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ALPO Comet News for July 2020

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#1 Carl H.

Carl H.

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Posted 03 July 2020 - 10:01 PM

ALPO COMET NEWS FOR JULY 2020
A Publication of the Comet Section of the Association of Lunar and Planetary Observers
By Carl Hergenrother - 2020-July-3

 

The monthly Association of Lunar and Planetary Observers (ALPO) Comet News PDF can be found on the ALPO Comet Section website @ http://www.alpo-astr....org/cometblog/. A shorter version of this report is posted here (minus magnitude estimates, images, and figures). The ALPO Comet Section welcomes all comet related observations, whether textual descriptions, images, drawings, magnitude estimates, or spectra. You do not have to be a member of ALPO to submit material, though membership is encouraged. To learn more about the ALPO, please visit us @ http://www.alpo-astronomy.org.

 

First there was C/2019 Y4 (ATLAS), the "Great Comet" that couldn’t hold itself together. Then along came C/2020 F8 (SWAN), the bright consolation prize that decided to star in its own break-up act. After the back-to-back let downs of ATLAS and SWAN, C/2020 F3 (NEOWISE) is at perihelion and currently as bright as 1st magnitude. Though it isn’t the best placed object for observing and will fade as the month progresses, NEOWISE should be a memorable comet and perhaps the best since C/2011 L4 (PANSTARRS), the Really Good Comet of 2013.

 

In addition to NEOWISE, there are a number of fainter comets within reach of small apertures. In the evening we have C/2019 U6 (Lemmon) at 6th-7th magnitude and 88P/Howell and C/2017 T2 (PANSTARRS) at 9th magnitude. Frequent inner solar system visitor 2P/Encke begins July at 7th-8th magnitude though only for southern hemisphere observers.

 

Bright Comets (magnitude < 10.0)

 

C/2020 F3 (NEOWISE) – The comet story of the month is C/2020 F3 (NEOWISE). After comets C/2019 Y4 (ATLAS) and C/2020 F8 (SWAN) broke our hearts, C/2020 F3 has made up for them by becoming the brightest comet since C/2011 L4 (PANSTARRS) in 2013 (not counting any SOHO comets that were never observed from the ground).

 

The Wide-field Infrared Survey Explorer (WISE) spacecraft was launched in 2009 into low-Earth orbit. The spacecraft spent two years conducted an all-sky infrared survey at four wavelengths (3.4, 4.6, 12, and 22 microns) with a 0.4-m (16”) telescope. After its cryogens were depleted, the detector heated up and the spacecraft was decommissioned in 2011. While the two longer wavelength bands were no longer useable, the bands at 3.4 and 4.6 microns were still operational. In 2013, the spacecraft was revived, rebranded as the Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE), and dedicated to the study and discovery of asteroids and comets. Since its launch, WISE/NEOWISE has discovered 33 comets and over 300 near-Earth asteroids.

 

C/2020 F3 (NEOWISE) was a 16th magnitude object when discovered on March 27. At that time the comet was 2.1 au from the Sun and 1.7 au from Earth. A 16th magnitude object at such a distance is usually nothing special, but after a rapid bout of brightening the comet reached 10th magnitude in late April. While its brightening slowed down, it was still brightening at a faster than expected 2.5n ~ 11 rate from late April till early June. The last observation submitted to the Comet Section before the comet was lost in the glare of the Sun was made on June 6 at magnitude 7.6 by Chris Wyatt.

 

CCD observations by Carl Hergenrother on April 13, 28, and May 14 showed a comet that was very dust poor. On those nights, its R magnitude was 2.5-3.1 magnitudes fainter than its V magnitude suggesting the majority of the comet’s brightness was due to gas with little contribution from dust. Dust poor comet are usually not expected to put on stunning visual displays.

 

Between June 23 and 27, the comet was visible in the field-of-view of the SOHO LASCO C3 coronagraph. A number of observers, myself included, measured the brightness of the comet in LASCO. On June 23.5 UT I found the comet at magnitude 3.6. By June 27.5 it had brightened to magnitude 2.1. This rate of brightening is actually slightly faster than what was observed between late April and early June.

