COUNTING COMETS

TALLY ENTRIES 531-540

531. COMET 2P/ENCKE          Perihelion: 2013 November 21.69, q = 0.336 AU

I discuss this famous comet, and my own personal history with it, in its "Countdown" entry for its 2007 return (no. 402). As I indicated there, the 2013 return was very favorable, being similar to the return of 1980 during which it reached close to magnitude 6 1/2 and became the first comet to be detected successfully via radar. (I should add, incidentally, that I did manage to make a couple of unsuccessful post-perihelion attempts at the very unfavorable return in 2010.) The comet passed 0.48 AU from Earth on October 17 and was well placed in the northern hemisphere's morning sky throughout this return.

This is now the 11th return of P/Encke that I have observed. I made my first attempt on the morning of September 6 and successfully picked it up as a vague, diffuse object just fainter than 13th magnitude. It brightened more-or-less as expected since then, being close to magnitude 10 1/2 in early October, and then reached 7th magnitude and easy binocular visibility by the beginning of November. I obtained my final observation on Novembet 11, after which it disappeared into the dawn. Curiously, the comet passed only 0.025 AU from Mercury on November 18, and (along with Comet ISON C/2012 S1 (no. 529)) was imaged by the MESSENGER spacecraft in orbit around that planet.

532. COMET LOVEJOY C/2013 R1          Perihelion: 2013 December 22.73, q = 0.812 AU

My friend Terry Lovejoy in Queensland discovered his fourth comet on the morning of September 7, 2013. I discussed Terry and his first two discoveries in the "Countdown" entry for his first comet, C/2007 E2 (no. 404), and then a few years later his third discovery, the Kreutz sungrazing Comet C/2011 W3, became a spectacular naked-eye object from the southern hemisphere and then became my 500th comet when the ghostly remnant of its coma had traveled far enough north for me to see. As he relates in his account, Terry found his latest comet on a series of CCD images he took on the 7th and verified these the following morning. After seeing this object listed on the Minor Planet Center's Near-Earth Object Confirmation Page, and then corresponding with him privately, I successfully located his comet on the morning of the 9th, when it was located 6 1/2 degrees east of the Great Orion Nebula M42; it appeared as a faint, small, and moderately condensed object of 14th magnitude.

Comet Lovejoy is traveling in a fairly steeply-inclined direct orbit (inclination 64 degrees), and has been well placed for observation from the northern hemisphere ever since its discovery, although it has remained in the morning sky throughout that time. It has brightened rapidly since its discovery, to 11th magnitude in early October, to 7th magnitude later that month, and for most of November and into December it has been a naked-eye object of 5th magnitude. It passed just under 0.40 AU from Earth on November 19 and was at its farthest north, declination +43 degrees, six days later, and by the time the comet passes perihelion in late December its declination will have dropped to +25 degrees and, due to its increasing distance from Earth, it will probably have faded by about a magnitude. It should then continue dropping southward and fading, remaining visually detectable for perhaps the first two months or so of 2014.

Comet Lovejoy has the personal distinction to me of being the comet of my 6000th visual comet observation, on the morning of November 29. It is also the comet that I will end up associating with the passing away of my mother, Ruth Perkins, who did so on December 7 at the age of 94; I observed the comet the following morning. Curiously, another naked-eye comet (Ikeya-Zhang P/2002 C1 (no. 301)) was in the sky when my father passed away in March 2002.

533. COMET LINEAR C/2012 X1          Perihelion: 2014 February 21.63, q = 1.599 AU

The LINEAR program in New Mexico discovered this comet on December 8, 2012, at which time it was 14 1/2 months from perihelion passage and located 5.20 AU from the sun. This is the last comet discovered by LINEAR as of this writing, and it appears that LINEAR ceased, or at least significantly curtailed, observations at the end of 2012. Since going on-line in early 1998 LINEAR has discovered 214 named comets, and this is the 61st of those comets that I have observed; since one of these is a periodic comet that I've seen on two returns the name "LINEAR" appears on my tally 62 times thus far. Even if LINEAR does not discover any more comets there are several periodic comets that the program has discovered, some of which I have already seen as well as some I have not yet seen, that I expect to observe on returns in the future, so the name "LINEAR" should still continue to appear on my tally from time to time.

This latest Comet LINEAR brightened slowly over the months subsequent to its discovery, and was reported as being between 16th and 17th magnitude when the last observations were obtained in late June 2013 prior to its conjunction with the sun (27 degrees north of it) in mid-September. By the latter part of October it was being to re-emerge into the morning sky, and was expected to be around 14th magnitude; however, when Japanese amateur astronomer Hidetaka Sato imaged it on the morning of October 20 he reported it as being as bright as magnitude 8 1/2, and suggested it might be in outburst. Despite low altitude and bright moonlight I was able to observe it visually two mornings later, and indeed saw it as being close to 8th magnitude, with a high-surface brightness coma three arcminutes in diameter. Over the course of the subsequent week it maintained this overall brightness but the coma doubled in size, and this behavior, combined with various images I have seen wherein the comet bears a striking resemblance to the appearance exhibited by Comet 17P/Holmes (no. 414) shortly after its large outburst in October 2007, strongly suggests that this is indeed another example (albeit on a somewhat smaller scale) of the same outburst phenomenon.

