|491. COMET 48P/JOHNSON Perihelion: 2011 September 29.30, q = 2.301 AU
I have now entered the "home stretch" of "Countdown," and I managed to do so in dramatic fashion, adding three comets to my tally on the morning of August 7 -- all within 2 1/2 hours of each other. In my over four decades of comet observing this is only the second time that I have managed to add three comets to my tally in one night (the other occasion being on the evening of December 14, 1993, when I added comets numbered 181 through 183).
The first of the night's trio of new additions is a periodic object originally discovered in August 1949 by Ernest L. Johnson from the Union Observatory in South Africa, the last of four comets (along with a dozen asteroids) he discovered in a career that spanned two decades (from the mid-1930s through the mid-1950s). The comet has been a dependable, if unremarkable, performer ever since, and, with an orbital period that has varied between 6.8 and 7.0 years, has been recovered at every return since its discovery. With its somewhat large perihelion distance it has never become bright, and I searched unsuccessfully for it at each of the three previous returns (in 1990, 1997, and 2004) -- each of which was slightly more favorable than the preceding one. On the present return it was recovered as long ago as July 8, 2010, in infrared images taken with the Wide-field Infrared Survey Explorer (WISE) spacecraft.
I really hadn't planned to attempt the comet this time around, even though, again, the viewing circumstances are slightly more favorable than they were in 2004. However, I noticed that some of the CCD-reported magnitudes on the recent "Observations and Orbits of Comets" Minor Planet Electronic Circulars suggested that it might be worth attempting visually, and it occurred to me that perhaps "the fourth time might be the charm." My first attempt was on the morning of the 7th, and I clearly saw a small and very faint diffuse and somewhat condensed object (slightly fainter than magnitude 14) that exhibited clear motion over the course of the subsequent two hours. I successfully observed it again on each of the following two mornings.
Comet Johnson went through opposition near the end of July and was nearest Earth (1.32 AU) at the beginning of August, and it is probably about as bright as it is going to get. It is currently located in southwestern Capricornus and is traveling towards the southwest, and after passing through its stationary point in early September will track eastward through far eastern Sagittarius and northwestern Microscopium before crossing back into Capricornus during the latter part of October. The comet will likely fade gradually over the coming weeks, and since it is already near the limit of visibility of the 41-cm telescope I will probably obtain only a handful of observations of it.
As it heads back out of the inner solar system Comet Johnson will pass 0.60 AU from Jupiter in December 2014; this approach will decrease the comet's perihelion distance to just over 2.0 AU and shorten its orbital period to just over 6.5 years. The following return, in 2018 (perihelion mid-August) is quite favorable, with opposition and perihelion happening almost simultaneously and with the comet's minimum distance from Earth being just over 1.0 AU; the brightness should peak between magnitudes 12 1/2 and 13. The geometry two returns later (perihelion late September 2031) is quite similar to the current one, although since the comet will be quite a bit closer to Earth it should reach 13th magnitude.
With my successful observations of Comet Johnson I sort-of, although not entirely, get one of my wishes, i.e., I had really wanted to observe at least one comet discovered by the WISE spacecraft. While WISE did discover 17 comets (as well as numerous near-Earth asteroids, including the recently-identified first-known "Earth Trojan" asteroid 2010 TK7) before its operations were shut down early this year, all of these were very faint objects (typically, around magnitude 20 or 21) and only three of them became bright enough for me to attempt (all unsuccessfully). One of these three, P/2010 JC81, has an orbital period of 23 years and passed through perihelion at the end of this past April, and was only very recently identified as being a comet after emerging into the morning sky; the reports I read suggested it might be detectable visually. I first attempted it on the morning of the 7th, and had I been successful it would not only have given me my full wish, but also would have given me an unprecedented fourth tally addition on a single night. Alas, it was not to be . . .
While waiting to confirm motion on my suspect for Comet 48P/Johnson on the morning of August 7 I turned the telescope toward the expected location for this comet, and saw it almost right away; despite its being very faint -- slightly brighter than magnitude 14 -- it appeared fairly small and condensed, and was not difficult to see. In contrast to Comet Johnson, which I've now just seen for the first time, Comet Gehrels 2 is an old friend that I've observed on three previous returns.
The comet was discovered in September 1973 by Tom Gehrels, the fourth of five comets he discovered in the early to mid-1970s while conducting a photographic survey program with the 1.2-meter Schmidt telescope at Palomar Observatory in California. Gehrels, whose name we have already encountered in "Countdown" as a result of a return of another one of those comets, led a very dramatic life with a number of fascinating elements both inside and outside of astronomy, and, sadly, passed away just last month. Among his many accomplishments was the development of the Spacewatch program in Arizona, and via that program he had one additional named comet discovery in 1997. I had the privilege of meeting him at a couple of astronomical conferences over the years.
At the time of its discovery Comet Gehrels 2 had an orbital period of just under 8 years and a perihelion distance of 2.35 AU. I didn't attempt it at either the discovery return or the following return in 1981, however I did try for it in 1989, and successfully obtained a handful of observations of it as a very faint object (no. 131). An approach to Jupiter of 0.62 AU in February 1995 shortened its orbital period to its current value of just over 7.2 years and decreased the perihelion distance to the present value of just over 2.0 AU, and I observed it again during its returns in 1997 (no. 234) and 2004 (no. 353). The geometrical viewing circumstances at this latter return were very favorable, with opposition occurring simultaneously with perihelion, and the comet became slightly brighter than 10th magnitude and was bright enough to see in binoculars.
At its present return Comet Gehrels 2 was recovered on May 3, 2011 by Japanese amateur astronomer Hidetaka Sato, who utilized a remote-controlled telescope in New Mexico. While the viewing circumstances this time around are not quite as favorable as they were in 2004, they are nevertheless reasonably good, with the comet's being at opposition shortly after mid-September. It is currently located in central Pisces a degree northeast of the star Omega Piscium, and is traveling slowly almost due northward as it approaches its stationary point just after mid-August. The comet actually spends the next six months in Pisces, initially traveling southwestward through it and spending most of October crossing the eastern half of the "circlet" asterism, before reaching its other stationary point at the end of that month. After that it initially tracks eastward before turning towards the northeast, and shortly after the middle of February 2012 crosses a corner of Cetus and then moves into southern Aries; towards the end of March it crosses into western Taurus. During the latter part of April the comet crosses the northwestern section of the Hyades star cluster, although by then the elongation in the evening sky will have shrunk to 35 degrees.
Based upon the brightness behaviour it exhibited in 2004, the comet should be close to 13th magnitude when near opposition in September, and should reach a peak brightness of perhaps 11th magnitude around November and December. It will likely have faded some, to perhaps 12th magnitude, by the time of perihelion passage in January, and will probably begin fading rapidly thereafter; I expect I will lose it by sometime in March.
