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Analysis of Comet Apparitions


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Current Fainter Comets of Interest


On images taken on Oct. 9, 2019 the Asteroid Terrestrial-Impact Last Alert System (ATLAS) discovered an asteroidal object in Canis Major, which showed cometary activity during the following days. Comet C/2019 T4 (ATLAS) displayed a 1.5" coma of total magnitude 19.0 and a 2" tail in p.a. 110°. It will pass perihelion on June 9, 2022 in the solar distance of 4.25 AU (CBET 4681). Despite the rather large perihelion distance it could become visible in amateur telescopes. Depending on the actual brightness development it could peak at magnitude 15.0 (n=3) or even 14.0 (n=4) in spring 2022. From mid-European locations it should be best visible between March and June 2022, moving northward from Hydra towards Crater and Virgo.

Pre-perihelion the comet showed an activity above average, whereas post-perihelion the activity was average, as is shown by 374 observations from 40 observers (until the start of February 2024). The brightness development is well represented by the following formulae
pre-perihelion: m = 0.3 mag + 5×log D + 14.3×log r
post-perihelion: m = 4.6 mag + 5×log D + 7.5×log r
This yields a maximum brightness of 11.9 mag in mid-April 2022. Until the opening of July 2023 the comet had faded to 13.5 mag, until end of January 2024 to 14.8 mag. Between April 2021 and May 2022 the coma diameter increased from 0.5' (90,000 km) to almost 2' (300,000 km). Between fall 2022 and summer 2023 the apparent diameter was constant at 1.5', as was the absolute coma diameter (325,000 km). In October 2023 it was estimated as 1.1' (290,000 km), in January 2024 as 0.5' (150,000 km). In 2021/22 the coma was significantly condensed (DC 5), but got more diffuse thereafter (spring 2023: DC 2-3). A tail of up to 6' (5 mio. km) length, pointing in southwesterly directions, could be observed between December 2021 and October 2023.

Total Brightness and Coma Diameter

FGK observations

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An asteroidal object of magnitude 21, which was already discovered in the constellation Lyra on Oct. 22, 2019 by the PanSTARRS project, showed a near-parabolic orbit. Therefore attention was paid to the appearance of cometary activity. In 2020 hints of such activity had been reported, but not prior to early April 2021 comet C/2019 U5 (PANSTARRS) clearly showed cometary morphology. Observers reported a 15x10", east-west elongated coma with a total magnitude of 17.2. The comet will reach its mid-range perihelion not until March 29, 2023, when it will get as close as 3.62 AU to the Sun (CBET 4953). Assuming a "new" comet it may get as bright as magnitude 13 at that time. It should be brighter than 16 mag between early 2022 and the end of 2024. During this period it will move through the constellations Hercules, Bootes, Canes Venatici, Coma Berenice, Virgo, Leo, Sextant, Hydra, Antlia, Vela and Puppis. From mid-European latitudes it may remain observable until the end of May 2023.

Based on 276 observations from 40 observers (until start of February 2024) the brightness development can be well described by the formulae
pre-perihelion: m =  3.6 mag + 5×log D + 11×log r.
post-perihelion: m = -1.3 mag + 5×log D + 20×log r.
The comet peaked at magnitude 12.0 during the second half of March 2023. After the conjunction with the Sun in 2023 it was of magnitude 14.5 in December. The apparent coma diameter increased from 0.7' at the start of the apparition to the maximum of 2.0' during the second half of March 2023, whereas the absolute diameter expanded from 150,000 km to 225,000 km. In winter 2023/24 it measured only 0.5' (90,000 km). Whereas the coma was significantly condensed (DC 4-5) during the first half of 2022 it had grown more diffuse (DC 3) at the opening of 2023. CCD-observers detected a tail up to 9' (9 Mio. km) long, constantly directed towards Northeast.

