|471. COMET MACHHOLZ C/2010 F4 Perihelion: 2010 April 6.11, q = 0.614 AU
"Back in the good old days," i.e., before the comprehensive survey programs that began to come on-line during the late 1990s, the comet discovery rate was significantly less than it is today, and a pretty sizable percentage of the comet discoveries that were made were by amateur astronomers who routinely swept the skies visually with small to moderate-sized telescopes. (Indeed, if one goes back several decades a large majority of the comets that were found were discovered in this manner.) I tried my own hand at this for several years -- unsuccessfully, as it turned out, with my one comet discovery being made by accident once I had essentially given up the deliberate searches. (I don't know if there's a lesson there or not.) Some individuals managed to make a respectable number of comet discoveries, and a fairly large percentage of the comet additions to my tally during my first couple of decades came as a result of these. In addition to observing these comets, I sometimes was able to confirm reported discoveries, often as a result of requests made by the IAU's Central Bureau for Astronomical Telegrams, and even on occasion by the discoverers themselves.
Since the advent of the comprehensive surveys visual comet discoveries of this nature have all but ended, since the survey programs are able to detect the comets when they are far from the sun and much too faint to be visually detectable. Only a handful of visual comet discoveries have been made since the beginning of the 21st Century, the most recent of these having been made almost 3 1/2 years ago (Comet Levy P/2006 T1 (no. 397), discovered by David Levy in Arizona; this turned out to be a periodic object apparently undergoing an outburst around the time of David's discovery, and it will pass slightly within 0.20 AU of Earth during its next return in early 2012). A growing consensus among comet astronomers is that the era of visual comet discoveries is essentially over.
But not entirely. On March 24 I received an e-mail from my longtime friend Don Machholz in California, and shortly thereafter had an interesting telephone conversation with him. Don began hunting comets in the mid-1970s and since that time had discovered ten comets. (I've seen all ten of these, beginning with his first one, 1978l (no. 31) and extending through his most recent one, the naked-eye object C/2004 Q2 (no. 355); we have already encountered his name previously in "Countdown" as a result of one of his periodic comet discoveries.) On the previous morning, i.e., March 23, Don had apparently found a comet about three degrees to the northeast of the star Eta Pegasi; however, over a 20-minute watch (that ended due to the onset of twilight) he did not detect any motion, and he had been clouded out the following morning. Since the weather forecast was again calling for him to have cloudy conditions on the following morning (March 25) he asked me if I might be able to confirm his discovery, as I had done with several others of his in the past.
I had clear skies on that next morning, and searched an area within a two- to three-degree radius of the position that Don had given me, and was distinctly surprised when I didn't see anything. In ensuing telephone conversations and e-mails I encouraged him to try for it again -- not that I think he needed much encouragement from me to do so -- and on the next morning (March 26) he managed to pick it up. It turns out that the comet was heading almost due eastward at over two degrees per day, and thus was some four degrees from the discovery position when I made my attempt -- outside of the region I was searching. After Don submitted his observations to the Central Bureau the comet appeared on the Minor Planet Center's Near-Earth Object Confirmation Page, and over the next few hours observers in Japan and Europe managed to observe and take images of it, and the discovery of Don's 11th comet was announced later that same day.
The following morning, March 27, would be the last morning with any dark time before the full moon. Unfortunately, the comet's continued rapid eastward motion was carrying it closer to the sun (elongation at that time 32 degrees), and from the location where I currently have the 41-cm telescope sited that is a bad direction, with a distant hill and trees to contend with. By the time the comet's field had cleared the trees twilight was already well underway, and after some diligent searching I was able to glimpse the comet for about two minutes in the rapidly brightening sky before twilight completely overwhelmed it. It was difficult to make any kind of physical measurements of the comet under these conditions, but overall it seemed to be between magnitudes 11 and 11 1/2, reasonably consistent with what other observers (including Don) were seeing.
That brief and, frankly, unsatisfying, observation of Comet Machholz will very probably be the only one I obtain of it. According to the preliminary orbital calculation that is available at this writing, it is traveling in an orbit that is essentially perpendicular to Earth's; its elongation has remained small for several months now (reaching a maximum of 50 degrees shortly after mid-February) which explains why it wasn't picked up by the surveys, and it was nearest Earth (1.15 AU) in mid-March. Its current rapid eastward motion will carry it through conjunction with the sun (22 degrees north of it) in early April, and although it enters the evening sky after that the elongation will remain small and decreases as its motion turns southward; the comet passes six degrees east of the sun in early May and is again in conjunction with the sun (10 degrees south of it) shortly after the middle of that month. The comet theoretically becomes accessible from the southern hemisphere by late June or early July but by then will almost certainly be a very faint, distant object.
Had it not been for Don's discovery, this comet might very well have made its passage through the inner solar system without ever having been detected (although it is apparently now faintly visible in images taken with the Solar Wind ANisotropies (SWAN) ultraviolet telescope on board the SOlar and Heliospheric Observatory (SOHO) spacecraft). It would seem that, even with all the comprehensive survey programs that are currently operating, not to mention the various spacecraft that are also finding comets, there is still a role -- albeit a small one -- for the visual comet hunter, and the days of such discoveries are not entirely finished just yet.
UPDATE: More recent orbital calculations have confirmed the general correctness of the preliminary orbit, and the viewing circumstances described above. I have no expectations of seeing this comet again.
