Fainter Comets 2017

Home=Current Comets | The German Group | Tutorials | Archive: Fainter Comets 2015 | Projects, publications | Images | Contact

An asteroidal object of magnitude 20.5, discovered by T. Bressi on Spacewatch images taken on May 21, 2011 near the borders of the constellations Ophiuchus/Serpens showed cometary morphology on images taken in April 2012. Comet C/2011 KP₃₆ (Spacewatch) displayed an 8" coma of total magnitude 20.0 and a very faint, 9" tail in p.a. 10°. The comet, intrinsically rather bright, will not pass its distant perihelion on its 235 years orbit prior to May 2016, then predicted to reach magnitude 14.5 (CBET 3109). It should be brighter than 15.5 mag between mid-2015 and the beginning of 2017. During this time it will move through the constellations Aquarius, Pisces and Cetus. The comet is expected to peak in September 2016.
The analysis can be based on 95 observations, which just cover a sufficient variance in the solar distance, to derive meaningful values. The brightness development can be described rather well with the parameters m₀=5.4 mag / n=3, yielding a maximum brightness of 13.6 mag in September 2016. The estimated coma diameter peaked at 1.2' (240.000 km) at the same time – in 2015 and 2017 it measured only 0.5' (90.000 km / 125.000 km). Throughout the apparition the coma was medium-condensed (constant at DC 3).

Total Brightness and Coma Diameter

--------------------

On March 16, 2012 PANSTARRS discovered a 21.0 mag comet near the border of the constellations Leo/Sextans. Comet C/2012 F3 (PANSTARRS) showed a coma only marginally larger than the Airy disks of nearby stars (1.7" versus 1.0") and a hint of a faint tail. It will pass perihelion in April 2015 and could peak around 14.0-14.5 mag for several months (CBET 3051 / MPEC 2012-G45). During the most interesting months it is positioned in the area of the constellations Serpens, Scutum and Aquila, being well situated for mid-European observers.
Based on only 20 observations the brightness parameters can be derived roughly as m₀=6.0 mag / n=4, yielding a maximum brightness of 13.6 mag in June 2015. The coma diameter was about 0.7' (85.000 km), the degree of condensation between DC 2...3.

Total Brightness and Coma Diameter

--------------------

An asteroidal object, discovered by C. Jacques, E. Pimentel and J. Barros with the 30cm telescope of the Southern Observatory for Near Earth Research (SONEAR) on Jan. 12 in the constellation Columba revealed its cometary nature in the course of follow-up observations. Comet C/2014 A4 (SONEAR) showed a diffuse 8" coma of magnitude 18, elongated towards Northeast. It will pass perihelion in September 2015, expected to reach magnitude 14 (CBET 3783). It should be brighter than magnitude 16 between the end of 2014 and mid-2016. During this period it will move through the constellations Eridanus, Cetus, Aries, Pisces, Pegasus and Andromeda.
According to the published CCD observations this comet peaked at 14.5-15.0 mag in October 2015, with the diameter of the significantly condensed (DC 5) coma measuring about 0.5'.

--------------------

On images taken with the NEOWISE satellite at a wavelength of 3.4 micrometers on July 4, 2014 a comet with R-magnitude 20 was discovered near the border of the constellations Fornax/Sculptor. Follow-up observations of comet C/2014 N3 (NEOWISE) showed a medium-condensed 30" coma of magnitude 15.5-16.0 and a 2' tail in p.a. 195°. The comet will pass its perihelion in mid-March 2015 and could get as bright as 14.5 mag in fall 2014 and as bright as 15.0 mag in fall 2015 (CBET 3921). During the first visibility for mid-European observers it will not reach acceptable altitudes before December, already disappearing from the evening sky in February 2015. During this visibility it will be positioned in the western part of Cetus, moving northward. Starting in mid-June 2015 it will reappear, moving through the constellations Triangulum and Andromeda until December, when it is expected to get fade below 16.0 mag.
The comet was observed, primarily via CCD, between July 2014 and December 2015. The estimates can be roughly represented with the brightness parameters m₀=8.5 mag / n=2. Thus the comet peaked at about 14.0 mag in fall 2014 and at about 14.5 mag in fall 2015. The weakly condensed (DC 3) coma was of diameter 0.7'.