Total Brightness and Coma Diameter

FGK observations

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On images taken on May 6, 2020 the PanSTARRS project discovered a comet of magnitude 20.2 in the constellation Draco. Comet C/2020 K1 (PANSTARRS) showed a miniscule coma of diameter about 1" and a 2" tail pointing towards Northeast. The comet will pass perihelion on May 9, 2023 at the solar distance of 3.07 AU, expected to reach 13 mag around this date (CBET 4779, MPECs). However, it will be positioned in the far-southern sky during the most interesting months. It should be brighter than 16 mag between April 2022 (located in the southern part of Hercules) and April 2024 (constellation Pictor). At mid-European locations the comet will disappear above the southwestern evening horizon already at the end of October 2022. At this time it will be positioned in the southern parts of Ophiuchus, expected to be of magnitude 15.

Based on 206 observations from 34 observers (until start of February 2024) the comet showed a break in the brightness development pre-perihelion. Until 280 days prior to perihelion (Aug. 1, 2022) the activity was above average, but during the next 280 days the activity was zero! Post-perihelion the comet faded steadily and in an average manner. The appropriate brightness parameters are
t < -280d: m0 = 2.3 mag / n = 5.3
-280d < t < 0d: m0 = 10.4 mag / n = 0
t > 0d: m0 = 5.6 mag / n = 4
Thus the comet peaked at 12.5 mag at the opening of June 2023. Until mid-September 2023 the comet had faded to 14.0 mag, until end of January 2024 to 14.5. Between April and June 2022 the coma diameter increased from 0.5' (110,000 km) to 1.4' (200,000 km). These values hold until August. In fall 2022 the diameter decreased to 1.1', which corresponds with a constant absolute coma diameter of 200,000 km. In spring 2023 the coma measured 1.3', corresponding to 160,000 km. It had shrunk to 0.6' by mid-September 2023 and to 0.5' (100,000 km in both cases) by January 2024. Surprisingly the degree of condensation decreased from the start of the apparition to fall 2022 from DC 5 to DC 3, where it remains since then. Reports of tail observations had been very rare.

Total Brightness and Coma Diameter

FGK observations

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An asteroidal object of magntiude 19, which was already discovered on Apr. 21, 2021 by the ATLAS-Team in the constellation Canis Major showed faint cometary signatures during follow-up observations. Until October 2021 additional observations clearly confirmed the cometary nature. Comet C/2021 G2 (ATLAS) will pass perihelion on Sep. 9, 2024 at the solar distance of 4.98 AU, expected to reach magnitude 15.0 in spring 2024 and 2025 (CBET 4988/5057). It should be brighter than 16 mag between November 2023 and August 2025. During this period it moves through the constellations Hydra, Corvus, Virgo and Libra. From mid-European latitudes it will appear in December 2024 above the southeastern morning horizon, and will change into the evening sky in May 2025.
At the start of February 2024 only 33 observations from 4 observers can be used for a rough analysis of the development. These indicate a brightness development that can be represented reasonably well with the parameters
m0 = 7.5 mag / n = 2.
These imply that the comet would reach a maximum brightness of 14.2 mag both at the end of April 2024 and at the end of April 2025. At the beginning of January 2024 the comet was of magnitude 14.5, showing a coma diameter of 0.6' (140,000 km). A tail of up to 2' (2.5 mio. km) length was pointing to the West.

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On Dec. 2, 2021 Alain Maury and Georges Attard discovered a slightly diffuse 19 mag object near the border of the consteallations Puppis/Pyxis. During the following weeks and months several observers reported cometary morphology. Early May 2022 comet C/2021 X1 (Maury-Attard) displayed a 9" coma of total magnitude 17.2 and a 10" tail in p.a. 100°. The comet will pass perihelion on May 27, 2023 in the solar distance of 3.23 AU (CBET 5119) and should peak at a maximum brightness of 14.5 mag in late summer 2023 (after reaching 15.0 mag in Dec. 2022). It should be brighter than 16 mag between October 2022 and end of 2023. During this interval it will move through the constellations Canis Mayor, Lepus, Eridanus, Cetus and Pisces towards the border of Pegasus/Aquarius. It will be near opposition in Pisces, well-placed for mid-European locations.

