted to detect the emission of water molecules at 22.2&nbsp;GHz over four days at the end of March 1970.{{r|Clark_1971}} In both cases, no such emissions could be detected.

=== Apollo 13 attempted photograph ===
Comet Bennett was intended to be photographed by the crew of [[Apollo 13]] during their journey to the [[Moon]]. Their first attempt on April 13, 1970, was unsuccessful. On April 14, 1970, after completing the maneuver to orient the spacecraft for a second attempt, [[Apollo 13#Accident|''Odyssey''{{'}}s service module ruptured]], forcing the cancellation of the mission's scientific objectives and touchdown on the lunar surface.{{r|apollo_13a|apollo_13b}}

== References ==
{{Reflist|refs=

<ref name="apollo_13a">{{cite book
| author1= E. M. Cortright
| title= Apollo Expeditions to the Moon
| url= https://ntrs.nasa.gov/api/citations/19760005868/downloads/19760005868.pdf
| chapter= Chapter 13: Houston, We've Had a Problem
| publisher= [[NASA]]
| date= 1975
| access-date= 5 June 2015
| pages= 247–264
| isbn= 978-9-997-39827-7
| hdl= 2060/19760005868
| hdl-access= free
| id= NASA-SP-350 }}
</ref>

<ref name="apollo_13b">{{YouTube 
| id= KWfnY9cRXO4
| title= Apollo 13 Accident – Flight Director Loop Part 1 }}
</ref>

<ref name="Bertaux_1970">{{cite journal
| author1= J. L. Bertaux
| author2= J. E. Blamont
| title= Observation de l'émission d'hydrogène atomique de la comète Bennett
| trans-title= Observation of atomic hydrogen emission from Comet Bennett
| url= http://gallica.bnf.fr/ark:/12148/bpt6k480291t/f1608.item.r=Archives%20de%20l'Acad%C3%A9mie%20des%20sciences%20Bertaux%20Blamont
| journal= Comptes rendus hebdomadaires des séances de l'Académie des sciences
| volume= 270
| year= 1970
| pages= 1580–1584
| bibcode= 1970CRASB.270.1581B
| language= fr }}
</ref>

<ref name="Bertaux_1973">{{cite journal
| author1= J. L. Bertaux
| author2= J. E. Blamont
| author3= M. Festou
| title= Interpretation of Hydrogen Lyman-Alpha Observations of Comets Bennett and Encke 
| url= https://ui.adsabs.harvard.edu/link_gateway/1973A&A....25..415B/ADS_PDF
| journal= Astronomy and Astrophysics
| year= 1973
| volume= 25
| pages= 415–430
| bibcode= 1973A&A....25..415B
| issn= 0004-6361 }}
</ref>

<ref name="Borra_1971">{{cite journal
| author1= E. F. Borra
| author2= W. H. Wehlau
| title= Narrow-Band Photometry of Comet Bennett (1969 i)
| url= https://iopscience.iop.org/article/10.1086/129098/pdf
| journal= Publications of the Astronomical Society of the Pacific
| year= 1971
| volume= 83
| issue= 492
| pages= 184
| doi= 10.1086/129098
| doi-access= free }}
</ref>

<ref name="Borra_1973">{{cite journal
| author1= E. F. Borra
| author2= W. H. Wehlau
| title= Narrow-Band Isophotes of Comets Tago-Sato-Kosaka and Bennett 
| url= https://iopscience.iop.org/article/10.1086/129525/pdf
| journal= Publications of the Astronomical Society of the Pacific
| year= 1973
| volume= 85
| issue= 507
| pages= 670
| doi= 10.1086/129525
| doi-access= free | url-access= subscription
}}
</ref>

<ref name="Burlaga_1973">{{cite journal
| author1= L. F. Burlaga
| author2= J. Rahe
| author3= B. Donn
| author4= M. Neugebauer
| url= https://ntrs.nasa.gov/api/citations/19730003086/downloads/19730003086.pdf
| title= Solar wind interaction with Comet Bennett (1969i)
| journal= Solar Physics 
| year= 1973
| volume= 30
| issue= 1
| pages= 211–222
| doi= 10.1007/BF00156190
| hdl= 2060/19730003086
| hdl-access= free
| id= NASA-TM-X-66087 }}
</ref>

