C / 2001 Q4 (NEAT)

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C / 2001 Q4 (NEAT) [i]
2001q4neat.JPG
Properties of the orbit ( animation )
Epoch:  May 16, 2004 ( JD 2,453,141.5)
Orbit type hyperbolic
Numerical eccentricity 1,00069
Perihelion 0.962 AU
Inclination of the orbit plane 99.6 °
Perihelion May 15, 2004
Orbital velocity in the perihelion 43.0 km / s
Physical properties of the core
Rotation period 23.2 h
history
Explorer NEAT
Date of discovery August 24, 2001
Source: Unless otherwise stated, the data comes from JPL Small-Body Database Browser . Please also note the note on comet articles .

C / 2001 Q4 (NEAT) is a comet that could be seen with the naked eye in 2004 . It had been discovered almost three years earlier as part of the Near Earth Asteroid Tracking (NEAT) project and became one of the brightest comets of 2004.

Discovery and observation

The NEAT project of the Jet Propulsion Laboratory (JPL) was actually aimed at detecting near-Earth asteroids in good time before they could become a collision risk for Earth . As a side effect, this project also led to the discovery of numerous comets.

On images from the Palomar Observatory from August 24 to 27, 2001, HH Pravdo, EF Helin and KJ Lawrence from the Jet Propulsion Laboratory discovered a round nebula-shaped spot with a brightness of about 20 mag. At the time of its discovery, the comet was more than 10  AU from the Sun , further than the planet Saturn , and thus the greatest distance at which a comet had ever been discovered.

During 2003, the comet's brightness slowly increased. For a long time it could only be seen from the southern hemisphere near the southern celestial pole . Observers in Brazil and Australia estimated the brightness to be about 12 mag at the beginning of September 2003, about 10 mag at the end of the year and about 8 mag in February 2004. A first sighting with the naked eye took place in late March in the Falkland Islands at around 6 mag.

The comet continued to gain in brightness, but could only be observed in the southern sky until May 2004 , where many observers followed it. From May 10th it could be found in the evening sky of the northern hemisphere , where it also reached its greatest brightness of about 3 mag at that time. A comet's tail was now also observed, the information on this was very different and reached values ​​of up to 11 ° longitude. At the same time, comet C / 2002 T7 (LINEAR) could also be observed in the morning sky . By the second half of May the brightness had fallen below 4 mag and the tail length had decreased to 1.5 °.

The brightness continued to decrease, at the beginning of June it sank below the threshold for observation with the naked eye, and a telescope was again necessary for observation by mid-September. The observations of the comet continued until the beginning of 2005. The final positioning succeeded August 18, 2006, almost exactly five years after its discovery, at the Observatory of Ageo in Japan .

The comet reached a maximum brightness of 2.8 mag, making it one of the 25 brightest comets since 1935.

C / 2001 Q4 taken together with the open star cluster Messier 44 (bottom left)

Scientific evaluation

Shortly after its discovery, preliminary orbital elements could be determined for the comet NEAT , which indicated that the comet could be a "dynamic new" comet from the Oort cloud , which would also achieve a high level of brightness when approaching the sun. Numerous observation programs were therefore planned at an early stage to study the comet in different wavelength ranges as it approached the sun and in the vicinity of the sun.

As early as mid-March 2002, when the comet was still 8.6 AU from the Sun, images were taken at the La Silla Observatory in Chile and spectroscopic examinations of the comet's coma were carried out in visible light. The coma, consisting of dust, already had a diameter of over 100,000 km at this distance from the sun, but no signs of gas emission of CN, C 2 or C 3 could yet be detected.

Most of the other observation programs were carried out shortly before and after the comet's perihelion passage in mid-May 2004, when the comet was at convenient distances of about 1 AU from the Sun and well below 1 AU from Earth .

Visible light

From May 13 to 19, 2004, spectroscopic and photometric investigations of the comet in the visible range were carried out at the Aryabhatta Research Institute of Observational Sciences in India . There were able emission lines of CN and C 2 detected and their production rate are derived. Investigations of the comet spectrum in the visible wavelength range were also carried out at the observatory in Andruschiwka in Ukraine in May and June 2004. On May 14th, the emission lines of C 2 , C 3 , CN, CH, NH 2 and H 2 O + were discovered and their intensities were determined.