--------------------

On Nov. 26, 2014 the PanSTARRS team discovered an 18.5 mag comet near the border of the constellations Cancer/Leo. Comet C/2014 W11 (PanSTARRS) showed a strongly condensed 8" coma. It will pass perihelion on its 30.6 years orbit in mid-June 2015, then expected to reach magnitude 17.5 (CBET 4031 / MPEC 2015-B177).
Surprisingly the comet grew much brighter than expected and could even be observed visually. In February 2015 it peaked at about magnitude 14.5, thereby showing a weakly condensed 0.3' coma.

--------------------

On Dec. 16, 2014 the PanSTARRS team discovered another comet in the constellation Lynx, which showed a faint, broad tail. Follow-up observations of comet C/2014 Y1 (PanSTARRS) showed a strongly condensed 18" coma of total magnitude 17.5 and a 30" tail in p.a. 275°. It will pass perihelion in mid-January 2016 and could then reach magnitude 13.0 (CBET 4037). However, at that time it will be situated in the southwestern part of Scorpius, being a very difficult object for mid-European observers. They can follow the comet only during the interval November 2015 and February 2016, when the comet should brighten from magnitude 14.5 to magnitude 13.0.
Only a small number of CCD-observations has been published. They indicate that the comet was 1 mag fainter than expected, with brightness parameters of about m₀=10.0 mag / n=4.

--------------------

In public website images obtained with the SWAN camera on the SOHO spacecraft, starting on Feb. 15, 2015, R. Matson found a moving object in the constellation Sculptor. The object brightened daily with the elongations decreasing. Terry Lovejoy succeeded in confirming the comet in CCD images taken on Feb. 25; they showed an 11 mag coma of diameter 2' and a short tail. On Feb. 26 Michael Mattiazzo could observe comet C/2015 C2 (SWAN) visually; he estimated the total brightness of the 1.5' coma as 11.5 mag. It passed perihelion at 0.71 AU at the start of March (CBET 4068 / MPEC 2015-H37). Post-perihelion only 2 observations came to my knowledge. According to these the comet was of about magnitude 9.5 on March 9 and 18, respectively, with the diffuse coma (DC 2...3) of diameter 1.5-3'. Thus, the comet brightened about 2 mag around perihelion.

--------------------

In public website LASCO3-images obtained on Feb. 18, 2015 with the SOHO spacecraft K. Battams discovered a 9 mag comet (perihelion on Feb. 19.7 UT at solar distance 0.03 AU). While approaching the Sun it gradually brightened, but K. Battams was surprised to see comet C/2015 D1 (SOHO) dramatically brighter on Feb. 19, displaying a short, faint tail. It peaked at 1.3 mag on Feb. 19.9 UT. When it left the LASCO3-field (on Feb. 21) it had faded to 6 mag. An image, obtained with a 15cm refractor on Feb. 27.8 UT, shows a cigar-shaped, 31 x 5' object (elongated towards 82°) of about magnitude 8.0 with no bright condensation. Simulations undertaken by Z. Sekanina suggests, that the remnant was composed of large dust grains, released during the period 0.6 hours prior to 3.2 hours past perihelion. This period is coincident with the observed flare-up (CBET 4067/73/74). Robin Hegenbarth could observe the remnant visually on Mar. 11 and 12, but due to the extremely low surface brightness he could not make a brightness estimate.

--------------------

On Feb. 23, 2015 Gennady Borisov discovered a comet in the constellation Vulpecula with a 30cm astrograph. Comet C/2015 D4 (Borisov) showed an elongated 10x15" coma of total magnitude 17.5 and a faint 40" tail in p.a. 195°. It passed perihelion (at solar distance 0.86 AE) already at the end of October 2014, then probably at magnitude 12, but situated rather near the Sun. It rounds the Sun with a period of about 650 years (CBET 4071 / MPEC 2015-H37).

--------------------

On March 23, 2015 a polish observer team discovered a comet in the constellation Telescopium by using a remote-controlled 10cm-astrograph located at the Polonia observatory in Chile. Comet C/2015 F2 (POLONIA) displayed a 7-10" coma of total magnitude 17.0. Additional observations showed a strongly condensed coma of diameter up to 33" and of total magnitude 16.5, which was elongated towards west. The comet will pass perihelion on its elliptical orbit with a period of about 220 years at the end of April 2015, expected to reach magnitude 15.5 (CBET 4083 / MPEC 2015-H37). According to the small number of published estimates the comet reached magnitude 14.5.

