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Analysis of Comet Apparitions


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Current Fainter Comets of Interest


On Oct. 31, 2010 A. Boattini discovered a 20.0 mag comet with the 1.5m-Mt.Lemmon-reflector near the border of the constellations Cetus/Aries. Comet C/2010 U3 (Boattini) showed a medium condensed 6-7" coma, elongated in p.a. 330°, harboring a 3-4" central condensation. Additional observations showed a 20" coma and a 25" tail in p.a. 330°. At discovery the comet stood in the record solar distance of 18.5 AU! It will not reach perihelion before spring 2019 at a distance of 8 AU. Nevertheless it could become as bright as 15 mag, then moving through far-northern regions (Camelopardalis, Ursa Major, Draco) (IAUC 9182 / 2010-V109). This implies an inherently bright comet which showed a coma diameter of already 250.000 km at discovery!
An analysis of the apparition, based on only two dozen observations, yields the brightness parameters m0=6.7 mag / n=2. Thus the comet peaked at magnitude 15.8 at the time of perihelion. Throughout the apparition the comet showed a constant coma diameter of about 0.4-0.5' (about 150.000 km).

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On images taken on July 19, 2015 the PanSTARRS team discovered a comet in the constellation Capricornus, near the border to Sagittarius. According to the team comet C/2015 O1 (PanSTARRS) displayed a 2.5" tail towards East and a miniscule coma of magnitude 19.5. Additional observers reported a coma of diameter 15x17" and of total magnitude 18.5 and a 4" tail in p.a. 100°. The comet will pass its rather distant perihelion (distance: 3.7 AU) in February 2018, expected to reach magnitude 13.5 (CBET 4119 / MPEC 2015-Q71). It should be brighter than 16 mag between January 2017 and April 2019. During this period it will move from Aquila through Hercules, Bootes, Ursa Major into Lynx. Thus it will be comfortably placed in the morning/night sky for mid-European observers during the interesting weeks.
Based on 126 observations from 24 observers the brightness estimates can be best represented by the parameters m0=4.5 mag / n=4, which imply a maximum brightness of 12.8 mag at the opening of April 2018. Whereas the coma measured only 0.7' (110.000 km) in diameter in spring 2017, the reports indicate the maximum coma diameter of 1.4' (200.000 km) in spring 2018. In winter 2018/19 it still measured 1.2', indicating a diameter of 225.000 km. During the apparition the coma got more and more diffuse. The degree of condensation was DC 4-5 in spring 2017, DC 4 in spring 2018, but only DC 2 in winter 2018/19.

Total Brightness and Coma Diameter

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On July 14, 2016 the PanSTARRS team discovered a comet of magnitude 21 in the constellation Hercules. Follow-up observations of comet C/2016 N6 (PanSTARRS) showed a strongly condensed 5x7" coma of total magnitude 20.0. The comet will pass perihelion at a solar distance of 2.7 AU in July 2018, expected to reach 14 mag (CBET 4309). It should be brighter than 16 mag between fall 2017 and spring 2019, with maximum brightness in spring 2018. During this period it will move through the constallations Bootes, Draco, Ursa Minor, Draco, Lynx (maximum brightness), Cancer, Hydra, Puppis, Canis Major and Lepus. Between mid-June and the start of September 2018 it will not be visible from mid-European sites.
Based on 174 observations from 29 observers the comet showed a very continuous brightness development, which can be well represented by the formula
m = 5.3 mag + 5×log D + 10.5×log r,
indicating a maximum brightness of 12.3 mag, which was reached at the beginning of April 2018 and at the opening of December 2018. The apparent coma diameter measured only 0.5' in 2017, but started to increase in February 2018, reaching 1.5' in May. In fall it reached its maximum of short of 2'. Thereafter it decreased, measuring short of 1' at the start of April 2019. The absolute coma diameter measured only 95.000 km in 2017, but started to increase in February 2018, reaching 225.000 km in May. In fall it peaked at 250.000 km. Thereafter it shrunk, measuring 125.000 km at the start of April 2019. The degree of condensation was constant at DC 3 in 2017, peaking at DC 5 in spring 2018, and was estimated at DC 4 in fall 2018 and DC 2-3 at the start of April 2019. Only CCD-observers detected a tail, with the length never exceeding 3' (1 Mill. km).

