Last updated: June 27, 2018

For planning purposes, on this page I will list the incoming comets that are expected to become moderately bright or otherwise notable within the next one to two years, and which I expect to add to my tally (if I haven't already). I don't intend this list to be exhaustive, but instead will focus on those comets that are worthy of attention from sky-watchers and other interested people (including, certainly, students) who would not normally be considered "comet astronomers." I plan to update this page every one to two months and/or as necessary.

The "long-range" comets listed at the end of this page are, as implied, mentioned here primarily for long-range planning purposes.


COMET ATLAS C/2017 T3     (Perihelion 2018 July 19)

I am unlikely to add this comet to my tally, but observers in the southern hemisphere might conceivably see it around perihelion passage. I made a few unsuccessful attempts earlier this year up through early March, but it is now disappearing until sunlight, and will be in conjunction with the sun in mid-May. By mid-July it emerges into the southern hemisphere's morning sky, possibly around 10th magnitude; unfortunately it remains on the far side of the sun from Earth (minimum distance 1.51 AU in early August) and the elongation remains small (reaching a maximum of 43 degrees shortly after mid-August). It is again in conjunction with the sun in mid-November, and if there is anything left of it I might conceivably see it as a very faint object late in the year.

NOTE ADDED JUNE 27, 2018: Within the past few days this comet has become accessible to observers in the southern hemisphere (albeit at a low elongation), and according to reports I've read it is between magnitudes 9 1/2 and 10 -- perhaps a half-magnitude or so brighter than the original expectation for this time. Whether or not it retains this higher brightness remains to be seen; if it does, that increases the possibility that I might eventually be able to detect it.

COMET PANSTARRS C/2017 S3     (Perihelion 2018 August 15)

With a perihelion distance of 0.21 AU this comet conceivably could become quite bright. However, it was still as faint as 19th magnitude in late March when it emerged into the morning sky following conjunction with the sun, which would not seem to bode well for a bright display. The comet remains in northern skies until perihelion; it passes 0.76 AU from Earth in early August but disappears into morning twilight shortly thereafter; afterwards, it remains hidden in sunlight until late this year.

COMET 21P/GIACOBINI-ZINNER     (Perihelion 2018 September 10)

The geometry of this year's return is almost identical to that of 1985, when it became the first comet to be visited by an artificial spacecraft. The viewing geometry before perihelion is very favorable for the northern hemisphere, and it passes 0.39 AU from Earth at the same time it is passing through perihelion. In 1985 the comet reached 7th magnitude and displayed a one-degree-long dust tail that was conspicuous even in binoculars, and I expect something similar this time around.

This comet is the parent comet of the Draconid meteor shower, which peaks each year around October 8. There have been some strong displays associated with some of the comet's previous returns (most notably in 1933 and 1946), and the conditions for at least a moderate display are reasonably good this year.

NOTE ADDED JUNE 1, 2018: I have just recently picked up this comet visually (no. 642). Initially, it seems to be running slightly fainter than it was in 1985, although at this early stage I am not too concerned (yet). Meanwhile, more recent predictions I've read suggest that, at best, there will probably only be moderate enhancements to the regular Draconid display this year.

(944) HIDALGO     (Perihelion 2018 October 26)

The first-known and, instrinsically, brightest of the potentially "extinct" of "dormant" Jupiter-family comets is well-placed for observation from the northern hemisphere, being located in northern circumpolar skies for the last three months of 2018 and first three months of 2019, reaching a peak northerly declination of +81.4 degrees in early February before going through opposition later that month. Hidalgo is nearest Earth (1.45 AU) in late November and should be near its peak brightness of 14th magnitude around that time, it should remain near that brightness for several months.

COMET 64P/SWIFT-GEHRELS     (Perihelion 2018 November 3)

The geometry of this year's return is moderately favorable, being similar to the discovery return in 1889 and to the return I observed in 1981. The comet is at opposition near the end of September and passes 0.44 AU from Earth a few days before perihelion passage, when it will be conveniently located in the evening sky. It should reach a peak brightness of close to 11th magnitude, perhaps slightly brighter.

