TALLY ENTRIES 681-690
|681. COMET ATLAS C/2019 N1 Perihelion: 2020 December 1.81, q = 1.705 AU
As we begin to approach the mid-way point of 2020 in this coronavirus-changed world, life continues on. I remain busy with "Ice and Stone 2020," and an article I wrote for Sky and Telescope about the 25th anniversary of my discovery of Comet Hale-Bopp has just come out in print. My younger son Tyler just earned his Bachelor's Degree in Electrical Engineering from New Mexico State University, although there was no formal graduation ceremony (and, in truth, he hadn't planned on attending anyway). For the time being my older son Zachary remains in Adelaide, South Australia, where his partner Karina is finishing up her Doctoral degree at Flinders University. Meanwhile, due to coronavirus concerns Vickie's father has now been living with us for over two months, and it is conceivable that that could become a permanent arrangement, although no decisions have been made as of yet.
We have had a decent amount of clear weather laterly, and I've been busy with comet observations, especially with the heavy pace of recent additions to my tally. Unfortunately, at least some of the hoped-for bright comet prospects have not panned out; Comet ATLAS C/2019 Y4 (no. 673), which should have been reaching its brightest right about now, has all but completely disintegrated, and Comet SWAN C/2020 F8 (no. 680), which I've been able to observe in morning twilight a couple of times but which remains poorly placed for observations from my latitude, also appears to be fading and diffusing out, and whether or not there will be anything of it left to see when it becomes somewhat accessible in my evening sky this coming week remains to be seen. Two additional comets that at present are only accessible from the southern hemisphere do show some promise: Comet Lemmon C/2019 U6 (no. 674) has brightened rapidly within the recent past and theoretically could be close to naked-eye brightness when it becomes accessible for me again near the end of June, and Comet NEOWISE C/2020 F3 (no. 676) also appears to be brightening steadily. I still have hopes that Comet NEOWISE will put on some kind of decent display during July to help me mark the anniversary of the Hale-Bopp discovery, but we'll have to wait and see what happens.
In the meantime, I've added one more comet to my tally. This object was discovered back on July 5, 2019, by the ATLAS program in Hawaii, at which time it was located in far northern circumpolar skies at a declination of +82 degrees and about 18th magnitude. It has remained in far northern skies ever since, traveling south to a declination of +60 degrees in early January 2020 before climbing back north to just north of declination +80 degrees in late April shortly after it had gone through opposition. Various reports I've read have indicated that it has been steadily brightening, and I made a couple of earlier unsuccessful attempts for it, however after taking a couple of recent images with the Las Cumbres Observatory network that indicated that it was close to being bright enough for visual observations I made an additional attempt under excellent sky conditions on the evening of May 21, and successfully spotted it as an extremely faint, small and condensed object of magnitude 14 1/2 near the limit of visibility, that exhibited the expected motion over the course of the next hour.
Comet ATLAS is traveling in a steeply-inclined orbit (inclination 82 degrees) and at this time is still a little over six months away from perihelion passage. For the time being it is still in northern circumpolar skies, in Draco at a declination of +75 degrees, and is traveling at half a degree per day, presently towards the south-southwest but turning more and more directly southward. After passing ten arcminutes northwest of the large galaxy NGC 4236 in early June and later crossing into Ursa Major, it travels through the eastern portion of the "bowl" of the Big Dipper late that month before crossing into Canes Venatici in late July and into Coma Berenices in mid-August; during the last week of that month it crosses the Coma Star Cluster (Melotte 111). By that time the comet will be getting low in the western sky after dusk and meanwhile may have brightened to about 13th magnitude.
After being in conjunction with the sun shortly before mid-October Comet ATLAS begins emerging into the morning sky around the time of perihelion passage in early December, at which time it will be located in southeastern Virgo and may have brightened to about 11th magnitude. Now traveling towards the south-southeast at somewhat over 40 arcminutes per day, it passes through eastern Hydra before crossing into Centaurus in mid-December and into Lupus at the beginning of January 2021; during the latter part of that month it enters southern circumpolar skies. The comet is nearest Earth (1.91 AU) in early February, at which time it will be located in Apus at a declination of -74 degrees; at the end of that month it passes just over 1 1/2 degrees from the South Celestial Pole. It travels back northward after that but remains in southern skies, and should remain visually detectable until perhaps April or May.