Total Brightness and Coma Diameter

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On images taken on Aug. 26, 2016 the PanSTARRS team discovered a comet on the border of the constellations Capricornus/Aquarius, estimating the brightness to be about 21.5 mag, noticing a broad, 6" tail towards North. Detailed observations of comet C/2016 Q2 (PanSTARRS) showed a strongly condensed, 12" coma of total magnitude 19.0 and a very broad 12" tail in p.a. 338°. The comet (with an orbital period of about 440 years) will pass its perihelion at the large distance of 7.2 AU in May 2021, expected to reach about 15.5 mag. It should be brighter than 16 mag between spring 2020 and fall 2022, moving through the constellations Cygnus, Lyra, Draco/Hercules towards Ursa Major during this period (CBET 4311 / MPEC 2016-V116).

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In the course of the LINEAR Sky Survey an asteroidal object of magnitude 19.5 was discovered on images taken on Jan. 26, 2017 near the border of the constellations Hydra/Corvus. Follow-up observations of comet C/2017 B3 (LINEAR) showed a significantly condensed 8" coma of total brightness 18.5 mag. This comet will pass perihelion at the beginning of 2019, expected to peak around magnitude 14-15 (CBET 4354). However, at this time it will be positioned in the far Southern Sky. It will not be observable from mid-European locations during the time interval when it is expected to be brighter than 16.0 mag.
At perihelion the comet reached magnitude 15.0, showing a coma of diameter short of 0.5'. It should hold this magnitude until summer 2019, starting to fade slowly thereafter.

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On May 21, 2017 the PanSTARRS team discovered a comet of magnitude 21.0 with a miniscule coma in the constellation Draco. Follow-up observations of comet C/2017 K2 (PanSTARRS) showed a moderately condensed 12" coma of total magnitude 19.0 (CBET 4393 / MPEC 2017-N26). The comet was detected in the record distance of 16.1 AU, indicating an absolute brightness of 1 mag and an absolute coma diameter of 140.000 km. The comet will reach perihelion at a distance f 1.80 AU not prior to the Christmas days 2022. It should be brighter than 16.0 mag from early 2020 to the end of 2025. During this interval it will move from the northern parts of Hercules through Ophiuchus and Scorpius, diving far south between October 2022 and March 2023, then reappearing for mid-European observers in Eridanus, then moving through Lepus, Orion and Taurus into Auriga. Its maximum brightness of about 5.5 mag should be reached around the turn of the years 2022/23. During the most interesting months it will be observable from mid-European locations in the evening sky until the end of August 2022 (then of magnitude 6.0), then from early September 2023 (then of magnitude 9.5) onwards in the morning sky.

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On June 21, 2017 the ATLAS team discovered an asteroidal object of magnitude 18.0 in the constellation Cepheus, which revealed its cometary nature during follow-up observations. Comet C/2017 M4 (ATLAS) showed a moderately condensed 13" coma of total magnitude 17.5 and a short tail pointing SW. It will reach perihelion at a distance of 3.24 AU not prior to Jan. 15, 2019, expected to reach 14.0 mag in summer 2019 (CBET 4408 / MPEC 2017-N58). It will be brighter than 16.0 mag during the whole year of 2018 thereby moving from the border of the constellations Cygnus/Lyra through Hercules (maximum brightness) into Ophiuchus. From mid-European locations it will be observable until November 2018.
Based on 54 observations from 14 observers (until the end of April 2019) the brightness develops according to the parameters m0=7.3 mag / n=3, indicating a first maximum of 14.0 mag in August 2018. If the comet should further develop in this way it will peak at 13.3 mag at the start of May 2019. Between February and August 2018 the apparent coma diameter increased from 0.3' (60.000 km) to 0.8' (130.000 km); this values are since constant. The coma is medium-condensed (DC 3 to DC 4), with the observations hinting towards a small but continuous decrease. So far, no tail sightings have been reported.

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Images, taken by the PanSTARRS project on Oct. 2, 2017 showed a faint comet with a miniscule coma in the constellation Eridanus. Follow-up observertions of comet C/2017 T2 (PanSTARRS) showed a significantly condensed 12" coma of total magnitude 19.3 and a 20" tail in p.a. 290°. The comet will pass perihelion on May 6, 2020 in the distance of 1.62 AU. It is expected to peak at magnitude 8.0 during several weeks (CBET 4445). It should be brighter than 16 mag during the years 2019 and 2020, being brighter than 12.0 mag between October 2019 and October 2020. During the most interesting months it will be better positioned in the morning sky until November 2019 for mid-European observers. Thereafter it will be better observable in the evening sky until the opening of September 2020. During this time interval it will move through the constellations Taurus, Auriga, Perseus, Cassiopeia, Camelopardalis (maximum brightness), Ursa Major, Canes Venatici, Coma Berenices and Virgo.

