CONTINUING WITH COMETS

TALLY ENTRIES 631-640

631. COMET 24P/SCHAUMASSE          Perihelion: 2017 November 16.93, q = 1.206 AU

A long-time acquaintance stops by for another visit. This comet was originally discovered as long ago as December 1911 by Alexandre Schaumasse, who observed from Nice Observatory in France. It was the first of three comets (the other two being long-period objects) that he discovered from Nice during the decade of the 1910s, a period of time during which he also served with the French Army during World War I and was severely injured. The comet was found to have an orbital period of close to 8 years (presently, 8.25 years) and while it has been recovered on most returns since its discovery, its perihelion distance of close to 1 AU means that on some returns it has remained on the far side of the sun for months at a time, and has gone unrecovered. On the other hand, on other returns it can become quite well placed for observation; in 1952 it passed 0.29 AU from Earth and at the same time apparently experienced an outburst of some kind, and for a while was as bright as 5th magnitude. The present return is the 11th (including its discovery return) at which it has been observed.

My personal history with Comet P/Schaumasse dates back to its 1984 return (no. 76), during the period of time when I was working with the Deep Space Network at the Jet Propulsion Laboratory in Pasadena, California, and was observing regularly with the experienced comet observer Charles Morris (who also worked at JPL). I followed the comet for 3 1/2 months during that return; when near perihelion in early December of that year it reached a peak brightness of magnitude 9 1/2 and I could faintly detect it with binoculars.

Less than two days before I obtained my first observation of Comet P/Schaumasse, I received the tragic news that my lifelong best friend, Mark Bakke, had died of an accidental gunshot wound the previous month. Mark and I became best friends when we were in the Fourth Grade, during which time his family lived in New Mexico, and that friendship would continue when his family moved to North Dakota five years later, and on beyond that. In and around all the various things that best friends of that age do, I managed to get Mark interested in astronomy, and he soon surpassed me; he was the first of us to acquire a telescope, he was the one who discovered resources like the magazine Sky & Telescope, and so on. He was with me on that fateful night in early February 1970 when I saw my very first comet (Comet Tago-Sato-Kosaka 1969g) for the first time. He was also with me when I saw my first total solar eclipse, on February 26, 1979, which we observed from near Boissevain, Manitoba.

During the early 1980s when I was in the U.S. Navy and stationed in southern California, Mark was in the U.S. Air Force and stationed at Holloman Air Force Base in New Mexico, and I would get to see him when I returned to New Mexico on leave. While I could not have known it at the time, I saw Mark for the very last time in early January 1982, shortly before his enlistment in the Air Force was up and he returned to North Dakota; it is only fitting that on that final occasion we observed a comet together, Comet Bowell 1980b (no. 46).

Mark Duane Bakke: March 20, 1957 -- September 24, 1984.
In my observing notes on the morning that I added Comet P/Schaumasse to my tally, I dedicated the observation to Mark and his memory, and in my mind I have always associated this comet with the memory of Mark. In addition to the sadness that came with losing the best friend I've ever had, I have long regretted that we never got to share in observing Comet Halley (no. 85), which came less than two years after his passing; also, we had long talked about discovering a comet -- possibly jointly -- and he never was able to share in the joy I experienced when I discovered my own comet the following decade. I am happy to say that I continue to remain in contact with members of his family.

I next observed P/Schaumasse on its return in 1993 (no. 174), during which it passed 0.55 AU from Earth and reached a peak brightness of 9th magnitude. That return came during the period of time during which it became necessary for me to leave my job at what is now the New Mexico Museum of Space History and during which I began to develop and build what is now the Earthrise Institute. P/Schaumasse next returned in early 2001 (no. 288), a somewhat mediocre return during which it got no brighter than 11th magnitude; nothing really dramatic happened in my life during that return, although I obtained my final observation just before departing for Zimbabwe for the June 21 total solar eclipse, and of course there were events that happened on a national and international scale later that year that dramatically affected the directions in which I eventually took Earthrise.

