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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 369 observations from 40 observers (until end of October 2023). 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 October to 14.5 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 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, can be observed since the opening of 2022.
Total Brightness and Coma Diameter
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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 252 observations from 40 observers (until start of July 2023) the brightness development can be well described by the formula
m = 4.3 mag + 5×log D + 10.0×log r.
The comet peaked at magnitude 12.0 during the second half of March 2023. Surprisingly, the observations prior to the conjunction with the Sun indicate a much faster fading. Thus it could be that the comet will appear significantly fainter at its reappearance in fall 2023 than the formula predicts. 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. 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
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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 189 observations from 34 observers (until end of October 2023) the comet showed a development below average pre-perihelion, whereas post-perihelion the activity decreases rather quickly. The appropriate brightness parameters are
pre-perihelion: m0 = 7.8 mag / n = 2.0
post-perihelion: m0 = 3.8 mag / n = 5.5
Thus the comet peaked at 12.3 mag around May 20, 2023. Until mid-September 2023 the comet had faded to 14.0 mag. 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' (100,000 km) by mid-September 2023. 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
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On images taken on Sep. 15, 2020 the ATLAS team discovered a comet of magnitude 19 in the constellation Caelum. Follow-up observations of comet C/2020 R7 (ATLAS) show a significantly condensed 6" coma of total magnitude 19.0, but no tail. The comet will pass perihelion in the solar distance of 2.96 AU on Sep. 16, 2022 (CBET 4859) and could peak at 13.5 mag in July 2022. However, at that time he will be moving through the far-southern sky. Between October 2021 (positioned in Pavo) and August 2023 it should be brighter than 16 mag. Observers at mid-European locations should be able to observe the comet starting in January 2023 (expected to be of magnitude 15.0). Until August 2023 it will move through the constellations Serpens, Ophiuchus, Hercules and Corona Borealis.
Based on 68 observations from 18 observers the comet showed a very steady development according to the parameters
m0 = 7.2 mag / n = 4
yielding a maximum brightness of 13.7 mag around July 20, 2022. The diameter of the significantly condensed (DC 4-5) coma peaked at 0.8' (100,000 km). A tail of up to 5' (2 mio. km) length, pointing approximately in southeastern direction, could be detected by CCD observers between May and October 2022.
Total Brightness and Coma Diameter
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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.
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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 89 observations from 18 observers can be used at the end of October 2023. The observations can be represented by the brightness parameters
m0 = 9.7 mag / n = 2.
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 diameter of the medium-condensed (DC 4) coma increased during the apparition from 0.4' (60,000 km) to 1.2' (130,000 km). 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
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On Dec. 26, 2021 an asteroidal object of magnitude 18.5 was discovered by the ATLAS project near the borders of the constellations Cassiopeia/Perseus/Andromeda. Follow-up observations identfied the object as a comet. Comet C/2021 Y1 (ATLAS) showed a strongly condensed coma of diameter 10" and total magnitude 17.5, but without a tail. It will pass perihelion in the solar distance of 2.03 AU on May 1, 2023, expected to peak at magnitude 12.5-13.0 between end of 2022 and mid-2023 (CBET 5089). The comet should be brighter than 16 mag between August 2022 and February 2024. During this period it will move through the constellations Perseus, Auriga, Taurus, Eridanus (perihelion), Columba, Puppis, Vela, Centaurus, Lupus and Norma. During the first months the comet will be a morning object, switching to the evening sky at the turn of 2022/23, disappearing for mid-European observers at the opening of March 2023 above the southwestern horizon (at magnitude about 12.5-13.0).
Based on 64 observations from 14 observers the comet shows a development above average which can be represented by the parameters
m0 = 6.7 mag / n = 6
Thus the comet peaked at 13.3 mag between mid-April and mid-May 2023. The diameter of the significantly condensed (DC 5) coma increased from 0.4' (60,000 km) in August 2022 to 0.8' (75,000 km) in October 2022 and to 1.2' (100,000 km) in March 2023. Beginning in November 2022 a tail of up to 3' (800,000 km) length, pointing towards North to Northeast, was detected.
Total Brightness and Coma Diameter
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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.
At the end of October 2023 only 41 observations from 8 observers can be used for an analysis, which are not yet sufficient for a reliable prediction. However, they indicate a brightness development below-average, which can be roughly represented by the parameters
m0 = 8.3 mag / n = 2.