Another faint and nondescript long-period comet makes its way onto my tally. This one was discovered on April 5, 2010 (evening of April 4, local time) by Andrea Boattini during the course of the Catalina Sky Survey in Arizona. (We've already encountered Andrea's name three times previously in "Countdown," and his discovery total now stands at 13.) The following day -- April 5, local time -- I happened to notice a fairly bright object listed on the Minor Planet Center's Near-Earth Object Confirmation Page, and that evening I successfully saw the "mystery" object as a diffuse 14th-magnitude comet that traveled slowly through the star field during the 45 minutes I watched it. (I initially had to wait for it to clear a 13th-magnitude star it was sitting upon.)
I will at most probably only see this comet another one or two times before it's gone. It is currently located in northeastern Taurus some seven degrees east of the Pleiades star cluster (M45), already at an elongation as low as 49 degrees. It travels towards the southeast during the coming weeks, crossing into northwestern Orion during the latter part of this month and with the elongation shrinking to 40 degrees by early May; by that time it will be south of the sun, thus becoming increasingly difficult to see from my latitude. Meanwhile, it has now already passed through perihelion and is also receding from Earth (minimum distance of 1.36 AU in early March) and thus should also be fading fairly rapidly. By the time the moon enters the evening sky after mid-April I will probably be finished with it.
14th magnitude is actually quite bright for a modern survey comet discovery, and one might ask why this one wasn't discovered earlier. The very heavy "El Nino" winter we've had in the southwestern U.S. (where most of the major survey programs are located) is certainly part of the answer, as is the fact that the comet has remained at a moderately small elongation in the evening sky (although at a fairly high northerly declination) for the past several months. Furthermore, it has spent most of that time traveling through rich Milky Way star fields in Cygnus, Cassiopeia, and Perseus. Only now, when near perihelion, has its presence become known, and accordingly it makes its brief appearance on my lifetime comet tally.
I had arisen early on Friday morning, April 16, to make an observation attempt for Comet McNaught C/2009 R1, and before doing so as is my custom I checked the Minor Planet Center's Near-Earth Object Confirmation Page. I was rather surprised to see a 13th-magnitude object listed there, located close to opposition. An object that bright on the NEOCP is almost always a comet, and I made plans to try to observe it; however, when I checked the field all I could see was a 13th-magnitude stellar object which nevertheless coincided with the position given on the NEOCP listing.
The object in question had been discovered just a few hours earlier by Jan Vales at the Crni Vrh Observatory in Slovenia. It turns out that the Catalina Sky Survey in Arizona had imaged that same region less that 24 hours earlier and had not recorded anything down to 20th magnitude; thus, just prior to its discovery it had undergone an outburst of at least seven magnitudes. Additional observations and images obtained around the world over the next few days showed that it was expanding into a small coma, and it soon became clear that Vales' object was a comet undergoing a large outburst somewhat similar to those that Comet 29P/Schwassmann-Wachmann 1 occasionally undergoes, and (on a smaller scale) like that underwent by Comet 17P/Holmes in late 2007. Some rainy weather here in southern New Mexico kept me from seeing it again for several nights, but finally under somewhat poor sky conditions on the evening of April 20 I was able to observe it as a clearly nonstellar "disk" about half an arcminute in diameter and near magnitude 12 1/2.
Vales' comet is traveling in a fairly low-eccentricity (0.19) orbit with a period of 7.6 years. The orbit, in fact, is fairly similar to those of the Hilda-type asteroids (that travel in a 3:2 resonance with Jupiter, i.e., they travel around the sun three times for every two orbits that Jupiter makes), and since these have occasionally been suspected of being dormant comets it is conceivable that Vales' comet is an example of this. Its orbit has been fairy stable for awhile, although it did pass 1.0 AU from Jupiter in May 1976. It is currently located in northern Virgo a little over a degree north of the star 78 Virginis and, having been at opposition right around the time it was discovered, is now traveling almost due westward at a little over ten arcminutes per day; over the coming weeks its motion turns more southward and it reaches its stationary point in early June when located about half-way between the stars Delta and Zeta Virginis. After that it turns towards the southeast, and remains in Virgo until early September when it crosses into western Libra.
Due to the uncertainties associated with an outburst it is difficult to predict just how long the comet will remain visible. If it follows a pattern similar to those of other outbursting comets it will likely continue to expand out over the coming days and weeks and grow more diffuse as it does so, perhaps remaining visible for one to two months before fading beyond the range of detectability. Whether or not it undergoes any additional outbursts, and in the meantime whether or not it can be identified with any object that might have been observed sometime in the past, remains to be seen.
My initially planned target on the morning of April 16 -- when I ended up adding the above comet -- was this comet. It was discovered back on September 9, 2009 by Rob McNaught during the course of the Siding Spring survey in New South Wales -- his 51st comet discovery, out of a total that currently stands at 54. At that time the comet was a fairly faint object of magnitude 17 or 18, and located at a declination of -34 degrees; since then it has slowly traveled northward and brightened, and after being in conjunction with the sun in mid-February has begun emerging into the morning sky over the past few weeks. Some observers in the southern hemisphere began reporting it at around 11th magnitude, and since it was south of the sun (and thus very low in my southeastern sky) I've briefly listed it under the "Southern Hemisphere Only" section of the "Countdown" update page; I did make an attempt with the 20-cm telescope on the morning of April 12 but at the low altitude I couldn't convince myself I was seeing anything. On the morning of the 16th I used the 41-cm telescope, and after having to play a little "dodge-the-trees" near the horizon I successfully observed it as a diffuse and somewhat condensed object slightly brighter than magnitude 11 1/2.