It does not appear, then, that I will be getting that many observations of this particular Comet ATLAS. When visible late this year it will be low in my southeastern morning sky, and it will probably only be accessible for a month of so -- perhaps six weeks -- before it drops below my southern horizon and I lose it. Given the uncertainty of all the goings-on right now, it will be interesting to see what the world, and my personal, circumstances are at that time.
INITIAL OBSERVATION: 2020 May 22.21 UT, m1 = 14.5, 0.3' coma, DC = 4-5 (41 cm reflector, 229x)
As I write these words shortly after mid-July 2020 I am quickly approaching the 25th anniversary of my discovery of Comet Hale-Bopp C/1995 O1 (no. 199) which, probably not surprisingly, turned out to be a major life-changing event for me. Among many, many other things, the discovery and the comet's appearance as a "Great Comet" a year and a half later made it possible for me to have a career, of sorts, and while life has certainly settled down for me during recent years, I have the satisfaction of knowing that I will have that object, and all that it has made possible, as my legacy.
And, as fate would have it, there is a relatively bright comet in the sky right now to help me mark the occasion: Comet NEOWISE C/2020 F3 (no. 676), which has been an easy and spectacular naked-eye object and which is the best comet I have seen since the one that bears my name. By a most interesting coincidence, it is closest to Earth (0.69 AU) on the very anniversary of the Hale-Bopp discovery (July 23). Meanwhile, the annual summer monsoon season, which was somewhat slow in starting this year but which seems to have picked up within the past few days, has made observing Comet NEOWISE a less frequent event than I might want, but I have still managed to obtain a few good observations and photographs (a couple of which I have posted in an update to that object's tally entry).
Although Comet NEOWISE has been gathering most of the attention right now, there are still other comets out there, including this new addition to my tally -- a comet which I never had any expectation of observing this year. It is a periodic object, originally discovered in September 1936 independently by Cyril Jackson at the (now closed) Union Observatory in South Africa and Grigory Neujmin at Simeis Observatory in Crimea in the then-Soviet Union. (Both of these individuals discovered other comets as well, including periodic comets that I have also observed.) The comet turned out to have an orbital period of 8.6 years (currently, 8.25 years), but due to unfavorably viewing geometry and uncertain calculations it was missed at the subsequent returns in 1945, 1953, and 1962 before being successfully recovered during the relatively favorable return in 1970. It was subsequently recovered during its returns in 1978, 1987, and 1995.
The 1995 return was a distinctly favorable one, and I was able to follow the comet visually for four months (no. 203); my first observation came less than two months after my discovery of Comet Hale-Bopp, and there were several nights, including the night of my first observation, when I observed both comets. Comet Jackson-Neujmin peaked at an unexpectedly bright 10th magnitude during that return, although, curiously, this took place over a month past perihelion passage and two months past its closest approach to Earth. This led to some speculation that the comet might have been in the act of disintegration, which was strengthened when it remained unrecovered during its subsequent returns in 2004 and 2012 (although it's fair to note that both of those returns, especially the latter one, were geometrically unfavorable).
In 2020 the comet was predicted to pass perihelion in late May, again under somewhat unfavorable viewing geometry, and especially after its failure to appear during the previous two returns there was no real expectation that it would be recovered. However, in early April Chinese researcher Hua Su reported that he had detected an apparent comet in images back to March 26 taken by the Solar Wind ANisotropies (SWAN) ultraviolet telescope aboard SOHO, the positions and motion of which were consistent with that expected of Comet Jackson-Neujmin. Armed with this information, Australian amateur astronomer Michael Mattiazzo imaged, in bright moonlight, a 11th-magnitude comet on April 7 that was soon verified as indeed being that object, although it was located over one degree away from its expected location which in turn indicated that its predicted time of perihelion was over two days off. (Curiously, on those very same SWAN images Mattiazzo detected another comet, which turned out to be a new discovery (C/2020 F8), and which became dimly visible to the unaided eye from the southern hemisphere in late April and early May before briefly becoming visible from the northern hemisphere (no. 680) around mid-May as it was disintegrating. Even more curiously, the two comets passed perihelion on the same day -- P/Jackson-Neujmin preceding the other by a little over two hours -- although they are completely unrelated to each other.)
