Home=Current Comets
| The German Group
| Tutorials
| Archive: Fainter Comets 2021
| Projects, publications
| Images
| Contact
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 4.99 AU on Nov. 3, 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.
The comet developed according to the predictions, peaking at magnitude 15.2 in June 2021. Based on 38 observations from 7 observers the brightness parameters m0=5 mag / n=4 are a best fit to the observations. The diameter of the signficantly condensed (DC 5) coma was constant at 0.4' (yielding a constant absolute diameter of 75.000 km).
--------------------
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 22, 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.
The comet showed a development clearly below average, peaking at only 14.8 mag in June/July 2021. Based on only 30 observations from 2 observers the brightness parameters can be roughly defined as m0≈9.5 mag / n≈2. However the estimates can also be represented by a wider range of possible values. The comet showed a significantly condensed (DC 5-6) coma of diameter 0.6' (80.000 km). A data base of only 2 observers is problematic, because their systematic errors have a larger than usual impact on the results.
--------------------
On images taken on Mar. 28, 2020 with the "Mobile Astronomical System of the Telescope-Robots" (MASTER) at the Sternberg Astronomical Institute at the Lomonosov Moskau University a comet of magnitude 16 was discovered in the constellation Apus. Follow-up observations of comet C/2020 F5 (MASTER) showed a compact 17" coma of total magnitude 15.5 and a 35" tail in p.a. 310°. The comet will pass its rather far perihelion at a solar distance of 4.32 AU on Mar. 24, 2021, expected to reach 14.0-14.5 mag in summer 2021 (CBET 4746). For mid-European locations it can only be glimpsed at altitudes less than 10° above the southern/southwestern evening horizon between mid-October 2021 and mid-January 2022. During this period it will move from Piscis Austrinus into the eastern part of Aquarius, fading from magnitude 15.5 to 16.0.
For the analysis 48 observations from 9 observers can be used. These indicate brightness parameters of m0=5.3 mag / n=4. The comet peaked at magnitude 14.6 in mid-August 2021. In summer 2021 the coma showed a maximum coma diameter of 0.6' (110.000 km). The degree of condensation increased slightly from DC 4 to DC 5. No tail has been observed so far.
Total Brightness and Coma Diameter
--------------------
On May 1, 2020 the "Southern Observatory for Near Earth Research" (SONEAR) discovered an asteroidal object of magnitude 16.5 in the constellation Grus. Follow-up observations revealed its cometary nature. Comet C/2020 J1 (SONEAR) showed a significantly condensed 12" coma of total magnitude 16.2, but no tail. The comet will pass perihelion at the solar distance of 3.26 AU on Apr. 15, 2021, when it could reach magnitude 13.5 (CBET 4769). It should be brighter than 16 mag between June 2020 and April 2022. Currently it moves southward, reaching the southernmost point in Pavo in August 2020. Thereafter it moves slowly northward, appearing for mid-European locations - at magnitude 14.0 – above the southern morning horizon in April 2021 in the constellation Scorpius. Until the start of August 2021 it moves through the constellations Libra and Virgo, where it will disappear – at magnitude about 14.5 - above the southwestern evening horizon. Maybe it can be glimpsed for a second period, beginning in mid-November 2021, in the morning sky, moving towards Bootes. However, it will then have faded to about 15.5 mag.
The comet got brighter than expected, based on 97 observations from 19 observers. It peaked at magnitude 12.8 in mid-May 2021. The comet showed very different brightness developments pre- and post-perihelion:
pre-perihelion: m0≈0.5 mag / n≈8
post-perihelion: m0=7.5 mag / n=2.5
resulting in a prolonged visibility post-perihelion. The apparent coma diameter increased from 0.4' at the start of the apparition to 1.8' at the opening of June 2021. The absolute coma diameter increased from 60.000 km at the start of the apparition to 225.000 km in July 2021. This value was hold until spring 2022. Throughout 2021 the coma was significantly condensed (DC 5), but was more diffuse in spring 2022 (DC 2-3). A small number of tail sightings have been published between end of May 2021 and mid-April 2022 with a maximum length of 5' (3.5 Mio. km). The tail pointed constantly towards SE.