For the analysis 98 observations from 19 observers could be used. The observations can be represented rather well by the brightness parameters
m0 = 8.3 mag / n = 3.
Thus the comet reached a first maximum of 14.7 mag during the second half of December 2022 and peaked at 14.3 mag in mid-September 2023. The very last observations seem to hint towards a rapid decline in activity. The diameter of the medium-condensed (DC 4) coma increased until September 2023 from 0.4' (60,000 km) to 1.2' (130,000 km), but decreased to 0.7' (90,000 km) until November 2023. A tail could be detected by CCD observers during the entire apparition. It reached a length of 15' in fall 2023, which would correspond to an absolute length of about 30 mio km. This is quite implausible, so it is much saver to assume a significant curvature of the tail.

Total Brightness and Coma Diameter

FGK observations

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An 18 mag asteroidal object, discovered by the ATLAS team on Mar. 7, 2022 in the constellation Antlia showed cometary morphology in the course of follow-up observations. Comet C/2022 E2 (ATLAS) showed a highly condensed 7" coma of total magnitude 18.0, but no tail. The comet will pass perihelion on Sep. 15, 2024 at the solar distance of 3.67 AU, expected to reach magnitude 13 (CBET 5109). It should be brighter than 16 mag between March 2021 and January 2026. During this interval it will move through the constellations Hydra, Cancer, Gemini, Lynx (perihelion), Camelopardalis, Cassiopeia, Lacerta and Pegasus. Thus it will be well-placed for mid-European locations during the most interesting months.

Based on 88 observations by 18 observers (until start of February 2024) the brightness parameters can be derived as:
m0 = 3.8 mag / n = 4.3
This results in a first maximum of 13.0 mag in February 2024 and the main maximum of 12.3 mag in the second half of November 2024 - two months after perihelion passage (as the comet is still approaching Earth after perihelion). During the first 13 months of the apparition the comet brightened from 15.0 mag to 13.0 mag and the coma diameter increased from 0.3' (70,000 km) to 1.2' (160,000 km). The coma is significantly condensed (constant DC 5). Since April 2023, a tail of up to 3' (4 million km) length has been observed, pointing towards SE.

Total Brightness and Coma Diameter

FGK observations

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Comet C/2022 JK5 (PANSTARRS), which was discovered on May 9, 2022 as a 21st magnitude object in Libra by the PANSTARRS project, became three magnitudes brighter than originally expected. It passed perihelion at a distance of 2.69 AU on Apr. 28, 2023 and did not got brighter than 16 mag until June 2023, brightening quickly thereafter. Based on only 38 observations by 10 observers the brightness development for the period starting at the end of July can be well represented with the parameters
m0 = 8.3 mag / n = 3.5
yielding a maximum brightness of 13.8 mag at the end of July 2023. During the apparition the diameter of the medium-condensed (DC 3-4) coma decreased from 1.5' (150,000 km) to 0.4' (55,000 km). No tail was reported.

Total Brightness and Coma Diameter

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On June 10, 2022 the "Asteroid Terrestrial-Impact Last Alert System" (ATLAS) - team discovered a comet near the border of the constellations Cygnus/Lyra. Comet C/2022 L2 (ATLAS) showed a strongly condensed 8" coma of total magnitude 18.5m, but no tail. The comet will pass perihelion on Mar. 17, 2024 at the solar distance of 2.76 AU, expected to reach magnitude 13.0 (CBET 5136). Between May 2023 and January 2025 it should be brighter than 16 mag. During this period it will move through the constellations Hercules, Serpens, Libra, northern Centaurus (maximum brightness), Hydra (opposition loop), Antlia, Vela and Puppis. From mid-European locations the comet should be observable until the opening of October 2023 (then at magnitude 15.5) in the midnight and evening sky, and then again between December 2023 and February 2024 (then at magnitude 13.5) in the morning sky. In April 2024 its altitude is below 10° and in early May it will disappear completely.

For the analysis of the development of this comet 55 observations from 11 observers can be used at the beginning of February 2024, which indicate a low activity. The resulting brightness parameters are
m0 = 10.0 mag / n = 2,
which yield a peak brightness of 13.5 mag at the beginning of April 2024. While the comet brightened from 16.2 mag to 14.5 mag from April 2023 to January 2024, the coma diameter has so far remained constant at 0.3-0.4' (about 60,000 km). The coma is only medium-condensed (DC 3). A tail oriented towards ENE can be detected by CCD observers.

