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On images, taken in the course of the ATLAS project on May 30, 2019 Ken W. Smith discovered a comet of magnitude 18 near the border of the constellations Piscis Austrinus / Grus. Follow-up observations of comet C/2019 K7 (Smith) showed a strongly condensed 12" coma of total magnitude 17.0 and a 90" tail at p.a. 340°. The comet will pass perihelion at the solar distance of 4.47 AU on June 16, 2020, expected to reach magnitude 15.5 (CBET 4645/48). At this time it will move through the constellations Delphinus and Sagitta, thus be observable the whole night.
The comet showed a brightness development below average, as is indicated by 40 observations from 11 observers. The brightness development can be well represented by the parameters m0=8.5 mag / n=2.6, indicating a maximum brightness of 15.5 mag in mid-July 2020. The coma showed a maximum diameter of only 0.4' (75.000 km) and was significantly condensed (DC 6).
Total Brightness and Coma Diameter
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On images taken in the course of the "Asteroid Terrestrial-Impact Last Alert System" (ATLAS) on July 5, 2019, an asteroidal object of magnitude 19 was discovered in Cepheus. Follow-up observations showed a strongly condensed 12" coma of total magnitude 18.0 mag and an 8" tail in p.a. 135°. Comet C/2019 N1 (ATLAS) will pass perihelion at the solar distance of 1.70 AU on Dec. 1, 2020 (CBET 4650). Assuming an activity parameter of n=4 the comet will peak at magnitude 10.5, assuming n=3 at magnitude 12.0. It should be brighter than 16 mag between the beginning of 2020 and fall 2021. For mid-European locations it will disappear above the evening horizon in mid-September 2020, when it should have brightened to 13.0 mag or 12.0 mag. During this interval it will move through the constellations Draco, Ursa Major, Canes Venatici and Coma Berenices. Thereafter it will move towards the Southern Sky.
Based on 68 observations from 20 observers the brightness development can be well described by the parameters m0=9.5 mag / n=2.5, yielding a maximum brightness of 12.6 mag in January 2021. The apparent coma diameter increased steadily from 0.5' to 1.0', indicating a rather constant absolute diameter of 85.000 km. The coma was quite condensed with a degree of condensation of about DC 4-5. Between mid-May and mid-August 2020 tail sightings have been reported, with the tail length not exceeding 2' (700.000 km).
Total Brightness and Coma Diameter
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The Brazilian Eduardo Pimentel discovered a comet near the border of the constellations Taurus/Orion/Eridanus on images taken, together with C. Jacques and J. Barros, on Apr. 13, 2020 with the 28cm-astrograph of the "Southern Observatory for Near Earth Research" (SONEAR). Follow-up observations of comet P/2020 G1 (Pimentel) showed a strongly condensed 20" coma of total magnitude 15.0, surrounded by a 50" outer coma. In addition a 20" tail in p.a. 90° could be discerned. The comet passed perihelion at the solar distance of only 0.51 AU on Mar. 17, 2020. At this time it should have peaked at magnitude 14.6, but was too near the Sun for being detectable by the automated search programs. This periodic comet surrounds the Sun in 7.1 years, but is always difficult to observe. During the following weeks it faded rapidly (Apr. 22: 15.5m, coma: 18", tail: 40" in p.a. 90°), reaching 16 mag already at the opening of May (CBET 4754/59). From mid-European locations the comet reached only altitudes of less than 15° (at the end of April).
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On images taken with the 0.68m-Schmidt-telescope of the Catalina Sky Survey on Apr. 26, 2020 Theodore Pruyne from the Lunar and Planetary Laboratory discovered a comet of magnitude 16 in the constellation Pegasus. Comet C/2020 H2 (Pruyne) showed a fan-like coma of diameter 15" and a 10" tail in p.a. 280°. Follow-up observations showed a significantly condensed inner and a 2.9' outer coma of total magnitude 13.8, but no tail. Alan Hale succeeded in observing the comet visually on Apr. 28. He estimated the comet to be of magnitude 13.2, showing a diffuse 1.4' coma. The comet passed perihelion in the solar distance of 0.83 AU on Apr. 27, 2020 (CBET 4761). It should peak at about 13.0 mag at the opening of May, but fade below 16 mag until mid-June. During this period it will move through the constellations Lacerta, Cepheus, Cassiopeia and Camelopardalis into Ursa Major, being well situated in the evening sky.