As early as September 2003 when the comet was about 3.7 AU from the Sun and then again in May 2004 when the comet was only about 1 AU from the Sun, the Very Large Telescope of the Paranal Observatory saw the European Southern Observatory in Chile undertook spectroscopic investigations in the violet to determine the ratio between the stable isotopes 12 C / 13 C and 14 N / 15 N in the CN radical . The measured values ​​changed only slightly with the distance from the sun of the comet and corresponded to those measured under similar conditions for comets C / 1995 O1 (Hale-Bopp) and C / 2003 K4 (LINEAR) . In order to obtain an independent measurement result, in May 2004 the two comets C / 2001 Q4 (NEAT) and C / 2002 T7 (LINEAR) were again measured spectroscopically with the Very Large Telescope, this time in the blue to use a different method the ratio of 12 C / 13 C in C 2 - molecule to be determined. The results were in agreement with the values ​​previously obtained from the observation of the CN radical.

From observations of the concentric dust shells around the comet's nucleus at the Pic-du-Midi-Observatory in France from May 14th to 19th, 2004 it was possible to derive a rotation period of the cometary nucleus of about 23.2 hours. From further observations of the morphological changes in the dust shells around the comet, which took place from April 16 to June 3, etc. a. at the Vainu Bappu Observatory in India and at the Las Campanas Observatory in Chile, the spatial orientation of the axis of rotation of the comet's nucleus and its inclination to the orbit plane could be determined. In addition, the positions of the active zones on the comet's core could be modeled and their total area in the time of the perihelion estimated to be around 40 km².

Infrared

With the Infrared Telescope Facility (IRTF) of NASA in Hawaii , spectroscopic examinations of the comet were carried out on May 11, 2004 in the mid- infrared at 10 µm wavelength. The course of the spectra obtained was very similar to those obtained during the observation of comet C / 1995 O1 (Hale-Bopp) in February 1997. In its composition of crystalline silicates in the form of olivine and orthopyroxene, the comet is largely similar to the comet Hale-Bopp. It was deduced that the two comets either formed in the same environment, or that crystalline silicates were generally widespread in the areas where comets formed when the solar system formed. From June 4th to 6th, further spectroscopic investigations of the comet NEAT and the comet C / 2002 T7 (LINEAR) in the wavelength range around 10 µm were carried out with the IRTF, which confirmed the previously obtained results. The dust grains from comet NEAT seemed to have been smaller than those from comet LINEAR. The signatures of crystalline silicate and olivine could also be detected in spectroscopic examinations at the Mount Lemmon Observatory in Arizona from May 14th to June 20th.

On May 28, 2004, high-resolution spectroscopic examinations of the comet in the near infrared were carried out at the 8 m Subaru telescope of the National Astronomical Observatory of Japan in Hawaii . For the first time, the nuclear spin temperature of methane was determined to be around 33 K from the measurement results . Similar values ​​were previously determined for the spin temperature of water and ammonia in other comets. The spin temperature probably corresponds to the temperature below which the molecule originally formed before it was trapped in the cometary material. Together with the determination of a numerically only small ratio between deuterium and hydrogen (protium) in methane, this indicates that the methane enclosed in the comet formed from a presolar primordial cloud at temperatures above 30 K and that consequently the sun also formed from a warm cloud at about 30 K and not, as previously assumed, from a cold one at about 10 K.

The simultaneous spectroscopic investigation of the emission lines of water in the infrared and that of the emission line of the NH 2 radical in visible light on May 24th brought very similar results . The numerical ratios between ortho and parahydrogen (OPR) in these molecules, which in turn correspond to spin temperatures of about 31 K, were determined from the spectra obtained . With an improved method, an even more precise value for the OPR in the NH 2 radical could subsequently be derived. In the cometary coma, the NH 2 radical is mainly created by the decomposition of the ammonia molecule (NH 3 ) under the ultraviolet radiation of the sun. The OPR of ammonia and its spin temperature could therefore also be determined to be about 30 K.

With the same improved calculation method, the measurement results for a total of 15 comets were revised, including the results of the observation of the comet NEAT from May 5 to 7, 2004 on the Very Large Telescope (see above). Here, too, a spin temperature for the NH 3 molecule of 30 K was obtained for the comet NEAT , as was the case with almost all other comets investigated, which also have a comparable isotope ratio of 14 N / 15 N in the CN radical .

The determination of the ratio between ortho and parahydrogen in the water molecules of the cometary coma also enables a new method in which the visible emission spectrum of the H 2 O +, which is essentially created by the ionization of water, is evaluated. This procedure was used for the first time with the comet NEAT and also led to values ​​of the spin temperature of water of about 30 K.