 

On the morning of July 1, observers (including your Section Coordinator) were able to observe NEOWISE from the ground even at a small elongation of 11 degrees! Through July 3, many observers have been able to observe and image NEOWISE. Magnitude estimates published across the internet place the comet between magnitude +0.4 and +2.5. My own estimates placed the comet at +1.0 on July 1 and +1.4 on July 3. The drop in brightness is probably not real but an artifact of difficult observing conditions (very bright sky, high airmass, uncertain atmospheric extinction, few nearby stars for comparison, and a small window to observe between comet rise and a too bright sky). While still located deep in bright twilight, the comet is displaying up to a 0.5-degrees of a dust tail. Note, that even though the comet may be 1st or even 0th magnitude it is not a naked eye object due to the bright sky. That should change as the comet moves higher in the sky though a bright Moon will also affect its visibility.

 

On July 3, the comet was seen in the 10x50 binoculars until 4:50 am local Tucson time, or ~35 minutes before sunrise, with the comet at an elevation of 7.1 deg and the Sun 6.6 degrees below the horizon. In Vixen 30x125 binoculars, the comet was visible for another 10 minutes till 5:00 am with the comet elevation at 8.9 deg and the Sun 4.7 deg below the horizon. It will be interesting to see if the comet is bright enough for daylight observations.

 

This month the comet can be found in Taurus (July 1-2), Auriga (2-12), Lynx (12-17), Ursa Major (17-29), and Coma Berenices (29-31). For northern observers (+40N), the comet is a morning object through mid-month with a maximum elevation at the start of nautical twilight (Sun at elevation of -12 degrees) of 8 degrees between June 10-15. The comet jumps into the evening sky around July 23 and rapidly moves away from the Sun. By the end of astronomical twilight on July 31, it is at an elevation of 27 degrees. Down south (-40N), the comet is invisible till the last week of the month.

 

Perihelion in on July 3 at 0.29 au and closest approach to Earth on July 22 at 0.69 au. The comet also reaches a maximum phase angle of 108 degrees on July 17. We do not know how quickly it will fade as it moves away from the Sun, so the brightness forecast in the ephemeris table below is uncertain.

 

After the disintegrations of C/2019 Y4 (ATLAS) and C/2020 F8 (SWAN), what is the likelihood that NEOWISE will follow the same path? SWAN was a dynamically new long-period comet meaning it was likely on its first trip through the inner solar system. Such comets are prone to be overly bright when inbound and then fading, brightening more slowly, or even falling apart as they near the Sun. ATLAS was a dynamically old comet and has likely been close to the Sun before. It also shared an orbit with the Great Comet of 1844 and was probably a smaller piece of the comet seen in 1844. The smaller components of split comets often fade from view in weeks or months with some lasting till the next perihelion. That seems to have been the case with ATLAS though we don’t know when it split from the 1844 comet (we do know it was not in 1844 but a previous return). NEOWISE is a dynamically old comet which was last at perihelion ~4500 years ago. Dynamically old long-period comets are much less prone to falling apart so there is confidence that it will not share the same fate as ATLAS and SWAN.

 

Usually the ephemerides in these reports give the maximum elevation between the end of evening and start of morning astronomical twilight. For NEOWISE, the elevations are for the time between the end of evening nautical and start of morning nautical twilight.

 

C/2020 F3 (NEOWISE)
T = 2020-Jul-03  q = 0.29 au                                      Max El
Dynamically old long period comet                                  (deg)
    Date     Mag    R.A.   Decl.     r       d    Elong  Const  40N  40S

2020-07-01   1.5   05 56  +26 13   0.306   1.240    10    Tau     0    0
2020-07-06   1.2   06 07  +34 07   0.303   1.070    16    Aur     5    0
2020-07-11   1.9   06 45  +41 54   0.372   0.896    21    Aur     8    0
2020-07-16   2.9   08 01  +47 24   0.474   0.764    26    Lyn    11    0
2020-07-21   3.9   09 46  +46 54   0.585   0.698    33    UMa    23    0
2020-07-26   4.8   11 21  +39 28   0.696   0.705    43    UMa    31    1
2020-07-31   5.9   12 23  +29 30   0.806   0.774    51    Com    35   14
2020-08-05   6.8   13 02  +20 34   0.912   0.887    56    Com    35   23
            Comet Magnitude Parameters --- H = 7.6, 2.5n = 12.7

 