Total Brightness and Coma Diameter

FGK observations

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On July 4, 2022 the PANSTARRS team discovered a comet of magnitude 20 in the constellation Sagittarius. Comet C/2022 N2 (PANSTARRS) showed a condensed 2" coma and a 3" tail in p.a. 260°. It will pass perihelion at the solar distance of 3.84 AU on Aug. 3, 2025, expected to peak at magnitude 14.5 in October/November 2025 (CBET 5148). At discovery it was still at a distance of 9.5 AU from the Sun! Between April 2025 and February 2026 it should be brighter than 16 mag. During this period it moves from central Pisces northeastward to the region near the border of the constellations Aries/Taurus. Thus the observing conditions are optimal for mid-European locations during the time the comet is brightest.

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On Feb. 1, 2023 the ATLAS team discovered a 19th magnitude asteroidal object near the border of the constellations Centaurus/Vela, which showed cometary morphology in follow-up observations. Comet C/2023 C2 (ATLAS) exhibited a 9" coma of total magnitude 19.0 with a central condensation. The comet will pass perihelion at the solar distance of 2.37 AU on Nov. 16, 2024 and should reach a maximum brightness of 13.5-14.0 mag in August 2024 (CBET 5240). It should be brighter than 16 mag between March 2024 and July 2025. During this period it moves through the constellations Apus, Triangulum Australis, Norma (maximum brightness), Scorpius, Sagittarius (perihelion), Capricornus, Aquarius, Pegasus, Andromeda and Cassiopeia. From central European locations the comet can be sighted just above the southwestern evening horizon between November 2024 (14.0 mag) and January 2025 (14.5 mag) during the first period. It then reappears over the eastern morning horizon in March 2025 (15.0 mag), slowly gaining altitude during the following months, thereby steadily fading.

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The PANSTARRS team discovered another comet on Sep. 7, 2023 near the border of the constellations Pisces/Andromeda. Comet C/2023 R1 (PANSTARRS) showed a 1.5" coma of total magnitude 19.5. It will not pass its mid-distance perihelion at the solar distance of 3.57 AU until Apr. 14, 2026 (then expected to be of magnitude 15) and should peak at 14 mag in June 2026 (CBET 5293). It should be brighter than 16 mag between July 2025 and October 2026, when it will move through the constellations Pegasus, Vulpecula, Sagitta, Aquila (perihelion), Scutum, Serpens Cauda, Ophiuchus, (maximum brightness), Serpens Caput and Libra. From Central European locations it can be followed until September 2026 - with the exception of the period from mid-December 2025 to the end of January 2026.

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Just three days later, on Sep. 10, 2023, the PANSTARRS team succeeded in discovering a comet near the border of the constellations Cetus/Eridanus. Comet C/2023 R2 (PANSTARRS) presented a highly condensed 8" coma of total magnitude 20.0 and a 5" tail in p.a. 150°. The comet will pass perihelion at the solar distance of 0.91 AU on Aug. 12, 2024, expected to peak at magnitude 13.0 during those days (CBET 5301). It should be brighter than 16 mag between mid-May and end of October 2024. During this period it will move through the constellations Taurus, Orion, Monoceros, Canis Minor, Cancer/Hydra, Sextans (perihelion), Leo, Virgo and Serpens Caput. Unfortunately, the comet will experience elongations of less than 24° during this period, so will be a challenging object.

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In images taken as part of the "Asteroid Terrestrial-Impact Last Alert System (ATLAS)" on Sep. 28, 2023, L. Denneau discovered a comet near the border of the constellations Libra/Serpens Caput/Ophiuchus, estimating a total magnitude of 15 of the 8" coma. Follow-up observations of comet C/2023 S2 (ATLAS) showed a moderately condensed coma (of diameter up to 2.5') with total magnitude 12.7, but no tail. The comet will pass perihelion at the solar distance of 1.07 AU on Oct. 15, 2023, but will probably not get any brighter. It should remain brighter than 16 mag until the end of January 2024. During this period, it will move through the constellations Ophiuchus, Serpens Cauda, Aquila, Aquarius and Pisces. From Central European locations it is an evening sky object above the southwestern horizon, whose altitude increases from 20° to 40° until the end of the year.
Only very few observations of this comet came to my knowledge. The brightness estimates can be roughly represented by the parameters
m0 = 12.0 mag / n = 4,
yielding a maximum brightness of about 13.0 mag in mid-October 2023. However, the comet exhibited a short-lived brightness increase around that time, which resulted in a peak brightness of 11.5 mag.