At the opening of May 2020 the comet peaked at the predicted magnitude of 13.0. The diffuse (DC 2) coma was of diameter 1.5' around this date. In mid-June the comet had already faded below 16 mag.
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On images taken with the 1.5m telescope at Mt. Lemmon on Apr. 21, 2020 Gregory J. Leonard discovered a comet near the border of the constellations Pegasus/Aquarius. Comet C/2020 H4 (Leonard) showed a diffuse 10" coma of total magnitude 19.5. It will pass perihelion at the solar distance of 0.93 AU on Aug. 29, 2020, expected to reach magnitude 14.5 (CBET 4766). It should be brighter than 16 mag between July and September. During this period it moves through the constellations Cepheus, Camelopardalis, Draco, Ursa Major and Leo Minor. Until end of August it will be well-placed in the morning and in the evening sky for mid-European locations, but at low altitudes in the morning sky in September.
Only a very small number of observations had been published. These hint toward a brightness development according to the parameters m0=14.0 mag / n=4. At the beginning of August 2020 the comet was of magnitude 15.0, showing a 2' coma. Thereafter no additional observations have been published, indicating a sudden drop in brightness.
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On images taken on May 25, 2020 by the CATALINA project and on June 7, 2020 by the ATLAS project a comet was discovered independently in the constellation Pegasus. Follow-up observations of comet C/2020 K8 (CATALINA-ATLAS) showed a diffuse 15" coma of total magnitude 18.5. The comet will pass perihelion in the solar distance of only 0.47 AE on Sep. 14, 2020, expected to peak at magnitude 11-12 (CBET 4796). However, the derived absolute magnitude is well below the Borte-limit. Thus it is very probable that this comet will dissipate on its way towards perihelion. If, against all odds, it should survive the solar radiance it would be brighter than 16 mag between mid-July and mid-October. During this interval it moves through the constellations Triangulum, Perseus (near the border to Aries), Taurus, Gemini, Cancer, Hydra, Sextant and Leo. It could be observed from mid-European locations until the first week of September in the morning sky, then exhibiting the maximum brightness.
Only a small number of observations of this comet came to my knowledge. Until end of July 2020, when it was of magnitude 14.0 and showed a 1' coma, the comet brightened according to the parameters m0=14.0 mag / n=4. Thereafter it did not brighten further until Aug. 20 and started to disintegrate – as expected.
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On NEOWISE images taken on Aug. 2, 2020 J.P. Chesley discovered a comet near the border of the constellations Chameleon/Musca. Follow-up observations of comet C/2020 P1 (NEOWISE) showed a medium-condensed 15" coma of total magnitude 16.0 and a 40" tail in p.a. 113°. The comet will pass perihelion in the solar distance of only 0.34 AU on Oct. 20, 2020. Depending on its brightness development it could peak at magnitude 9.5 (n=3) or 7.5 (n=4) (CBET 4825). However, the derived absolute magnitude is 4 mag below the Bortle-limit. Thus, it is very probable that this comet will dissipate while still approaching the Sun. If it nevertheless should survive the solar radiance it would appear above the eastern morning horizon – located in the constellation Virgo – during the last week of October. It should then be of magnitude 10 (n=3) or 8 (n=4). Until mid-November it will move into Coma Berenices, thereby gaining altitude but fading rapidly to 14.0 mag (n=3) or 12.5 mag (n=4).
Until Sep. 21, when it was of magnitude 12.0, the comet brightened according to the parameters m0=13.5 mag / n=4. On Sep. 22 the brightness increased suddenly to 10.5 mag. Thereafter the comet brightened slowly to 10.0 mag until Oct. 5, hinting towards the start of a disintegration process. The comet survived the perihelion passage. Michael Jäger succeeded in taking an image of the comet on Oct. 28, which showed a faint central condensation and a short tail. The comet, which gradually got ever more diffuse, was followed until Dec. 9, 2020.