C/2019 U6 (Lemmon) – C/2019 U6 (Lemmon) was discovered by Rich Kowalski (University of Arizona) on October 31 with the Mount Lemmon Survey’s 1.5-m reflector. Comet Lemmon is a dynamically old comet which last reached perihelion about 10,000 years ago. As is typical of dynamically old comets, Lemmon rapidly brightened. From the beginning of the year through early May, it brightened at a much faster rate than is usually for comets. From early May through mid-June that rate slowed down to a typical 2.5n ~ 7.5-10. Around the middle of June, the comet peaked at magnitude ~6.4 to 6.5. Since then, the comet has actually been fading intrinsically even with little change in its heliocentric and geocentric distances (perihelion on June 18 at 0.91 au and minimum distance to Earth on July 1at 0.83 au). The most recent observations place the comet at magnitude 7.0 (July 1.92, Willian Souza) and 7.6 (July 3.37, Chris Wyatt).

 

This month Lemmon is visible from both hemispheres in the evening sky as it moves through Sextans (July 1-4), Leo (4-11), Virgo (11-22), and Coma Berenices (22-31). If the comet continues its recent fading trend it could be significantly fainter than the values shown below. So far, no one has reported any evidence of splitting or disintegration.

 

C/2019 U6 (Lemmon)
T = 2020-Jun-18  q = 0.91 au                                      Max El
Dynamically old long period comet                                  (deg)
    Date     Mag    R.A.   Decl.     r       d    Elong  Const  40N  40S

2020-07-01   6.9   10 25  -02 11   0.940   0.828    60    Sext    2   44
2020-07-06   7.0   11 01  +02 02   0.964   0.845    61    Leo     8   42
2020-07-11   7.2   11 34  +06 00   0.996   0.879    62    Leo    14   39
2020-07-16   7.5   12 05  +09 30   1.034   0.927    64    Vir    19   37
2020-07-21   7.7   12 33  +12 29   1.077   0.987    65    Vir    24   34
2020-07-26   8.0   12 58  +14 56   1.125   1.055    65    Com    28   32
2020-07-31   8.3   13 21  +16 54   1.176   1.130    66    Com    31   30
2020-08-05   8.6   13 42  +18 28   1.230   1.209    66    Boo    34   29
            Comet Magnitude Parameters --- H = 7.5, 2.5n = 8.0

 

2P/Encke – Comet Encke has the shortest known orbital period of any comet (not counting asteroidal objects that appear cometary due to impacts or rotational splitting) at 3.3 years. This year marks Encke’s 65th observed return since 1786. Perihelion occurred on June 26 at 0.34 au. Northern summer/southern winter returns of Encke result in very poor placement pre-perihelion and then good placement after perihelion but only for southern hemisphere observers.

 

Chris Wyatt was the first visual observer of Encke this year. He picked it up at magnitude 7.5 on June 29 at an incredible elongation of 18 degrees! Sure, C/2020 F3 was observed at an elongation of 11 degrees but it was also 6-7 magnitude brighter. Encke should rapidly fade to 10th magnitude by the end of July as it moves through Cancer (July 1-12), Hydra (12-14), Sextens (14-23), Crater (23-30), and Corvus (30-31) in the evening sky.

 

2P/Encke

T = 2020-Jun-26  q = 0.34 au                                      Max El
Jupiter-family comet                                               (deg)
    Date     Mag    R.A.   Decl.     r       d    Elong  Const  40N  40S
2020-07-01   7.3   08 04  +17 44   0.364   1.052    20    Cnc     0    1
2020-07-06   7.6   08 39  +13 18   0.431   0.925    25    Cnc     0    7
2020-07-11   7.8   09 14  +08 19   0.516   0.816    30    Cnc     0   12
2020-07-16   8.2   09 50  +02 45   0.608   0.730    36    Sext    0   19
2020-07-21   9.0   10 29  -03 24   0.700   0.668    43    Sext    0   26
2020-07-26   9.7   11 12  -09 51   0.791   0.632    51    Crt     0   34
2020-07-31  10.4   11 58  -16 04   0.879   0.622    59    Crv     0   42
2020-08-05  11.1   12 45  -21 26   0.964   0.639    66    Crv     0   50
Comet Magnitude Parameters - H = 10.3, 2.5n = 7.0 (July 1-15, ref. Yoshida)
                             H = 12.3, 2.5n = 15.7 (July 15-31, ref. Yoshida)