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On their images taken on Nov. 5, 2023 with two 28cm-SC and CMOS cameras at the Hakos Astrofarm, the Spanish amateur Jordi Camarasa and the Swedish amateur Grzegorz Duszanowicz discovered a comet of magnitude 18.5, showing a tail, in the constellation Horologium. Follow-up observations of comet C/2023 V4 (Camarasa-Duszanowicz) showed a strongly condensed, 8" coma of total magnitude 18.5 and a 0.3' long curved tail in p.a. 340°. The comet will pass perihelion at the solar distance of 1.12 AU on May 30, 2024, but will then unfortunately be on the opposite side of the sun relative to Earth and therefore difficult to observe. The comet is expected to peak at magnitude 14.0-14.5 in June 2024 (CBET 5315). It should be brighter than 16 mag between March and August 2024. During this period it will move through the constellations Cetus, Aries, Perseus, Auriga, Lynx, Ursa Major and Canes Venatici. For Central European locations it is positioned very low above the western to northwestern evening horizon until mid-June. It then begins to rise, reaching a maximum altitude of 30° at the end of July.

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Comet P/2011 NO1 (Elenin) was rediscovered on Nov. 18, 2023, but was initially confused to be a minor planet, for which was given the designation 2023 WM26. Maik Meyer was the first to recognize that this comet had indeed been rediscovered. On Dec. 23 the comet exhibited a highly condensed, 5" coma with a total magnitude of 19.5. Comet P/2023 WM26 (Elenin) will pass perihelion on May 5, 2024 at a distance of 1.24 AU, expected to reach magnitude 14 (CBET 5340). It should be brighter than 16 mag between March and June. During this period, it will pass through the constellations Canis Minor, Monoceros and Hydra (south of Corvus). From Central European locations it can be seen in the evening sky until the beginning of May.

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On Dec. 4, 2023 G.J. Leonard discovered a comet in the constellation Coma Berenice with the 0.68m Catalina Sky Survey Schmidt telescope, estimating the total magnitude of its 8" coma as 17.5. Numerous observations of comet C/2023 X1 (Leonard) during the following days showed a very diffuse, 2' coma of total magnitude 14.5, displaying a significant central condensation; however, no tail was observed. The comet passed perihelion at the solar distance of 0.95 AU on Oct. 18, 2023. The comet was then probably at magnitude 14.5, but was just above the horizon for the observers worldwide (CBET 5322). It does not reach comfortable altitudes until the course of November. In the course of December 2023 it probably became fainter than magnitude 16. During this period it moved through the constellations Volans, Carina, Vela, Antlia, Hydra, Crater (perihelion), Virgo, Coma Berenice, Canis Venatici and Ursa Major. From Central European locations the comet appeared above the ESE morning horizon at the beginning of November and subsequently gained rapidly altitude, but started to sink towards the horizon at the end of December.

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On Jan. 3 the first comet of 2024 was discovered by the ATLAS project. The comet was located near the borders of the constellations Volans/Pictor/Carina, showing an 8" coma of total magnitude 18.5 and a 5" tail in p.a. 300°. Comet C/2024 A1 (ATLAS) will pass perihelion at the solar distance of 3.88 AU on June 13, 2025, but will then be positioned very close to the Sun (CBET 5333). It should peak at 15.5 mag in February 2025. The comet should be brighter than 16 mag between December 2024 and April 2025 and again between October 2025 and January 2026. During the first period it will move through the constellations of Puppis, Canis Major and Monoceros, during the second period through the eastern part of the constellation Lynx. From Central European locations it will be observable at moderate altitudes in the morning sky at first during the first period, but will move into the evening sky (at higher altitudes) during the course of this first visibility. During the second visibility it will be at higher altitudes in the morning sky.