The comet was badly placed for observation at its return in 2009, and it was not recovered. On its present return it was recovered on July 24, 2017 by Jean-Gabriel Bosch and Alain Maury from the Observatoire de la Cote d'Azur's San Pedro facility in Chile's Atacama Desert, as a rather faint object of 19th magnitude. After one unsuccessful attempt in early October I successfully picked it up during my first attempt of the current dark run, on the morning of October 21; it appeared as a vague, diffuse object of 13th magnitude.

The current return is slightly inferior in quality to that of 1984, and similar to that of 2011 (with the exception that that was an evening-sky return). The comet remains in the morning sky throughout this return, and in fact remains near a constant elongation between 55 and 60 degrees for the next two months before this gradually increases. It is presently located in central Leo approximately eight degrees east of the bright star Regulus (and about 14 degrees east of the previous comet which, curiously, passes through perihelion only 19 hours before this one does) and is traveling towards the east-southeast at one degree per day. It crosses into northwestern Virgo in early November and spends the rest of 2017 traveling through that constellation. Just after perihelion passage it spends the next few days traveling through the southern section of the Virgo galaxy cluster, and it is nearest Earth (1.46 AU) on November 21. In early January 2018 Comet P/Schaumasse crosses into western Libra and spends the next month traveling across that constellation before crossing into northern Scorpius in early February and then into Ophiuchus shortly after the middle of that month, where it remains for the next 3 1/2 months.

Based upon the brightnesses I have observed during previous returns, I expect P/Schaumasse to reach a peak brightness between 10th and 11th magnitude during the second half of November, perhaps extending into early December. After that it should begin fading and diffusing out, and I will probably lose it in late January or early February.

Unlike what happened during some of the earlier returns of this comet, I don't seem to have to much in the way of dramatic events in my life happening at this time -- at least, not yet, anyway -- although as I continue the healing process that I discussed in my July 6 personal statement I am starting to see some potential future activities for Earthrise beginning to coalesce in my mind, and I may have something to write about in that regard before too much longer; stay tuned! Meanwhile, some unfortunate life circumstances have forced my younger son Tyler to relocate from Oregon back to New Mexico for at least the near-term foreseeable future; he arrived back here just a week ago, and most unfortunately experienced a rather severe car accident while en route (although, fortunately, he walked away from it with only minor injuries).

P/Schaumasse's next return, in 2026 (perihelion early January) is a distinctly favorable one, similar to that in 1993, with a minimum separation from Earth of 0.59 AU. This is somewhat after the "retirement" timetable I describe in my accompanying statement to "Continuing with Comets," although how closely I will actually stick to that timetable, and, indeed, what I might actually mean by "retirement," are things that remain to be seen. It occurs to me, though, that, given the association I have in my mind between Mark and this comet, and given that Mark was with me at the very beginning of my comet-observing "career," perhaps it might be appropriate to close out that "career" with this comet. Time will tell . . .

INITIAL OBSERVATION: 2017 October 21.46 UT, m1 = 12.8, 1.6' coma, DC = 1 (41 cm reflector, 70x)

     

632. COMET PANSTARRS C/2015 V1          Perihelion: 2017 December 17.73, q = 4.267 AU

During the time that I have been preparing this entry and the above entry, one of the most exciting discoveries in the entire history of solar system astronomy has been unfolding. On October 18 the Pan-STARRS program in Hawaii discovered a fast-moving object of about 20th magnitude, and over the course of the next couple of days additional observations indicated that it was traveling in an extremely elongated orbit and had passed perihelion at a very small perihelion distance (initially reported as about 0.15 AU, now more firmly established as 0.25 AU) over a month earlier; it was then placed on the Minor Planet Center's Possible Comet Confirmation Page. When I saw the object's listing on the PCCP on the 21st it seemed very strange that a comet as apparently instrinsically faint as this one seemed to be could have survived perihelion passage at such a small distance from the sun, and I wondered if perhaps there might be a dim outer coma attached to it that would make it brighter intrinsically and would be detectable visually; this occurrence is rare, but I have noticed it in a handful of previous comets. I made an attempt for it that evening, but didn't see anything.