 

C/2017 T2 (PANSTARRS) – For the past half year C/2017 T2 (PANSTARRS) has been a fixture in the northern evening sky. This month the comet becomes better placed for southern hemisphere observers. Now 2 months passed its May 4th perihelion at 1.62 au, the comet is fading. In fact, its post-perihelion fading seems to be faster than expected. During June visual observations by Michel Deconinck, J. J. Gonzalez, Carl Hergenrother, and Chris Wyatt placed PANSTARRS between magnitude 8.8 and 9.8. PANSTARRS should continue to fade this month as it moves south through the evening constellations of Canes Venatici (July 1-14) and Coma Berenices (July 15-31).

 

C/2017 T2 (PANSTARRS)

T = 2020-May-04  q = 1.62 au                                      Max El
Long-Period comet - dynamically new                                (deg)
    Date     Mag    R.A.   Decl.     r       d    Elong  Const  40N  40S

2020-07-01   9.3   12 31  +41 39   1.787   1.795    73    CVn    49    8
2020-07-06   9.4   12 41  +37 44   1.816   1.841    72    CVn    47   12
2020-07-11   9.6   12 51  +33 56   1.847   1.893    71    CVn    44   16
2020-07-16   9.8   13 00  +30 16   1.880   1.951    70    Com    41   20
2020-07-21   9.9   13 09  +26 45   1.914   2.016    69    Com    39   23
2020-07-26  10.1   13 17  +23 23   1.949   2.085    68    Com    36   25
2020-07-31  10.3   13 25  +20 11   1.986   2.159    66    Com    33   27
2020-08-05  10.5   13 33  +17 09   2.024   2.238    64    Com    31   29
            Comet Magnitude Parameters --- H = 4.6, 2.5n = 13.5

 

88P/Howell – Short-period comet 88P/Howell is making its 9th observed return. 88P was discovered on photographic plates taken with the 0.46-m Palomar Schmidt in August 1981 by then Caltech student, and currently my fellow University of Arizona OSIRIS-REx team member, Ellen Howell. In addition to being found in pre-discovery observations from 1955, 88P has been observed at every return since 1981. The comet’s perihelion distance has gradually fallen from 1.92 au in 1955, to 1.62 au in 1981, to 1.41 au in 1993 to its current 1.35 au. As a result, comet Howell now often peaks brighter than 10th magnitude. Its brightest return was in 2009 when it peaked at 8th magnitude. This year it comes to perihelion on September 28 and should again peak around 8-9th magnitude.

 

During June, 88P was observed by Michel Deconinck, J. J. Gonzalez, and Chris Wyatt. The later observed the comet on June 20.94 UT at magnitude 10.7. This month, 88P will continue to brighten and should be a 9th magnitude object by the end of the month. Its location in Virgo near the celestial equator makes it a good target for both hemispheres in the evening sky.

 

88P/Howell

T = 2020-Sep-28  q = 1.35 au                                      Max El
Jupiter-family comet                                               (deg)
    Date     Mag    R.A.   Decl.     r       d    Elong  Const  40N  40S

2020-07-01  10.7   12 56  -05 32   1.648   1.201    95    Vir    26   56 
2020-07-06  10.4   13 02  -06 27   1.620   1.216    92    Vir    24   57
2020-07-11  10.2   13 08  -07 27   1.592   1.230    89    Vir    22   58
2020-07-16  10.0   13 16  -08 30   1.566   1.243    87    Vir    20   58
2020-07-21   9.8   13 24  -09 37   1.540   1.256    84    Vir    18   59
2020-07-26   9.6   13 33  -10 47   1.516   1.268    82    Vir    16   59
2020-07-31   9.4   13 43  -11 59   1.493   1.279    80    Vir    15   59
2020-08-05   9.2   13 54  -13 14   1.471   1.289    78    Vir    14   59
              Comet Magnitude Parameters --- H = 3.1, 2.5n = 33

 

Fainter Comets of Interest (fainter than magnitude 10.0)


 

58P/Jackson-Neujmin - 58P/Jackson-Neujmin was discovered at 12th magnitude in September 1936 by Cyril Jackson (Union Observatory, South Africa, 3 comet discoveries) and Grigory Neujmin (Simeis Observatory, Crimea, 6 comet discoveries). This year marks the comet’s 6th observed return with perihelion on May 27 at 1.38 au. In 1995 the comet passed within 0.43 au of Earth and peaked around magnitude 10.0. This year is not a good apparition and the comet was expected to remain faint. Michael Mattiazzo (Swan Hillm Victoria, Australia), the discoverer of C/2020 F8 (SWAN), noticed 58P in outburst in SWAN data going back to March 20.