Whether or not I will see Comet Gehrels 2 again after this return is over is, at best, uncertain. The next two returns, in 2019 and 2026 (perihelion passages in early April and late June, respectively) are quite unfavorable, and if the comet is visible at all it will be very faint at a fairly small elongation from the sun. Then, it makes a very close approach to Jupiter (0.02 AU) in September 2029, which will increase its perihelion distance to 4.1 AU and its orbital period to 13.5 years. Any "Countdown" participants who might want to observe this comet, and, perhaps, pay homage to its remarkable discoverer, should take advantage of the decent viewing conditions it provides us over these next few months.
The last of my three tally additions on the morning of August 7 was the faintest of the three comets, being only slightly brighter than magnitude 14 1/2 -- just barely above the limit of the 41-cm telescope. Because of its faintness, and also the fact that it is currently moving rather slowly against the background stars, I wasn't sure I had it until I was able to obtain a confirming visual observation two mornings later.
The comet was originally discovered in September 1991 by Rob McNaught, whose name we have seen repeatedly throughout the course of "Countdown." However, unlike all his recent discoveries which have been made in the course of the Siding Spring survey based in New South Wales, he found this one during the course of a photographic survey program at Siding Spring that pre-dated the current CCD-based survey. In keeping with the procedure followed at the time for Siding Spring-based comet discoveries, the comet was assigned the name of its discoverer (McNaught) as well as the individual who took the discovery photographic plates (Shaun Hughes). With this addition to my tally Rob's name now appears 20 times, tying him for second place with Carolyn Shoemaker; meanwhile, Rob's overall discovery total now stands at 64, including one he found at the beginning of this month.
After its discovery the comet was found to have passed perihelion the previous June, and to be traveling in a short-period orbit with a period of 6.7 years (currently, 6.65 years). I made one unsuccessful visual attempt for it shortly after its discovery, but didn't bother with it at the subsequent returns in 1998 and 2004. On the current return it was recovered as long ago as March 13, 2010 by Jim Scotti -- a personal friend of mine, incidentally -- in the course of the Spacewatch program in Arizona. I hadn't planned on looking for it this time around, either, but as was the case with Comet 48P/Johnson, I noticed that some of the CCD-reported magnitudes on the recent "Observations and Orbits of Comets" Minor Planet Electronic Circulars seemed to suggest it might be worth attempting, and -- rather to my surprise -- I managed to pick it up.
The comet passed through perihelion seven weeks ago, and will be closest to Earth (1.16 AU) near the end of this month before going through opposition in early September, and thus is probably as bright as it is going to get. At most, then, I will only be getting a handful of observations of it. It is currently located in eastern Aquarius and it spends the next several weeks tracking southwestward across that constellation, until reaching its stationary point near the south-central part of it shortly before mid-October.
I really don't know if I'll see this comet again, or even look for it again, anytime after this return. A moderately close approach to Jupiter (0.59 AU) in January 2015 will decrease the perihelion distance to 1.82 AU and shorten the orbital period to 6.2 years, however both of the subsequent two returns (perihelion passages in January 2018 and April 2024) are unfavorable. A more distant approach to Jupiter (1.12 AU) in July 2026 will increase the perihelion distance to 1.96 AU and increase the orbital period to 6.5 years, but it turns out that the return in 2030 (perihelion mid-September) is relatively favorable, with the comet perhaps reaching a peak brightness somewhere between magnitudes 13 and 14. Although I hope to be active at some level then, whether or not I'll still be pursuing faint comets like this at the age of 72 remains to be seen.
I've commented before in previous entries on the irony that, depsite the fact that they are, by far, the two cloudiest months of the year here in New Mexico, the monsoon months of July and August have also been, far and away, my most successful months for adding comets to my tally ever since my return to New Mexico in 1986. This current year of 2011 dramatically illustrates this; while I only added four comets to my tally during the entire first six months of the year, I have now added seven comets to my tally during these past two months. To be sure, the monsoon activity has been somewhat below average this year, but it has nevertheless produced its share of rainy weather and cloudy nights.
This newest comet was discovered by the LINEAR program in New Mexico on September 21, 2010, at which time it was located at a rather distant 8.85 AU from the sun. It has been moving slowly inward since then, and after conjunction with the sun (although some 44 degrees north of it) in mid-April it has been climbing steadily higher into the morning sky. There have been some reports, CCD and otherwise, that suggested the comet might be bright enough to attempt visually, and I began doing so in late July, initially unsuccessfully. (The rich Milky Way star fields in eastern Cassiopeia that the comet has been traveling through have not helped.) Finally, on the early morning of August 28 when it was located in a somewhat "clean" star field 2 1/2 degrees west-northwest of the star Epsilon Cassiopeiae (the easternmost star of the "W") I successfully spotted the comet as a small and extremely faint (magnitude 14 1/2) object that exhibited the expected motion over the 1 1/2 hours that I watched it.
Comet LINEAR has the somewhat unusual distinction of having the third-largest perihelion distance of any comet on my tally; only the Centaur comet 95P/Chiron (no. 196), at 8.45 AU, and Comet Skiff C/1999 J2 (no. 277), at 7.11 AU, have had larger perihelion distances. Furthermore, when I obtained my first sighting of it Comet LINEAR was located at a heliocentric distance of 7.35 AU, the largest distance at which I've ever observed a long-period comet; the only two comets I've seen at greater distances are Chiron (which I followed out to 8.94 AU) and my other Centaur comet, 174P/Echeclus (no. 384), which was at 13.05 AU when I first saw it.
Because of its large perihelion distance and its high intrinsic brightness Comet LINEAR should be visually detectable for quite some time, but on the other hand it will never get very bright. It is traveling in a somewhat steeply-inclined retrograde orbit (inclination 125 degrees) and spends much of its period of detectability in northern skies; unfortunately, it also remains fairly close to the galactic equator throughout the entire period and thus visual observers will often have to contend with rich Milky Way star fields. Currently it is traveling westward somewhat to the north of the "W" of Cassiopeia, reaching a peak northerly declination of +66 degrees shortly after mid-September and then being at opposition at the end of that month. It then travels southwestward through western Cassiopeia (passing 15 arcminutes northwest of the star cluster M52 during the second week of November) and then southward through eastern Lacerta beginning in mid-December, before looping eastward into western Andromeda during the latter part of January 2012. The comet is in conjunction with the sun (53 degrees north of it) in early March, and after emerging back into the morning sky traverses through northwestern Andromeda, southern Cepheus, and then (after being at opposition shortly after mid-August) northeastern Cygnus starting at the beginning of September, where it begins a bit of a southward plunge and passes just over half a degree east of the bright star Deneb shortly after mid-October. After crossing the central regions of the Veil Nebula during the first half of January 2013 the comet is again in conjunction with the sun (46 degrees north of it) in early February.