The fact that Comet Jackson-Neujmin was located so far away from its expected position, and furthermore was over six magnitudes brighter than expected, has further strengthened speculation that it may be going through its "death throes," and at the very least had been undergoing a major outburst that might quickly subside. However, the comet brightened to almost 10th magnitude around the time of perihelion passage, and although observation reports have been rather spotty, it seems to have faded only slowly and gradually since that time.
The comet was south of the sun at an elongation not much larger than 30 degrees at the time of its recovery, and thus observations were restricted to the southern hemisphere. This has remained the case ever since, with the elongation only increasing very gradually, and I suspected rather strongly that it would fade beyond the range of visual observations by the time it finally became accessible from my location around mid-July. However, the slow rate of fading has suggested that visual observations for me might indeed now be possible, especially after examining a set of images I took with the Las Cumbres Observatory network a few days ago (within which it appeared rather prominent), and during the past few mornings I have tried to make attempts for it. The monsoon conditions have made this a problematical and at times frustrating exercise, and on a couple of mornings I briefly observed faint suspects but was then clouded out before I could verify anything. Finally, on the morning of July 21 the clouds held off, and I successfully observed the comet as a small and moderately condensed object of magnitude 12 1/2. (While it is possible that I did in fact see the comet on one or both of the previous occasions, since I am unable to verify this one way or the other I do not consider these as being valid "observations.")
I am not at all certain how many additional observations I may be able to obtain of Comet Jackson-Neujmin this time around, or even if I will be able to observe it again. It remains south of the sun and with a present elongation of 50 degrees (being located five degrees southeast of the Hyades star cluster in Taurus) it is still very low in my eastern sky before dawn; since it is traveling due eastward at 40 arcminutes per day the elongation will continue to increase only gradually. Furthermore, since the comet is now almost two months past perihelion it will almost certainly continue fading, and with the current monsoon conditions I will likely not be able to attempt many more observations. At best, I will probably only see it another two or three times before it fades beyond visual range.
The next return of Comet Jackson-Neujmin, in 2028 (perihelion early September) is a very favorable one, with a minimum distance from Earth (0.49 AU) taking place later that month. If the comet maintains the same intrinsic brightness then that it has now, it could be a relatively bright object close to 8th magnitude. However, if as I suspect we are indeed now seeing the comet's "death throes," or at the very least a significant extended outburst, then it will likely be significantly fainter than that, or perhaps not even visible at all. Whether or not I am still actively observing comets at that time also remains to be seen, so it is distinctly possible that whatever observations of this comet I might be able to make over the next couple of weeks will be my last.
INITIAL OBSERVATION: 2020 July 21.44 UT, m1 = 12.5, 1.2' coma, DC = 4 (41 cm reflector, 70x)
For the second time in a row, a comet that I had no expectation of seeing this year gets added to my tally. I discuss this famous comet in the "Countdown" entry for its 2007 return (no. 402) and also in its "Comet of the Week" presentation for "Ice and Stone 2020." After observing it during its favorable return in 2013 (no. 531), I followed it for two months during its rather mediocre return in 2017 (no. 610), however during its return this year its visibility was restricted to post-perihelion, which is usually the exclusive domain for observers in the southern hemisphere. Despite this, I nevertheless managed to pick it up on its way out before it faded from view. While I also observed it post-perihelion during its 1997 return (no. 231), that happened while I was visiting Australia (in significant part to view Comet Hale-Bopp C/1995 O1 (no. 199) after it had left the northern hemisphere's skies), and thus this is the first time that I have observed Comet Encke post-perihelion from the northern hemisphere. Overall, this is the 13th return at which I have observed Comet Encke.