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On Aug. 17, 2020 Gennady Borisov discovered a comet near the border of the constellations Taurus/Auriga using the 0.65m-astrograph at the MARGO Observatory (Krim). He reported a 25" coma of total magnitude 17.5. Follow-up observations of comet C/2020 Q1 (Borisov) showed a coma of diameter up to 2' with total magnitude 16.0. The comet passed perihelion at the solar distance of 1.31 AU on Aug. 14, 2020, approaching Earth until the end of September. In consequence the maximum brightness of 14.5 mag may be reached not until mid-September (CBET 4836). It should be brighter than 16 mag until mid-October. During this period it moves through the constellations Auriga, Camelopardalis, Cassiopeia, Cepheus and Cygnus, thus will be observable throughout most of the night.
Only 22 observations came to my knowledge. These indicate that the comet peaked at magnitude 12.5 in mid-September 2020. In mid-August it was of magnitude 15.0, reaching this magnitude again by mid-October. The rather diffuse coma (DC 2) reached a diameter of 1.5' (60.000 km).
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In November/December 2020 several CCD observers could observe comet 11P/Tempel-Swift-LINEAR (P=6.28a). The comet passed perihelion on Nov. 26, 2020 in the solar distance of 1.55 AU. It was 3 mag brighter than expected, peaking at magnitude 13.5. The brightness development can be roughly described with the parameters m0 = 11.5 mag / n = 6. The coma diameter measured about 1.0'. In February 2021 it had already faded below 16 mag.
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In mid-November 2020 comet 162P/Siding Spring (P=5.43a) should rise as an object of magnitude 13.0 above the southern evening horizon for mid-European observers. Until mid-February 2021 it will gain altitude, but will fade to 14.5 mag. During this period it will move from the constellation Piscis Austrinus into Triangulum.
Only about a dozen observations came to my knowledge. They indicate a maximum brightness of 15.5 mag in November 2020. The comet seems to have shown a low acitivity level (about m0 = 15.0 mag / n = 2). The medium-condensed (DC 4) coma measured only 0.3'.
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On Apr. 7, 2010 comet 210P/Christensen (P=5.62a) will pass perihelion at the solar distance of 0.53 AU, expected to reach magnitude 12.0. It should get brighter than 16.0 mag at the start of March, but will then be at very small elongations to the Sun. Not before the second week of April will it appear above the western evening horizon for mid-European locations. Until mid-May it will rise to a maximum altitude of 25°, but will fade rapidly to 16 mag until then. During this interval it will move from the consteallation Aries into Gemini.
Observers worldwide could first see this comet after its perihelion passage and it rapidly faded during the following weeks. Based on 34 observations from 12 observers the analysis yields the brightness parameters m0=13.3 mag / n=3.0, implying a maximum brightness of 11.8 mag at perihelion. The comet faded to 14.0 mag at the end of May and below 16 mag by the end of June.
The coma diameter measured quite constant 1.0' (50.000 km), but got ever more diffuse with passing time (DC 4-5 to DC 3). CCD-observers could detect a 1' (100.000 km) eastward pointing tail.
Total Brightness and Coma Diameter
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Although Comet 246P/NEAT (P=8.05a) will pass perihelion in the solar distance of 2.86 AU not prior to Feb. 22, 2021, it is already observed since mid-January 2020. It can be observed from mid-European locations until end of July 2020, expected to fade temporarily from 15.0 mag to 15.5 mag. It moves from Coma Berenices into Virgo. During the second apparition, in 2021, it will not be observable in a reasonable manner from mid-European locations, because it is located in Sagittarius and moves southward.
Total Brightness and Coma Diameter
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Comet 249P/LINEAR (P=4.62a) will pass perihelion in the solar distance of 0.51 AU on June 29, 2020, expected to reach magnitude 11.5. Between mid-April and the start of August 2020 it should be brighter than 16.0 mag, but will disappear above the western evening horizon in mid-April for mid-European locations. During this interval it will move through the constellations Crater, Hydra and Cancer.