On the 24th the Minor Planet Center formally announced the Pan-STARRS discovery as a comet under the designation C/2017 U1. Attention was called to the fact that all orbital solutions indicated a strongly hyperbolic orbit with an eccentricity near 1.2 which, if confirmed, can only mean one thing: this object came from interstellar space, perhaps having been ejected from another planetary system hundreds of millions of years ago, or longer. The fact that it arrived in the inner solar system from the general direction of the solar apex only strengthens this conclusion, as this is where we might expect interstellar comets to come from. Meanwhile, as of this writing, additional observations continue to support the hyperbolic orbit, however very deep imaging with very large telescopes has failed to reveal any signs of cometary activity, and thus it has been reassigned the designation A/2017 U1 (the "A" indicating the object is an asteroid that happened to be assigned a cometary designation). Regardless of what the object's true physical nature turns out to be, this clear detection of an apparent escapee from another planetary system is a most important discovery, and among other things tells us that the processes that go on in our solar system go on in other planetary systems as well. For what it's worth, the small perihelion distance, as well as the even closer approach to Earth's orbit -- indeed, it passed only 0.16 AU from Earth itself on October 14 -- brings to mind, and indeed is eerily reminiscent of, the "Rama" vehicle in the 1973 Arthur C. Clarke novel "Rendezvous with Rama," which passed through the inner solar system on a similarly hyperbolic orbit.

The newest addition to my comet tally is another Pan-STARRS discovery, but far more mundane than A/2017 U1. It was found almost two years ago, on November 2, 2015, at which time it was a very faint object near 20th magnitude located 7.4 AU and 7.1 AU from the sun and Earth, respectively. Because of its relatively large perihelion distance I never expected it to get bright enough to detect visually, however some of the recent reports I have read, and some of the recent CCD images I have seen (which show the presence of a distinct tail) suggested it might be worth attempting. After an unsuccessful attempt earlier in October I tried again on the evening of October 22 under very good sky conditions, and seemed to see an extremely faint "something" of magnitude 14 1/2 right near the limit of visibility of my telescope; I detected clear motion over an interval of two hours. On the following night the sky conditions seemed to be even better, and I once again saw the comet, which after an hour moved into a very good location with respect to the surrounding star field; despite its extreme faintness I could detect some structure within the moderately condensed coma, although I couldn't see any sign of the tail.

The comet is currently located in eastern Pisces approximately six degrees west of the star Eta Piscium, and -- traveling in a moderately inclined retrograde orbit (inclination 139 degrees) -- is moving towards the southwest at slightly less than half a degree per day. It remains within Pisces for the next 4 1/2 months, gradually moving over into the south-central part of that constellation. Although it is currently still over a month and a half away from perihelion passage, since it was already at opposition in mid-October and was closest to Earth (3.31 AU) on October 20, it is likely as bright now as it is going to get, and in fact should begin fading within the not-too-distant future. Since it is already near the extreme limit of my detectability, I will at most likely obtain only one or two more observations of it; indeed, it is distinctly possible that the two observations I have now are the only times I will see this comet.

CONFIRMING OBSERVATION: 2017 October 24.17 UT, m1 = 14.5, 0.6' coma, DC = 5-6 (41 cm reflector, 229x)

UPDATE (November 17, 2017): More or less as I expected, by early November Comet C/2015 V1 had faded beyond my range of visual detectability with the 41-cm telescope, and thus the two consecutive-night observations I obtained in October will remain my only sightings of this comet.

Meanwhile, the object designated A/2017 U1 that I discuss at the beginning of this entry continues to make news. Orbital calculations continue to indicate both a "before" and "after" eccentricity near 1.2, confirming that it entered the solar system from interstellar space, and will recede back into interstellar space (in the general direction of the "Great Square" of the constellation Pegasus). The Minor Planet Center has assigned it the permanent designatiuon of "1I" (the "I" indicating it is an interstellar object), and it has been given the name " 'Oumuamua" (from Hawaiian words meaning "a messenger from afar arriving first") by the Pan-STARRS discovery team.

         

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