As Comet Encke approached perihelion this year it did so from behind the sun (as seen from Earth), and thus was inobservable from the ground. It spent several weeks, meanwhile, within the field-of-view of the LASCO C3 coronagraph aboard SOHO, however it remained too faint for visibility; even when it exited the C3 field on June 18 -- at which time it should have been close to 7th magnitude -- it still was not visible. I was concerned that this might be a sign that the comet was close to disintegrating, however just before the end of June observers in the southern hemisphere began picking it up in evening twilight as a 7th-magnitude object. Historically, Comet Encke tends to diffuse out and fade fairly rapidly as it recedes from perihelion, and by the time moonlight began to interfere during the third week of July the southern hemisphere observers were reporting it to be around 9th magnitude, pretty much as expected. The comet was closest to Earth (0.62 AU) on July 30.
By the end of the first week of August, after the moon (which was full on August 3) had cleared from the evening sky, Comet Encke had started to become accessible from my location, very low in the southwest during late dusk, but due to its historical trend of rapid fading and diffusing out after perihelion I had no expectation of seeing it; indeed, on two previous returns that were similar to this year's I had attempted it under similar circumstances, unsuccessfully. However, I read a recent report from an observer in the southern hemisphere that indicated the comet was still visually detectable near magnitude 10 1/2, so after waiting through a couple of cloudy nights -- this being monsoon season here in New Mexico -- I was able to attempt it under somewhat mediocre sky conditions on the evening of August 7, and to my surprise I seemed to see a vague and diffuse object of 11th magnitude at the comet's expected position. Under somewhat better sky conditions the following evening I was clearly able to detect the comet -- thus confirming the previous night's suspect -- despite its being less than 10 degrees above the horizon and within the brightened background sky of late twilight.
At the time of my observations Comet Encke was located in eastern Hydra, about two degrees south of the star Gamma Hydrae. It is traveling towards the east-southeast, presently at two degrees per day but decreasing to slightly over one degree per day by the end of August; it crosses into northeastern Centaurus on August 19 and then into Lupus two days later before entering Scorpius on September 2. While it gradually becomes slightly higher in my evening sky over time, it is also continuing to fade and diffuse out, and especially with the monsoon conditions prevalent right now it is somewhat likely that I will not be observing it again. I'm not complaining, though; I'm quite glad to have gotten it this time around!
Comet Encke's next return (perihelion late October 2023) is much more favorable for the northern hemisphere; it will be conveniently accessible in the morning sky before perihelion and should reach at least 8th magnitude, possibly 7th. Provided that I am still observing comets then -- and, at this time, I plan to be -- I should be able to say "hello!" to this comet again, under distinctly better viewing circumstances than this year's. Hopefully the external world's circumstances will be better as well.
CONFIRMING OBSERVATION: 2020 August 9.13 UT, m1 = 10.9 (extinction corrected), 3' coma, DC = 1-2 (41 cm reflector, 70x)
In this bizarre pandemic-laden summer of 2020, the comet activity has been relatively high, although the annual summer monsoon here in New Mexico has curtailed my observations quite a bit. Following its spectacular naked-eye display last month, Comet NEOWISE C/2020 F3 (no. 676) has now faded, although it remains a decent comet in binoculars, near 7th magnitude and still with a respectable (albeit faint) dust tail. A handful of other moderately bright comets have also inhabited the evening sky lately, although they, too, are fading, with the exception of Comet 88P/Howell (no. 678) which is presently around 10th magnitude and which may brighten by perhaps another magnitude by the time of its perihelion passage five weeks from now. The morning sky, meanwhile, has been relatively quiet, the only comet I've been observing lately being 29P/Schwassmann-Wachmann 1 (no. 498), which underwent one of its characteristic outbursts in late July and which is presently observable near 13th magnitude, although its coma has now grown rather large and diffuse.