Total Brightness and Coma Diameter
--------------------
Comet C/2020 M5 (ATLAS), which was discovered on June 30, 2020 by the ATLAS team, developed as predicted throughout 2021 and peaked at 16.0 mag around perihelion (Aug. 19, 2021 at q=3.01 AU), displaying a coma of 0.8' (110.000 km) diameter. However, in mid-January 2022 it suddenly brightened, peaking at 14.5 mag in early March, thereby displaying a 1.5' (170.000 km) coma. During the following weeks it faded, reaching magnitude 16.0 in early May.
--------------------
On July 1, 2020 the PanSTARRS team discovered an asteroidal object of magnitude 20.5 in the constellation Andromeda, which showed up its cometary nature in the course of follow-up observations. In mid-July comet C/2020 N1 (PanSTARRS) showed a significantly condensed coma of total magnitude 20.2, but without a tail. The comet will reach perihelion on Mar. 12, 2021 in the solar distance of 1.32 AU, expected to reach magnitude 14.0 (CBET 4815). Between December 2020 and May 2021 it should be brighter than 16 mag. It will be observable in the evening sky until the end of April from mid-European locations. During this interval it will move through the constellations Andromeda, Pisces, Aries, Taurus, Orion and Monoceros.
The comet could only be observed by CCD-observers. Based on 33 observations from 10 observers the brightness development can be described roughly with the parameters m0 = 14.5 mag / n = 2, indicating a development below average. The maximum brightness of 15.5 mag was reached at the start of March 2021. The coma diameter reached 0.5', the degree of condensation DC 3.
--------------------
Already on June 21, 2020 the PanSTARRS project discovered an asteroidal object of magnitude 22 in the southwestern part of Cetus, which showed cometary morphology in May 2021. Comet C/2020 PV6 (PanSTARRS) showed a significantly condensed 20" coma of total magnitude 16.0 and a 50" tail in p.a. 210-240°. The comet will pass perihelion on Sep. 25, 2021 in the solar distance of 2.30 AU and could reach magnitude 14.5 at end of July (CBET 4969). It should be brighter than 16.0 mag until mid-December 2021. During this period it moves through the constellations Pegasus, Vulpecula, Lyra and Hercules. Mid-European observers can observe this comet in the morning sky at first and the whole night long during the most interesting weeks. It will disappear above the western evening horizon at the end of November.
The comet experienced a very high level of activity, based on 74 observations from 19 observers. The derived brightness parameters are m0=3.8 mag / n=10, resulting in a maximum brightness of 14.5 mag at the opening of August 2021. The coma diameter peaked at 0.8' (80.000 km) at the start of September 2021, with the coma medium-condensed (DC 4-5). Between mid-June and the opening of October 2021 a larger number of tail sightings have been reported. The tail reached a maximum length of 5' (1.25 Mio. km) and rotated from Southwest via South towards ENE.
Total Brightness and Coma Diameter
--------------------
On images taken on Jan. 3, 2021 by the NEOWISE satellite an asteroidal object with an interesting motion was detected in the constellation Bootes. Follow-up observations showed a 8" coma of total magnitude 18.0 and an 11" tail in p.a. 300°. Comet C/2021 A4 (NEOWISE) will pass perihelion on Mar. 20, 2021 in the solar distance of 1.14 AU, expected to reach magnitude 14.0. It should be brighter than 16 mag between end of January and end of March. During that period it moves from Ursa Major through Camelopardalis and Auriga into Taurus, being well observable at mid-European locations.
The published observations show a large scatter. Therefore the development can only be derived roughly. Based on 52 observations from 20 observers the brightness parameters are about m0 = 12.0 mag / n=14, yielding a maximum brightness between magnitude 13.0 and 13.5 around Feb. 20, 2021. Due to the high activity parameter the comet faded rapidly thereafter. The coma diameter reached short of 1.5' (30.000 km) with the coma only moderately condensed (DC 2-3). A tail up to 2' (100.000 km) length was observed by several observers. It pointed towards Southeast at first, turning towards ENE during the following weeks.