Upon emerging back into the morning sky a couple of months later Comet LINEAR spends the next several months traversing westward across southern Cygnus, being at opposition during the latter part of July before crossing into Vulpecula during the first week of August. It crosses the western region of the "Coathanger" star cluster (Collinder 399) during the third week of September before crossing into western Sagitta shortly before the end of that month and into western Aquila two weeks later. The comet remains in Aquila for several months thereafter, being again in conjunction with the sun (27 degrees north of it) in mid-January 2014, and after its emergence into the morning sky tracks westward, then southwestward, across that constellation through its next opposition in early July before finally crossing a corner of Serpens Cauda and entering Scutum during the first half of August. Afterwards, it treks southward through the western region of that constellation before again being in conjunction with the sun at the very end of the year.
Comet LINEAR will probably remain quite faint for the remainder of the current viewing period, perhaps brightening by about half a magnitude by early next year. Around the time of opposition in 2012 it may be around magnitude 13 1/2, and it might brighten an additional half-magnitude or so around the time of opposition in 2013, when it will be closest to perihelion. It may still be around magnitude 13 1/2 when near opposition in 2014, but it will likely begin fading quite steadily after that, and I will likely lose it sometime during the last few months of that year. Even so, there would seem to be a reasonable possibility that I could end up following this comet for three years or more, and thus giving it a couple of more "distinctions" before all is said and done.
I now have only six more comets to go until I complete "Countdown." While the last few comets have come in quite rapid succession, I don't believe that this will be the case for the near foreseeable future; there are in fact no comets that I unequivocally expect to add to my tally before the end of this year, although there are some that I consider "possible" and it is likely that I will end up adding at least a couple of these. Unless we get a flurry of bright new discoveries over the next few months, then, I can predict that I will probably achieve comet no. 500 sometime during the first three months of 2012. As for what happens afterward, I am open to suggestions; I will certainly continue observing comets for at least the short-term foreseeable future, and hopefully will do so at some level for some time yet to come. I would like to have a comet-observing element to Earthrise as I work to get Earthrise back up and running over the next several months and beyond, and I welcome suggestions from "Countdown" participants and mentors, and anyone else who might be interested.
Another SWAN comet! This is the second comet since the beginning of "Countdown" to be discovered in images taken with the Solar Wind ANisotropies (SWAN) ultraviolet telescope on board the SOHO spacecraft, and the eighth "real-time" SWAN comet over the past decade; with the addition of this comet to my tally I am now a perfect eight-for-eight for these comets. They haven't all been easy, though, and in fact a few have been rather difficult to observe; this comet, certainly, is among that group.
The comet was independently detected by Vladimir Bezugly in the Ukraine and Robert Matson in California in SWAN images dating back to August 23. By the time the first ground-based images were obtained on September 4 and the comet's existence was announced a day later the moon was already into its waxing gibbous phase, and this, combined with its location south of the sun and thus its being very low in my southwestern sky during and after dusk, made it essentially impossible to observe from my latitude. (I nevertheless did attempt it on a couple of nights, but the low elevation and bright moonlight conspired to make it impossible to see.) I thus had to wait out the Harvest Moon (which was full on the night of September 11-12) and then a couple of days of monsoon activity before I could make a reasonable attempt for it. Finally, on the evening of September 16 I successfully observed the comet, even though it was only a few degrees above my southwestern horizon shortly before the end of dusk; it appeared as a diffuse, slightly condensed object of 11th magnitude.
Comet SWAN is traveling in a somewhat steeply-inclined retrograde orbit (inclination 148 degrees) and, according to the most recently determined orbit at this writing, seems to be an intermediate-period object with an orbital period of approximately 280 years. In theory, it could have been discovered much sooner than it was; at the end of July it had passed 0.65 AU from Earth and three degrees from the south celestial pole, and, theoretically, should have been about a magnitude brighter than it is now. (An apparent rapid brightenening like this is fairly consistent with its being an intermediate-period comet, so that may explain why it wasn't detected earlier than it was.) It is currently located in southeastern Virgo a little less than one degree southwest of the star Lambda Virginis and is traveling almost due northward, passing half a degree due west of that star on September 21; meanwhile its elongation, already at a small 40 degrees, decreases to below 30 degrees by the end of this month, and since it remains south of the sun during this period I will probably only get one or two additional observations of it at most. (Observers in the southern hemisphere may be able to follow it for a little bit longer.) After being in conjunction with the sun in late October the comet begins emerging into the morning sky by about the beginning of December as it is crossing from Virgo into Bootes; I expect it will have faded beyond the range of visual detectability by then, however. It passes 2 1/2 degrees east of the bright star Arcturus just before the end of the year.
While I'm following this and some of the other recent "Countdown" comets (including Comet Garradd C/2009 P1, which is now a fairly bright and easy binocular object in the evening sky, and Comet 45P/Honda-Mrkos-Pajdusakova, which has just reappeared in my morning sky), there are a couple of other interesting astronomical events and discoveries going on as well. First, there is the bright Supernova 2011fe which appeared in the bright spiral galaxy M101 shortly before the end of August; lately it has been around 10th magnitude, being not only the brightest supernova of the past two decades but also the brightest supernova I have ever observed. Second, last week came the announcement of the discovery of what has been called in the popular press a "Tatooine"-type planet (i.e., a planet orbiting outside a binary star system and thus experiencing two suns in its sky, similar to the fictional planet depicted in the "Star Wars" movie franchise) by NASA's Kepler mission. I feel a particular kinship to this discovery, since the lead scientist of the discovery team, Laurance Doyle, is a long-time friend and colleague of mine, and among other things played a significant role in the spawning of the idea for my Ph.D. dissertation. Back in the mid-1990s when I was still heavily involved in extrasolar planet research he and I co-wrote a paper where we suggested that solar-type stars in eclipsing binary star systems (like the system for this recently-discovered planet) would be a good place to search for extrasolar planets. It appears we were right!
UPDATE: Somewhat surprisingly, I was still able to detect Comet SWAN in the morning sky after its conjunction with the sun; on the morning of December 1 I saw it as a vague, diffuse object between magnitudes 13 and 13 1/2 fairly low in the eastern sky near the beginning of dawn. It is currently crossing from northeastern Virgo into southern Bootes and is traveling almost due northward at approximately 20 arcminutes per day, and as indicated above it passes somewhat close to the bright star Arcturus at the end of the month. Although for the time being the comet is drawing closer to Earth, it is also almost 2 1/2 months past perihelion passage and thus receding from the sun, and thus should be fading; I doubt if I will be following it for very long.
Incidentally, Supernova 2011fe in the bright spiral galaxy M101 (which I mentioned above) is also still visible; after I had finished with my observation of Comet Swan on the morning of December 1 I was easily able to detect the supernova at 12th magnitude.
