C / 1969 T1 (Tago-Sato-Kosaka)

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C / 1969 T1 (Tago-Sato-Kosaka) [i]
Properties of the orbit ( animation )
Epoch:  January 21, 1970 ( JD 2,440,607.5)
Orbit type long-period
Numerical eccentricity 0.999926
Perihelion 0.473 AU
Aphelion 12820 AU
Major semi-axis 6410 AE
Sidereal period ~ 510,000 a
Inclination of the orbit plane 75.8 °
Perihelion December 21, 1969
Orbital velocity in the perihelion 61.3 km / s
history
Explorer A. Tago , Y. Sato, K. Kosaka
Date of discovery October 10, 1969
Older name 1969 IX, 1969g
Source: Unless otherwise stated, the data comes from JPL Small-Body Database Browser . Please also note the note on comet articles .

C / 1969 T1 (Tago-Sato-Kosaka) is a comet that could be seen with the naked eye in 1969 and 1970 . It was the first comet to be observed from an orbiting satellite .

Discovery and observation

The comet was first discovered on the evening of October 10, 1969 (local time) by Akihigo Tago in Tsuyama ( Japan ) with a 15 cm reflector . He estimated the brightness to be 10 mag and described the comet as diffuse. Two days later he was able to watch him again and informed the responsible authorities in Tokyo . Almost at the same time, two other independent discoveries were made by Yasuo Sato in Nishinasuno and Kozo Kosaka in Akasaka . Tago and Sato were involved in the discovery of another comet the year before and had searched for new comets for 344 and 182 hours, respectively.

In the following days, the comet was also observed and photographed at observatories in Australia , Japan, Great Britain , USA and New Zealand , while its brightness did not change significantly until the end of the month. During the course of November the comet approached the sun and could only be found a few times at dusk.

After the comet had passed the sun as seen from Earth , it was seen again by an observer in Argentina on December 8th at a brightness of 6 mag . A tail could not yet be observed. The brightness now increased rapidly and reached about 4 mag by the end of December, when a broad tail over 4 ° long had also developed.

The comet had moved southward in the sky since its discovery and was high in the southern sky when it began to move north again in early January 1970 and soon became visible again to observers in the northern hemisphere . The brightness, which reached values ​​of 3.5 mag in January, slowly decreased again and had fallen to 5 mag by the end of the month. From February onwards, the comet could no longer be observed with the naked eye, but a brief outbreak of brightness around 1 magnitude was reported around February 6th.

A plasma tail with a length of 7 ° was already observed at the beginning of January, and a diffuse dust tail was also found up to March. At the beginning of March the brightness was still 8 mag and had fallen further to below 10 mag by April. The last recordings of the comet were taken by Elizabeth Roemer in Arizona on May 4, 1970 with a brightness of only 18 mag.

The comet reached a maximum brightness of 3.5 mag, making it one of the 32 brightest comets since 1935.

Scientific evaluation

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 observation of a comet in the ultraviolet was therefore possible for the first time from January 14, 1970 for several weeks when the Orbiting Astronomical Observatory (OAO-2) recorded the spectrum of the comet Tago-Sato-Kosaka and detected the predicted gas envelope. Due to the successful observation with OAO-2, an ultraviolet image of the comet was also obtained on January 25 with the aid of a spectrograph on board an Aerobee rocket at an altitude of 100–150 km. After the necessary digital post-processing of the image, a circular zone around the comet, 800,000 km in diameter, glowing diffusely in the light of the Lyman α line. According to the measurements of the OAO-2, the gas envelope made of hydrogen was almost twice the size and thus the extent of the sun. The source of the hydrogen in the gas envelope was assumed to be the splitting of water molecules from the comet's nucleus triggered by the sun's radiation . The production rate of these atoms or radicals was determined from the observations of the emission lines of H and OH with the satellite OAO-2 . Their production rates were in an approximate ratio of 3: 1 to each other during the entire observation period, which suggests that the comet's nucleus consists mainly of water.

Around the turn of the year 1969/1970, various astronomical objects were examined for the presence of polarization in their light at the Kitt Peak National Observatory in Arizona , including the comet Tago-Sato-Kosaka in the near ultraviolet and visible from January 20 to February 1 Light. Although a clear linear polarization could be determined in the comet, as with the other objects examined, there was no significant proportion of circular polarization.

Observations of the comet in the infrared were made in late January to mid-February 1970 at the Lunar and Planetary Laboratory in Arizona. In addition, on February 4 and 5, 1970, observations with an infrared telescope were made on board a Learjet . The visually observed outbreak of brightness of the comet around February 6th (see above) could also be determined in the infrared, where at the same time an increase in brightness by a factor of 2 occurred.

At the Goddard Space Flight Center in Maryland from February 11th to 14th, 1970 images of the comet were made with interference filters at different wavelengths in the purple, blue and green regions of the spectrum. In particular, the emission lines of CN, C 2 and C 3 were evaluated and maps of the comet's coma with lines of equal brightness (isophotes) up to a distance of 100,000 km from the nucleus were created.

Similar research was also conducted at the University of Western Ontario's Hume Cronyn Memorial Observatory, in Canada , from January 22nd to February 7th . There, too, images of the comet were made with an interference filter in the violet part of the spectrum. In particular, the emission line of CN was measured and its intensity represented in the form of isophotes.

With recordings made on January 5th to 12th, 1970 at the Boyden Observatory in South Africa , the kinematic behavior of the plasma tail of the comet could be examined and the speed of the structures in it could be derived. For the first time, it was also possible to take into account the solar wind measurement data recorded by satellites . With additional images, which were made from December 25, 1969 to January 11, 1970 at the Cerro Tololo Inter-American Observatory in Chile , it was possible to show that the structures in the plasma tail of the comet were not subject to any major disturbances during this time.