Total Brightness and Coma Diameter
--------------------
On publicly available images taken by the SWAN instrument aboard SOHO between Feb. 19 and 25, 2021 Michael Mattiazzo (Australia) discovered a suspect, probably cometary object. On Feb. 27 Michael Jäger succeeded in taking a first image of comet C/2021 D1 (SWAN), showing a strongly condensed 3.5' coma of total magnitude 10.5, but no tail. During the following days the comet was also found by other observers which described it as a 11 mag object at elevations of less than 10°. The comet passed perihelion at the solar distance of 0.90 AU on the far side of the Sun on Feb. 27, 2021 (CBET 4939). From mid-European locations the comet hovered more than 10° above the western evening horizon between early March and mid-May (with a maximum altitude of about 20° in mid-April). During this period it moved through the constellations Pegasus, the northern parts of Pisces, Triangulum and the southern parts of Perseus and Auriga, thereby expected to fade from 11.0 mag to 13.0 mag.
For a preliminary analysis I could use 32 observations from 11 observers. The observations indicate brightness parameters of about m0=10.0 mag / n=5. Thus the comet peaked at 10.5 mag in early March, fading rapidly during the following weeks. The maximum coma diameter was reached by the end of March at 2' (160.000 km). While the degree of condensation was at DC 3-4 at first, it decreased rapidly, reaching DC 1 at the end of March. No tail was observed.
Total Brightness and Coma Diameter
--------------------
On July 21, 2021 the Japanese Amateur Hideo Nishimura discovered a comet near the border of the constellations Auriga/Gemini, using a digital camera with a 200mm-tele. He assumed that the comet was 8P/Tuttle during an outburst. But additional observations during the following days showed it to be a new one. Comet C/2021 O1 (Nishimura) hovered above the northeastern morning horizon and was therefore a difficult object. It showed a significantly condensed 2.5' coma of total magnitude 9.2 and a 5' tail in p.a. 285°. The comet will pass perihelion on Aug. 13, 2021 in the solar distance of 0.79 AU, but will be situated on the opposite side of the Sun. Therefore it will not get brighter than 9.0 mag (CBET 5004/08). In addition the observational circumstances deteriorate rapidly worldwide. For mid-European locations the comet disappeared above the northeastern morning horizon already a few days after discovery.
Very few observers succeeded in observing this comet. After discovery it rapidly grew fainter and was soon lost in the Sun's glare. When it reappeared in late 2021 it had already faded below detection.
--------------------
On Aug. 29, 2021 the "Asteroid Terrestrial-Impact Last Alert System" (ATLAS) team discovered a comet in the constellation Gemini. The team determined the brightness of the 6" coma to be 17.0 mag. Follow-up observations of comet P/2021 Q5 (ATLAS) showed a 20x12" coma of total magnitude 15.5, but no tail. The periodic comet with an orbital period of 5.64 years passed perihelion already on Aug. 30, 2021 at the solar distance of 1.23 AU (CBET 5029). It could be brighter than 16 mag until January 2022. During this period it will move through the constellations Cancer, Sextans, Crater/Corvus. At mid-European locations it can be observed in the morning during the first months, then near the end of year for the whole night.
The small number of published observations indicate a maximum brightness of about 13.0-13.5 mag (large scatter in the estimated values) and an apparent diameter of the very diffuse coma of about 1.5' in mid-September.
--------------------
Comet 4P/Faye (P=7.48a) will appear in the morning sky at the opening of July 2021 as an object of magnitude 12. It will pass perihelion on Sep. 9, 2021 in the solar distance of 1.62 AU, expected to reach 10.5 mag (assuming the parameters m0=6.0m / n=8). Until March 2022 the comet will move through the constellations Aries, Taurus and Gemini and will experience an oppositional loop near the border of the constellations Monoceros/Gemini. Earth will be siutated near the orbital plane during the first half of October.