What happens to comets when they "die?" Many of them just simply disintegrate; I've witnessed this several times during the years I've been observing comets, and we've seen it with a couple of "Countdown" comets, including the very recent Comet Elenin C/2010 X1. (If Earth should happen to intercept the comet's orbit, we might see a meteor shower; this happened in the mid-19th Century with the famous comet 3D/Biela.) However, for a few comets, especially short-period ones, a different fate might be in order: they either run out of "gas," and/or their surfaces become so coated with dust and other material, that they essentially become inert, and become objects that are indistinguishable from asteroids. We know many examples of what appear to be "extinct" (or perhaps "dormant") comets, and I've observed several of these objects over the years; I've listed these on the "Countdown" update page over the past 4 1/2 years whenever there has been any that I've had under observation, but I do not include them as part of my tally (unless some future observations indicate that they are active at some level and thus should be considered a "comet," in which case I will add them to my tally retroactively).
This particular comet has long been considered a "transition" object, i.e., a comet on its way towards "shutting down" and becoming one of these pseudo-asteroids. It has a current orbital period of 6.72 years, and was initially discovered in February 1951 by Sylvain Arend (a name we have previously encountered in "Countdown") and Fernand Rigaux during the course of a photographic patrol program being conducted at the Royal Observatory in Uccle, Belgium. Despite being a somewhat bright 11th magnitude and being located just over half an AU from Earth, the comet exhibited little more than a prominent central condensation within a tiny diffuse coma less than an arcminute in diameter. At its next three returns (1957, 1964, and 1971) it appeared completely asteroidal (although it's fair to note that these were unfavorable returns, and the comet was far from the sun and Earth at the times it was detectable). Finally, at the somewhat favorable return in 1978 it did exhibit some cometary activity, including gas emissions; an article in Sky & Telescope magazine at the time was entitled "Comet Arend-Rigaux: Not Dead Yet." The following return, in 1984, was even more favorable, with the comet's coming to within 0.6 AU of Earth; it again exhibited weak cometary activity, and detailed scientific investigations at the time revealed the nucleus to be rather large (ten to thirteen km, or six to eight miles, in diameter), but extremely dark (an albedo of only 0.03), with the implication being that only about 1% of its nucleus is active.
Although it reached 13th magnitude in 1978 I did not attempt it during that return (being in my sophomore year at the U.S. Naval Academy and otherwise preoccupied at the time), but I did observe it extensively during its return in 1984 (no. 79), at one point seeing what was apparently an outburst from its nucleus (the overall appearance going from nothing but a condensation at the one point to a diffusing out over the next several days). I attempted it a handful of times unsuccessfully at the mediocre return in 1991 and didn't attempt it at the unfavorable return in 1998, however I did manage to observe it on a few occasions during its somewhat favorable return in 2005 (no. 366), although it never got brighter than magnitude 13 1/2. Since it was observed when near aphelion following its 1984 return it is considered an "annual" comet and thus isn't formally "recovered;" the initial observations at the current return were made by the WISE spacecraft on May 15, 2010. After one earlier unsuccessful attempt I successfully picked it up on the morning of October 1; the comet was very faint (slightly fainter than 14th magnitude) and small (a coma only 1/3 of an arcminute across) and exhibited distinct motion during the half-hour that I followed it.
P/Arend-Rigaux's current return is, at best, only slightly better than mediocre. It is currently located in southwestern Cancer, and between now and the end of the year it travels due eastward across that constellation and (beginning in late October) Leo, and in fact it remains between declinations +7.5 degrees and +9 degrees until mid-December when it begins turning northward and enters northwestern Virgo. I don't expect much brightening; perhaps by at most about a half-magnitude or so by November, and it will most likely fade beyond the range of visual detectability by sometime in December. For what it's worth, the comet traverses the northwestern regions of the Virgo galaxy cluster around mid-January (passing half a degree southeast of the galaxy M100 in the process), is nearest Earth (1.02 AU) in early February, and is at opposition around the time of the March equinox, but I expect it to have faded well beyond my range by the time any of this happens.
While the comet thus remains quite faint this time around, at least I'm able to observe it. That won't be true during the next two returns, in 2018 (perihelion mid-July) and 2025 (perihelion early April). However, the following return, in 2032 (perihelion early January) is the best one since the comet's original discovery, and in fact is the best of the entire 21st Century; it passes just within 0.56 AU of Earth in late December 2031 and should reach 11th magnitude. It should certainly be amenable to widespread scientific scrutiny at that time, and assuming that I remain active at some level I'll presumably be viewing it again then as well.
As I add my final comets in my approach to no. 500 an old friend stops by for what will probably be a brief visit. This particular comet has a rather storied history from an observational and scientific standpoint, and it has been around for some of the big events in my life as well. Although my life has settled down somewhat from the upheavals that it was undergoing about two years ago, there are still some interesting things in the works, so it's at least conceivable that its appearance now could coincide with some interesting goings-on for me.
The comet was originally discovered in December 1900 by the French astronomer Michel Giacobini, whose name we have already encountered previously in "Countdown." The observations then were sufficient to show that it is a short-period object, and after being missed in 1907 it was expected to return again in 1914, under what were expected to be very unfavorable conditions; however, in October 1913 a German astronomer, Ernst Zinner (who would later go on to be a renowned science historian) accidentally re-discovered it. Its orbital period has remained close to 6 1/2 years (currently, 6.60 years), and it has been recovered at most of its returns since then; the current return is the 15th at which it has been observed. Since, intrinsically, Comet 21P is one of the brighter Jupiter-family periodic comets, and since it has a rather small perihelion distance, it is definitely among the brighter periodic comets that we can see; for example, during its 1946 return it briefly reached 6th magnitude as it was passing 0.26 AU from Earth.
The descending node of Comet 21P's orbit passes very close to Earth's orbit, and as a result this produces the Draconid meteor shower during the second week of October. Normally, the Draconids are a rather weak shower, but have been known to have produced very strong displays around times the comet has returned; for example, in both 1933 and 1946 very strong but brief displays of up to several thousand meteors per hour were seen. Although not quite as strong as those displays, moderately strong showers have appeared around the times of more recent returns; just this past October 9, the Draconids produced a display that briefly reached a few hundred meteors per hour, as seen from Europe.
During its 1985 return Comet 21P achieved additional notoriety by becoming the first comet ever to be visited by an artificial spacecraft. The International Sun-Earth Explorer 3 (ISEE-3) spacecraft, which had been launched in 1978 and which was stationed at the L1 Lagrangian point directly sunward of Earth, was, after a complex series of lunar flybys calculated by planetary scientist Robert Farquhar, rechristened the International Cometary Explorer (ICE) and passed through Comet 21P's ion tail 4800 miles (7700 km) "downwind" from its nucleus on September 11, 1985. ICE did not possess any cameras or imaging equipment, but did carry on board several scientific instruments which gave us a lot of information about the electrical environment around the comet and its interaction with the solar wind.