In 1973, Delsemme and Rud first tried to determine the radius and the albedo of several comets, including the comet Tago-Sato-Kosaka, from measurements of brightness during long distances from the Sun and 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 as it approaches the sun , an albedo of around 0.63 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

For the comet, an elliptical orbit could be determined from 305 observation data over a period of about half a year , which is inclined by about 76 ° to the ecliptic . At the point of the orbit closest to the sun ( perihelion ), which the comet passed on December 21, 1969, it was located at a distance of 70.7 million km from the sun in the area of ​​the orbit of Venus . On December 4, 1969, it passed Mercury at a distance of about 40.0 million km and on January 20, 1970, it came close to Earth to within 0.38  AU / 56.9 million km.

In the vicinity of the ascending node of its orbit, the comet Tago-Sato-Kosaka moved in close proximity to the earth's orbit around January 28, 1970, and in fact at a distance of only about 0.00051 AU / 76,000 km. However, the earth had already passed this point almost four weeks earlier on January 2nd.

The comet moves in an elongated elliptical orbit around the sun. As early as 1978 Marsden , Sekanina and Everhart had determined orbital elements and parameters for the original and future shape of the comet from 281 observation data. According to the currently known relatively precise orbital elements (which, however, do not take into account non-gravitational forces), some time before its passage through the inner solar system in 1969/70 , its orbit still had an eccentricity of around 0.99976 and a semi-major axis of around 1980 AU, so that its orbital period was around 88,000 years. The comet did not approach any of the major planets except for Jupiter on October 23, 1969 to a distance of about 5 ⅓ AU, so that its orbit was not influenced by the gravitational pull of the planets. After leaving the inner solar system, its orbit will have an eccentricity of about 0.99980 and a semi-major axis of about 2330 AU, so that its orbit will then be about 113,000 years.

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. ↑ M. Beyer: Physical observations of comets. XVII. In: Astronomical News. Vol. 293, 1972, pp. 241-257 ( bibcode : 1972AN .... 293..241B ).
  3. ^ 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. 245-250.
  4. ^ BG Marsden: Comets in 1970. In: Quarterly Journal of the Royal Astronomical Society. Vol. 12, 1971, pp. 244-273 ( bibcode : 1971QJRAS..12..244M ).
  5. ↑ International Comet Quarterly - Brightest comets seen since 1935. Retrieved April 29, 2016 (English).
  6. ^ BG Marsden: IAUC 2201: 1969g; Periods of Four Southern Pulsars; (1566); 1969h. IAU Central Bureau for Astronomical Telegrams, January 21, 1970, accessed May 3, 2016 .
  7. ^ 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 SP-310, Washington 1972, pp. 109-114 ( PDF; 196.6 MB ).
  8. ↑ EB Jenkins, DW Wingert: The Lyman-Alpha Image of Comet Tago-Sato-Kosaka (1969g). In: The Astrophysical Journal. Vol. 174, 1972, pp. 697-704 doi: 10.1086 / 151531 ( bibcode : 1972ApJ ... 174..697J ).
  9. ^ DA Mendis, TE Holzer, WI Axford: Neutral Hydrogen in Cometary Comas. In: Astrophysics and Space Science. Vol. 15, 1972, pp. 313-325 doi: 10.1007 / BF00649925 ( bibcode : 1972Ap & SS..15..313M ).
  10. ^ HU Keller, CF Lillie: Hydrogen and Hydroxyl Production Rates of Comet Tago-Sato-Kosaka (1969 IX). In: Astronomy & Astrophysics. Vol. 62, 1978, pp. 143-147 ( bibcode : 1978A & A .... 62..143K ).
  11. ^ GW Wolf: A Search for Elliptical Polarization in Starlight. In: The Astronomical Journal. Vol. 77, 1972, pp. 576-583 doi: 10.1086 / 111321 ( bibcode : 1972AJ ..... 77..576W ).
  12. ^ 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 ).
  13. Jump up ↑ J. Rahe, CW McCracken, KL Hallam, BD Donn: Monochromatic Observations of Comet Tago-Sato-Kosaka 1969g (1969IX). In: Astronomy and Astrophysics Supplement Series. Vol. 23, 1976, pp. 1-12 ( bibcode : 1976A & AS ... 23 .... 1R ).
  14. ^ 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 ).
  15. ↑ K. Jockers, Rh. Lüst, Th. Nowak: The Kinematical Behavior of the Plasma Tail of Comet Tago-Sato-Kosaka 1969 IX. In: Astronomy & Astrophysics. Vol. 21, 1972, pp. 199-207 ( bibcode : 1972A & A .... 21..199J ).
  16. ^ FD Miller: Comet Tago-Sato-Kosaka 1969 IX: Tail Structure 25 December 1969 to 12 January 1970. In: Icarus. Vol. 37, 1979, pp. 443-456 doi: 10.1016 / 0019-1035 (79) 90007-1 ( PDF; 4.56 MB ).
  17. ↑ 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 ).
  18. ↑ NASA JPL Small-Body Database Browser: C / 1969 T1 (Tago-Sato-Kosaka). Retrieved April 29, 2016 .
  19. ^ 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, no. 1, 1978, pp. 64-71 doi: 10.1086 / 112177 ( bibcode : 1978AJ ..... 83 ... 64M ).
  20. ↑ A. Vitagliano: SOLEX 11.0. Archived from the original on September 18, 2015 ; accessed on May 2, 2014 .