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Comet 32P/Comas Sola (P=9.73a) will pass perihelion at the solar distance of 2.02 AU on Apr. 20, 2024, but will come closest to Earth on Nov. 30, 2023. As a result the comet is expected to peak at magnitude 14.0 at the beginning of February 2024. The comet should be brighter than 16 mag between October 2023 and August 2024. During this period it will move through the constellations Aries, Taurus, Auriga, Gemini, Cancer and Leo. From central European locations the comet will appear in the night sky at first, but will change to the evening sky in December 2023 and will disappear above the Northwestern horizon in February 2024.
Starting in fall 2023 the comet was predominantly observed by CCD observers. At the start of February 2024 the 56 observations by 19 observers indicate a brightness increase from 16.5 mag in mid-September 2023 to 14.1 mag at the end of January 2024. The brightness development can be well represented with the parameters
m0 = 7.5 mag / n = 6.5,
yielding a maximum brightness of 14.1 mag in the second half of January 2024. The coma diameter measured 0.4' (30,000 km) at the beginning of the apparition, increasing to a maximum of 1.2' (80,000 km) by mid-December, but has since slowly decreased again. The coma was well-condensed (DC 5). A tail up to 3' (1.2 mio. km) length has been observed since mid-October. Until mid-November it pointed towards Southwest, thereafter towards East.

Total Brightness and Coma Diameter

FGK observations

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During the summer months of 2023 comet 126P/IRAS (P=13.35a) should be observable, expected to peak at magnitude 12.0. However, the spring observations indicate a much fainter object, so that no reliable prediction is possible. The comet moves from the constellation Cetus to Triangulum. Thus it is a convenient object in the morning sky for central European locations.

While the comet was hardly observed before perihelion, quite reliable statements can be made about the time after perihelion. Based on 70 observations by 25 observers the brightness development can be represented by the parameters
m0 = 8.5 mag / n = 7.5,
which means that the comet peaked at 13.8 mag in the first half of August 2023. At the beginning of December the comet had faded to 17 mag. The coma diameter peaked at 1.6' (95,000 km) at the end of August 2023, but decreased to 0.4' (30,000 km) by the beginning of December. With a constant degree of condensation of DC 3 the coma was quite diffuse. CCD observers were able to detect a tail up to 5' (500,000 km) long between mid-August and mid-October, the orientation of which changed from Southwest to South.

Total Brightness and Coma Diameter

FGK observations

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Comet 207P/NEAT (P=7.65a) has been observed since the turn of the year 2023/24, mainly via CCD. Between the turn of the year and the beginning of February 2024 it brightened from 17.0 mag to 14.5 mag, the coma diameter increased from 0.4' to 0.8'. The brightness parameters appear to be around m0=17.0 mag / n=4, which means that the comet should peak at magnitude 14.0 at the end of February 2024. By the end of March the comet could already be fainter than 16 mag. It moved from the constellation Cetus in the direction of the constellation Sextans, making it an evening object at medium altitude.

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Comet 237P/LINEAR (P=6.58a) passes perihelion on May 14, 2023 at the solar distance of 1.99 AU. It moves slowly northward in the constellation Aquila, changing from the morning to the night sky during the summer months.

The current apparition is surprisingly well documented. The analysis can be based on 184 observations from 33 observers. These show a steady brightness development, which can be represented quite well with the parameters
m0 = 6.0 mag / n = 8.
The comet peaked at magnitude 12.2 at the end of June 2023. The coma diameter increased from 0.5' (30,000 km) at the beginning of the apparition to the maximum of 2.0' (110,000 km) in mid-June. Thereafter it decreased, measuring 0.5' (40,000 km) at the end of September. The coma was always moderately condensed (constant DC 3-4). CCD observers reported a tail pointing WSW with a maximum length of 7' (1.1 mio. km) between mid-May and mid-July 2023.

Total Brightness and Coma Diameter

FGK observations

Andreas Kammerer


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