If this development is confirmed by future observations the comet would reach a first maximum of 14.0 mag in February 2024 and a peak brightness of 13.5 mag in the second half of November 2024. However, parameters up to m0 = 4.3 mag / n = 4 are currently still possible. At the end of October 2023 the observers reported a tiny coma of diameter 0.3' and of total magnitude 15.0.
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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 28 observations by 8 observers the brightness development for the period starting at the end of July (when more observations were published), can be well represented with the parameters
m0 = 7.5 mag / n = 4
yielding a maximum brightness of about 13.5 mag at the end of July 2023. The coma measured just under 1.5' (140,000 km) and became more diffuse in the course of the apparition (DC 4 --> DC 2-3). A tail was not observed.
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.
At the end of October 2023 a first preliminary analysis can be based on only 59 obsrvations from 13 observers. These indicate a brightness development according to the parameters
m0 = 9.7 mag / n = 2
yielding a maximum brightness of 13.0-13.5 mag in April 2024. During summer 2023 the comet was of magnitude 15.0, showing a coma of 0.7' (100,000 km) diameter.
Total Brightness and Coma Diameter
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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 images taken with the 1.5m-reflector at Mount Lemmon on Nov. 26, 2022 Gregory Leonard discovered a comet in the constellation Leo Minor. Comet C/2022 W3 (Leonard) showed a medium-condensded 6" coma of total magnitude 19.5 and a broad 10" tail in p.a. 240-260°. The comet will pass perihelion in the solar distance of 1.40 AU on June 22, 2023, expected to reach magnitude 15.0. Until mid-August it will approach Earth, passing it in the distance of 0.76 AU and could then peak at magnitude 14.0 (CBET 5204). It should be brighter than 16.0 mag between May and September 2023. During this period it will move through the constellations Cassiopeia (perihelion), Cepheus, Cygnus (perigee), Vulpecula, Sagitta, Aquila, Scutum and Sagittarius. From mid-European locations it will be visible in the morning sky during the beginning, but will change to the evening sky by mid-August. During the first weeks it will be visible the whole night through. Earth will cross the orbital plane on Aug. 5.
The analysis can be based on 30 observations from 11 observers, which show a very large scatter. Thus the brightness development can be brepresented only with a rather large uncertainty by the parameters
m0 = 13.5 mag / n = 2
The comet peaked around magnitude 14.0 in July 2023. The estimates give a maximum diameter of the coma of 1.0' (60,000 km). CCD observers could detect a short tail.
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The "Asteroid Terrestrial-Impact Last Alert System" (ATLAS) team discovered an 18th magnitude asteroidal object on Feb. 22, 2023 near the border of the constellations Serpens/Libra/Virgo. Subsequently, Minor Planet Center staff identified three positions of a Jan. 9, 2023 object assumed lost, which had been transmitted from China's Purple Mountain Observatory, with the asteroidal object. Since comets discovered by this observatory are designated Tsuchinshan by Chinese astronomers, this comet was given the designation C/2023 A3 (Tsuchinshan-ATLAS). Additional observations of the comet in the last days of February showed a strongly condensed 6" coma of total magnitude 18.0, but no tail. The comet will come quite close to both the Sun and Earth in the fall of 2024. It was at the large solar distance of 7.3 AU at the end of February 2023. Thus, it is a very interesting comet, but its activity level is currently very uncertain. In the following a new comet is assumed, whichs brightness increases with n=3. The comet will pass perihelion on Sep. 28, 2024 at the distance of 0.39 AU and could then reach 3rd magnitude (CBET 5228). Thereafter it will pass Earth on Oct. 13 at a distance of 0.47 AU, but will be near the Sun-Earth line und thus close to the Sun on the sky. Between November 2023 and September 2025 the comet should be brighter than 16 mag. During this period it will move through the constellations Libra, Virgo, Leo, Sextant, Leo/Crater (perihelion), Virgo (perigee), Serpens Caput, Ophiuchus, Serpens Cauda, Aquila, Delphinus, Vulpecula, Lyra and Hercules. For central European locations the first observing window will last from early December 2023 (15-16 mag, morning sky) to mid-June 2024 (11 mag, evening sky). The second, very unfavorable observation window lasts from about Sep. 25 to Oct. 5, 2024 (3-4 mag), but during this time the comet can only be seen extremely low above the eastern morning horizon during twilight. The third observation window is the most interesting. The comet will emerge above the western evening horizon on Oct. 12 (3-4 mag), reaching altitudes near 40° by early November, but fading to 6-7 mag during these two weeks. According to my empirical formulae, it should show a coma diameter of 20' during the days of greatest approach to Earth and a tail up to 5° long, which probably will be rather faint, thus difficult to observe visually. In the mid-January (11-12 mag) the comet disappears again above the western evening horizon. Exactly at this time it appears in the morning sky and finally reaches maximum elevations of 70° in June (14-15 mag). During the next weeks it will change to the night and finally to the evening sky, where it should become fainter than 16 mag. Overall an interesting, but probably not a spectacular object.