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On images taken with the &quto;Asteroid Terrestrial-impact Last Alert System" (ATLAS) on Jan. 10, 2018 an asteroidal object was discovered in the northern part of Virgo. Follow-up observations revealed its cometary nature. Comet C/2018 A3 (ATLAS) showed an 8" coma of total magnitude 18.0. It will pass perihelion in the solar distance of 3.28 AU on Jan. 11, 2019, expected to peak at magnitude 15.0 (CBET 4476 / MPEC 2018-B155). It should be brighter than magnitude 16.0 between November 2018 and February 2019, thereby moving from the central part of Ursa Mayor to the southwestern part of Camelopardalis, thus being observable for mid-European observers during the whole night.
Only a small number of observations had been published. These indicate a maximum brightness of 15.0-15.5 mag in January 2019 with the coma measuring about 0.7'. The brightness parameters are about m0=8.0 mag / n=4.

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On Jan. 15, 2018 A.R. Gibbs discovered a 19 mag comet in Leo. Follow-up observations of comet C/2018 A6 (Gibbs) showed a highly condensed, 10" coma of total magnitude 18.8 and a fan-shaped 15" tail (PW=110-17°). The comet will pass perihelion in the solar distance of 2.86 AU on May 24, 2019, expected to peak at magnitude 15 (CBET 4479). However, after the start of 2019 (then 16.0 mag) it will be situated far in the southern sky.
Until the end of April 2019 only a small number of observations have been published. These show the comet at magnitude 14.0 mag with a considerably condensed coma of diameter 0.5' at the end of April 2019.

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In the course of the ATLAS project a comet was discovered on June 6, 2018 in Centaurus. Comet C/2018 L2 (ATLAS) showed a 20" coma of total magnitude 15.5 and a 27" tail in p.a. 92°. It will pass perihelion on Dec. 2, 2018 at the solar distance of 1.71 AU, when it is expected to reach magnitude 14.0 (CBET 4522). It should be brighter than 16 mag until April 2019. The comet will be visible from mid-European locations between October 2018 and April 2019 low above the evening horizon (SW to NW at altitudes of less then 20°) and in the morning sky during the first four months of 2019 above the eastern horizon (maximum altitude: 25°). During this interval it will move through Serpens, Ophiuchus, Hercules, Vulpecula, Cygnus and Lacerta into Andromeda.
The comet showed an outburst with a magnitude of more than 3.5 mag! Whereas the comet was of total brightness 13.8 mag on Sep. 5, 2018, the observers reported a magnitude of 10.1 on Oct. 1, 2018. After Oct. 6 (60 days prior to perihelion) the comet faded slowly, according to the formula
t > -60d: m = 8.8 mag + 5×log D + 0.010×(t-T),
but was still of magnitude 12.0 at the opening of March 2019. The coma diameter developed in a manner typical of an outburst. Whereas it measured 1.0' (100.000 km) at the start of September 2018, it swallowed to 4.0' (430.000 km) shortly after the outburst. Thereafter it decreased, measuring 2.0' (200.000 km) at the opening of February 2019 and short of 1' (125.000 km) at the start of March. Surprisingly, the outburst had no impact on the development of the degree of condensation. Until end of 2018 it was constant at DC 3-4. In 2019 the coma got more and more diffuse, reaching DC 2 at the opening of March. A tail was not observed.

Total Brightness and Coma Diameter

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On July 7, 2018 the ASASSN team discovered a comet of magnitude 16 in the central part of Eridanus. Follow-up observations of comet C/2018 N2 (ASASSN) showed a strongly condensed 25" coma and a 15" tail in p.a. 220°. The comet will pass perihelion on Nov. 11, 2019 at a distance of 3.13 AU, expected to reach magnitude 11 (CBET 4534). It should be brighter than 16 mag until spring 2021, brighter than 13.5 mag between mid-2019 and mid-2020. During the latter time span it moves from Aries into Cepheus. Thus it will be well placed for mid-European observers during the most interesting weeks. Assuming an average activity parameter (n=4) the absolute brightness is magnitude 4.0, hinting towards a large object, which, alas, will not come close to the Sun.
At the opening of February 2019 only 32 observations from 5 observers can be used for a first preliminary analysis. So far the brightness evolves according to the parameters m0=7.2 mag / n=2, indicating a development clearly below average. If this development should continue the comet will peak at only 11.5 mag at perihelion. At the end of 2018 the comet showed a coma of diameter 0.8' (170.000 km) and a degree of condensation of DC 3-4. No tail has been reported so far.