--------------------

On low-resolution public website SWAN images of Aug. 3/4 M. Mattiazzo noticed a moving object, which he could confirm as a comet via a CCD image taken on Aug. 9. Comet C/2015 P3 (SWAN), positioned near the border of the constellations Virgo/Coma Berenices, showed a weakly condensed coma of diameter 2' and of total magnitude 11.8. Alan Hale could observe the comet visually on Aug. 10, reporting a magnitude of 12.2 and a coma diameter of 2.3'. Additional observers estimated the comet at magnitude 11.5 and the coma of diameter 2-2.5' during those days. The comet approached the Sun to within 0.71 AU on July 27, but should not have been significantly brighter (CBET 4136 / MPEC 2015-Q71). During the following days/weeks it moved rapidly southward and was therefore not visible for mid-European observers. The orbital period is in the order of 3.000 years.

--------------------

On images taken with the NEOWISE satellite on Dec. 14, 2015, a comet was discovered near the border of the constellations Canis Venatici / Coma Berenices, which moved northward. Additional observations of comet C/2015 X8 (NEOWISE) showed a strongly condensed 50" inner coma of total magnitude 16.0 and a very diffuse outer coma of diameter 2'. Alan Hale observed the comet visually on Dec. 18, reporting the extremely diffuse coma to be of magnitude 12.8 and diameter 2.4'. The comet passed perihelion on its elliptical orbit with a period of 82 years at the end of October 2015 (CBET 4225 / MPEC 2016-A127). It approached Earth to within 0.83 AU on Jan. 2, 2016, fading rapidly thereafter. The maximum brightness of 12.5 mag was reached at the end of December. The extremely diffuse coma (DC 0...1) reached a maximum of about 2.5'.

--------------------

On Dec. 31, 2015 the PanSTARRS team recovered comet P/2010 V1 (Ikeya-Murakami) in the southeastern corner of Lynx. Follow-up observations of comet P/2015 Y2 (Ikeya-Murakami) showed a 9" coma of magnitude 19.0 and a very broad, very faint 20" tail in p.a. 240°. In addition a secondary, very diffuse component was found with the Canada-France-Hawaii-telescope 87" SE of component A. This component B was only a bit fainter than A, but showed an extremely diffuse 15" coma and a 20" tail in p.a. 290°. The comet will pass perihelion on its orbit with a period of 5.42 years in mid-March 2016, when it should be one magnitude brighter. These observations support the suggestion that this comet was discovered in the course of an outburst in fall 2010 (the brightness faded in a time-dependent manner). Because the disintegration did not spur greater activity the comet hast not been visible visually in this apparition.
Additional observations during the following weeks detected additional components/fragments: On Jan. 8 and 11 a component C (magnitude 22.0) was discovered 12" E of B, which was more condensed than B and which was eventually recognized as the main component of this comet. On Jan. 18 fragment D (22.5 mag) was discovered within the fragmentary component B. It disintegrated rapidly. On Feb. 4 fragment E (about 20.3 mag) was discovered 2.5' WNW of A. On Feb. 5 fragment F was discovered 15" from E and furthermore fragments G and H. All fragments were strung on a line stretching away from C in p.a. 289°. The following distances (relative to C) and magnitudes were reported: A: 2'25"/18.2mag, B: 21.0"/21.0mag, main component C: 17.8mag, D: 4'50"/20.8mag, G: 15'04"/21.0mag, H: 20'44"/21.0mag. On Feb. 6 fragment J was discovered at Pic-du-Midi 70" from E. The observers reported the following magnitudes: A: 19.0mag, B: 21.0mag, C: 18.2mag, E: 21.0mag, F: 22.6mag.
According to Z. Sekaninas analysis the outburst in fall 2010 resulted in a massive disruption of the nucleus, which then disintegrated continuously. Component A disintegrated at the start of Dec. 2012, B in mid-2013 and D in fall 2015. Components B and D will not survive this perihelion passage (CBET 4230/31/35/50/54, MPEC 2016-C51). In the meantime the comet received the permanent designation 332P/Ikeya-Murakami.