Comet McNaught has the potential to become a fairly bright object, perhaps becoming visible to the naked eye, in a couple of months, although unfortunately it never becomes too well placed for observations. The good news is that it is currently running somewhat brighter than the ephemeris predictions, which theoretically bodes well for its future performance; on the other hand, it appears to be making its first visit in from the Oort Cloud, and such objects often fail to live up to initial expectations (being bright initially but then "slowing down" dramatically as they approach perihelion). It is always good to keep in mind that comets can become quite unpredictable, especially in situations like this.
The comet is currently located in western Pisces, just west of the "circlet," and is at an elongation of 42 degrees. Over the coming few weeks it travels towards the northeast, passing through the constellations of Pegasus and Andromeda, being at its maximum elongation (48 degrees) during mid-May. During the second week of June it crosses into western Perseus (passing one degree northwest of the star cluster M34 in the process), with its motion then turning more towards due east; it is nearest Earth (1.14 AU) in mid-June and at its farthest north point (slightly north of declination +48 degrees) a few days later. The comet's elongation then begins to decrease rapidly, and it is in conjunction with the sun (20 degrees north of it) on June 26. It may be briefly visible in the evening sky for a few days after that, but by the time it passes through perihelion it will only be 15 degrees from the sun, and thereafter will be lost to sight.
Keeping in mind the above caveats about its brightness, it seems likely that Comet McNaught may be somewhere around 9th or 10th magnitude around the beginning of May and one to two magnitudes brighter than that by the latter part of that month. By early June it could be somewhere around 6th or 7th magnitude, and anywhere between 3rd and 5th magnitude during the second half of that month; since it will then be quite close to the horizon in twilight it will likely be a difficult naked-eye object but should be easily detectable in binoculars. Because it is on the far side of the sun from Earth there is no potential for enhancement of its brightness due to forward scattering of sunlight, and in the meantime we'll just have to see how much of a tail the comet develops as it approaches perihelion.
After perihelion Comet McNaught should become visible from the southern hemisphere around the beginning of August; it will be in western Hydra and possibly around 7th or 8th magnitude. It travels towards the south-southeast over the subsequent weeks and months, through Antlia, Vela, and Centaurus, and by the end of October is in southern circumpolar skies; by that time it will likely have faded beyond the range of visual detectability. For what it's worth, the comet passes within one degree of the south celestial pole shortly after mid-January 2011.
For the past two years and more I've been hinting at some major upcoming changes in my personal life. While I didn't quite know it at the time, Comets Vales and McNaught were the first two comets that I added to my tally after my divorce from my ex-wife Eva became final (the final decree had been signed on the 15th, although I didn't find this out until a few days later). I am currently in the process of moving to a new location (still in Cloudcroft, and not too far away from my former residence where Comet Hale-Bopp was discovered), and for the past few weeks I've been somewhat "displaced" while all this has been going on (and, among other things, I haven't been able to make astronomical observations as much as I might have liked). I am hopeful that I will be able to move into my new residence within the next one to two weeks, and I will discuss that in more detail in these pages as that happens. If Comet McNaught behaves reasonably well as it approaches perihelion, I just might have a fairly nice comet with which to mark the beginning of this new phase of my life.
UPDATE: Comet McNaught performed more or less as expected, reaching a peak brightness of magnitude 5 1/2 shortly after mid-June and displaying an ion tail several degrees long. After a very brief appearance in the evening sky at the end of June it disappeared into twilight, and apparently there were no detections of it during the July 11 total solar eclipse when it was located ten degrees due east of the sun. Although it apparently remained visible in images taken with the SWAN ultraviolet telescope aboard SOHO until early September, when ground-based observers in the southern hemisphere began attempting it late that month they were unsuccessful in detecting it, suggesting that it may have disintegrated by then.
After the flurry of recent new discoveries, I once again add an old friend to my tally. This particular comet was discovered in July 1873 by Wilhelm Tempel, a German astronomer who observed from Marseille, France until 1870 after which he relocated to Milan, Italy, and later to Arcetri. Overall, Tempel is credited with twelve comet discoveries between 1859 and 1877, four of these being short-period objects; 9P/Tempel 1 (which, incidentally, was "lost" between 1879 and 1967) was the "Deep Impact" comet at its most recent return in 2005 (no. 367) and will be visited by the Stardust spacecraft next February, while 55P/Tempel-Tuttle is the parent comet of the Leonid meteor shower and last returned in 1998 (no. 238). One of his long-period comets, Comet Tempel 1864 II, which briefly became a fairly bright naked-eye object when it passed 0.10 AU from Earth, has the distinction of being the first comet ever to have its spectrum observed.
P/Tempel 2 has been a very dependable performer ever since its discovery, and the current return is the 22nd at which it has been observed. During this time its orbital period has varied between 5.2 and 5.5 years and its perihelion distance between 1.32 and 1.48 AU; as a result of a distant approach to Jupiter (1.63 AU) in late 2002 its current orbital period is 5.37 years. It was observed around aphelion following its 1988 return and thus is an "annual" comet that is not formally recovered; the first observations at the current return were obtained by the Mt. Lemmon survey in Arizona on January 10, 2008, less than three months after it had gone through aphelion.
I've seen P/Tempel 2 on three previous returns, in 1983 (no. 57), 1988 (no. 119), and 1999 (no. 265). In 1983 I happened to add it to my tally on the same night that Comet IRAS-Araki-Alcock 1983d (no. 56) made its close approach to Earth (0.031 AU); a month later it became one of the first comets that I observed from the southern hemisphere, and during that return it peaked at 9th magnitude. During 1988 it reached 8th magnitude, and although the geometry was similar in 1999, perhaps because of an increased perihelion distance (1.48 vs. 1.38 AU) to my eyes it didn't seem to get any brighter than magnitude 10. At the current return, because of poor weather and the "displacement" I mentioned in the previous entry I didn't get a chance to try for it earlier, but after reading a couple of reports that suggested the comet was bright I attempted it on the morning of April 25 (the last morning before the full moon during which there would be any dark time) and successfully saw it as a faint, somewhat condensed object near magnitude 13 1/2.