As I indicated above, I have my own storied history involving this comet. It had a moderately favorable return in 1972, however my sole source of information about observable comets at the time was Sky & Telescope magazine, and although it mentioned that the comet would be returning then, it never provided an ephemeris, and thus I missed seeing it. After the unfavorable return in 1979 I finally picked it up during its return in 1985 (no. 82), which was a very favorable one; the comet reached 7th magnitude and displayed a bright one-degree-long tail that I could detect in binoculars. In addition to all the observations I made then, I was working at the Jet Propulsion Laboratory in California at the time, and I "witnessed" the ICE encounter from the Space Flight Operations Center at the Lab. During that return of Comet 21P I also got married, and it so happened that on the morning of my wedding day it passed just two degrees from the inbound Comet 1P/Halley (no. 85); my "bachelor party," as it were, was observing this cometary conjunction with some amateur astronomer friends of mine in the mountains east of San Diego.
The comet's following return in 1992 was very unfavorable and I didn't look for it; curiously, though, it passed through perihelion slightly over eleven hours after the birth of my younger son Tyler. I did successfully observe the comet during its returns in 1998 (no. 248) and 2005 (no. 370), and during this latter return I managed to observe it in the morning sky one day before my older son Zachary graduated from Cloudcroft High School.
On its present return Comet 21P was recovered on May 1, 2011, independently by Francois Kugel at the Observatoire Chante-Perdrix at Dauban, France, and by Jean-Francois Soulier at Seine et Marne, also in France, and it went through opposition a little over two weeks later. In actuality, the geometrical circumstances of this return are quite unfavorable, and I never had any expectations of looking for it or seeing it, however during the past few weeks I've been made aware of CCD brightness measurements that suggested it might be worth attempting. I tried for it once in late October and didn't see anything, but on my first attempt after the recent full moon, on the evening of November 14, I successfully picked it up as a small and moderately condensed object slightly fainter than magnitude 13 1/2.
The comet is currently located in eastern Ophiuchus some 4 1/2 degrees south of the star Gamma Ophiuchi, and over the coming weeks travels eastward through Serpens Cauda and Aquila, then enters Aquarius during the second week of January 2012. The elongation is already a relatively small 38 degrees, and this shrinks steadily, to 35 degrees at the end of November, to below 30 degrees after mid-December, and to 28 degrees by the end of 2011. Somewhat in compensation the comet should brighten throughout this time, perhaps being somewhere between magnitudes 11 and 12 at the end of the year. In theory, it could remain visible for quite some time, since the elongation reaches a minimum of 24 degrees around the time of perihelion in February while at the same time the brightness should peak perhaps a little brighter than 11th magnitude; any such observations likely will be quite difficult, however, and in all honesty I doubt if I'll be following the comet for very long. For what it's worth the elongation begins increasing after perihelion, but only reaches a peak of 28 degrees in late April before shrinking again; the comet itself, of course, should be fading throughout that time.
While Comet 21P will likely remain fairly faint and elusive this time around, the opposite will be true at the next return in 2018 (perihelion early September), which turns out to be the best return of the 21st Century, with its passing only 0.39 AU from Earth. The geometrical circumstances are quite similar to those in 1985, and the comet should again reach 7th magnitude. Furthermore, early indications are that the chances for a strong Draconid display that year are reasonably high. So, along with several other periodic comets (including some that I have previously mentioned in "Countdown") that are making good returns the year I turn 60, I will have this one to look forward to; as to whether or not I will again observe it during a bachelor party, that remains to be seen . . .
One of the most unusual comets that we know about was initially discovered in November 1927 by the German duo of Arnold Schwassmann and Arno Wachmann from the Hamburg Observatory in Bergedorf, Germany. It was initially reported as being around 13th magnitude, but faded quite rapidly, and as astronomers continued to follow it over the subsequent months and years it continued to exhibit outbursts from time to time. Once orbital calculations revealed that: a) the comet has passed perihelion over 2 1/2 years prior to its discovery; b) its perihelion distance was a distant 5.48 AU (a record at that time); and c) it was traveling in a near-circular low-eccentricity orbit entirely between the orbits of Jupiter and Saturn, its unusual nature began to become clear. While the comet is normally quite faint (16th to 18th magnitude), at unpredictable intervals it will undergo outbursts, usually to 12th or 13th magnitude but sometimes even brighter -- once, in 1946, it almost reached 9th magnitude -- before subsiding. While, on average, the comet undergoes two to three outbursts per year, this can vary widely; there have been periods when it has undergone numerous outbursts over a span of a few months, while at other times it has gone two or three years or more without an outburst.
Except for the times when it is near conjunction with the sun, Comet 29P has been under almost continuous observation ever since its discovery. In 1931 a pair of photographs taken in 1902 showing the comet were identified. Meanwhile, an extended encounter with Jupiter in the 1970s increased the perihelion distance (from 5.5 AU to the present 5.8 AU), shortened the orbital period (from 16.1 years to the present 14.8 years), and decreased the orbital eccentricity (from about 0.14 to the present 0.04). As for what is causing the outbursts in the first place, that is still a matter of some research, but in a paper published in 1990 then-University of Hawaii astronomer David Jewitt proposed that they are due to phase changes in "amorphous ice" in the nucleus that is occasionally exposed by the comet's regular level of activity that it undergoes at its present distance from the sun.
When I began to consider monitoring this comet for outbursts in the early 1980s, I had to resolve the matter of how I would include it in my tally. I had already established the precedent of counting separate returns of the same periodic comet as separate comets, and decided that I would apply the same practice to this comet, with a "return" being defined as aphelion to aphelion. I began searching for Comet 29P in early 1981, at which time it was outbound from its perihelion passage in 1974, and in early May of that year, while on a camping trip to Yosemite National Park in California (and thus completely unaware that it had already been in outburst for over a week) I saw it for the first time (no. 47). I observed two additional outbursts over the course of the next year, however shortly thereafter it went through aphelion and began to approach its next perihelion passage in 1989. All of my observations during that time frame were thus part of that second "return" (no. 111), although the comet was quiet for the first few years and I didn't pick it up in outburst until the latter part of 1987.
Comet 29P went through aphelion again in late January 1997, and less than two weeks later I picked it up in outburst (no. 226) -- during which time, of course, I was intensely involved in observing Comet Hale-Bopp C/1995 O1 (no. 199) which was already a conspicuous naked-eye object. Perihelion passage for this "return" took place in July 2004, and for the first few years after aphelion it behaved more-or-less "normally," i.e., undergoing outbursts once or twice a year, but beginning around 2002 and continuing up through the present its level of activity has increased substantially, with several outbursts taking place every year and with occasional periods where it remains in almost a continuous state of outburst for months at a time. Some of these outbursts have been quite strong, with a couple of these during the last two to three years reaching close to magnitude 10 1/2. (I have included Comet 29P on the Comet Update page throughout the duration of "Countdown" and have discussed these incidents when they have taken place.) In 2011, for example, after remaining quiet for the first couple of months following its emergence into the morning sky after conjunction with the sun, it began to undergo weak outbursts (14th magnitude) in late January, but continued to undergo additional outbursts on a semi-regular basis up until the time I lost it in dusk in the evening sky in late June; the brightest outburst was to about magnitude 12 1/2 in late May.