 

The comet has stayed around 10-11th magnitude since March. Chris Wyatt estimated 58P at magnitude 10.9 on June 21.77 UT with a 2.6’ coma in 0.25-m reflector (74x). After being solely a southern hemisphere object, 58P finally becomes visible from the northern hemisphere as its moves through Taurus (July 1-23) and Orion (23-31) in the morning sky.

 

58P/Jackson-Neujmin

T = 2020-May-27  q = 1.38 au                                      Max El
Jupiter-family comet                                               (deg)
    Date     Mag    R.A.   Decl.     r       d    Elong  Const  40N  40S

2020-07-01  10.9   03 38  +12 19   1.437   1.971    44    Tau     3   25
2020-07-06  11.0   03 54  +12 41   1.455   1.971    45    Tau     5   26
2020-07-11  11.2   04 09  +12 58   1.475   1.972    46    Tau     7   26
2020-07-16  11.4   04 23  +13 09   1.496   1.973    47    Tau     9   26
2020-07-21  11.5   04 38  +13 16   1.520   1.974    49    Tau    11   26
2020-07-26  11.7   04 52  +13 18   1.545   1.975    50    Ori    13   27
2020-07-31  11.9   05 05  +13 15   1.571   1.975    52    Ori    16   27
2020-08-05  12.1   05 18  +13 08   1.599   1.974    53    Ori    19   27 
              Comet Magnitude Parameters --- H = 5.5, 2.5n = 25.0

 

249P/LINEAR – 249P/LINEAR is making its 4th observed return after returns in 2006, 2011, and 2015. It was discovered in October 2006 by the LINEAR (Lincoln Laboratory Near-Earth Asteroid Research) project with a 1-m telescope based outside of Socorro, New Mexico.

 

This comet is odd in a few different ways. For starters, its nucleus is slightly blue and resembles a B-type asteroid rather than the highly red, D-type, nuclei of most Jupiter-family comets. Its orbit and nucleus color suggest that it may more closely related to active asteroid in the Main belt rather than comets from the outer Solar System. For its second odd characteristic, 249P is only active when very close to the Sun. In fact, the comet didn’t show any sign of activity until late in May when it was already within 1 au of the Sun and even then, it was only around 16th magnitude.

 

While 249P was out of view from the ground, it finally woke up and was next seen brightening to around magnitude 7.5 in SOHO LASCO C3 images taken between June 16-June 21. 249P was expected to brighten to around magnitude 10 or so at perihelion. As it was passing through the C3 field, it was observed at a phase angle of 171 degrees resulting in ~6 magnitudes of dust forward scattering enhancement. If the comet were at 0 degrees phase angle it would have been magnitude ~13.5 and completely invisible to the LASCO C3 instrument.

 

Assuming the comet does brighten as it did in past apparitions, the comet could be a 9th-10th magnitude object as in the morning sky at the start of the month. Some of this brightness is the result of modest forward scattering. Unfortunately, it should rapidly fade to 14th magnitude by the end of the month. I attempted to observe 249P on the morning of July 3 but was not able to detect anything fainter than magnitude 8.3. No other observations have been made of 249P since it reappeared for ground-based observers. Perhaps the comet is still significantly fainter than predicted.