This year's return of P/Tempel 2 is a distinctly favorable one. It is currently located in southwestern Aquarius, in the morning sky some 90 degrees from the sun; over the coming weeks it tracks eastward across that constellation and then enters Cetus in early July, where it remains for the rest of the year. The comet is nearest Earth (0.65 AU) in late August and goes through opposition shortly before mid-October. Historically, P/Tempel 2 has been one of those comets like 6P/d'Arrest that remain faint until shortly before perihelion, and then brighten almost explosively until a short time after perihelion, after which they slowly diffuse out and fade away. If that remains true this year, the comet should brighten rapidly over the coming few weeks, reaching a peak brightness perhaps somewhere between 8th and 9th magnitude during July and August, and remaining visible as it fades until perhaps November or December.
The next return of P/Tempel 2, in 2015 (perihelion mid-November), is a mediocre one, with the elongation at perihelion being 50 degrees in the evening sky; it will probably be visually detectable but will likely remain rather faint. The return after that, in 2021 (perihelion late March), is even less favorable, and the comet is unlikely to be picked up visually. The 2026 return, however, is the most favorable one of the entire 21st Century, with perihelion occuring at the beginning of August, while at the same time it will be making its closest approach to Earth (0.41 AU); the comet should reach a peak brightness between 7th and 8th magnitude.
Meanwhile, with the addition of this comet to my tally I am now 3/4 of the way through "Countdown." Readers who have been with me through all this know that, throughout a good part of "Countdown," my personal life has been marked by uncertainty and upheaval as it has undergone some significant changes; while things are not entirely settled yet, I am now at a point where I can see things beginning to reach that kind of state. Hopefully by the time I reach comet number 500 -- which, the way things have been going, looks like will be sometime during the second half of 2011 -- my personal life will have reached its new equilibrium, and I'll be able to continue on from there.
Following my recent divorce I underwent a two-month-long period of "displacement" while my new residence was being prepared for occupancy. Although at this writing things are not completely finished yet, they have nevertheless progressed to the point where I have been able to move in, and I did so on Thursday, May 20. That night was clear, and I decided to mark the occasion by collecting some astronomical observations the following morning after the first-quarter moon had set. While most of the objects I observed were "Countdown" comets listed on the update page, I also attempted a couple of other comets which I have not observed previously. One of them was this object, which I've been attempting unsuccessfully off and on since mid-March and for which I thought I would make one final attempt before writing it off completely. I'll admit I was somewhat surprised when I saw a tiny and very faint diffuse object -- slightly fainter than 14th magnitude -- in the expected position, and which traveled slowly northward over the course of the next hour and a half. I successfully observed it again the following morning.
The comet was discovered back on January 14, 2010 by the LINEAR program based in New Mexico -- the second and decidedly less interesting of two comets discovered by that program during January. (The other comet, P/2010 A2, has an orbital period of only 3.47 years and travels entirely within the inner portion of the main asteroid belt; it may not be a "true" comet at all, but rather may be the debris train resulting from a collision between two asteroids. It has, not surprisingly, been the subject of intense investigations ever since its discovery, and among other things has been imaged with the Hubble Space Telescope.) This second January LINEAR comet has also turned out to be periodic, with an orbital period of 11.5 years.
Comet LINEAR is currently located in northwestern Scorpius, 4 1/2 degrees southwest of the bright star Antares. It is slowly traveling almost due northward and passes four degrees west of Antares shortly before mid-June; by the end of that month its motion turns toward the east and it crosses into southwestern Ophiuchus during the second week of July. It is currently at opposition and was nearest Earth (0.74 AU) on May 16; since it is already over a month past perihelion passage it is probably as bright as it is going to get, and although I will probably make an attempt for it once the upcoming full moon has cleared from the evening sky it is quite conceivable that the two observations I have just made will be the only ones I obtain of it.
With its current orbital period successive returns alternate between favorable ones like this year's and unfavorable ones. Thus, the next return, in 2021, is unfavorable, however the following one, in 2033 (perihelion early April) is favorable. The comet does not come as close to Earth as it did this year (the minimum distance being about 0.82 AU, near the end of May) and it will likely be even fainter than it was during this year's return. Even if I am still actively observing at that time, unless I have access to larger visual equipment than I have now Comet LINEAR will probably be beyond my range, and thus it would appear that I have probably made the only observations of it that I will ever make.
In addition to the divorce and relocation, other interesting things are happening in my life as well. On this upcoming weekend my younger son Tyler graduates from Cloudcroft High School, and although he will be staying around for a good part of the summer participating in various activities, before long he will be heading off to Las Cruces, New Mexico to join his older brother Zachary at New Mexico State University, and I of course will be facing the "empty nest" syndrome. Meanwhile, on that same weekend our local acting troupe stages the opening performances of our newest play -- and, yes, I'm in the cast, although I'm not portraying the villain this time. Life, indeed, keeps moving on . . .
2 1/2 months have now elapsed since I moved into my new residence. The process of unpacking and settling in has been a slow but fairly steady one, a "work in progress" being how I usually refer to it. I've been busy during the interim, with my regular teaching duties and with teaching at the Summer Science Camps at the New Mexico Museum of Space History in Alamogordo, and there have been other things going on as well, for example, I was in the cast of a recent play put on by our local acting troupe and will be in the cast of the next one coming up in a month -- I play the part of a duck! Meanwhile, my younger son Tyler, who graduated from Cloudcroft High School at the end of May (and who was in the most recent play, playing the part of both the hero and the villain), is leaving home within the next week for Las Cruces, New Mexico, where he begins his life as a college student at New Mexico State University in a few weeks (and I, of course, now face the "empty nest" syndrome). Finally, although it's still fairly early in the process, I seem to have a new love in my life, and perhaps will write more about that in a future "Countdown" entry.