Even though the comet was quite faint 287 observations from 55 observers could be used for the analysis. The estimates can be quite well represented by the brightness parameters
m0 = 9.8 mag / n = 2.5
indicating a surprisingly low activity and a maximum brightness of 11.2 mag in mid-November 2021. The apparent coma diameter increased from 0.7' at the start of the apparition to 2.8' at the end of October 2021, thereafter decreased, measuring 1.5' at the start of March 2022. Until end of October 2021 the absolute coma diameter constantly measured 130.000 km, decreasing thereafter and measuring 90.000 km at the start of March 2022. The degree of condensation decreased throughout the apparition from DC 4-5 to DC 2. CCD-observers could detect a tail throughout the apparition, peaking at 10' (1.2 Mio km) in September and October 2021, pointing constantly towards West.
Total Brightness and Coma Diameter
--------------------
Comet 7P/Pons-Winnecke (P=6.31a) should become brighter than 16.0 mag during February 2021. It will pass perihelion on May 27, 2021 in the solar distance of 1.23 AU, expected to reach magnitude 11.5. Until the start of June the comet moves from the constellation Serpens into Aquarius, being situated in the morning sky. The altitudes decrease from 55° to 0°.
The comet showed a significant difference in the brightness development pre- and post-perihelion. Based on 79 observations from 22 observers the following parameters result:
pre-perihelion: m0 = 13.0 mag / n = 3.5
post-perihelion: m0 = 12.5 mag / n = 2
The comet showed a quite low activity parameter for an aged comet. The maximum brightness of 11.2 mag was reached in early June 2021. The coma diameter increased constantly between mid-March and mid-July from short of 1' (35.000 km) to 4' (100.000 km), thereafter decreasing to short of 1' (50.000 km) by mid-September. The coma was significantly condensed (DC 5) for most of the apparition. Starting in mid-August it got more diffuse (early September: DC 3). Tail sightings have been extremely rare.
Total Brightness and Coma Diameter
--------------------
Only Southern hemisphere observers can observe comet 8P/Tuttle (P=13.63a) during the current apparition. The comet will pass perihelion on Aug. 27, 2021 in the solar distance of 1.03 AU, but will be positioned near the Sun on the Sky. It should peak at magnitude 9 at end of August or start of September.
Based on only 21 observations from 7 observers the brightness parameters m0=7.4 mag / n=4.3 can be derived. Thus the comet peaked at 8.8 mag at the opening of September 2021. The significantly condensed (DC 5) coma displayed a diameter of 3.5'.
--------------------
On March 24, 2021 comet 10P/Tempel (P=6.31a) passed perihelion at the solar distance of 1.41 AU. At mid-European locations it will appear in the morning sky around July 20, situated in the southern part of Taurus. Observations of this comet are difficult, because it normally exhibits a very diffuse coma.
With only 29 observations from 8 observers this apparition is not well-documented. Nevertheless yield the estimates rather accurate brightness parameters (m0=5.0 mag / n=11) and a well-defined maximum brightness of 10.8 mag at the end of March 2021. The coma diameter shrunk throughout the apparition from 3' (280.000 km) to 0.4' (30.000 km), with the coma being rather diffuse (DC 3-4). No tail was observed.
Total Brightness and Coma Diameter
--------------------
Starting in mid-July 2021 comet 15P/Finlay (P=6.56a) can be followed in the morning sky in the northern part of Taurus. It will pass perihelion at the solar distance of 0.99 AU on July 13, 2021. The brightness development is uncertain, because the comet showed an erratic behavior with two outbursts during its last perihelion passage in 2014/15. Most probably should it be of magnitude 10-11 at the time it enters the morning sky. Earth will be situated near the orbital plane during the first half of October.
In this apparition the comet did not surprise the observers with short-lived brightness outbursts. Instead the brightness developed very steadily and showed an activity parameter usual for an older comet. Based on 65 observations from 23 observers the brightness development can be well represented by the formula
m = 10.7 mag + 5×log D + 15×log r
This yields a maximum brightness of 11.0m at the start of July 2021. Pre-perihelion no coma diameter estimates have been published. Post-perihelion the coma shrunk from short of 3' (150.000 km) to short of 1' (100.000 km). During this interval the coma grew more diffuse; the degree of condensation decreased from DC 4 to DC 2. Few CCD observers reported a tail of up to 8' (500.000 km) length, oriented towards WSW.