Ultraviolet and X-rays

From September 14, 2003 to November 2, 2004, the comet NEAT was observed with the Solar Wind Anisotropies (SWAN) camera on board the Solar and Heliospheric Observatory (SOHO) satellite, this period includes the movement of the comet from a distance of 3 ¼ AU distance from the Sun before its perihelion to a distance of 2 ¾ AU after its perihelion. Regular recordings of the hydrogen distribution in the interplanetary medium in the light of the Lyman α line at 121.5 nm enabled an almost complete recording of the production rate of water for the comet. Numerical values ​​of the water production in molecules per second depending on the distance from the sun in the form of power laws could be derived from this. Before the perihelion, the comet was about two to three times as productive as after it, which could have been due to the orientation of its axis of rotation in relation to the sun in connection with an elongated shape of the comet's nucleus or an asymmetrical distribution of active areas on its surface.

On April 24, 2004, observations of the comet with the Far Ultraviolet Spectroscopic Explorer (FUSE) in the region of the far ultraviolet began. This was the first use of this satellite after a failure in 2001. Numerous emission lines could be identified, with similar intensity to three comets observed in 2001, including the lines of CO, O and H, while around two dozen other lines remained unidentified. The CO line showed a regular fluctuation with a clear factor of 1.6 between minimum and maximum and a period of around 17.0 hours. From the measurements it was possible to determine the production rate of CO compared to that of water.

For the first time, comet C / 2001 Q4 (NEAT) was able to detect an emission line of atomic deuterium in the spectrum. The corresponding Lyman α line at 121.534 nm was detected with sufficient certainty during observations of the comet from April 24 to 28, 2004 with the Space Telescope Imaging Spectrograph (STIS) on board the Hubble space telescope . Although the determination of an exact production rate of deuterium was problematic, an initial estimate of the ratio of deuterium to hydrogen (protium) could be made.

From May 8 to 15, 2004, the Far-Ultraviolet Imaging Spectrograph (FIMS) on board the Korean satellite STSAT-1 was able to make further observations of the comet in the far ultraviolet. A picture of the comet and spectra with the emission lines of S, C and CO could be obtained from this. The production rates of these substances could be determined from the measurements.

When ions of the solar wind collide with neutral atoms and molecules in the comet's shell, charge exchange can result in soft X-rays and short-wave ultraviolet radiation (EUV) (as was also found in the observation with FUSE). The favorable circumstances during the perihelion passage made it possible for the first time in the period from April 21 to May 21, 2004 to observe the comet NEAT both with the X-ray telescope on board the Chandra satellite and with the EUV spectrograph on board the CHIPSat satellite . The X-ray spectrum obtained with Chandra enabled the emission lines of ionized C, N, O, Mg, Fe, Si, S and Ne in the solar wind to be detected. The measured EUV lines were only very weak.

Micro and radio waves

With the submillimeter telescope on board the Odin satellite, which was launched in 2001, twelve comets were observed up to 2005, including comet C / 2001 Q4 (NEAT) from early March to mid-May 2004. In particular, the emission line of water at 557  GHz has been studied intensively in order to obtain an exact measurement of its production rate. The emission line of H 2 18 O at 548 GHz could also be registered and thus the ratio between the isotopes 16 O and 18 O could be determined, which at about 530: 1 almost corresponds to the value measured on earth. As an experiment, an ammonia (NH 3 ) emission line at 572 GHz was also searched for. In the case of the comet NEAT, it was weakly detected at the end of April 2004 and could be deduced from the fact that ammonia was emitted from the comet in an amount 200 times less than water. The outgassing rate of water showed a regular fluctuation during the observation period, which corresponded to a variation in the production rate of approximately ± 40%, and the period of which could be determined to be approximately 19.6 hours. A fluctuation with a similar period was also found in the observations of the emission line of CO with FUSE in the far ultraviolet (see above).

Using the 12-meter radio telescope at the Kitt Peak National Observatory in Arizona , the emission lines of HCN, CO and H 2 S were discovered from May 6 to 18, and their production rates compared to that of water were examined to determine whether the Comet is impoverished in one of these molecules. As before with comet C / 1995 O1 (Hale-Bopp), observations of the emission lines of formaldehyde (H 2 CO) at 211 and 218 GHz were also carried out there on comet NEAT on May 15 and 26, 2004 . The production rate of the molecule and the ratio of this production rate to that of water could be determined from the measurements. Some of the formaldehyde is possibly released from grains rich in silicate in the dust of the cometary coma, interspersed with organic molecules, so that despite its rapid decay it could be detected at a greater distance from the comet's nucleus.