I have, of course, kept busy with my astronomical observations during these past 2 1/2 months -- an endeavor which included the brief period of naked-eye visibility of Comet McNaught C/2009 R1 (no. 474) back in mid-June -- although the heavy monsoon season we've been having here in the southern New Mexico mountains has put a bit of a damper on that activity. As I recounted in its "Countdown" entry, I added my most recent comet on the very night after I moved in, but had not added any more comets to my tally since then; while going this long without adding a comet is somewhat unusual in this era of the comprehensive sky surveys, it does happen from time to time. That long stretch is finally over now, with the addition of this latest comet.
The comet in question is an old friend. It was originally discovered in March 1986 by Malcolm Hartley (whose name we have already encountered in a previous "Countdown" entry) during the course of a photographic survey program that was being conducted from Siding Spring Observatory in New South Wales. At discovery it was a fairly faint object of 17th or 18th magnitude, and was found to have passed perihelion over nine months earlier; the perihelion distance right near 1.0 AU kept it too close to the sun to be detected for quite a few months afterward. A close approach to Jupiter (0.33 AU) in 1982 had placed it into its discovery orbit; prior to that its returns had occurred under similarly poor geometry, and prior to a very close Jupiter approach (0.09 AU) in 1971 it had been in a more distant orbit. Meanwhile, some moderately close Jupiter approaches in 1993 and 2005 have placed it into its present orbit, with a current period of 6.47 years.
P/Hartley 2's first return after its discovery was in 1991, when it passed 0.77 AU from Earth and reached 8th magnitude; I read of its recovery on the day I returned from a trip to southern Baja California to observe the great total solar eclipse that July, and added it to my tally (no. 160) the very next morning. It again reached 8th magnitude at the subsequent return in 1997 (no. 235), but the intervening return, in 2004, was a very poor one geometrically and I didn't attempt it. At the present return it was recovered as long ago as May 5, 2008 by Colin Snodgrass and Rachel Gilmour utilizing the 8-meter Very Large Telescope at the European Southern Observatory's Cerro Paranal facility in Chile; only nine months past aphelion at the time, it was a very faint object of 24th magnitude but still showed a trace of coma. I began searching for it (in and around the monsoon rains) this past July, and although I had faint suspects on a couple of occasions I never saw anything I found convincing. Finally, on the evening of August 4 I successfully observed the comet as a faint 14th-magnitude object, and followed it for an hour as it moved against the background stars.
This return of P/Hartley 2 is an outstanding one, as the comet passes only 0.121 AU from Earth on October 20 (incidentally, the 7th closest approach to Earth of all the comets in my tally). It is presently located in northern Pegasus some seven degrees west-southwest of the star Beta Pegasi (the northwestern of the stars in the "Great Square" of Pegasus), and over the coming few weeks tracks northward and eastward through Lacerta, Andromeda, and Cassiopeia (traveling along just south of the "W" and reaching a peak northerly declination of +56.8 degrees in early October) before turning southward through Perseus and Auriga, being located a few degrees south of the bright star Capella and traveling three degrees per day at the time of its closest approach to Earth. The comet enters Gemini in late October (where it will be located when it passes through perihelion) then passes rapidly through Canis Minor and Monoceros during November before entering Puppis (and passing one degree east of the bright star cluster M47) near the end of that month. It is at opposition in early January 2011 and, heading back northward, crosses back into Monoceros late that month, where it remains for the next few weeks.
If P/Hartley 2 behaves as it has at its previous returns it should brighten steadily over the coming weeks, and may be as bright as 5th or 6th magnitude -- and thus dimly visible to the naked eye -- around the time of perihelion and closest approach to Earth. Although it should begin fading after that, the earth continues to keep up with it rather well, and it may still be as bright as 10th or 11th magnitude at the end of 2010, and remain visually detectable until perhaps February or March of next year.
In addition to the close passage by Earth, this year's return of P/Hartley 2 is special in that it will have a spacecraft visitor. Following its successful encounter of Comet 9P/Tempel 1 in 2005 (no. 367), wherein it fired a projectile at the comet's nucleus, the remaining section of the Deep Impact spacecraft was given two additional missions, christened Extrasolar Planet Observation and Characterization (EPOCh) -- a subject, incidentally, which was near and dear to my heart early in my career and in which I still retain a strong interest -- and Deep Impact eXtended Investigation (DIXI); these two have been combined into the acronym EPOXI. EPOXI was originally scheduled to pass by Comet 85P/Boethin in December 2008, however when it failed to show up on recovery attempts a year earlier the destination was changed to P/Hartley 2. (Despite very favorable viewing geometry in 2008 P/Boethin was never recovered or observed, and thus seems to have disintegrated.) This decision is what led to the early recovery of P/Hartley 2, and in addition to those early observations it was observed in the infrared with the Spitzer Space Telescope in August 2008, which revealed a nucleus slightly over one kilometer in diameter.
EPOXI is scheduled to pass 700 kilometers (435 miles) from Hartley 2's nucleus on November 4. At that time the comet will be located in northern Monoceros approximately nine degrees east of the Rosette Nebula (NGC 2237) and a similar distance west of the bright star Procyon, and should still be a bright object of 6th or 7th magnitude.