The comet is traveling in a moderately-inclined orbit (inclination 44 degrees) with an approximate period of slightly over 1900 years (and thus is not a first-time visitor from the Oort Cloud). It remains in the morning sky for the next several months, traveling slowly towards the east-southeast, and even when at perihelion its elongation from the sun will be only 51 degrees. Not too long thereafter it begins a turn towards the south, and when nearest Earth (1.55 AU) in late June it will be at a declination of -30 degrees and approaching its stationary point. The comet is at opposition shortly after mid-August, by which time its declination will be -49 degrees, and it drops south of declination -50 degrees by the end of that month.

By mid-December the outburst had seemingly subsided, although the comet remains a moderately bright object near magnitude 9 1/2. Ostensibly, around the time of its perihelion passage it should be perhaps a magnitude or so brighter than it is now, and could remain visually detectable for several months thereafter. However, its recent outburst activity suggests that any brightness predictions may be rather problematical, and we will just have to wait and see what the comet does over these next few months.

534. COMET 290P/JAGER P/2013 N1          Perihelion: 2014 March 12.48, q = 2.156 AU

This comet was originally discovered in October 1998 (no. 253) by Michael Jager, an amateur astronomer and astrophotographer who resides in the Wachau valley in eastern Austria. He has specialized in photographing and imaging comets for over 30 years and is widely regarded as one of the best in the world at this; I used some of his images for the image gallery pages in "Countdown." This is his only comet discovery, however in 1994 he discovered the first-known secondary component of Comet 141P/Machholz 2 (no. 193) on that object's discovery return, and subsequently independently co-discovered two of the other secondary components. (His original secondary component also returned with the main comet at P/Machholz 2's subsequent return in 1999 (no. 273), but soon faded out.) Jager has also occasionally recovered periodic comets making expected returns, and his name appeared within "Countdown" in this context as well.

Jager's comet was about 12th magnitude at discovery, and reached a peak brightness near magnitude 10 1/2 in early 1999 prior to passing perihelion in March of that year. It was found to be periodic, with an orbital period of slightly over 14.9 years. The comet turns out to have had an interesting history prior to its discovery: for several centuries it traveled in a near-circular orbit nearly 10 AU from the sun (i.e., slightly beyond Saturn's orbit), with a period near 31 years. A series of approaches to Saturn beginning in 1962 nudged it in slightly closer, until a very close approach to Saturn (0.017 AU) in July 1991 placed the comet in its present orbit and brought it close to the sun, possibly for the first time.

At its subsequent return Jager's comet was recovered on July 12, 2013, by Krisztian Sarneczky at the Piszkesteto Station of the Konkoly Observatory in Hungary; he subsequently identified pre-recovery images that had been taken four days earlier by Gabor Marschalko with the same telescope. The viewing geometry is almost identical to that of the discovery return, with the respective perihelion dates being only two days apart; it should remain well-placed for observation for the next few months, with opposition occurring near the end of December. Not surprisingly, however, the comet seems to be somewhat fainter than it was in 1998-99; after a handful of unsuccessful attempts during October I finally succeeded in picking it up on the early morning of November 7 as a very faint and small object of 14th magnitude. Based upon this, I expect it may reach a peak brightness near 12th magnitude in early January around the time it is nearest Earth, and remain visually detectable until perhaps March.

On its way out from perihelion Jager's comet again passes somewhat close to Saturn (0.52 AU) in June 2020, an encounter which slightly increases its perihelion distance (to 2.3 AU) and its orbital period (to 15.5 years), but thereafter it remains in a relatively stable orbit for a few more centuries. The next return (perihelion July 2029) is quite unfavorable, however the following one (perihelion January 2045) is very favorable; whether or not I'm still alive, and still observing comets, at the age of 86 remains to be seen, however.

535. COMET NEVSKI C/2013 V3          Perihelion: 2013 October 29.91, q = 1.387 AU

Vitali Nevski of Belarus was one of my mentors back during "Countdown," and is also one of the co-discoverers of Comet ISON C/2012 S1 (no. 529). On November 7, 2013, he discovered his first comet to have his name, using the same International Scientific Optical Network facility at Kislovodsk, Russia, from which he and Artyom Novichonok discovered Comet ISON. I happened to notice this comet on the Minor Planet Center's new Possible Comet Confirmation Page a few hours later, and early that same morning I successfully observed it as an extremely faint, vague and diffuse object of 14th magnitude. This observation came less than two hours after I had first picked up the previous comet, and marks the second time in 2013, and 26th time overall, that I have added two or more comets to my tally in the same night.