From May 7th to May 11th, 2004, spectroscopic examinations of the comet NEAT were carried out with the submillimeter telescope at the Mount Graham International Observatory (MGIO) in Arizona to determine the composition of the supposedly “dynamically new” comet NEAT with that of “dynamically old” comets to compare. In particular, the search was carried out for the emission lines of HCN, H 2 CO, CO, CS, CH 3 OH and HNC in the range of 225-270 GHz. The measurements made it possible to determine the production rates of these molecules and their relationships to the production rate of water.

From May 8 to 17, 2004, a search for ammonia (NH 3 ) emission lines at 24 GHz in the comet's coma was carried out with the 100 m Effelsberg radio telescope of the Max Planck Institute for Radio Astronomy . No such emissions could be detected, while a control measurement of the lines of the OH radical confirmed the correct orientation of the antenna.

With the BIMA millimeter interferometer at the Hat Creek Radio Observatory in California , spectroscopic investigations of the emission lines of HCN at 88.6 GHz were carried out from May 23 to 24, 2004. The production rate of HCN and its relationship to the production rates of water and CN could be determined from the measurement results using various mathematical models. The ratio of the production rate of HCN to that of water was comparable to the value that had already been observed previously for comet C / 1996 B2 (Hyakutake) . From May 20 to 24, signals from larger molecules such as methanol , acetonitrile , propionitrile , ethanol and methyl formate , as well as signatures from smaller compounds such as CS, SiO, HNC, HN 13 C and 13 CO wanted in the frequency range of 87–110 GHz. In the case of the comet NEAT, only methanol could be clearly detected and its production rate determined. Here, too, the ratio of this production rate to that of water was comparable to the value that had already been observed with comet Hyakutake.

From the beginning of May to mid-June 2004, the Nançay radio telescope in France was used to observe the 18 cm OH emission line at the comet NEAT.

polarization

In May and June 2004, observations of the linear polarization of the light from the cometary coma were made at the Mount Abu Observatory in India . A high degree of polarization was determined and a typical composition of the dust grains of silicates and organic substances was derived from it, similar to comet C / 1996 B2 (Hyakutake).

From May 21 to 23, 2004, measurements of the linear and circular polarization of light from cometary coma and dust tail were carried out at the Crimean Observatory with a polarimeter . A significant correlation was found between the circular polarization and the parameters of the linear polarization. This indicates non-spherical and aligned particles in the comet's dust that are inhomogeneously or anisotropically distributed. As was already noted with three other comets, a predominantly left-handed polarization was noticeable.

Others

From April 24 to June 2, the comet could be observed together with the two comets C / 2002 T7 (LINEAR) and C / 2004 F4 (Bradfield) also with the Solar Mass Ejection Imager (SMEI) on board the Coriolis satellite . Around May 5th, the interaction of a coronal mass ejection (CME) of the sun with the plasma tail of the comet NEAT as well as wave-like influences on the plasma tails of NEAT and LINEAR by fluctuations in the solar wind could be observed for the first time. The plasma tail of Comet Bradfield, on the other hand, remained undisturbed, presumably because at the time of the observation it was no longer near the equatorial plane of the Sun, as was the case for the other two comets. Further investigations showed that the influences on the plasma tails are caused by fluctuations in the radial speed of the solar wind of typically 50-100 km / s, which in turn are likely to be spatially limited, as there is no correlation with the measurements of more distant satellites, e.g. B. ACE could be determined.

Orbit

For the comet a very precise hyperbolic orbit could be determined from 2630 observation data over a period of almost 5 years , which is inclined by around 100 ° to the ecliptic . Its orbit is thus almost perpendicular to the planets of the planets. At the point of the orbit closest to the sun ( perihelion ), which the comet passed on May 15, 2004, it was located somewhat within the range of the earth's orbit at a distance of 143.9 million km from the sun. It had already approached Earth itself on May 6th to about 0.32 AU / 48.0 million km. On May 13th, the closest distance to Venus was reached with about 39.4 million km .

In the vicinity of the ascending node of its orbit, the comet C / 2004 Q4 moved around May 16, 2004 in the immediate vicinity of the earth's orbit, and in fact at a distance of only 0.043 AU / 6.4 million km from it. However, the earth had already passed this point almost a month earlier on April 20th.