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Eight observers succeeded in observing comet 277P/LINEAR (P=7.56a). The comet passed perihelion on Dec. 30, 2020 in the solar distance of 1.90 AU. The 30 observations can be represented only by using time-dependent brightness formulae:
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N. Erasmus at the South African Astronomical Observatory discovered a comet in the constellation Cetus on images taken in the course of the "Asteroidal Terrestrial-Impact Last Alert System" (ATLAS) on Aug. 11, 2020. Follow-up observations of comet P/2020 P2 showed a significantly condensed 10" coma of total magnitude 19.0 and a 15" tail in p.a. 270°. Few days later it was recognized that this was a recovery of comet P/2009 Q4 (Boattini). The comet will pass perihelion at the solar distance of 1.31 AE on Dec 25, 2020, expected to peak at magnitude 14.5 (CBET 4829). It should be brighter than 16 mag between the opening of November 2020 and mid-February 2021. During these weeks the comet moves from the constellation Eridanus towards the borders of the constellations Orion/Taurus/Gemini, being an object of the whole night. In the meantime the comet got the permanent designation 398P/Boattini (P=5.53a).
Total Brightness and Coma Diameter
Andreas Kammerer
Based on 93 observations from 20 observers the comet showed a very different brightness development in the year 2020 (pre-perihelion) and 2021 (post-perihelion). Whereas the comet showed an extremely rapid increase in activity pre-perihelion, post-perihelion the heliocentric magnitude was constant until at least November 2021, as the following formulae demonstrate:
pre-perihelion : m = -12.6 mag + 5×log D + 39×log r
post-perihelion: m = +12.6 mag + 5×log D
Thus, the comet peaked twice at magnitude 14.0, in mid-July 2020 and at the start of July 2021. However, the variance in solar distance is rather small, so the formulae exhibit a larger degree of uncertainty than usual. Whereas the apparent coma diameter increased from 0.3' to 0.7' during the first half of 2020, it decreased from 0.8' to 0.5' in 2021. The absolute coma diameter increased from 40.000 km to 95.000 km in 2020, but measured constantly 60.000 km in 2021. The degree of condensation increased from DC 4 to DC 5 in 2020, and was constant at DC 5 in 2021.
Michael Jäger detected a 100' long tail (pointing towards p.a. 297°) on his images taken on April 15 and 25. It showed a 10' gap near the coma and was brightest 30-50' away from the coma. On May 17 the tail showed a length of more than 2.2° (going outside the field-of-view) and was oriented in p.a. 293°. These observations have been confirmed by several observers at the Astronomical Institute of the Romanian Academy (CBET 4793/99).
According to the very small number of published observations the comet was about 2.0 to 2.5 mag fainter than expected in March/April 2020, estimated to be only of magnitude 17.5-18.0.
t < +15d: m = 14.5 mag + 5×log D + 0.05×|t – T|
t > +15d: m = 13.5 mag + 5×log D + 0.01×|t – T|
Thus the comet peaked at magnitude 14.5 in mid-January 2021, 15 days after perihelion passage. The coma diameter measured 0.5' (25.000 km).
The comet surprised during this apparition. Between November 2020 and January 2021 it was less than 0.5 AU distant from Earth, with closest approach at 0.38 AU occurring shortly before the Christmas days. Based on 77 observations from 24 observers the brightness development can be represented by the parameters m0 = 10.4 mag / n = 13, yielding a maximum brightness of 12.0 mag around perihelion – more than 2.5 mag brighter than predicted. The coma diameter increased slowly from 0.5' (12.000 km) at the start of the apparition to the maximum of 1.7' (30.000 km) at the turn of 2020/21. Thereafter it decreased rather quickly, measuring short of 0.5' (12.000 km) at the end of January 2021. During the apparition the coma grew gradually more diffuse. The degree of condensation decreased from DC 5 to DC 2-3. No visual tail sightings were reported.
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