COMET 38P/STEPHAN-OTERMA     (Perihelion 2018 November 10)

This Halley-type comet (period 38 years) returns under geometrical conditions reasonably similar to those at its previous return in 1980, when I successfully observed it for five months. It should reach a peak brightness close to 9th magnitude during the last two months of 2018; it is closest to Earth (0.77 AU) in mid-December and at opposition near the end of January 2019, by which time it should be fading from view.

COMET 46P/WIRTANEN     (Perihelion 2018 December 12)

This will be the most favorable return that this comet has ever made, or will make. On December 16 it passes just 0.078 AU from Earth, and should become a naked-eye object of perhaps 4th magnitude, remaining visible to the unaided eye for a week or two on either side of that date. Overall it should remain visually detectable from about August or September until perhaps March 2019.


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COMET PANSTARRS C/2017 K2     (Perihelion 2022 December 19)

Despite being located at a heliocentric distance of 16.1 AU, this comet was clearly active, and a relatively bright 19th to 20th magnitude, when discovered in May 2017. Even more remarkably, in pre-discovery images taken as far back as May 2013, the comet is clearly active even at a heliocentric distance of 23.7 AU. The high intrinsic brightness, and high activity level at such large distances from the sun, is somewhat reminiscent of Comet Hale-Bopp C/1995 O1 (no. 199).

Unfortunately, the comet's perihelion distance is still a relatively large 1.80 AU. Even more unfortunately, the comet is on the far side of the sun from Earth at the time, never coming closer than 2.23 AU. While naked-eye visibility, perhaps even conspicuous naked-eye visibility, would seem to be almost a certainty, the comet is unlikely to become "Great."

And even more unfortunately for northern hemisphere observers, the comet is in southern circumpolar skies at the time of perihelion. Indeed, the comet is inaccessible from the northern hemisphere for almost a full year (September 2022 through August 2023).

Comet PANSTARRS C/2017 K2 (small diffuse object in center) as imaged on March 6, 2018, by the Las Cumbres Observatory facility at McDonald Observatory in Texas. At the time this image was taken, the comet's heliocentric distance was 14.4 AU.
COMET 12P/PONS-BROOKS     (Perihelion 2024 April 21)

This "classical" Halley-type comet (period 70 years) last returned in 1954, four years before I was born. The viewing geometry in 2024 is, unfortunately, rather unfavorable, as during the run-up to perihelion the comet remains on the far side of the sun from Earth and is only visible for a brief period of time in the northwestern sky after dusk, at a small elongation (37 degrees in mid-March, shrinking to 28 degrees by month's end and to 23 degrees by perihelion). Despite the poor viewing geometry, the comet is intrinsically rather bright, and should reach a peak brightness close to 5th magnitude. After perihelion the comet travels southward and is visible from the southern hemisphere as it recedes and fades.

COMET 13P/OLBERS     (Perihelion 2024 June 30)

This other "classical" Halley-type comet (period 68 years) last returned in 1956, two years after the above comet and two years before I was born. Also as with the above comet, the viewing geometry remains relatively poor, with the comet's remaining on the far side of the sun from Earth; on the other hand, it is almost identical to the viewing geometry in 1956. It remains in the northern hemisphere's evening sky throughout the period of prime visibility, albeit at a small elongation (dropping below 30 degrees in early May, to a minimum of 25.5 degrees in early June before increasing back to 30 degrees by perihelion to a maximum of 39 degrees in August). Based upon the reported brightnesses in 1956, the comet should reach a peak brightness between 6th and 7th magnitude.

Around mid-April 12P/Pons-Brooks and 13P/Olbers will be located some 15 degrees from each other, the latter comet being higher (to the east and north) of the former one.


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