Shortly after its discovery, Brian Marsden determined the first preliminary orbital parameters of the comet. On the basis of the results, he suspected as early as 2002 that the comet came from the Oort cloud and could have penetrated the inner solar system for the first time as a “dynamic new” comet. After further observations were available, he found in 2004 that the comet was still moving on an elliptical orbit with a semi-major axis of 23,800 AU before it approached the Sun and gave parameters for the effect of non-gravitational forces on the movement of the comet.

In a 2010 study, Królikowska and Dybczyński determined new values ​​for the orbital elements, taking into account 2661 observation data over the entire observation period of the comet. They also determined values ​​for the original and future shape of the orbit before and after passing through the inner solar system. They also came to the conclusion that considering non-gravitational forces in this comet leads to significantly better results than a purely gravitational calculation and that a purely gravitational orbit calculation leads to incorrect evaluations of the original and future orbit shape. According to their investigations, the comet was moving on an elliptical orbit with a semi-major axis of around 16,400 AU and thus had an orbital period of around 2.1 million years before it approached the sun .

In addition, they found through a simulation of comet dynamics with statistical methods , taking into account the gravitational pull of the galactic disc and the galactic center, as well as gravitationally disturbing stars in the solar environment, that comet C / 2001 Q4 (NEAT) is not, as previously generally assumed, a “dynamic new one “Was a comet, but could have already penetrated into the area of ​​the planets during its previous orbit around the sun.

In a further study from 2012, they also found that the determination of the orbit parameters of the comet with even greater accuracy is possible if only the observations at greater distances from the Sun are used for the calculation and those near the passage of the perihelion are omitted because they are incalculable are influenced by spontaneous outgassing effects on the comet's surface. Under this condition, you will get a result that differs slightly from the previous calculations, according to which the comet moved on an elliptical orbit with an eccentricity of about 0.999953 and a semi-major axis of about 20,300 AU and thus an orbital time before it approached the sun of about 2.9 million years ago. However, this type of calculation also confirms that the comet was definitely not "dynamically new", but had already been close to the Sun at least once before and had crossed the orbits of Saturn and Jupiter inwards to a distance of about 3.3 AU.

During the last passage through the inner solar system, however, its orbit was significantly changed by about 8 ½ AU on June 7, 2000 and on Jupiter on January 3, 2001 in about 9 zieh AU due to the gravitational pull of the planets, especially when passing close by Saturn and on May 27, 2004 at a distance of about 4 ¾ AU, the orbital eccentricity was increased to about 1,00067, so that the comet is now departing on a hyperbolic orbit. He will therefore no longer return to the inner solar system.

See also

Web links

Commons : C / 2001 Q4 (NEAT)  - album with pictures, videos and audio files

A variety of photographs of comet C / 2001 Q4 (NEAT) exist on the Internet. The following web links show only a small selection of them:

Individual evidence

  1. ↑ a b D. WE Green: IAUC 8349: C / 2001 Q4; 2004by. IAU Central Bureau for Astronomical Telegrams, May 31, 2004, accessed April 6, 2016 .
  2. ^ DWE Green: IAUC 7695: C / 2001 Q4; V4739 Sgr = N Sgr 2001 No. 2. IAU Central Bureau for Astronomical Telegrams, August 28, 2001, accessed April 12, 2016 .
  3. ^ J. Shanklin: The comets of 2001: Part 1. In: Journal of the British Astronomical Association. Vol. 123, 2013, pp. 338-352.
  4. ↑ C / 2001 Q4 (NEAT). IAU Minor Planet Center, accessed April 12, 2016 .
  5. ↑ International Comet Quarterly - Brightest comets seen since 1935. Retrieved April 12, 2016 (English).
  6. ↑ GP Tozzi, H. Boehnhardt, G. Lo Curto: Imaging and spectroscopy of comet C / 2001 Q4 (NEAT) at 8.6 AU from the Sun. In: Astronomy & Astrophysics. Vol. 398, 2003, pp. L41-L44 doi: 10.1051 / 0004-6361: 20021878 ( PDF; 232 kB ).
  7. ↑ M. Singh, BB Sanwal, B. Kumar: Spectrophotometric study of the comet C / 2001 Q4 (NEAT). In: Bulletin of the Astronomical Society of India. Vol. 34, 2006, pp. 273-279 ( bibcode : 2006BASI ... 34..273S ).
  8. ↑ AV Ivanova, PP Korsun, SA Borisenko, Yu. N. Ivashchenko: Spectral studies of comet C / 2001 Q4 (NEAT). In: Solar System Research. Vol. 47, 2013, pp. 71-79 doi: 10.1134 / S0038094613010036 .
  9. ↑ J. Manfroid, E. Jehin, D. Hutsemékers, A. Cochran, J.-M. Zucconi, C. Arpigny, R. Schulz, JA Stüwe: Isotopic abundance of nitrogen and carbon in distant comets. In: Astronomy & Astrophysics. Vol. 432, 2005, pp. L5-L8 doi: 10.1051 / 0004-6361: 200500009 ( PDF; 219 kB ).
  10. ↑ P. Rousselot, E. Jehin, J. Manfroid, D. Hutsemékers: The 12 C 2 / 12 C 13 C isotopic ratio in comets C / 2001 Q4 (NEAT) and C / 2002 T7 (LINEAR). In: Astronomy & Astrophysics. Vol. 545, 2012, A24 pp. 1–7 doi: 10.1051 / 0004-6361 / 201219265 ( PDF; 885 kB ).
  11. ^ R. Vasundhara, P. Chakraborty, S. Muneer, G. Masi, S. Rondi: Investigations of the Morphology of Dust Shells of Comet C / 2001 Q4 (NEAT). In: The Astronomical Journal. Vol. 133, 2007, pp. 612-621 doi: 10.1086 / 509603 ( PDF; 1.15 MB ).
  12. ^ DH Wooden, CE Woodward, DE Harker: Discovery of Crystalline Silicates in Comet C / 2001 Q4 (NEAT). In: The Astrophysical Journal. Vol. 612, 2004, pp. L77-L80 doi: 10.1086 / 424593 ( PDF; 110 kB ).
  13. ^ DE Harker, CE Woodward, DH Wooden, MS Kelley: The Dust Mineralogy of Two Long-Period Comets: C / 2001 Q4 (Neat) and C / 2002 T7 (Linear). In: Bulletin of the American Astronomical Society. Vol. 36, 2004, p. 1434.
  14. ^ DWE Green: IAUC 8360: 2004ci, 2004cr; C / 2001 Q4. IAU Central Bureau for Astronomical Telegrams, June 23, 2004, accessed April 15, 2016 .
  15. ↑ H. Kawakita, J. Watanabe, R. Furusho, T. Fuse, DC Boice: Nuclear Spin Temperature and Deuterium-to-Hydrogen Ratio of Methane in Comet C / 2001 Q4 (NEAT). In: The Astrophysical Journal. Vol. 623, 2005, pp. L49-L52 doi: 10.1086 / 429872 ( PDF; 98 kB ).
  16. ↑ H. Kawakita, N. Dello Russo, R. Furusho, T. Fuse, J. Watanabe, DC Boice, K. Sadakane, N. Arimoto, M. Ohkubo, T. Ohnishi: Ortho-to-Para Ratios of Water and Ammonia in Comet C / 2001 Q4 (NEAT): Comparison of Nuclear Spin Temperatures of Water, Ammonia, and Methane. In: The Astrophysical Journal. Vol. 643, 2006, pp. 1337-1344 doi: 10.1086 / 503185 ( PDF; 266 kB ).
  17. ↑ Y. Shinnaka, H. Kawakita, H. Kobayashi, Y. Kanda: Revisit to the Nuclear Spin Temperature of NH 3 in Comet C / 2001 Q4 (NEAT) Based on high-dispersion spectra of cometary NH 2 . In: Publications of the Astronomical Society of Japan. Vol. 62, 2010, pp. 263-271 doi: 10.1093 / pasj / 62.2.263 ( PDF; 657 kB ).