 

249P/LINEAR

T = 2020-Jun-26  q = 0.50 au                                      Max El
Jupiter-family comet? / Active Asteroid?                           (deg)
    Date     Mag    R.A.   Decl.     r       d    Elong  Const  40N  40S

2020-07-01   8.9   04 57  +28 47   0.498   0.649    23    Aur     1    2 
2020-07-06  10.0   04 53  +28 22   0.517   0.749    29    Tau     5    5
2020-07-11  11.1   04 57  +27 57   0.557   0.851    33    Tau     8    7
2020-07-16  12.0   05 05  +27 33   0.611   0.948    36    Tau    10    9
2020-07-21  12.8   05 16  +27 10   0.675   1.036    38    Tau    13   10
2020-07-26  13.7   05 27  +26 47   0.745   1.115    40    Tau    15   11
2020-07-31  14.5   05 39  +26 24   0.818   1.185    42    Tau    18   12
2020-08-05  15.2   05 50  +25 59   0.892   1.245    45    Tau    20   12
Comet Magnitude Parameters --- Post-perihelion: H = 15.5, 2.5n = 16.0

 

New Discoveries, Recoveries and Other Comets in the News

 

Newly Numbered Comets – The following comets were announced as numbered on CBET 4802.

 

396P/Leonard = P/2020 F1 = P/2002 E4
395P/Catalina-NEAT = P/2005 JD108 = P/2020 H1
394P/PANSTARRS = P/2020 F4 = P/2011 GN5
393P/Spacewatch-Hill = P/2009 SK280 = P/2019 S5
392P/LINEAR = P/2004 WR9 = P/2019
391P/Kowalski = P/2006 F1 = P/2019
390P/Gibbs = P/2006 W1 = P/2019

 

12P/Pons-Brooks – Earlier this year, Maik Meyer identified previous apparitions of the Halley-family comet 12P/Pons-Brooks in 1385 and 1457. Previously the only known observed apparitions were in 1812, 1883, and 1954. The Meyer linkages must have generated interest in the comet, for a team of comet researchers led my Matthew Knight used the 4.3-m Discovery Telescope at Lowell Observatory to recover 12P on June 10 and 17 at an astonishing ~11.9 au from the Sun and 4 years before perihelion! The new observations have allowed orbit computers S. Nakano and T. Kobayashi to bolster another linkage suggested by Meyer, that of the comet of 245 AD.

 

The Discovery Telescope observations show evidence of a short tail suggesting that 12P is not only active but has been for some time which is quite surprising for a Halley-type object at that distance. Though active, it was still a faint object with magnitudes ranging from 22.7 to 24.0.

 

The comet reaches perihelion on 2024 April 21 at 0.78 au. Unfortunately, the 2024 return will be a poor one with the comet getting no closer than 1.6 au to Earth and located at low elevations near perihelion. Still if its brightness follows what was seen in 1954, 12P/Pons-Brooks will peak at 4th-5th magnitude in 2024.

 

325P/Yang-Gao – Maik Meyer identified poorly observed comet P/1951 K1 with short-period comet 325P/Yang-Gao. P/1951 K1 was discovered on a single photographic plate exposed by Cornelis Johannes van Houten and George van Biesbroeck with the 0.25-m Cooke telescope at McDonald Observatory. The comet was subsequently lost. Meyer was able to identify 2 more images of the comet from the discovery night, 1951 May 28.

 

Rui Yang and Xing Gao independently discovered 325P in 2009 as a 12th magnitude object with a Canon 350D + 0.11-m f/2.8 lens from Xingming Observatory in China. The comet passed within 0.30 au in 2009 making it as good a return as possible at the time (perihelion distance of 1.30 au in 2009). 325P was observed again at its next perihelion in 2015. Eight perihelion passages were missed between the 1951 and 2009 apparitions. The comet’s next perihelion is on 2022 March 29 at 1.43 au.

 

C/2020 M3 (ATLAS) – The ATLAS 0.5-m f/2 astrograph on Mauna Loa, Hawaii discovered C/2020 M3 on June 27 at ~19th magnitude. The comet comes to perihelion on 2020 October 24 at 1.31 au. This is another one to watch as it will be close to Earth (0.40 au) near the time of perihelion. The current prediction is for C/2020 M3 to brighten to 13-14th magnitude. Here’s hoping this one also brightens more than expected.

 

P/2020 M2 = P/2012 SB6 (Lemmon) – H. Sato recovered this comet on June 29 at 17th magnitude with a 0.51-m f/6.8 iTelescope. The comet was only 10 days passed perihelion (q = 2.28 au). This is the comet’s first return since its 2012 discovery apparition. The comet may be outburst as it is 1-2 magnitude brighter than expected.