Another comet has now joined the morning sky, although it is faint and it probably won't be around for very long. It was originally detected as an apparently asteroidal object by the Catalina Sky Survey in Arizona on three separate mornings (May 25, 28, and 29, 2020) -- all under separate preliminary designations -- and then independently by the ATLAS program in Hawaii on June 7. Robert Weryk of the University of Hawaii then successfully linked all four reports as being the same object and, based upon its orbit, suggested it might be a comet; this was soon verified by other observers. At the time of its discovery the comet was a very faint object of 19th magnitude but it has brightened steadily since then; a couple of recent sets of images I've taken with the Las Cumbres Observatory network suggested it might be bright enough for visual observations, and I made an unsuccessful attempt on the morning of August 1. After the moon had cleared from the morning sky I tried again on August 18, and successfully detected it as a faint, vague, and diffuse object of 14th magnitude that traveled rapidly across the telescopic field of view during the half-hour that I followed it. At that time it was located in western Gemini crossing the supernova remnant IC 443.
Comet Catalina-ATLAS was closest to Earth (0.60 AU) on August 14 and the time of my initial observation was racing towards the east-southeast at three degrees per day. It slows down somewhat over the next few weeks as it continues crossing southern Gemini (passing two degrees south of Venus on August 22) before crossing into Cancer late this month and into Hydra in early September (traversing the "head" of that constellation as it does so) and finally crossing into southern Leo shortly before the end of that month. Meanwhile, the elongation decreases fairly rapidly, to below 40 degrees by the last week of August and to below 30 degrees after the first week of September.
The comet's relatively small perihelion distance is potential cause for excitement, and ostensibly it might brighten by one or two magnitudes by the time it starts to disappear into morning twilight. However, it appears to be quite faint intrinsically, and it may very well start to disintegrate as it approaches perihelion -- although, thus far, it has not exhibited any signs of doing so. If it does start to disintegrate, it is at least conceivable that it might undergo a temporary surge in brightness, like that exhibited a couple of years ago by Comet PANSTARRS C/2017 S3 (no. 647) and earlier this year by Comet ATLAS C/2019 Y4 (no. 673). Meanwhile, if it does manage to survive perihelion passage it recedes from the inner solar system on the far side of the sun from Earth, and while it remains in the morning sky it also remains at a small elongation and in any event will almost certainly be too faint for visual observations.
INITIAL OBSERVATION: 2020 August 18.44 UT, m1 = 14.2, 0.8' coma, DC = 2 (41 cm reflector, 229x)
I have written often in previous tally entries of the summer monsoon that strikes New Mexico during the months of July and August, producing a significant fraction of our annual rainfall and, accordingly, a fairly large number of cloudy nights. Normally the monsoon starts to sputter somewhat during the latter part of August, although it usually continues on in some fashion well into September -- indeed, the most intense monsoon thunderstorm I have ever experienced occurred in mid-September seven years ago and led to significant flooding in my neighborhood. In terms of rainfall this year's monsoon has perhaps been a bit below average, although we still have had the usual cloudy nights. Furthermore, several major fires in California and Colorado have generated a large amount of smoke that has drifted over and remained over this area for well over a week now, with the result being that even when the nights have been "clear" the overall sky transparency has been mediocre at best. I accordingly have not had much opportunity to observe comets (or any other astronomical objects) within the recent past.
With the full moon coming up next week I wanted one more session with the comets in the morning sky, so despite the less-than-ideal sky conditions I spent the morning of August 26 looking for several comets, including a couple of comets I have been following -- in the process obtaining what will quite likely be my last observation of the previous comet -- as well as three comets that I have not seen (or, at least, have not seen yet). One of these three comets was this object, which had been discovered on June 27, 2020 by the ATLAS program in Hawaii. At that time it was a very dim object of 19th magnitude, but I expected it to become bright enough for visual observations around the time of its perihelion passage, and indeed I had expected to begin making attempts for it next month. A recent report suggested, however, that it might already be bright enough for such attempts, but when I looked for it I couldn't see anything convincing. The mediocre sky conditions, the fact that the comet was quite deep in my southern sky (at a declination of -36 degrees), and was also close to some bright field stars, all probably contributed to my failure to see it, for a couple of images I took with the Las Cumbres Observatory network shortly thereafter indicated that it might very well be within visual range. On the following morning the comet was in a better star field, and moreover the sky conditions were somewhat better than they had been the previous morning, and I successfully detected it as a very faint and slightly condensed object a little fainter than magnitude 13 1/2. Since that time I have read very recent reports from and seen images taken by observers in the southern hemisphere -- where the comet is much higher in the sky -- that suggest the comet may now be even brighter, perhaps close to 11th magnitude.