--------------------

Comet 10P/Tempel (P=5.36a), well-known for its extremely diffuse coma, will reach perihelion for another time in mid-November 2015. Its brightness evolution is extraordinary too: pre-perihelion the comet brightens very rapidly, followed by a period during which the heliocentric magnitude is rather constant, finally fading, but much slower compared to the pre-perihelion brightening. At the start of June 2015 the visual and photovisual observers reported a brightness of about 14.0 mag. During the weeks around perihelion a magnitude of 10-11 mag is expected. However, at mid-European locations the comet's altitudes will not reach 10° at the end of twilight from mid-August 2015 onwards.
Based on only 11 observations from 2 members of the German Comet Section and 46 international observations the brightness evolution can be derived only preliminary. Recognizable is the early period of very rapid brightening, followed by the period, during which the comet's heliocentric magnitude is usually rather constant. The currently derivable formulae are:

Total Brightness and Coma Diameter

--------------------

According to the small number of published observations of comet 19P/Borrelly (P=6.83a) it evolved as expected in its apparition 2015 (m₀=6.0 mag / n=6). The observed maximum brightness was 12.0 mag shortly after it had appeared in the morning sky in September 2015. The coma diameter reached a bit more than 1' and was medium-condensed (DC 4).

--------------------

In August 2015 comet 51P/Harrington (P=7.16a) will pass perihelion, expected to peak at magnitude 14.5. It is located in the northern part of Cetus, thus being visible in the morning sky. At the end of May 2015 the fragment D - at magnitude 22.0 - was recovered (MPEC 2015-L08).
According to a very small number of observations the comet reached only magnitude 15.5-16.0 in summer 2015.

--------------------

Comet 61P/Shajn-Schaldach (P=7.06a) will reach perihelion at the start of October 2015, expected to peak at magnitude 14.5. During summer 2015 it moves from Pisces towards the border of the constellations Cetus/Aries, thus being observable in the morning sky.
According to the small number of published observations the comet seems to evolve slower than expected, fitting the brightness parameters m₀=7.5 mag / n=8. It peaked at magnitude 14.5 in October, with the diameter of the very diffuse coma in the order of 0.6'.

--------------------

Comet 141P/Machholz (P=5.25a), prone to disintegration, will reach perihelion at the end of August 2015, expected to peak at magnitude 11. However, the predictions show a wide range of maximum brightnesses, with the CBAT predicting even 8.5 mag. Due to the relative proximity of the comet to Earth it moves quickly - near the ecliptic - from Pisces into Leo during summer.
The number of published observations is too small for a serious analysis. However, the observations are compatible with the parameters m₀=15.0 mag / n=10 pre- and m₀=13.0 mag / n=6 post-perihelion, derived on previous perihelion passages. The comet peaked at magnitude 11.5 at the end of August 2015, showing a diameter of the extremely diffuse (DC 1-2) coma of about 2.5'.
The comet continued to disintegrate in 2015. On Aug. 19 a new fragment was discovered, which was designated H. In addition the MPC announced two further fragments (F and G), which have been discovered recently in images of 1994 (MPEC 2015-R12). The comet seems to have peaked at only magnitude 11.5-12.0 at the end of August 2015.

--------------------

Comet 218P/LINEAR (P=5.45a), which will pass perihelion at the end of April 2015, seems to evolve as expected. Thus it should peak around 15.0 mag. During May/June it is situated in the western part of Aquarius.
According to a small number of CCD observations the comet peaked at 14.0 mag at the end of April 2015, with the coma estimated to be about 0.5'. Thus it was about one magnitude brighter than expected.

--------------------

Surprisingly comet 230P/LINEAR (P=6.27a) could be observed visually in December 2015 and January 2016, peaking at magnitude 13.5 in December. 22 observations indicate an unusually high activity, with the heliocentric magnitude getting still brighter after perihelion passage. The coma was rather faint, measuring only 0.7', but showing a pronounced central condensation, perhaps explaining the reported degree of condensation of about DC 5.

--------------------

On images taken on Mar. 31, 2015 with the 0.4m-MASTER-telescope at the South African Astronomical Observatory, an 18.0 mag comet was discovered in the constellation Microscopium. G.V. Williams located the comet on images taken with the PanSTARRS-telescope on June 29, 2014 (21.0 mag, constellation Lupus) and identified it with comet P/McNaught-Hartley (1994n = 1994 N2) - some 25' from the predicted position - which showed the magnitude expected from its apparition in 1994. The indicated correction to the prediction by B.G. Marsden on MPC 79351 is dT=-2.0d. Comet 318P/McNaught-Hartley = C/2014 M6 (McNaught-Hartley) will pass perihelion on its elliptical orbit with a period of 20.60 years at the end of October 2015, then expected to peak at 15.5 mag. During the time of its maximum brightness it will be positioned in the southeastern part of Piscis Austrinus.
The comet reached a maximum brightness of magnitude 15.0 at the opening of September 2015.

Andreas Kammerer