 

P/2020 M1 (NEAT) – PANSTARRS discovered this comet on June 17. Pre-discovery observations back to May 24 were also found. The comet was consistently observed around 20th-21st magnitude. It is well passed its 2019 December 21 perihelion at 2.66 au. It is currently fading from its discovery brightness. It is a short-period object on a 11.5-year orbit.

 

P/2020 K9 (Lemmon-PANSTARRS) – A tag team discovery, P/2020 K9 was seen by the Mount Lemmon Survey and PANSTARRS on two nights in May. After the two nights were recognized as belonging to an object on a cometary orbit, the MPC placed the object on the Possible Comet Confirmation Page. Follow-up observations detected cometary activity by mid-June. The comet comes to perihelion on 2021 February 12 at 2.85 au. The comet will likely get no brighter than 18th magnitude this apparition. It is a short-period object on an 8.6-year orbit.

 

C/2020 K8 (Catalina-ATLAS) – This object was observed as an apparently asteroidal object on multiple nights in May and June 2020 by both the 0.68-m Catalina and 0.5-m ATLAS schmidt telescopes. C/2020 K8 was 19th magnitude in the earliest observation on May 25.

Though currently faint, K8 has a small perihelion distance of 0.47 au on 2020 September 14. It is predicted to reach 10-11th magnitude. Like C/2020 M3, observers should watch to see if this comet brightens faster than expected.

 

P/2013 J4 (PANSTARRS) = P/2019 Y2 (Fuls) – Sam Deen suggested that short-period comets P/2013 J4 (PANSTARRS) and P/2019 Y2 (Fuls) were one and the same. The comet was only observed for a week in 2013 so its preliminary orbit was just different enough from reality to delay a linkage till now. The present apparition saw the comet come to perihelion on 2020 January 31 at 2.12 au. Presumably, the comet will be renamed P/PANSTARRS-Fuls.

 

As always, the Comet Section is happy to receive all comet observations, whether textual descriptions, images, drawings, magnitude estimates, or spectra. Please send your observations via email to < carl.hergenrother @ alpo-astronomy.org >.

 

Thank you to everyone who contributed to the ALPO Comet Section!

 

Stay safe and enjoy the sky!
- Carl Hergenrother (ALPO Comet Section Coordinator)


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#2 Aquarellia

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Posted 04 July 2020 - 12:38 AM

Another rich month for us, CN and Alpo comet fan!

Thank you so much Carl to share those information with us all

Michel



#3 Carl H.

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Posted 04 July 2020 - 09:25 AM

It was clear again this morning (July 4.5 UT) in Tucson. The sky was more transparent then yesterday with much less forest fire smoke in the direction of the comet.

 

This morning was the first time I could definitely see the comet naked eye. It looked stellar and was on the threshold of naked eye visibility, but it was there. This was also the first time I saw the tail first, rising from behind a nearby ridge, before seeing the head of the comet appear (in 30x125 binoculars).

 

I estimated the brightness of the comet at +1.7: magnitude with about a degree of tail in 10x50 binoculars. I tried to only measure the brightness of bright inner coma, though it is impossible to not be affected by some of the tail. I'm sure the error bars on my measurement is plus/minus a few tenths of a magnitude.

 

Note, that my magnitude estimates have been getting fainter with time: July 1.49, +1.0; July 3.49, +1.4; July 4.49, +1.7. I don't believe the comet is fading. In fact, visually it has looked just as strong on each of the nights. I believe the apparent fading is due to observational effects. On the 1st, I only had a few minutes to make a measurement and was rather rushed. The difference between July 3 and 4 may be due to the atmospheric extinction coefficient I used. On the 3rd, I assumed greater atmospheric extinction due to the obvious presence of forest fire smoke. Perhaps the extinction wasn't as great as I thought. When I use the same extinction values as on the 4th, I get a magnitude of +1.7 for the 3rd as well.

 

The comet was still visible in the 10x50s until 25 minutes before sunrise (sun was 5.3 degree below the horizons). In the 30x125s, the comet was visible until 17 minutes before sunrise (3.9 deg below the horizon).


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#4 cometguy

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Posted 05 July 2020 - 04:36 AM

Great job Carl, it would be interesting to compare binocular with naked eye estimates once the comet get's higher.  I don't believe the comet is fading either from my measurements, which might be similiar to what you would estimate with a telescope have been mag 2.2,2.2,2.0 over 3 mornings starting July 2, using Oscar Martín Mesonero's images.



