ALAN'S COMETS

TALLY ENTRIES 731-740

731. COMET PANSTARRS C/2019 U5          Perihelion: 2023 March 29.85, q = 3.624 AU

As I write these words, the calendar year of 2022 is drawing to its close. For me personally, 2022 was a relatively quiet and uneventful year -- perhaps not a bad thing at my present age -- with the biggest happenings being my older son Zachary's moving back to Australia in August (although he and his girlfriend Karina paid a visit back here earlier this month) and an unpleasant physical ailment I had to deal with, also in August. On the wider national and international scene many things remain quite unsettled, although there were some occasional hopeful signs here and there. From the perspective of astronomy and space 2022 could be considered a positive and productive year, which included the successful DART mission (which I discuss in my tally entry for (65803) Didymos (no. 725)), the recently-completed unmanned Artemis 1 mission (which, despite my lifelong interest in and advocacy for human spaceflight, I am actually somewhat ambivalent about, since I have come to feel that there are a host of serious issues here on Earth that we as humans need to confront and deal with before we can seriously consider expanding into space, and in any event I believe any decisions to such effect should be left to the generations that follow mine), and the successful deployment of the James Webb Space Telescope, which among many, many other wondrous accomplishments managed to image Comet Hale-Bopp (no. 199) -- at the enormous heliocentric distance of 46.2 AU -- in early July.

Before the year ends, I have managed to add one additional comet to my tally, giving me my 19th tally addition and, overall, my 26th comet, for the year, something that strikes me as at least somewhat remarkable since I now consider myself "semi-retired" from visual astronomical activities. The comet in question was discovered by the Pan-STARRS survey in Hawaii as far back as October 22, 2019, at which time it was located at a heliocentric distance of 10.4 AU and almost 3 1/2 years away from perihelion passage. At the time of its discovery it appeared as a stellar object near 21st magnitude and didn't exhibit any cometary activity, and was accordingly announced under the designation A/2019 U5. About a year later large telescopes began to detect weak activity, and in April 2021 it was formally re-designated as a comet.

Comet PANSTARRS is traveling in a steeply-inclined retrograde orbit with an inclination of 113.5 degrees. It was at opposition in early May 2022, and according to various reports I've read and images I've seen it was apparently close to 14th magnitude around that time, i.e., bright enough for visual observations, and had I been operating at my previous level of activity I almost certainly would have looked for it and, more than likely, would have successfully detected it. As it was, I waited until after it went through conjunction with the sun (23 degrees north of it) in mid-October and subsequently re-emerged into the morning sky; again, various reports and images (including a set of images I obtained via the Las Cumbres Observatory network on December 20) indicated it was bright enough to detect visually. On the morning of December 22 I successfully did so; it appeared as a small, moderately condensed object slightly brighter than 14th magnitude.

At present the comet is located in central Virgo some four degrees northwest of the star Tau Virginis and, having just passed through a stationary point, is traveling almost due southward at a relatively slow 6 arcminutes per day. Over the coming weeks it accelerates and curves toward a more directly westward motion, and will pass through opposition (and be at its closest to Earth, 2.63 AU) during the latter part of March, when it will be located three degrees west-southwest of the star Eta Virginis and traveling at half a degree per day. (At that time it will also be close to perihelion passage, making the viewing geometry about as favorable as it can be.) The comet crosses into southeastern Leo in early April and into Sextans a month later, but not too long thereafter it starts curving more directly southward as it goes through its other stationary point at the beginning of July. By that time it is becoming inaccessible from my latitude, although observers in the southern hemisphere will still be able to follow it; meanwhile, it enters Hydra in early August and is in conjunction with the sun (25 degrees south of it) shortly before the end of that month. It begins emerging into the southern hemisphere's morning sky by November and is at opposition again in early February 2024, when it will be located at a declination of -46 degrees about three degrees southwest of the star Lambda Velorum.

Since it is faint and distant and otherwise relatively nondescript, I will probably only be observing Comet PANSTARRS on an occasional basis over the next few months. It may brighten by perhaps a half-magnitude or so by the time of perihelion passage, and I may follow it for perhaps a month or so thereafter, but once it starts fading and getting low in my southwestern sky I will probably be done with it. Observers in the southern hemisphere may still be able to detect it visually as it approaches its opposition in early 2024, but it will likely soon fade from view for them as well.