  18. ↑ Y. Shinnaka, H. Kawakita, H. Kobayashi, E. Jehin, J. Manfroid, D. Hutsemékers, C. Arpigny: Ortho-to-para Abundance Ratio (OPR) of Ammonia in 15 Comets: OPRs of Ammonia Versus 14 N / 15 N ratios in CN. In: The Astrophysical Journal. Vol. 729, 2011, pp. 1–15 doi: 10.1088 / 0004-637X / 729/2/81 ( PDF; 519 kB ).
  19. ↑ Y. Shinnaka, H. Kawakita, H. Kobayashi, DC Boice, SE Martinez: Ortho-to-para Abundance Ratio of Water Ion in Comet C / 2001 Q4 (NEAT): Implication for Ortho-to-para Abundance Ratio of Water . In: The Astrophysical Journal. Vol. 749, 2012, pp. 1–6 doi: 10.1088 / 0004-637X / 749/2/101 ( PDF; 793 kB ).
  20. ↑ MR Combi, JTT Mäkinen, J.-L. Bertaux, Y. Lee, E. Quémerais: Water Production in Comets 2001 Q4 (NEAT) and 2002 T7 (LINEAR) Determined from SOHO / SWAN Observations. In: The Astronomical Journal. Vol. 137, 2009, pp. 4734-4743 doi: 10.1088 / 0004-6256 / 137/6/4734 ( PDF; 155 kB ).
  21. ↑ PD Feldman, HA Weaver, D. Christian, MR Combi, V. Krasnopolsky, CM Lisse, MJ Mumma, DE Shemansky, SA Stern: FUSE Observations of Comet C / 2001 Q4 (NEAT). In: Bulletin of the American Astronomical Society. Vol. 36, 2004, p. 1121.
  22. ^ HA Weaver, MF A'Hearn, C. Arpigny, MR Combi, PD Feldman, MC Festou, G.-P. Tozzi: Detection of Deuterium Emission from C / 2001 Q4 (NEAT). In: Bulletin of the American Astronomical Society. Vol. 36, 2004, p. 1120.
  23. ↑ Y.-M. Lim, K.-W. Min, PD Feldman, W. Han, J. Edelstein: Far-Ultraviolet Observations of Comet C / 2001 Q4 (NEAT) with FIMS / SPEAR. In: The Astrophysical Journal. Volume 781, 2014, pp. 1–7 doi: 10.1088 / 0004-637X / 781/2/80 ( PDF; 722 kB ).
  24. ↑ TP Sasseen, M. Hurwitz, CM Lisse, V. Kharchenko, D. Christian, SJ Wolk, MM Sirk, A. Dalgarno: A Search for Extreme-Ultraviolet Emission from Comets with the Cosmic Hot Interstellar Plasma Spectrometer (CHIPS). In: The Astrophysical Journal. Vol. 650, 2006, pp. 461-469 doi: 10.1086 / 507086 ( PDF; 288 kB ).
  25. ↑ N. Biver, D. Bockelée-Morvan, J. Crovisier, A. Lecacheux, U. Frisk, Å. Hjalmarson, M. Olberg, H.-G. Florén, Aa. Sandqvist, S. Kwok: Submillimeter observations of comets with Odin: 2001-2005. In: Planetary and Space Science. Vol. 55, 2007, pp. 1058-1068 doi: 10.1016 / j.pss.2006.11.010 ( arxiv : astro-ph / 0610779 ).
  26. ↑ N. Biver, D. Bockelée-Morvan, P. Colom, J. Crovisier, A. Lecacheux, U. Frisk, Å. Hjalmarson, M. Olberg, Aa. Sandqvist: Periodic variation in the water production of comet C / 2001 Q4 (NEAT) observed with the Odin satellite. In: Astronomy & Astrophysics. Vol. 501, 2009, pp. 359-366 doi: 10.1051 / 0004-6361 / 200911790 ( PDF; 427 kB ).
  27. ↑ M. Womack, S. Choi, M. Gesmundo: CO, HCN and H 2 S in Comet C / 2001 Q4 (NEAT). In: Bulletin of the American Astronomical Society. Vol. 39, 2007, p. 521.
  28. ↑ SN Milam, AJ Remijan, M. Womack, L. Abrell, LM Ziurys, S. Wyckoff, AJ Apponi, DN Friedel, LE Snyder, JM Veal, P. Palmer, LM Woodney, MF A'Hearn, JR Forster, MCH Wright, I. de Pater, S. Choi, M. Gesmundo: Formaldehyde in Comets C / 1995 O1 (Hale-Bopp), C / 2002 T7 (LINEAR), and C / 2001 Q4 (NEAT): Investigating the Cometary Origin of H 2 CO. In: The Astrophysical Journal. Vol. 649, 2006, pp. 1169–1177 doi: 10.1086 / 506501 ( PDF; 335 kB ).