Total Brightness and Coma Diameter
--------------------
Comet 17P/Holmes (P=6.93a) passed perihelion already on Feb. 19, 2021 at the solar distance of 2.08 AU, but was situated too near the Sun until the end of June 2021. For a very approximate analysis 38 observations from 10 observers could be used. These show a fading from 14.0 mag in June to 18.0 mag at the end of December, indicating brightness parameters of about m0=-3.5m / n=17. Thus the comet should have peaked around 12.5 mag at perihelion.
--------------------
A major outburst showed comet 57P/du Toit-Neujmin-Delporte (P=6.40a) in mid-October 2021. The brightness increased within a few days from 17.0 mag to 12.0 mag, as was documented by 26 observations from 13 observers. It is very probable that the comet has now reached the maximum brightness and will fade during the next weeks. But in which way must be shown by additional observations. The coma diameter increased from 0.3' (20.000 km) to short of 2' (160.000 km) during the outburst. Contrary the degree of condensation decreased from DC 6 at the start to DC 3-4 on Nov. 6.
Total Brightness and Coma Diameter
--------------------
On Sep. 10, 2021 comet 108P/Ciffreo (P=7.23a) will pass perihelion in the solar distance of 1.66 AU, expected to reach magnitude 15. During late summer and fall it will move from the Hyades toward Castor, being well observable in the morning sky. In mid-November Earth will be situated near the orbital plane of the comet.
The analysis can use 41 observations from 11 observers. These yield a maximum brightness of 14.5 mag between end of October and mid-November 2021. The brightness development can be represented quite well by the formula m = 11.2 mag + 5×log D + 13×log r. The coma diameter did not exceed 1.0' (40.000 km), with the degree of condensation somewhere between DC 3 and DC 4. No tail was observed.
Total Brightness and Coma Diameter
--------------------
Comet 132P/Helin-Roman-Alu (P=7.66a) will pass perihelion on Nov. 13, 2021 at a solar distance of 1.69 AU, expected to reach magnitude 14.5-15.0. During late summer and fall the comet will move in a southward direction along the border of the constellations Cetus/Pisces, thus being observable for the whole night. During this period the comet should brighten from 16.0 mag to 14.5 mag. Earth will be near the orbital plane from Sep. 10 to 25.
The comet showed a high activity throughout the apparition and got a bit brighter than expected, as is shown by 61 observations from 15 observers. It peaked at magnitude 13.7 at the end of October 2021. Pre-perihelion the activity increased considerably faster than it decreased post-perihelion, as is demonstrated by the following formulae:
pre-perihelion: m = 2.3 mag + 5×log D + 52×log r
post-perihelion: m = 8.5 mag + 5×log D + 25×log r
In September and October 2021 the apparent diameter increased from about 0.5' to 0.8', thereafter remaining constant. The absolute coma diameter increased continuously during the apparition from 15.000 km to 40.000 km. Contrary the degree of condensation decreased from DC 4-5 to DC 3-4. CCD-observers could document a tail up to 2' during the whole apparition. This was considerably shortened because it was stretched nearly face-on for observers on Earth. It was directed towards WSW during the first weeks, rotating rapidly towards Northeast around Oct. 20, when Earth passed the comet.
Total Brightness and Coma Diameter
--------------------
Comet 252P/LINEAR (P=5.33a) became significantly brighter during the perihelion passage 2021 too, as was the case in 2016. The few published observations hint towards a maximum brightness of 11.0 mag on the days near perihelion (June 11, 2021) and to a high activity parameter (m0 = 10.0 mag / n = 10). In mid-September it had already faded to magnitude 14.5. The diameter of the diffuse (DC 2-3) coma peaked at about 2'.
Andreas Kammerer