<ref name="Clark_1971">{{cite journal
| author1= T. A. Clark
| author2= B. Donn
| author3= W. M. Jackson
| author4= W. T. Sullivan, III
| author5= N. Vandenberg
| title= Search for Microwave H20 Emission in Comet Bennett (1969i)
| url= https://ui.adsabs.harvard.edu/link_gateway/1971AJ.....76..614C/ADS_PDF
| journal= The Astronomical Journal
| year= 1971
| volume= 76
| pages= 614
| bibcode= 1971AJ.....76..614C
| doi= 10.1086/111171
| doi-access= free
| id= NASA-TM-X-65556 }}
</ref>

<ref name="Code_1972">{{cite web
| author1= A. D. Code
| author2= T. E. Houck
| author3= C. F. Lillie
| title= Ultraviolet Observations of Comets: The Scientific Results from the Orbiting Astronomical Observatory (OAO-2)
| url= https://archive.org/download/NASA_NTRS_Archive_19720024170/NASA_NTRS_Archive_19720024170.pdf
| publisher= [[NASA]]
| pages= 109–114
| id= SP-310 }}
</ref>

<ref name="cometography">{{cite web
| author1= G. W. Kronk
| title= C/1969 Y1 (Bennett)
| url= http://www.cometography.com/lcomets/1969y1.html
| website= Cometography.com
| access-date= 14 December 2024 }}
</ref>

<ref name="Delsemme_1973a">{{cite journal
| author1= A. H. Delsemme
| author2= D. A. Rud
| title= Albedos and Cross-sections for the Nuclei of Comets 1969 IX, 1970 II and 19711
| journal= Astronomy & Astrophysics
| year= 1973
| volume= 28
| pages= 1–6
| bibcode= 1973A&A....28....1D }}
</ref>

<ref name="Delsemme_1973b">{{cite journal
| author1= A. H. Delsemme
| author2= J. L. Moreau
| title= Brightness Profiles in the Neutral Coma of Comet Bennett (1970 II) 
| url= https://ui.adsabs.harvard.edu/link_gateway/1973ApL....14..181D/ADS_PDF
| journal= Astrophysical Letters
| year= 1973
| volume=14
| pages= 181
| bibcode= 1973ApL....14..181D
| issn= 0004-6388 }}
</ref>

<ref name="Delsemme_1976a">{{cite journal
| author1= A. H. Delsemme
| author2= M. R. Combi
| title= The Production Rate and Possible Origin of O ((1) d) in Comet Bennett 1970 II 
| url= https://ui.adsabs.harvard.edu/link_gateway/1976ApJ...209L.149D/ADS_PDF
| journal= The Astrophysical Journal
| year= 1976
| volume= 209
| pages= L149
| bibcode= 1976ApJ...209L.149D
| doi= 10.1086/182286
| doi-access= free }}
</ref>

<ref name="Delsemme_1976b">{{cite journal
| author1= A. H. Delsemme
| author2= M. R. Combi
| title= Production Rate and Origin of H20(+) in Comet Bennett 1970 II
| url= https://ui.adsabs.harvard.edu/link_gateway/1976ApJ...209L.153D/ADS_PDF
| journal= The Astrophysical Journal
| year= 1976
| volume= 209
| pages= L153
| bibcode= 1976ApJ...209L.153D
| doi= 10.1086/182287
| doi-access= free }}
</ref>

<ref name="Delsemme_1979">{{cite journal
| author1= A. H. Delsemme
| author2= M. R. Combi
| title= O/1D/ and H2O/+/ in comet Bennett 1970. II
| url= https://ui.adsabs.harvard.edu/link_gateway/1979ApJ...228..330D/ADS_PDF
| journal= The Astrophysical Journal
| year= 1979
| volume= 228
| pages= 330–337
| bibcode= 1979ApJ...228..330D
| doi= 10.1086/156850
| doi-access= free }}
</ref>

<ref name="Hackwell_1971">{{cite journal
| author1= J. A. Hackwell
| title= 10 micron emission spectrum of Comet Bennett
| url= https://ui.adsabs.harvard.edu/link_gateway/1971Obs....91...33H/ADS_PDF
| journal= The Observatory
| date= 1971
| volume= 91
| pages= 33–34
| bibcode= 1971Obs....91...33H
| issn= 0029-7704 }}
</ref>

<ref name="Hendrie_1999">{{cite journal
| author1= M. J. Hendrie
| title= Comet Bennett 1969i
| url= https://ui.adsabs.harvard.edu/link_gateway/1999JBAA..109...14H/ADS_PDF
| journal= Journal of the British Astronomical Association
| year= 1999
| volume= 109
| issue= 1
| pages= 14–21
| bibcode= 1999JBAA..109...14H
| issn= 0007-0297 }}
</ref>