#5 Zorbathegeek

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Posted 05 July 2020 - 06:29 PM

Carl, or anyone on here, could you explain the large divergence of magnitude estimates, regarding 88P/Howell, between visual, which have the comet around 11.7, and CCD which have the comet around 15.7 magnitude. 

 

Thanks, Ray.



#6 Carl H.

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Posted 06 July 2020 - 04:11 PM

Carl, or anyone on here, could you explain the large divergence of magnitude estimates, regarding 88P/Howell, between visual, which have the comet around 11.7, and CCD which have the comet around 15.7 magnitude. 

 

Thanks, Ray.

Ray, CCD brightness measurements can be many magnitudes fainter than visual estimates. There are number of reasons for this.

 

1 - Some CCD photometry only measure the inner coma and do not include the photometric contribution of the outer coma. This is especially true for those observations primarily meant for astrometry. CCD observers need to be careful and try to measure the full extent of the coma, which can be difficult in practice especially if the field-of-view is small or there is a background brightness gradient.

 

2 - CCD and visual observers can be observing different wavelengths. The eye's wavelength response is not replicated by any widely available filter. While V and Green filters are a good match for the eyes's daytime response, they don't extend as far into the blue as the dark adapted eye. As a result, the dark adapted eye detects more of the gas coma which can be substantial for many objects.

 

3 - Many CCD images are taken through a clear or Luminance filter. Since many CCD cameras are red sensitive, you again run into the issue of the CCD seeing different wavelengths than the eye.

 

Some CCD observers do a very good job and produce photometry that agrees with visual observers, for example, Thomas Lehmann (ICQ code LEHaaI) who wrote his own comet photometry software package.


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#7 Carl H.

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Posted 06 July 2020 - 04:42 PM

This morning (July 6) was cloudy. I did catch the comet for a few seconds in a gap in the clouds. That's makes 6 straight mornings of NEOWISE observing here in Tucson.

 

The previous morning (July 5) I estimated the following:

 

Naked eye

m1 = 1.4

Tail length = 0.5 deg

 

10x50 binoculars

m1 = 1.6

Tail length = 1.2 deg


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#8 Carl H.

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Posted 08 July 2020 - 04:29 PM

There are a whole bunch of NEOWISE related forums running now. So this info has been posted on other forums.

 

Visual observations at July 8.48 UT from NE of Tucson, AZ

 

Naked eye

m1 = 1.8

Tail length = ~1 deg

 

10x50 binoculars

m1 = 1.8

Tail length = ~2 deg

 

And finally I was able to get some images.

 

C2020F3 NEOWISE 2020-Jul-08 Carl Hergenrother.jpg

 

And a screen shot from the University of Arizona's Dept. of Atmospheric Sciences webcam.

 

C2020F3 NEOWISE 2020-Jul-08 UAz Webcam.jpg


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#9 Jure Atanackov

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Posted 15 July 2020 - 04:25 PM

Have there been any recent observations of C/2020 K8 (Catalina-ATLAS)? Kind of an interesting object, if it is within visual range by now; COBS only has CCD photometry from late June so far.

Jure


Edited by Jure Atanackov, 15 July 2020 - 04:29 PM.


#10 Carl H.

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Posted 16 July 2020 - 11:39 AM

Have there been any recent observations of C/2020 K8 (Catalina-ATLAS)? Kind of an interesting object, if it is within visual range by now; COBS only has CCD photometry from late June so far.

Jure

The MPC has observations up till July 9, but I don't trust the photometry. Now that the Moon is less of a problem in the morning sky, hopefully more observations will come in.



#11 Carl H.

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Posted 17 July 2020 - 06:10 PM

I was able to observe C/2020 K8 (Catalina-ATLAS) last night with the iTelescopes.net T16 0.15-m refractor. At July 17.10 UT, the comet was only V magnitude 15.8 with a 50' coma. While it would not surprise me if the comet were a magnitude brighter than my measure, it sure doesn't look like Catalina-ATLAS is brightening at a fast rate.

 

The latest orbit from the MPC suggests it is a dynamically new long-period comet. This also does not bode well for its performance or survival.




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