Although 71 observations from 15 observers can already be used for an analysis at the end of October 2023 no reliable prediction are yet possible, as the variance in the solar distance is comparatively small and the scatter in the observations is comparatively large. In purely mathematical terms, the parameters
m0 = 5.7±1.3 mag / n = 3.5±1.6
result. Applying these a maximum brightness of 1.5 mag can be derived, but with an uncertainty of ±7 mag! Between mid-April and early September 2023 the comet only brightened from 17.0 mag to 16.0 mag, showing a coma diameter of 0.4' (100,000 km).
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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.
Observations during the first half of October 2023 document a brightening from 13.0 mag to about 11.5 mag, indicating an activity above average. However, as only about a dozen observations can be used so far, no analysis is currently being made. If the comet continues to follow this trend, it will probably not fade below 16 mag until the end of February 2024.
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On Aug. 24, 2023, Alan Hale rediscovered comet 13P/Olbers (P=69.25a) remotely with the 1.0m Schmidt-Cassegrain telescope at Las Cumbres Observatory. The stellar comet was located in the constellation Eridanus and had a magnitude of about 21.5 mag. The comet was observed during its last perihelion passage in 1956. The next perihelion passage at the solar distance of 1.18 AU will take place on June 30, 2024 with an expected maximum brightness of 7.5 mag (CBET 5289). At this time my empirical formulae predict a maximum coma diameter of 5-6' and a maximum visual tail length of just under 0.5°. It should be brighter than 16m between December 2023 and August 2025. During this period it will move through the constellations Eridanus, Cetus, Taurus, Auriga, Lynx (perihelion), Leo Minor, Ursa Major, Coma Berenice, Bootes, Virgo, Libra, Ophiuchus and Sagittarius. Observing from Central European locations it will be an object visible during the whole night in the first few weeks, but will change to the evening sky in January 2024. In February 2024 it will reach its maximum altitude of 35° before starting to sink towards the horizon. In the most interesting weeks (May to September 2024) it will unfortunately experience altitudes of less than 20° (in May even less than 10°). At the end of October 2024 it will disappear above the western evening horizon. From February to mid-June 2025 it will reappear in the morning sky, but the altitudes will be less than 15°. On June 17, 2024 and on Dec. 17, 2024 the Earth will cross the comet's orbital plane.
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Comet 71P/Clark (P=5.56a) passed perihelion at the solar distance of 1.59 AU on Jan. 22, 2023, but was then positioned too close to the Sun. In April 2023 the comet was observed as an object of about magnitude 13.0, showing a diffuse (DC 3) coma of diameter 1.5'. Thus it was a half to a full magnitude fainter than predicted.
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Comet 77P/Longmore (P=6.90a) will pass perihelion in the solar distance of 2.35 AU on Apr. 3, 2023, expected to peak at magnitude 13. During winter 2022/23 it moves from northwestern Virgo towards the border to Libra, and then until perihelion into the southeastern part of Hydra.
Based on 53 observations from 13 observers a brightness development is shown which is on the one hand time-dependent, on the other hand shows an increase in activity up to 35 days after perihelion passage and finally reveals clear differences pre- and post-perihelion. The corresponding formulas are as follows:
t < +35d: m = 13.7 mag + 5×log D – 0.015×(t-T)
t > +35d: m = 13.0 mag + 5×log D + 0.005×(t-T)
The peak brightness of 13.9 mag was reached at the opening of May 2023. The coma diameter increased steadily from 0.6' (35,000 km) at the start of the apparition to the maximum of 0.8' (50,000 km) around perihelion, but decreased thereafter, measuring just 0.4' (25,000 km) in mid-July. The coma was significantly condensed (DC 4-5). Very few tail observations have been reported.