<ref name="Huebner_1970">{{cite journal
| author1= W. F. Huebner
| author2= L. E. Snyder
| title= Radio Search for Formaldehyde in Comet Bennett (1969i)
| url= https://ui.adsabs.harvard.edu/link_gateway/1970AJ.....75..759H/ADS_PDF
| journal= The Astronomical Journal
| year= 1970
| volume= 75
| pages= 759–761
| bibcode= 1970AJ.....75..759H
| doi= 10.1086/111021
| doi-access= free }}
</ref>

<ref name="IAUC_2196">{{cite journal
| author1= B. G. Marsden
| title= Comet Bennett (1969i)
| url= http://www.cbat.eps.harvard.edu/IAUCs/IAUC2196.jpg
| journal= Central Bureau for Astronomical Telegrams
| volume= 2196
| date= 31 December 1969 }}
</ref>

<ref name="ICQ1">{{cite web
| title= Comet Names and Designations
| url= http://www.icq.eps.harvard.edu/names1.html
| website= International Comet Quarterly
| access-date= 14 December 2024 }}
</ref>

<ref name="ICQ2">{{cite web
| author1= J. E. Bortle
| title= The Bright Comet Chronicles
| url= http://www.icq.eps.harvard.edu/bortle.html
| website= International Comet Quarterly
| year= 1998
| access-date= 12 February 2023 }}
</ref>

<ref name="Jockers_1973">{{cite journal
| author1= K. Jockers
| author2= Rh. Lust
| title= Tail Peculiarities in Comet Beunett Caused by Solar Wind Disturbances 
|url=https://ui.adsabs.harvard.edu/link_gateway/1973A&A....26..113J/ADS_PDF
| journal= Astronomy and Astrophysics
| year= 1973
| volume= 26
| pages= 113–122
| bibcode= 1973A&A....26..113J
| issn= 0004-6361}}</ref>

<ref name="jpl1">{{cite web
| title= C/1969 Y1 (Bennett) – JPL Small-Body Database Browser
| url= https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=1969Y1
| website= ssd.jpl.nasa.gov
| publisher= [[Jet Propulsion Laboratory]]
| access-date= 14 December 2024 }}
</ref>

<ref name="jpl2">{{cite web
| author1= D. K. Yeomans
| title= Great Comets of History
| url= https://ssd.jpl.nasa.gov/sb/great_comets.html
| website= ssd.jpl.nasa.gov
| publisher= [[Jet Propulsion Laboratory]]
| access-date= 17 April 2023 }}
</ref>

<ref name="Keller_1973">{{cite journal
| author1= H. U. Keller
| title= Hydrogen Production Rates of Comet Bennett (1969i) in the First Hall of April 1970
| url= https://ui.adsabs.harvard.edu/link_gateway/1973A&A....27...51K/ADS_PDF
| journal= Astronomy and Astrophysics
| year= 1973
| volume= 27
| pages=51
| bibcode= 1973A&A....27...51K
| issn= 0004-6361 }}
</ref>

<ref name="Keller_1974">{{cite journal
| author1= H. U. Keller
| author2= C. F. Lillie
| title= The Scale Length of OH and the Production Rates of H and OH in Comet Beunett (1970 II)
| url= https://ui.adsabs.harvard.edu/link_gateway/1974A&A....34..187K/ADS_PDF
| journal= Astronomy and Astrophysics
| year= 1974
| volume= 34
| pages= 187
| bibcode= 1974A&A....34..187K
| issn= 0004-6361 }}
</ref>

<ref name="Keller_1975">{{cite journal
| author1= H. U. Keller
| author2= G. E. Thomas
| title= A cometary hydrogen model: comparison with OGO-5 measurements of comet Bennett (1970 II)
| url= https://ui.adsabs.harvard.edu/link_gateway/1975A&A....39....7K/ADS_PDF
| journal= Astronomy and Astrophysics
| year= 1975
| volume= 39
| pages= 7–19
| bibcode= 1975A&A....39....7K
| issn= 0004-6361 }}
</ref>

<ref name="Kleinmann_1971">{{cite journal
| author1= D. E. Kleinmann
| author2= T. Lee
| author3= F. J. Low
| author4= C. R. O'dell
| title= Infrared Observations of Comets 1969g and 1969i
| url= https://ui.adsabs.harvard.edu/link_gateway/1970AJ.....75..759H/ADS_PDF
| journal= The Astrophysical Journal
| year= 1971 
| volume= 165
| pages= 633
| bibcode= 1970AJ.....75..759H
| doi= 10.1086/150927
| doi-access= free }}
</ref>