Total Brightness and Coma Diameter

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On images taken on Sep. 7, 2018 with the 1.5m-reflector atop Mt. Lemmon a 19 mag comet was discovered near the border of the constellations Aquarius/Capricornus. Comet C/2018 R3 (Lemmon) showed a strongly condensed 8" coma and a 4" tail pointing towards East. The comet will pass perihelion in the solar distance of 1.29 AU on June 7, 2019, expected to reach magnitude 13-14 (CBET 4556). It should be brighter than 16 mag between April and August 2019, thereby moving through the constellations Pegasus, Andromeda, Cassiopeia, Camelopardalis, Lynx (maximum brightness) and Leo. However, for mid-European observers the comet will be low above the horizon, attaining no more than 25° at the start of May in the morning sky and no more than 20° at the opening of June in the evening sky.

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An asteroidal object of magnitude 20, discovered by the Lemmon project already on Oct. 27, 2018 near the borders of the constellations Cygnus/Lyra/Draco, showed its cometary nature by follow-up observations. Comet C/2018 U1 (Lemmon) showed a stellar coma and a 5" tail pointing eastward. It will pass perihelion in the solar distance of 4.98 AU on Nov. 1, 2021, expected to reach 15.0 mag (CBET 4574). Between spring 2021 and summer 2022 it should be brighter than 16.0 mag. However, for mid-European locations it will disappear already in September 2021. During this interval it will move from the eastern part of Serpens through Ophiuchus to the northern part of Scorpius.

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On Nov. 27, 2018 B.M. Africano discovered a comet in Canes Venatici with the 1.5m telescope of Mt. Lemmon Observatory. Nearly at the same time H. Groeller recognized the comet on an image taken with the 0.68m-Catalina Sky Schmidt Telescope, however reported his finding after the discovery had already been published on the CBET pages. Comet C/2018 W2 (Africano) presented a 7" coma of total magnitude 18.5 and a southwestward pointing tail of serveral arcminutes length. The comet will pass perihelion in the solar distance of 1.45 AU on Sep. 6, 2019, expected to reach magnitude 10.5 (CBET 4580 / MPEC 2018-Y71). On Sep. 27, 2019 it will pass Earth in a distance of only 0.49 AU at an expected magnitude of 9.5. However, with a calculated coma diameter of about 5' it will not be an easily detectable object then. Between April 2019 and January 2020 it should be brighter than 16.0 mag. It should be observable from mid-European locations until mid-October 2019. During this period it will move through the constellations Cepheus, Cassiopeia, Camelopardalis, Perseus, Andromeda, Pegasus (maximum brightness), Pisces and Aquarius.

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On Feb. 26, 2019 Heather Flewelling discovered a comet in the constellation Scutum in the course of the "Asteroid Terrestrial-Impact Last Alert System" (ATLAS). Comet C/2019 D1 (Flewelling) was of magnitude 15.5, showing a highly condensed, 20" coma and a 1.5' tail in p.a. 260°. It will pass perihelion in the solar distance of 1.58 AU on May 11, 2019, expected to reach magnitude 14 (CBET 4614). It should have faded to magnitude 16 at the end of September. During this period it should move through the constellations Aquila, Delphinus, Pegasus, eventually reaching Andromeda. Thus it will be an object in the morning sky.
However, observations done in April 2019 indicate a maximum brightness of only 15.0 mag in mid-May.