Total Brightness and Coma Diameter
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Comet 81P/Wild (P=6.41a) should get observable in mid-September 2022 in the morning sky. It passes perihelion at the solar distance of 1.59 AE on Dec. 15, 2022. The comet moves in southeastern direction from the constellation Leo into Virgo. It should brighten from 13.0 mag to 11.0 in mid-November and should peak at 10.5 mag in mid-December 2022.
All in all 189 observations from 34 observers can be used for the analysis. They indicate a different development pre- and post-perihelion. While the pre-perihelion development can be described very well with the following formula, the development after perihelion is difficult to reproduce with one formula. The reason seems to be that the comet experienced a significant drop in activity shortly after perihelion, only to partially recover during the following weeks. The appropriate parameters are:
pre-perihelion: m0 = 5.0m / n = 9
post-perihelion: m0 = 7.0m / n = 6.5
The comet peaked at magnitude 11.0 around Dec. 20, 2022. The apparent coma diameter increased from 1.5' at the beginning of the apparition to the maximum of 2.3' in November/December 2022, thereafter steadily decreasing to 1.0' at the end of the apparition. The absolute coma diameter steadily decreased from 200,000 km at the start of the apparition to 55,000 km at the end of the apparition. In parallel, the coma became steadily more diffuse; the degree of condensation decreased from DC 4-5 to DC 2-3 during the apparition. A westward-pointing tail of up to 7' (1.5 mio. km) length was reported between late October 2022 and late March 2023.
Total Brightness and Coma Diameter
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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.
The rather faint comet was monitored surprisingly intensively during this apparition. As many as 62 observations from 24 observers can be used for the analysis. These show a brightness development that can be represented moderately well with the parameters
m0 = 9.5 mag / n = 6.
The comet thus reached a maximum brightness of only 14.0 mag in mid-August 2023. The coma diameter increased from 0.8' (55,000 km) at the beginning of the apparition to the maximum of 1.5' (85,000 km) in September 2023. The coma was rather diffuse (DC 3). CCD observers were able to detect a tail up to 5' (600,000 km) long during the entire apparition, which pointed in a southwesterly direction.
Total Brightness and Coma Diameter
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At the opening of July 2023 the number of published observations of comet 185P/Petriew (P=5.46a) is very small, a consequence of the fact that the comet was at small elongations around perihelion (on July 12 at the distance of 0.93 AU). The comet peaked at about magnitude 13.0 around perihelion. At mid-European locations the comet could not be observed in a reasonable way.
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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 182 observations from 33 observers. These show a steady brightness development, which can be represented quite well with the parameters
Total Brightness and Coma Diameter
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On its way to its perihelion (taking place on May 14, 2023 at the solar distance of 0.80 AU) comet 364P/PANSTARRS (P=4.89a) will approach Earth to within 0.121 AU on Apr. 8, expected to reach magnitude 10.5. Thus this will be a favorable morning apparition. The comet should get brighter than 16 mag at the start of March, then moving through the constellation Bootes, being situated at high altitudes. At the start of April, 11-12 mag bright and moving through Hercules, it will reach maximum altitude. Thereafter it rapidly sinks towards the horizon and will disappear between Apr. 15 and 20 (at 11.0 mag) above the eastern morning horizon.
This comet was observed for only two months. On the basis of only 37 observations from 20 observers, which show a noticeable scatter, only a preliminary analysis can be performed. The comet is a rather small body with a surprisingly high activity. The brightness development can be simulated moderately well with the following parameters
Total Brightness and Coma Diameter
Andreas Kammerer
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.
pre-perihelion: m0 ≈ 16.5 mag / n = 9
post-perihelion: m0 ≈ 14.7 mag / n = 2
Thus, the activity increased very rapidly pre-perihelion and decreased very slowly post-perihelion. The maximum brightness of 11.5 mag was reached on Apr. 13, 2023, and was about one magnitude below the predictions. The apparent coma diameter increased from 0.3' in early March to the short-term maximum of 1.2' around Apr. 20, then decreased to 0.8' by early May. The absolute coma diameter increased from only 5,000 km to 10,000 km during the same period. Estimates of the degree of condensation vary widely, with mean values of DC 4...5. Tail sightings have been reported throughout the apparition with maximum values of 5' (50,000 km). The tail was initially directed towards West, but slowly turned towards Southwest.
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