<ref name="Lillie_1976">{{cite journal
| author1= C. F. Lillie
| author2= H. U. Keller
| title= The Gas Production Rate of Comet Bennett
| url= https://ui.adsabs.harvard.edu/link_gateway/1976NASSP.393..323L/ADS_PDF
| journal= [[NASA]]
| year= 1976
| volume= 393
| pages= 323–329
| bibcode= 1976NASSP.393..323L
| id= NASA-SP-393 }}
</ref>

<ref name="Maas_1970">{{cite journal
| author1= R. W. Maas
| author2= E. P. Ney
| author3= N. J. Woolf
| title= The 10-MICRON Emission Peak of Comet Bennett 1969i
| url= https://ui.adsabs.harvard.edu/link_gateway/1970ApJ...160L.101M/ADS_PDF
| journal= The Astrophysical Journal
| year= 1970
| volume= 160
| pages= L101
| bibcode= 1970ApJ...160L.101M
| doi= 10.1086/180537
| doi-access= free }}
</ref>

<ref name="Marsden_1971">{{cite journal
| author1= B. G. Marsden
| title= Comets in 1970
| url= https://articles.adsabs.harvard.edu/pdf/1971QJRAS..12..244M
| journal= Quarterly Journal of the Royal Astronomical Society
| year= 1971
| volume= 12
| pages= 244–273
| bibcode= 1971QJRAS..12..244M
| issn= 0035-8738 }}
</ref>

<ref name="Miller_1992">{{cite journal
| author1= F. D. Miller
| title= The side-ray systems of Comet Bennett, 1970 March 7–18
| url= https://ui.adsabs.harvard.edu/link_gateway/1992AJ....104.1207M/ADS_PDF
| journal= The Astronomical Journal
| year= 1992
| volume= 104
| pages= 1207
| bibcode= 1992AJ....104.1207M
| doi= 10.1086/116309
| doi-access= free }}
</ref>

<ref name="Mobberley_2011">{{cite book
| author1= M. Mobberley
| title= Hunting and Imaging Comets
| publisher= [[Springer Publishing|Springer]]
| year= 2011
| pages= 64–66
| isbn= 978-1-441-96905-7
| doi= 10.1007/978-1-4419-6905-7 }}
</ref>

<ref name="Pansecchi_1987">{{cite journal
| author1= L. Pansecchi
| author2= M. Fulle
| author3= G. Sedmak
| title= The nature of two anomalous structures observed in the dust tail of Comet Bennett 1970. II - A possible Neck-Line Structure
| url= https://ui.adsabs.harvard.edu/link_gateway/1987A&A...176..358P/ADS_PDF
| journal= Astronomy and Astrophysics
| year= 1987
| volume= 176
| issue= 2
| pages= 358–366
| bibcode= 1987A&A...176..358P
| issn= 0004-6361 }}
</ref>

<ref name="Rahe_1976">{{cite journal
| author1= J. Rahe
| author2= C. W. McCracken
| author3= B. D. Donn
| title= Monochromatic and white-light observations of comet Bennett 1969i (1970 II). 
| url= https://articles.adsabs.harvard.edu/pdf/1976A&AS...23...13R
| journal= Astronomy and Astrophysics Supplement Series
| year= 1976
| volume= 23
| pages= 13–35
| bibcode= 1976A&AS...23...13R
| issn= 0365-0138 }}
</ref>

<ref name="Wurm_1972a">{{cite journal
| author1= K. Wurm
| author2= A. Mammano
| title= Contributions to the kinematics of type I tails of comets
| journal= Astrophysics and Space Science
| year= 1972
| volume= 18
| issue= 2
| pages= 273–286
| doi= 10.1007/BF00645393 }}
</ref>

<ref name="Wurm_1972b">{{cite journal
| author1= K. Wurm
| author2= A. Mammano
| title= The motion of dust and gas in the heads of comets with type II tails 
| journal= Astrophysics and Space Science
| year= 1972
| volume= 18
| issue=2
| pages= 491–503
| doi= 10.1007/BF00645412 }}
</ref>

}}

== External links ==
* {{JPL Small Body|name=C/1969 Y1|id=1001139}}
* [https://hdr-astrophotography.com/simulations-of-past-comets/ HDR Astrophotography: Simulations Atlas of Past Comets (1900 to 1999)] by Nicolas Lefaudeux

{{Comets}}
{{Authority control}}

{{DEFAULTSORT:Bennett, 1969 Y1}}
[[Category:Non-periodic comets]]
[[Category:Great comets]]
[[Category:Discoveries by amateur astronomers]]
[[Category:Astronomical objects discovered in 1969]]
[[Category:1969 in science]]
[[Category:1970 in science]]