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On March 29, 2019 B.M. Africano discovered a comet near the border of the constellations Bootes/Libra on images taken in the course of the Mount Lemmon Survey. G.V. Williams recognized that this object had already be announced the night before by the "Asteroid Terrestrial Impact Last Alert System" (ATLAS). Comet C/2019 F1 (ATLAS-Africano) showed a highly condensed coma of diameter 10" and total magnitude 18.5 and a hint of a tail towards NW. The comet will pass perihelion in the solar distance of 3.60 AU on June 23, 2021, expected to peak at magnitude 13.5 (CBET 4619). However, at this time it will be positioned near the celestial South Pole. It should be brighter than 16 mag between spring 2020 and late summer 2022. During this period it will move from the southwestern part of Libra through the constellations Hydra and Lupus towards Octans. Thereafter it will slowly move northward, reaching Fornax in late summer 2022. Mid-European locations will lose sight of the comet in June 2020, when the comet is expected to be of magnitude 15.5.

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Comet 60P/Tsuchinshan (P=6.58a) will pass perihelion for another time on Dec. 11, 2018 in the solar distance of 1.62 AU. In November 2018 it should become brighter than 16 mag, brightening to 14.5 mag until mid-February 2019. The comet moves from the southwestern part of Leo towards the border of the constellations Virgo/Sextans, being visible in the morning sky.
Until the beginning of February 2019 only 29 observations from 14 observers came to my knowledge, which correlate not well. Assuming the brightness parameters m0=11.5 mag / n=4 the comet should peak at magnitude 13.5 in mid-February 2019. In January 2019 the diameter of the significantly condensed coma measured short of 1.0'.
The comet peaked at 13.4 mag in early February 2019. Thus, the maximum brightness was reached 60 days past perihelion, because the comet approached Earth until the end of February. Based on 67 observations from 22 observers the brightness development can be well described by the following formula:
m = 11.5 mag + 5×log D + 9.5×log r
Due to the approach to Earth until the end of February the brightness increased slowly during the first weeks (14.2 mag in mid-November). Thereafter the apparent brightness decreased rapidly to 15.0 mag at the end of April. The coma diameter increased until early April continuously from 0.6' (35.000 km) to 1.1' (50.000 km), thereafter decreasing. Interestingly the degree of condensation decreased continuously during the whole apparition from DC 5 to DC 3-4. Between mid-November 2018 and end of January 2019 the comet showed a tail. It was observed visually and by CCD, showing a maximum length of 9' (1 Mio. km), thereby pointing constantly towards p.a.≈300°.

Total Brightness and Coma Diameter

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Comet 78P/Gehrels (P=7.23a) can be observed during winter 2018/19, reaching perihelion on Apr. 2, 2019 at the solar distance of 2.01 AU. However, at this time it will be situated too near the Sun for observations. For mid-European observers it will be situated low above the evening horizon, moving from the northeastern part of Capricornus towards the border of the constellations Pisces/Cetus. It should brighten from magnitude 13.5 to 13.0.
Until the start of February 2019 only 27 observations from 8 observers came to my knowledge. The brightness estimates can be rather well represented by the parameters m0=9.5 mag / n=3, indicating a maximum brightness of 13.5 mag at the start of October 2018. At the same time the diameter of the medium-condensed (DC 3-4) coma reached its maximum of 1.0' (75.000 km). No tail was reported.

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In autumn 2018 comet 123P/West-Hartley (P=7.58a) should become brighter than 16.0 mag. It will pass perihelion at the distance of 2.13 AU on Feb. 5, 2019, expected to reach magnitude 13. In winter 2018/19 it will make an opposition loop near the borders of the constellations Leo Minor/Leo/Ursa Major.
The comet is under surveillance since the beginning of 2019. At the end of April 2019 the available 74 observations from 18 observers can be described with a broad set of brightness parameters, with the values m0=7.5 mag / n=6 showing a slightly better plausibility. The maximum brightness of 12.8 mag was reached at the end of February 2019. The coma diameter increased from 1.0' (65.000 km) at the start of the apparition to 1.8' (90.000 km) at the end of February 2019, only to decrease to 1.1' (75.000 km) until the end of April. The coma got more diffuse during the whole apparition, with the degree of condensation decreasing from DC 5-6 to DC 3-4. During February observations of a tail with up to 2' (700.000 km) length have been reported sporadically.

Total Brightness and Coma Diameter

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At the beginning of July 2019 comet 260P/McNaught (P=6.89a) should become visible as an object of about magnitude 15.0 in the morning sky. Until mid-August it is expected to brighten to 13.0 mag. During this period it will move from the southwestern part of Cetus into Aries. It will pass perihelion in the solar distance of 1.42 AU on Sep. 9, 2019, expected to reach 12.0 mag.

Andreas Kammerer


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