At present Comet ATLAS is located in the southern
|constellation Fornax, and is near its southernmost declination. For the time being it is traveling mostly eastward, but over the next few weeks it gradually starts turning more and more northward, crossing into Eridanus shortly after mid-September, into Lepus in mid-October, then into western Orion at the end of that month (and passing just over one degree east of the bright star Rigel during the first week of November and 20 arcminutes east of the star Gamma Orionis (Bellatrix) in mid-November). At that time the comet will be at its nearest to Earth (0.36 AU) and will be traveling almost due northward at 80 arcminutes per day; it is at its stationary point a week later, crosses into Taurus in late November, into Auriga in late November (passing one degree west of the star Beta Tauri in the process) and is at opposition during the second week of December. The comet passes through its other stationary point at the very end of 2020 and passes half a degree west of the bright star Capella three days later. It reaches a maximum northern declination just south of +49 degrees at the end of January 2021 and thereafter begins a slow turn towards the east-southeast, but|
|Comet ATLAS C/2020 M3 on August 26, 2020 -- one day before my first successful visual observation -- as imaged by the Las Cumbres Observatory facility at Haleakala Observatory in Hawaii. The bright star (7th magnitude) at upper left is HD 17169.|
remains in Auriga for the next few months. Based upon the brightness I observed it might peak near 10th or 11th magnitude around the time of perihelion passage and its closest approach to Earth, and if one takes the recent reports from the southern hemisphere at face value, these would suggest the comet might even become as bright as 8th magnitude. In any event, it should remain visually detectable through the first one to two months of 2021 as it recedes from the sun and Earth.
Comet ATLAS turns out to be a Halley-type object, with the most recent calculations indicating an approximate orbital period of 139 years. This suggests that the previous perihelion passage might have taken place sometime during the early 1880s, and perhaps depending upon what time of year perihelion occurred it might have been detectable by the comet hunters of that era. As it is, there do not seem to be any comets from that time frame that appear to be good candidates for the previous return of Comet ATLAS; the closest match in terms of orbital elements is Comet Dodwell-Forbes 1932n, which reached a peak brightness near 8th magnitude around the time of its perihelion passage at the very end of 1932. In addition to the discrepancy in orbital period -- and, indeed, calculations indicate that Comet Dodwell-Forbes' orbital period is about 262 years -- while some of its orbital elements are quite similar to those of Comet ATLAS, others are different enough to suggest that the similarities are likely nothing more than coincidental. Perhaps anyone who might be around to view Comet ATLAS around 2160 would be able to shed some further light on this issue . . .
INITIAL OBSERVATION: 2020 August 27.42 UT, m1 = 13.7, 0.8' coma, DC = 2 (41 cm reflector, 229x)
UPDATE (September 16, 2020): Following my initial observation of Comet ATLAS, clouds and weather prevented any further observations up until the time moonlight washed out the morning sky, and then after waiting out the moon I had to contend with several nights of extremely hazy skies due to smoke from fires in California and elsewhere. I finally had some relatively decent sky conditions this morning, and could tell that the comet is indeed a relatively large and diffuse object of 11th magnitude, consistent with the reports from the observers in the southern hemisphere, along with various recent images I have seen. If the comet brightens "normally" from here on out it should reach perhaps 9th magnitude around the time it is closest to the sun and Earth a month and a half from now.
MOST RECENT OBSERVATION: 2020 September 16.45 UT, m1 = 10.8, 4' coma, DC = 3 (41 cm reflector, 70x)
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