  29. ↑ M. de Val-Borro, M. Küppers, P. Hartogh, L. Rezac, N. Biver, D. Bockelée-Morvan, J. Crovisier, C. Jarchow, GL Villanueva: A survey of volatile species in Oort cloud comets C / 2001 Q4 (NEAT) and C / 2002 T7 (LINEAR) at millimeter wavelengths. In: Astronomy & Astrophysics. Vol. 559, 2013, A48 pp. 1–20 doi: 10.1051 / 0004-6361 / 201322284 ( 3.06 MB ).
  30. ↑ J. Hatchell, MK Bird, FFS van der Tak, WA Sherwood: Recent searches for the radio lines of NH 3 in comets. In: Astronomy & Astrophysics. Vol. 439, 2005, pp. 777-784 doi: 10.1051 / 0004-6361: 20052801 ( PDF; 207 kB ).
  31. ↑ DN Friedel, AJ Remijan, LE Snyder, MF A'Hearn, GA Blake, I. de Pater, HR Dickel, JR Forster, MR Hogerheijde, C. Kraybill, LW Looney, P. Palmer, MCH Wright: BIMA Array Detections of HCN in Comets LINEAR (C / 2002 T7) and NEAT (C / 2001 Q4). In: The Astrophysical Journal. Vol. 630, 2005, pp. 623-630 doi: 10.1086 / 432107 ( PDF; 206 kB ).
  32. ↑ AJ Remijan, DN Friedel, I. de Pater, MR Hogerheijde, LE Snyder, MF A'Hearn, GA Blake, HR Dickel, JR Forster, C. Kraybill, LW Looney, P. Palmer, MCH Wright: A BIMA array Survey of Molecules in Comets LINEAR (C / 2002 T7) and NEAT (C / 2001 Q4). In: The Astrophysical Journal. Vol. 643, 2006, pp. 567-572 doi: 10.1086 / 502713 ( PDF; 161 kB ).
  33. ↑ The Nançay database of OH 18-cm lines in comets. Retrieved April 14, 2016 .
  34. ^ S. Ganesh, UC Joshi, KS Baliyan: Optical polarimetry of Comet NEAT C / 2001 Q4. In: Icarus. Vol. 201, 2009, pp. 666-673 doi: 10.1016 / j.icarus.2009.01.008 ( arxiv : 0901.2789 ).
  35. ^ V. Rosenbush, N. Kiselev, N. Shakhovskoy, S. Kolesnikov, V. Breus: Circular and linear polarization of comet C / 2001 Q4 (NEAT). Why circular polarization in comets is predominantly left-handed? In: G. Videen, M. Mishchenko, MP Mengüç, N. Zakharova (Ed.): Peer-Reviewed Abstracts of the Tenth Conference on Electromagnetic & Light Scattering. Bodrum, 2007, pp. 181-184 doi: 10.1615 / ICHMT.2007.ConfElectromagLigScat.480 ( PDF; 317 kB ).
  36. ↑ SMEI. Retrieved December 11, 2018 .
  37. ↑ TA Kuchar, A. Buffington, CN Arge, PP Hick, TA Howard, BV Jackson, JC Johnston, DR Mizuno, SJ Tappin, DF Webb: Observations of a comet tail disruption induced by the passage of a CME. In: Journal of Geophysical Research. Vol. 113, A04101, 2008, pp. 1–11 doi: 10.1029 / 2007JA012603 ( PDF; 434 kB ).
  38. ↑ A. Buffington, MM Bisi, JM Clover, PP Hick, BV Jackson, TA Kuchar: Analysis of Plasma-Tail Motions for Comets C / 2001 Q4 (NEAT) and C / 2002 T7 (LINEAR) Using Observations from SMEI. In: The Astrophysical Journal. Vol. 677, 2008, pp. 798-807 doi: 10.1086 / 529039 ( PDF; 1.03 MB ).
  39. ↑ NASA JPL Small-Body Database Browser: C / 2001 Q4 (NEAT). Retrieved April 12, 2016 .
  40. ↑ A. Vitagliano: SOLEX 11.0. Archived from the original on September 18, 2015 ; accessed on May 2, 2014 .
  41. ↑ B. Marsden: MPEC 2004-K64: COMET C / 2001 Q4 (NEAT). IAU Minor Planet Center, May 29, 2004, accessed April 13, 2016 .
  42. ↑ B. Marsden: MPEC 2004-L37: COMET C / 2001 Q4 (NEAT). IAU Minor Planet Center, June 12, 2004, accessed April 13, 2016 .
  43. ^ M. Królikowska, PA Dybczyński: Where do long-period comets come from? 26 comets from the non-gravitational Oort spike. In: Monthly Notices of the Royal Astronomical Society. Vol. 404, 2010, pp. 1886–1902 doi: 10.1111 / j.1365-2966.2010.16403.x ( PDF; 9.40 MB ).
  44. ↑ M. Królikowska, PA Dybczyński, G. Sitarski: Different dynamical histories for comets C / 2001 Q4 and C / 2002 T7? In: Astronomy & Astrophysics. Vol. 544, A119, 2012, pp. 1–12 doi: 10.1051 / 0004-6361 / 201219408 ( PDF; 2.36 MB ).