The comet was already receding from perihelion at the time of its discovery and ostensibly was near its peak brightness, and I considered it rather possible that I wouldn't be seeing it again. However, when I attempted it four mornings later it had clearly brightened, being close to magnitude 12 1/2 and definitely appearing more "solid" than it had earlier. Reports and images from other observers in subsequent days indicated that the comet continued to brighten and clearly seemed to be undergoing an outburst, and when I was able to view it again on the 15th (after some cloudy weather) it had brightened to magnitude 9 1/2 and was faintly visible in binoculars; the overall coma was quite large and diffuse. By early December it had faded by about a magnitude, but thus far it has maintained its large and diffuse coma. It is difficult at this poit to predict just how long it may remain visually detectable, but for what it's worth, according to the most recently calculated orbit Comet Nevski is nearest Earth (0.86 AU) shortly after mid-December and will be at opposition (at a declination near +55 degrees) in early March 2014, although I suspect it will have faded from visibility well before then.

Meanwhile, orbital calculations now indicate that Comet Nevski is a Halley-type object, with an approximate orbital period of 45 years. Unusual brightness changes are not unheard-of in Halley-type comets, although normally not to the degree that this comet has exhibited.

536. COMET BOATTINI C/2013 V1          Perihelion: 2014 April 21.23, q = 1.661 AU

This comet was discovered on November 4, 2013, by Andrea Boattini during the course of the Catalina Sky Survey in Arizona. Andrea's name showed up several times during "Countdown," beginning with his first comet discovery; this is the 25th comet he has discovered that has received his name, and the fifth of those that I have seen. I noticed it as a moderately bright object listed on the Minor Planet Center's Possible Comet Confirmation Page, and a couple of days after its discovery made an attempt for it, but didn't see anything convincing. After the subsequent full moon I attempted it again on the early morning of December 4, and successfully observed it as a small and moderately condensed object of 14th magnitude.

This newest Comet Boattini was at opposition shortly before the end of November, and will be nearest Earth (1.47 AU) in late December. It should reach a peak brightness of 12th or 13th magnitude during the first few months of 2014, although by the time of perihelion passage it will be getting quite low in the northwestern sky after dusk. By the middle of May the comet will have entered northern circumpolar skies and thus it may remain accessible for a while longer as it fades, although it will continue to remain fairly low in the northwestern sky throughout that time.

537. COMET SIDING SPRING C/2013 A1          Perihelion: 2014 October 25.30, q = 1.399 AU

From a purely scientific perspective, this is one of the most fascinating comets that have appeared in the inner solar system in some time. It was discovered on January 3, 2013 by Rob McNaught during the course of the Siding Spring survey in New South Wales; because it was not immediately apparent that the new object was a comet, it was given the name "Siding Spring." Being over 21 1/2 months away from perihelion passage and located 7.20 AU from the sun at discovery, the comet was a relatively faint object of 18th or 19th magnitude, but has brightened steadily since then, and after conjunction with the sun in early June has been accessible for the past several months, passing through opposition in late November. After a handful of unsuccessful attempts beginning in early October I succeeded in locating the comet on the evening of December 24 as an extremely faint object slightly fainter than 14th magnitude.

Comet Siding Spring should brighten slowly over the coming months, and I should be able to follow it until perhaps March 2014 before I lose it en route to conjunction with the sun (39 degrees south of it) near the beginning of May. Once it re-emerges into the morning sky a month or so later visibility will probably be restricted to the southern hemisphere, although it's conceivable I might be able to view it low in the southeast before dawn in late July and early August, the comet perhaps being 9th or 10th magnitude around then. By the latter part of August it enters southern circumpolar skies, and it reaches a peak southerly declination just north of -75 degrees in early September, near which time it is also nearest Earth (0.89 AU) and perhaps as bright as 7th or 8th magnitude. By late that month it should once again be accessible from my latitude in my southwestern sky after dusk, traveling almost due northward.

A most remarkable event takes place on October 19, when Comet Siding Spring passes extremely close to Mars. According to the latest calculation the nominal approach distance is 0.00096 AU (143,000 km, or 89,000 miles), slightly over 1/3 of the Earth-moon distance, with the formal uncertainty suggesting a minimum approach distance of 0.00089 AU (133,500 km, or 83,000 miles). It is conceivable that the emergence of as-yet unseen non-gravitational forces could reduce this minimum approach distance, although the possibility of an impact into Mars, which some of the earliest calculations suggested could occur, must now be regarded as vanishingly small. Still, it is possible that the comet's coma could envelop Mars, and a bevy of spacecraft both in Mars orbit and on the Martian surface will have a ringside view of this very close encounter.

Following its close approach to Mars the comet remains visible in the evening sky for about another month before disappearing into twilight. It is again in conjunction with the sun (21 degrees north of it) shortly after mid-December, and should become accessible in the morning sky during the first half of January 2015, perhaps between 10th and 11th magnitude. It should then fade gradually over the subsequent months, perhaps fading beyond the range of visual detectability around the time it goes through opposition in early May.

         

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