After being in conjunction with the sun shortly after mid-September the comet began emerging into the morning sky by November, and I began making attempts for it during the latter part of that month after the moon had cleared from the morning sky. Meanwhile, on December 1 it went through aphelion (6.262 AU from the sun) and, among other things I removed it from the "Update" page, since any additional observations after that point would constitute a new "return" and thus a new addition to my tally. As recently as December 26 I failed to detect any sign of the comet, however three days later astronomer Jean-Francois Soulier, who observes from his observatory in Seine et Marne, France, reported an outburst and posted an image suggesting that one had just commenced. On the next morning, December 30, I clearly saw the comet as a small and fairly condensed object half an arcminute in diameter (which is a typical appearance for early in an outburst); with a total brightness slightly fainter than magnitude 13 1/2 this outburst is a relatively weak one.
Due to its large distance and its near-circular planet-like orbit, Comet 29P's annual motion involves a general west-to-east shift against the background constellations, with a significant retrograde loop each year. It is currently located in northeastern Corvus about a degree southwest of the "Sombrero Galaxy" M104 and for the time being is traveling slowly towards the southeast, but after reaching its stationary point in late January 2012 it begins retrograde (westward) motion, heading towards opposition in late March when it will be located four degrees north-northwest of the star Delta Corvi (and a similar distance west of its current location). Retrograde motion continues until the comet reaches its other stationary point at the end of May, and thereafter it again heads eastward until it begins disappearing into evening twilight around mid-August, when it will be located close to where it is right now.
This same basic pattern repeats every year, shifted by slightly less than one month later each year, and shifted eastward by approximately 25 degrees on the celestial sphere. For example, after begin in conjunction with the sun in October 2012 it begins emerging into the morning sky in early December when it will be located in southern Virgo somewhat to the southwest of the star 89 Virginis; retrograde motion begins in mid-February 2013, opposition takes place shortly after mid-April (when the comet will be in Hydra, located some 5 1/2 degrees south of the above star), retrograde motion stops in late June, and the comet disappears into evening twilight around mid-September (when it is located some five degrees southeast of the above star). The overall eastward trend is, of course, along the ecliptic, although due to the comet's orbital inclination of 9 degrees the extreme north and south points are shifted a bit; the comet reaches a maximum southerly declination near -32 degrees around the time of its opposition in June 2015 (when it will be located in eastern Scorpius slightly north of the open star cluster M6), and a maximum northerly declination just north of +32 degrees in November 2021 shortly before its opposition the following month (when it will be located in southwestern Auriga a few degrees southwest of the star Iota Aurigae).
For what it's worth, the comet is near conjunction with the sun, and thus is undetectable, around the time of its perihelion passage in March 2019. Meanwhile, it is again at aphelion (6.318 AU from the sun) at the end of September 2026 and, curiously, will again be in conjunction with the sun around that time.
As for the comet's brightness behavior, we will just have to wait and see. The current outburst, being a relatively small one, has already started to expand outward, and should disperse over the next two to three weeks, although it is always possible that additional, and perhaps stronger, outbursts could take place within the not-too-distant future. Indeed, if the activity of the past few years is any guide, we could easily see numerous outbursts throughout this current viewing season, and during the future ones as well. Whether or not this heavy activity will indeed continue for the next several years, or whether we'll see some "quiet" years like it has occasionally exhibited in the past, or something in-between, is something we will just have to let the comet itself reveal to us.
For my part, it seems likely that I will have this comet to examine for as long as I remain alive and active in comet observing, and I expect to continue monitoring it for outbursts for as long as I'm active. I cannot help noticing that it is at perihelion on my 61st birthday (and it becomes only the second comet on my tally to pass perihelion on my birthday, the first being Comet LONEOS-Hill P/2005 XA54 (no. 386), which did so on my 48th); meanwhile, I will be 68 when it again goes through aphelion, and I can scarecly imagine what things my happen, both to me personally and to the larger world, between now and then. For what it's worth, after being at aphelion in 2026 the comet begins to approach its next perihelion passage in February 2035, however it will then be entering another extended encounter with Jupiter that will ultimately increase its perihelion distance to 5.9 AU, its orbital eccentricity to 0.07, and its period to 15.9 years. Over the long term, the orbit is chaotic (in a mathematical sense); at some point Jupiter will either perturb it into a smaller, shorter-period orbit in the inner solar system, or else place it into a hyperbolic orbit and eject it from the solar system altogether. Of course, I will be long gone well before either of those scenarios happen . . .
It appears that 2011 wasn't quite finished with me, as far as adding comets to my tally is concerned. On the morning of December 30, after finishing my observation of the above comet, I turned my telescope towards the location of this one, an object I had made a couple of attempts for back in September and then, after conjunction with the sun in mid-October, I had attempted a few times following its emergence into the morning sky in late November. I did seem to see a fairly strong, but very faint, suspect, and unfortunately it was located in a fairly blank star field which made detection of motion impractical. On the following morning -- New Year's Eve -- in a better star field I clearly saw the comet, and followed it for over an hour as it moved against the background stars; it appeared small and condensed, and slightly fainter than 14th magnitude. Incidentally, this marks the 23rd time that I have added two or more comets to my tally on the same night, and curiously, three of those occasions have taken place in 2011.
The comet was discovered on March 17, 2011 by the LINEAR program in New Mexico, which has already contributed several comet discoveries to "Countdown." While it is not the dominant force in comet discoveries that it was a decade ago, LINEAR continues to discover comets from time to time, and because of the near-monopoly it had in the late 1990s and early 2000s it remains the leading comet-discovering entity from the earth's surface. The exact number of LINEAR comet discoveries is difficult to give, depending upon how one wishes to define multiple-component comets, but as I have defined them, this is the 200th comet (out of 206 as of this writing) that LINEAR has discovered and which has received the name "LINEAR." LINEAR is, by far, the biggest contributor to my tally; this is the 56th comet I've observed that contains the name "LINEAR;" since one of these is a "repeat" periodic comet I have seen 55 out of that total of 206, or slightly over one-quarter.