INITIAL OBSERVATION: 2022 December 22.46 UT, m1 = 13.7, 0.6' coma, DC = 4-5 (41 cm reflector, 229x)

 

732. COMET 118P/SHOEMAKER-LEVY 4          Perihelion: 2022 November 24.33, q = 1.829 AU

My first tally addition of 2023 is a long-time acquaintance. After its discovery by the team of Carolyn and Eugene "Gene" Shoemaker and David Levy in 1991, I observed it during its subsequent return in 1996-97 (no. 222), during which it reached a peak brightness near 12th magnitude and for a time shared the sky with Comet Hale-Bopp C/1995 O1 (no. 199). Following an unfavorable return in 2003 I observed it again during its return in 2009-10 (no. 464) as a part of "Countdown," and I give a more detailed discussion of its history in its "Countdown" entry. The comet was somewhat fainter than I expected during that return, reaching a peak brightness near 13th magnitude.

As I indicated in its "Countdown" entry, Comet 118P returned under unfavorable geometry in 2016 (although it was duly recovered and, according to the astrometric measurements that were reported, reached a peak brightness perhaps near 16th magnitude), and then in 2020 made a moderately close approach to Jupiter which shortened its orbital period and its perihelion distance. On the present return it was recovered on May 25, 2021 by a team of French astronomers utilizing a remotely-controlled telescope in Chile, although there apparently were no further observations until August of that year, and meanwhile following its conjunction with the sun in late March 2022 it has been followed somewhat extensively since emerging into the morning sky three months later. Although -- again, as I indicated in its "Countdown" entry -- the reduced perihelion distance and the favorable viewing geometry this time around suggested it might become at least somewhat bright, the comet instead seems to have continued the overall fading trend it has exhibited during previous returns, as the reports and images I saw, including some occasional images I took via the Las Cumbres Observatory (LCO) network, indicated it was remaining too faint to be worth attempting visually. However, some of the most recent reports I've seen have suggested it might have brightened some during the recent past, and some additional LCO images I took in mid-January 2023 seemed to support this, so after having to wait out a series of "mini"-snowstorms that were moving through the area I made my first visual attempt on the evening of January 18, and successfully detected it as a diffuse, slightly condensed object of 13th magnitude.

Although Comet 118P passed through perihelion almost two months ago, it is right now as its closest approach to Earth (0.92 AU) and will be at opposition just before the end of January, and accordingly is probably as bright as it is going to get. It is currently located in southern Cancer some 3 1/2 degrees west of the open star cluster M67 and is traveling towards the north-northwest at approximately 15 arcminutes per day; after passing through its stationary point (about 7 degrees north-northwest of its present location, and 4 1/2 degrees southwest of the Praesepe, or "Beehive," star cluster M44) shortly before the end of February it begins traveling just northward of due east and passes a little over one degree north of the center of M44 at the end of March. Since the comet is now pulling away from both the sun and Earth it will likely start fading pretty quickly, and at most I will probably only see it another one or two times.

While I wasn't at all sure I would even be looking for, let alone seeing, Comet 118P this time around, as I wind down my visual observational activities I am actually quite glad that I was in fact able to observe it and add it once again to my tally. Via their many discoveries both the Shoemakers and David Levy made frequent appearances on my tally during much of my earlier years, but during more recent years their only appearances have been due to returns of some of the periodic comets they found; indeed, this is the first time that either of their names appear since this comet's previous return. The Shoemakers terminated their survey program at Palomar in the mid-1990s, and Gene tragically died in a car accident in Australia in 1997, while Carolyn passed away just a year and a half ago. David Levy, meanwhile, remains active in astronomical educational and promotional activities, although in the teeth of all the current survey programs he has not made any comet discoveries since his most recent one in 2006 (Comet 255P/Levy P/2006 T1, no. 397); I last saw him at the 50th Anniversary (and penultimate) Riverside Telescope Makers Conference in 2018. This return of Comet 118P gives the Shoemakers their 21st entry on my lifetime tally and David Levy his 18th, which currently puts them in 4th and 6th place, respectively, for most appearances. I don't expect any more appearances for either of them.

INITIAL OBSERVATION: 2023 January 19.16 UT, m1 = 13.2, 1.4' coma, DC = 2-3 (41 cm reflector, 70x)

 

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