None of the future returns of P/Hartley 2 are as favorable as this year's, but on the other hand there aren't any more close approaches to Jupiter coming up for some time, and with its current period near 6 1/2 years future returns will alternate between favorable and unfavorable for the next few decades. The next return, in 2017 (perihelion mid-April) is unfavorable, however the one after that, in 2023 (perihelion mid-October) is another excellent one, with the comet's passing 0.38 AU from Earth and probably reaching about 7th magnitude. Following another poor return in 2030 (perihelion early April) there is yet another good one in 2036 (perihelion late September); the comet passes 0.63 AU from Earth and should reach 8th magnitude.
UPDATE: In early September EPOXI began taking images of P/Hartley 2 in preparation for its encounter with the comet in early November. As of this writing in late September EPOXI's most recent image is available here.
UPDATE: On September 25 P/Hartley 2 was imaged with the Hubble Space Telescope, and an infrared image taken by the WISE spacecraft back in May has also been recently released. By early October (three weeks before its closest approach to Earth) the comet had reached 7th magnitude and was exhibiting a large, diffuse coma approximately 20 arcminutes in diameter.
UPDATE: Shortly before P/Hartley 2's closest approach to Earth on October 20 I was measuring an overall brightness of magnitude 5 1/2 and could faintly detect it with my naked eye; the overall coma diameter was well over half a degree, giving it the appearance of a large, diffuse, slightly condensed cloud. By early November it had faded to about 6th magnitude and I could no longer convincingly see it with my naked eye, although the coma was still about half a degree across.
The EPOXI encounter on November 4 was successful, with the spacecraft passing the expected 700 km (435 miles) from P/Hartley 2's nucleus. The images obtained during the closest approach reveal the nucleus as a peanut-shaped object some 2 km (1.2 miles) long along its longest dimension, with significant jetting activity occurring at both ends but with a smooth, inactive plain between these two ends.
After the long 2 1/2-month-long gap that preceded my previous tally addition, I have now added my second comet within a span of three nights. Like the previous comet, this one has the potential to become a somewhat bright object, and something that should be of considerable interest to "Countdown" participants.
The comet was discovered almost a year ago, on August 13, 2009, by Gordon Garradd during the course of the Siding Spring survey based in New South Wales. This is Gordon's 13th comet discovery (of 17 so far at this writing), and the fourth of his comets that I have seen as well as the third time we've seen his name as a part of "Countdown" (his most recent "Countdown" comet having been a fairly bright binocular object during the summer of 2009). At the time of its discovery it was a rather faint object (around 18th magnitude) somewhat deep in southern skies; after being in conjunction with the sun in mid-March of this year it began emerging into the morning sky by about June. I made a couple of unsuccessful attempts for it during July, and after the recent full moon made my first attempt of the current dark run on the morning of August 7. Despite less-than-ideal sky conditions (courtesy of the current monsoon) and a fairly low elevation above my southern horizon (the comet's current declination being slightly south of -36 degrees), I clearly saw a small, diffuse, and moderately condensed object of magnitude 13 1/2 that traveled slowly against the background stars during the hour I followed it. I successfully observed it again the following morning.
Comet Garradd is over 16 months away from perihelion passage; with the exception of the "returns" of Comet 29P/Schwassmann-Wachmann 1 and the Centaur comet 174P/Echeclus (no. 384) there are only two other comets on my tally that I have ever picked up this far in advance of perihelion (Hale-Bopp C/1995 O1 (no. 199) and Christensen C/2006 W3 (no. 422) -- which, incidentally, I am still following, although I will probably be finished with it in the near future). It is currently located in southwestern Sculptor just over a degree north of the star Beta Sculptoris and half a degree south of the fairly bright spiral galaxy IC 5332 (which has been in the same low-power telescopic fields during my initial observations); it is traveling slowly towards the west-southwest, crossing into Grus around mid-August, and will be at opposition in early September before reaching a maximum southerly declination of -38 1/4 degrees during the middle of that month (during which time it will be located some nine degrees due south of the bright star Fomalhaut). The comet then turns gradually northward, entering Piscis Austrinus towards the end of October, and remains accessible in my evening sky until near the end of this year; southern hemisphere observers may be able to follow it for a week or two longer. If it brightens "normally" it should be perhaps a magnitude brighter then than it is now.
After being in conjunction with the sun in late February 2011 Comet Garradd emerges into the morning sky in early April; it will be located in eastern Aquarius and perhaps somewhere around 11th magnitude. Traveling in a steeply-inclined retrograde orbit (inclination 106 degrees) it begins a slow but gradually accelerating northward climb through Pegasus that then turns westward through Delphinus, Sagitta, and Hercules; it is at opposition during late August. By November it ceases its westward trek some six degrees north of the star Alpha Ophiuchi (Rasalhague) and resumes its northward climb, which will carry it through conjunction with the sun (46 degrees north of it) in mid-December and into the northeastern morning sky by the time of perihelion.
For the first few weeks of 2012 the comet continues climbing northward through Hercules, crossing declination +50 degrees and entering Draco (a few degrees southwest of the "head" of that constellation) in mid-February and then beginning a turn towards the northwest. By the latter part of that month it is in northern circumpolar skies, and during March it travels rapidly westward between the Big and Little Dippers, reaching a peak northerly declination of +70.7 degrees during the second week of that month and going through opposition a few days later. In early April it will be located in southwestern Ursa Major and over the next few months it drops southward through Lynx and Cancer, being again in conjunction with the sun in mid-August. Afterwards it again emerges into the morning sky around October, being located in western Hydra; over the next several months it slowly travels southward, and is at opposition again in early February 2013 when it will be located some seven degrees west of the star Alpha Hydrae (or Alphard).