This latest Comet LINEAR is currently located in northern Bootes four degrees north of the star Beta Bootis and is traveling slowly towards the east-northeast, although over time this motion takes a more northerly turn. After going through its stationary point in early March it loops back northwestward through southern Draco, passing twenty arcminutes north of the bright edge-on spiral galaxy NGC 5907 shortly after mid-April and then reaching a maximum northerly declination slightly south of +57 degrees at the end of that month before going through opposition in early May; by this time it should have brightened to perhaps 12th magnitude. Towards the end of May the comet commences a southward plunge through western Bootes that lasts for the next four months, passing 4 1/2 degrees east of the bright star Arcturus at the end of August (when it will probably be somewhere between 10th and 11th magnitude) and gradually curving more southeasterly by the time it enters Serpens Caput shortly before the end of September. It passes 1 1/2 degrees northeast of the globular star cluster M5 in early October and shortly thereafter begins entering evening twilight, by which time it will likely have further brightened to 9th or 10th magnitude. Afterwards, the comet remains lost in sunlight for some time, and, curiously, passes almost directly behind the center of the sun (as seen from Earth) on December 16.
Following its conjunction with the sun the comet remains in sunlight for some time thereafter, finally beginning to emerge into the southern hemisphere's morning sky by late February or early March 2013, at which time it will located in Microscopium slightly south of declination -40 degrees, and still probably around 9th or 10th magnitude. For the next 4 1/2 months it travels almost directly eastward across Grus, Phoenix, Eridanus, and eventually into Horologium by mid-July; fading will likely be fairly slow initially, since the comet is nearest Earth (2.56 AU) in early April, but afterwards may be more rapid, being perhaps 11th magnitude in July. It begins another southward plunge then, gradually turning more westerly as it reaches its peak southerly declination of -54 degrees in mid-October before starting to turn back northward. There is a chance I might be able to pick it up again in December after it has traveled far enough north to be accessible to me, but it will likely be quite faint, and even southern hemisphere observers will probably lose it not too long thereafter.
So now -- coincidentally, at the start of a new year -- I am one comet away from achieving my target of comet no. 500. I doubt if I will have to wait for long: I can think of at least three comets that I might potentially add to my tally before the end of January 2012. One of these -- and the one that I am secretly hoping for -- is the Kreutz sungrazer Comet Lovejoy C/2011 W3, which over the past couple of weeks has put on an outstanding show for my friends in the southern hemisphere (and for astronauts aboard the International Space Station) but which has frustratingly, and maddeningly, been completely inaccessible from the northern hemisphere. During the last week of January it will have finally traveled far enough north that I will be able to access it (albeit low above my southern horizon), however according to the reports from the southern hemisphere it is fading rapidly, and it is not at all certain that there will still be anything left to see by the time I'll have my chance. The good news is that there may be additional Kreutz sungrazers on the way -- but any such objects would appear long after I will have reached comet no. 500.
Did it! Slightly less than 42 years after I obtained my first comet observation, and a little bit less than five years after I inaugurated "Countdown," I achieve my goal of visually observing my 500th comet. And as befitting the occasion, the comet in question turns out to be one of the most dramatic, and one of the most scientifically interesting, comets of recent years, although I had to work very hard to earn adding it to my tally. I only wish I could have seen it at something close to its best, but as is true with many things in life, we sometimes have to take whatever we can get.
Comet Lovejoy is a type of comet known as a Kreutz sungrazer, so called due to late 19th Century German astronomer Heinrich Kreutz, who was the first to study them as a group. As the name "sungrazer" implies, these comets have extremely small perihelion distances, and are believed to be fragments of one very large comet that first entered the inner solar system thousands of years ago, and which split up due to the intense heat it encountered just outside the solar photosphere. As these fragments returned (generally with orbital periods of a few to several centuries) they in turn split up as well. Many of the Kreutz sungrazers have been among the brightest comets ever seen in recorded history, with some of these becoming easily visible to the unaided eye in broad daylight around the time of perihelion.
Owing to their history of fragmentation, many Kreutz sungrazers tend to arrive in "clusters" of several arriving within one to two decades of each other. One such "cluster" appeared shortly before I began comet observing, and featured the brilliant Comet Ikeya-Seki 1965f, by far the brightest comet of the 20th Century. (I was seven years old at the time it appeared, and was obsessed with dinosaurs then; had I known of its appearance I very likely would have seen it.) The last member of that "cluster" was Comet White-Ortiz-Bolelli 1970f, which appeared just a few months after I began comet observing, however it was visible only from the southern hemisphere and furthermore faded quite rapidly, and was long gone before I ever learned of it.
Since that time, however, numerous Kreutz sungrazers have been detected with space-based coronagraphs, first with the SOLWIND coronagraph aboard the American Department of Defense satellite P78-1 which detected several sungrazers between 1979 and 1984, and then the Solar Maximum Mission (SMM) satellite, which detected a similar number between 1987 and 1989. Following its launch in late 1995 the joint NASA/ESA SOlar and Heliospheric Observatory (SOHO) mission has since detected well over 2000 Kreutz sungrazers, and the twin spacecraft of the Solar TErrestrial RElations Observatory (STEREO) mission have also detected numerous sungrazers over the past four years. All of these comets disintegrated as they passed through perihelion and none have been seen from the ground (with the apparent exception of Comet C/2008 O1, which seems to have been photographed during the total solar eclipse of August 1, 2008). I have tried several times -- unsuccessfully, obviously -- to detect any of these comets during the total solar eclipses I have traveled to (and, as I related during my entry for Comet 19P/Borrelly (no. 436), I ended up not going to the 2008 eclipse), and I have even tried (with almost no expectation of success) on a handful of occasions to detect one of these comets in daylight or bright twilight (again, obviously, unsuccessfully).
This steady stream of SOHO sungrazers suggests that the production of these comets is almost continuous, and furthermore seems to suggest that additional bright sungrazers might be on the way. A few years ago JPL astronomers Zdenek Sekanina and Paul Chodas examined both the historical sungrazers and SOHO sungrazers in detail, and in a paper published in 2007 they argued that another new "cluster" was on its way in, and would likely arrive within the next one to two decades.
What may well be the first comet of this Sekanina-Chodas "cluster" was discovered on the morning of November 27, 2011 by amateur astronomer Terry Lovejoy of Thornlands, Queensland, whose name we have already encountered previously in "Countdown;" this is his third comet discovery. At that time it was a relatively dim object of 13th magnitude located a couple of degrees south of the star Gamma Centauri, and it brightened somewhat slowly as it approached the sun, with the elongation decreasing rapidly; the final ground-based observations were obtained on December 9, by which time its elongation had shrunk to 20 degrees but by which it was also beginning to exhibit a distinctive tail. By that time it was also visible in some of the STEREO instruments, and on December 14 it entered the field of view of the LASCO C3 coronagraph aboard SOHO, already the brightest sungrazer that SOHO had ever dectected coming into the field of view.
While Comet Lovejoy, as expected, brightened as it approached the sun over the next two days, the general consensus among astronomers was that it would likely disintegrate as it passed through perihelion. Indeed, by late in the day on December 15 as it disappeared behind the occulting disk in the C2 coronagraph, its tail was left behind, suspended, it seemed, in space. However, within a few hours it emerged from behind the occulting disk and began traveling away from the sun; initially tail-less, it quickly grew a new tail that soon rivaled the old one (which, curiously, remained visible for sevefal additional hours). Throughout this time Comet Lovejoy was extensively examined by a variety of scientific instruments aboard several spacecraft, including the Solar Dynamics Observatory as well as the Japanese Hinode probe. A detailed discussion of these observations, which reflects the overall atmosphere of excitement that astronomers were experiencing, can be found at the SOHO sungrazer web site.
By around December 21 Comet Lovejoy's tail began emerging out of the twilight into the southern hemisphere's morning sky, and within a couple of days the head itself could be seen close to the horizon. From that point on up through the end of the year and into early January 2012 it put on a spectacular show for observers in the southern hemisphere, as it exhibited a long, relatively straight tail (typical of Kreutz sungrazers) up to 30 degrees long or longer, with many observers according it "Great Comet" status. Many outstanding images of the comet were taken and can be found at various sites around the web; two representative sites are one maintained by Rob McNaught and featuring the images he obtained from Siding Spring Observatory in New South Wales, and another one maintained by "Countdown" participant Con Stoitsis and featuring images taken by members of the Astronomical Society of Victoria. Astronauts aboard the International Space Station were also able to view the comet and take some spectacular photographs from that unique vantage point.
From my viewing perspective, Comet Lovejoy was essentially a total wash. The Kreutz sungrazer orbit strongly favors the southern hemisphere over the northern in any event, and a perihelion passage in December essentially excludes the northern hemisphere entirely. On December 15 and 16 I made several attempts to view the comet as it was traveling toward and receding from perihelion (using the telescope and techniques that allowed me to observe successfully Comet McNaught C/2006 P1 (no. 395) in daylight when it was near perihelion) but apparently it wasn't quite bright enough for me to detect. Once it emerged into the morning sky the viewing perspectives from the northern hemisphere were hopeless, as the comet rapidly headed straight southward, passing 1 1/2 degrees from the south celestial pole on January 9 two days after its closest approach to Earth (0.50 AU). Although it began heading rapidly northward after that, the reports from the southern hemisphere indicated that it was fading rapidly, and perhaps more ominously, that there was essentially no coma, i.e., the comet was essentially a "headless" tail (which matches the description of some of the past Kreutz sungrazers). Although visual observers continued to detect the tail (still close to 30 degrees long) as a faint "ghostly" object, and high-contrast images continued to show it, the comet was clearly on its way towards complete disintegration, and all I could do was hope that "something" remained of it by the time it came far enough north for me to observe during the latter part of January.
On the evening of January 20, when the comet's declination was -54.5 degrees, I drove to the top of a ridge 8500 feet (2590 meters) high with a straight shot to the southern horizon -- the same place where I obtained my final observation of Comet Hale-Bopp C/1995 O1 (no. 199) from New Mexico, when its declination was -56.7 degrees -- for an attempt with my old 8-inch (20 cm) telescope. I suspected "something" near the comet's expected location, however in retrospect I tend to think this was just imagination, and I discount this "observation." Two nights later the comet was accessible above the range of hills to my south from my regular observing site at my home, and with the 41-cm telescope I seemed to see an extremely pale and vague diffuse glow -- about the same surface brightness as the gegenschein -- that traveled at the comet's expected rate and direction of motion during the 1 1/2 hours that I followed it. After two nights of clouds (including a small snowstorm on the second night) I was able to confirm this sighting when I once again could detect this extremely pale and vague glow that again traveled at the expected rate and direction of motion during the two hours that I followed it. While I am convinced that the comet -- or whatever was left of it -- was unmistakably "there," these observations unquestionably rank as among the most difficult and challenging comet observations I have ever obtained. For what it's worth, I measured a brightness of close to 12th magnitude, although I'm not sure this means all that much; the ill-defined "coma," as it were, sometimes appeared to be around three arcminutes in diameter, but at other times appeared to be about double that.
While I'm glad I was finally able to view Comet Lovejoy, considering how much it has fallen since the dramatic show it put on for my southern hemisphere friends a month ago, and considering how difficult it is to view now, it actually seems rather anti-climactic. I am also now almost certainly done with it, since the moon is now starting to wash out the evening sky, and I'm quite certain there will be nothing left to see by the time that the moon clears out. For what it's worth the comet continues its decelerating northward trek over the coming weeks, being currently located in southern Caelum; it travels through portions of Eridanus and Lepus before entering southwestern Orion in mid-March and passing two degrees southeast of the bright star Rigel a few days later.
So, here I am now at comet no. 500. It's been an interesting trip with "Countdown" for these past five years, and I'd like to thank all the students and others who observed and imaged these various comets with me during this time. I did go through some significant life upheavals during these past five years; when I started "Countdown" I had some vague thoughts in my mind that my marriage was likely in its final stages, and as "Countdown" readers know, after two grueling years my divorce was final in April 2010. I do, however, now have a wonderful new woman in my life, with whom I've now been for slightly over two years. As expected, my younger son Tyler graduated from high school two years ago, and left home two months later (thus imparting to me the "empty nest" syndrome); he and his older brother Zachary are both now attending college at New Mexico State University. There are no impending marriages on their end, and no prospects of any grandchildren anytime soon, all of which is fine with me.
On the professional side, three years ago I began teaching on-line university classes with the American Public University System, and while I initially taught introductory astronomy courses, I have recently also started teaching graduate-level courses in subjects like Space Policy, and I do enjoy working with the graduate students. I had to put much of Earthrise itself on the back burner while I was going through my divorce and the other upheavals, but now that I am safely past them I have begun working diligently again on Earthrise-related matters, and I am happy to report that there are some rather positive developments that have the potential of becoming reality within the not-too-distant future. Life, indeed, continues on . . .
With the addition of Comet Lovejoy to my tally, "Countdown" is now complete. There will be a successor program, although it will probably take me another two to three months to put it together; I'd advise anyone interested to just "watch this space!" During the interim I will continue updating the "update" page on a fairly regular basis, although I will not have any fanfare announcments of any new additions to my tally. And speaking of which, yes, I am already looking for comet no. 501, and indeed have already attempted three comets (all unsuccessfully) since adding Comet Lovejoy. For the time being, I will continue to look for the comets that are around, and in fact in the essay I posted when I began "Countdown" I mention some of the forthcoming comets that I hope to see. To that list I might add objects like Comet PANSTARRS C/2011 L4, which conceivably could become a northern hemisphere "Great Comet" a little over a year from now, and, hopefully, more Kreutz sungrazers from the incoming Sekanina-Chodas "cluster" (at least one of which will hopefully pass through perihelion during September or October and thus become accessible to the northern hemisphere). So, yes, for at least the immediately foreseeable future, and likely well beyond, I will be out there, watching these nebulous and mysterious visitors from space as they make their brief passages through both the inner solar system and through my life.