As has been recounted before in previous "Countdown" entries, predicting a comet's brightness is a tricky endeavor, and can be especially problematical in a case like this where we are still so far away from perihelion passage. It is clear that, intrinsically, Comet Garradd is a very bright comet, and it is most unfortunate that not only does it not come all that close to the sun, it also stays relatively far from Earth (minimum distances being 1.39 AU in late August 2011 and 1.27 AU in early March 2012); it it were to have come closer, there is the potential that it could have become a "Great" comet. As it is, a straightforward extrapolation of my initial brightness measurements suggests it could be 6th magnitude or brighter (and thus, theoretically at least, visible to the naked eye) from about September 2011 through about March or April 2012; my measurements also suggest a peak brightness near magnitude 5 1/2 around February 2012. It is always possible that the comet could be a few -- or even several -- magnitudes fainter, or brighter, than this scenario predicts; we'll just have to wait and see what it actually does. For what it's worth, it appears that Comet Garradd is not a first-time visitor from the Oort Cloud, so that is one bit of possible good news.
In any event, barring something very unusual happening it would seem that Comet Garradd is going to be visible for a long time -- probably in excess of two years -- and although it probably won't become very bright it should still be bright enough, and for a long enough period of time, that it should be an easy object for observation for participating students of "Countdown" (particularly those in the northern hemisphere). As is true for any comet that will be visible for this long, a lot of changes will likely take place, both in my personal life and in the wider world, by the time I am finished with it; I do hope that my life will have settled into some sort of equilibrium following the recent upheavals I have experienced, and that Earthrise will again be moving forward (since I had to put much of it on "standby" while getting through the recent goings-on). It occurs to me, incidentally, that by the time I am done observing Comet Garradd I will have reached -- and, probably, long passed -- comet number 500, and will be moving on to whatever lies beyond that.
UPDATE: After its conjunction with the sun in early 2011 Comet Garradd became visible in the morning sky during April for observers in the southern hemisphere, and I successfully picked it up again during the first week of May. To my eyes it appeared as a relatively condensed object near magnitude 11 1/2, slightly fainter than what its brightness during late 2010 might suggest but not dramatically so. Based upon its present brightness I would suspect that the comet will not become any brighter than 6th magnitude anytime during its apparition.
Slowly but surely, my life is starting to settle into a new kind of normality following the upheavals it has undergone over the past many months. I am now an "empty nester," my younger son Tyler having left home four weeks ago to attend college at New Mexico State University; meanwhile in addition to my regular teaching duties I am now able to start turning my attention back to Earthrise activities. I'm getting rave reviews for the "duck act" I'm performing in the current play being put on by our local acting troupe, and things continue to progress with the new love in my life that I've mentioned earlier.
And, of course, "Countdown" continues, and I've now added another comet to my tally. This one was discovered on December 17, 2009 by Rik Hill with the Catalina Sky Survey in Arizona, although it wasn't immediately apparent that it was a comet (hence the name "Catalina"). I had made my first attempt for it at the beginning of September and although I thought I possibly might have been seeing "something" I didn't consider it convincing enough to follow up on it. However, when I attempted it again on the evening of September 9 -- what would have been my late father's 92nd birthday, incidentally -- I clearly saw an extremely faint 14th magnitude diffuse object and was able to follow it for the next hour as it moved against the background stars. I successfully observed it again the following night.
For the most part, this is another one of those faint, nondescript long-period comets that crop up in my tally with some regularity. It is currently located in northern circumpolar skies, at a declination of +71 1/2 degrees in western Draco, and best viewed in the northwestern sky after dusk. Traveling in a steeply-inclined retrograde orbit (inclination 107 degrees), it remains in this same basic part of the sky for the next few months, traveling eastward through Draco and then Ursa Minor, reaching a peak northerly declination of +72 degrees near the end of September before beginning a gradual turn towards the south; it passes south of the "bowl" of the Little Dipper shortly before mid-October (passing half a degree south of the star Gamma Ursae Minoris in the process) and then crosses back into Draco by the end of that month. The comet is nearest Earth -- still a relatively distant 2.48 AU -- during the latter part of November, around which time it should be near its peak brightness of perhaps 13th magnitude; by then it is entering northwestern Cygnus and will be traveling southeastward through the dense Milky Way starfields of that constellation. At year's end it will be located some two degrees west of the nearby double star 61 Cygni, and over the ensuing weeks it takes a more direct southward trajectory through Cygnus and into Pegasus; at the beginning of March it is in conjunction with the sun, 31 degrees north of it. By about the end of April the comet emerges into the morning sky and over the subsequent months continues its general southward trajectory, making another distant approach to Earth (2.33 AU) in mid-August before being at opposition at the beginning of September. Theoretically it may still be visually detectable throughout this time, but if so it is likely to be extremely faint -- probably about the same brightness that it is now.
Many "Countdown" readers have probably noticed that a non-trivial fraction of the comets on my tally are faint, distant, long-period objects that for the most part are relatively nondescript (such as the previous comet). At first glance, this is another faint and distant long-period comet, although in actuality it is quite bright intrinsically, and in some respects it is rather notable. Its large perihelion distance -- the 12th largest of any comet on my tally, and the 6th largest for long-period comets -- will keep it from ever becoming bright, but on the other hand I should be able to follow it for an unusually long period of time, perhaps for almost three years.
The comet was discovered as long ago as September 19, 2006, by the LONEOS program based in Flagstaff, Arizona, as a very faint object between 19th and 20th magnitude. At discovery it was located an incredible 14.29 AU from the sun, the largest heliocentric distance at which any long-period comet has ever been discovered (only a couple of Centaur comets have been discovered at larger heliocentric distances). The interval of five years, seven months before perihelion when it was discovered is also a record for long-period comets (again, this record is beaten by a couple of Centaur comets). It is traveling in a retrograde orbit that is inclined only 14 degrees to the ecliptic (thus, an actual inclination of 166 degrees), and it appears to be making its first visit into the inner solar system from the Oort Cloud; gravitational perturbations will subsequently eject it from the solar system following perihelion, and thus this is the only visit it will ever make to our corner of the universe.
Comet LONEOS has been slowly making its way in towards the inner solar system ever since its discovery four years ago. It was most recently at opposition in early August 2010, and I had actually begun searching for it back during the latter part of May; after several unsuccessful searches over the subsequent months (including on the night in August after my younger son Tyler left home and I officially became an "empty nester") I was about to the point where I was going to give up for this year. However, a CCD image taken in late September by Australian amateur astronomer Paul Camilleri (remotely with the Tzec Maun telescope in New Mexico) suggested that it had brightened somewhat within the fairly recent past, and after he alerted me to this I made another attempt on the evening of September 26 and suspected an extremely faint "something" at the comet's expected position; unfortunately there was only a very brief "window" that night before light from the recently full moon began to overwhelm the nighttime sky, and I couldn't confirm anything. After cloudy weather the following evening I again saw the comet on the evenings of September 28 and 29 and was able to verify my initial sighting. It appeared very faint and small, around magnitude 14 1/2, near the limit of what the 41-cm telescope can achieve for diffuse, "cometary" objects.
At the time of these initial observations Comet LONEOS was located in southwestern Aquila about four degrees southeast of the star Theta Aquilae and one degree west-southwest of the star 68 Aquilae. It is traveling slowly towards the southwest and will be at its stationary point in late November, thereafter resuming direct (eastward) motion, and will disappear into evening twilight by the end of this year. I really don't expect it to get much, if any, brighter between now and then, so I will probably (temporarily) lose it within the next one to two months. After conjunction with the sun in late January 2011 it begins emerging into the morning sky by the latter part of March, when it will be located fairly close to where it is right now and presumably a half-magnitude or so brighter. Over the subsequent several months it tracks generally westward across Aquila, then (beginning in late July) the rich Milky Way star fields of Scutum (passing slightly less than one degree south of the "Wild Duck" star cluster M11 shortly before the end of that month) and then (beginning in late August) Serpens Cauda. The comet is at opposition during the second week of July, and should be around 13th magnitude during the weeks around that time. Meanwhile, by November it is once again disappearing into twilight, and will be in conjunction with the sun during the latter part of December.
The 2012 viewing season, when the comet is finally passing perihelion, should be reasonably good for observations. It emerges into the morning sky by early February -- still in Serpens Cauda -- and over the next several months continues to track westward, crossing into central Ophiuchus in mid-May (passing just over half a degree north of the globular star cluster M107 in early June), into northern Scorpius in mid-June, and into northern Libra near the beginning of July. The comet is at opposition at the beginning of June -- only a month and a half after perihelion passage -- and throughout this time should be near a peak brightness between magnitudes 12 1/2 and 13 (based upon its present brightness). Subsequently it should begin to fade noticeably, and by early October disappears into twilight en route to its next conjunction with the sun in mid-November. By the end of the year Comet LONEOS is again emerging into the morning sky, and during the first several months of 2013 it continues its westward trek across Libra and (beginning during the latter part of April, when it is also near opposition) Virgo. It may be as bright as magnitude 13 1/2 around that time, but once it goes through opposition it should fade rapidly, and I'll probably lose it permanently by July or August.
I have now started to put some distance between myself and the upheavals that my life has undergone over the past couple of years, and things are slowly settling into a new kind of normality. The past couple of weeks have been busy (which partially explains why it took me so long to get this particular "Countdown" entry written); one of the classes I've been teaching just finished its term and I've had to grade final exams and final projects, and in the meantime this past weekend my girlfriend Susanne and I attended a concert by the rock band Muse in Albuquerque. I've also recently had some interesting contacts with agents representing the firm Virgin Galactic, which within the next couple of years expects to be flying sub-orbital flights out of the commercial spaceport that is being built here in New Mexico, and it is distinctly conceivable that by the time I'm finished following this particular comet I may be getting ready to take -- or perhaps may already have taken -- that ride to space that I've always wanted to take.
UPDATE: After its conjunction with the sun in early 2011 I successfully picked up the comet in the morning sky at the beginning of April. It is still a very faint object of magnitude 14 1/2 -- essentially the same brightness it was exhibiting when I was following it in late 2010 -- but presumably it will brighten some over the coming several weeks as it approaches both the earth and the sun.
Comet LONEOS is no longer the record-holder among long-period comets for the largest heliocentric distance at discovery, and the earliest pre-perihelion discovery. Those distinctions now belong to Comet Boattini C/2010 U3, which was discovered on October 31, 2010 by Andrea Boattini during the course of the Mt. Lemmon survey in Arizona; at discovery the comet was located at the remarkable distance of 18.36 AU from the sun -- a larger distance than even any of the Centaur comet discoveries. The orbit is still somewhat in the process of being pinned down at this time, but according to the most recently published calculation Comet Boattini doesn't reach perihelion until February 2019 (almost 8 1/2 years after discovery), when it will still be located at a very large 8.48 AU from the sun. Although only about 20th magnitude at discovery, the comet could theoretically become bright enough for visual observations (14th magnitude) around the time of its perihelion passage, when it will be located in northern circumpolar skies.