April 8, 2020

On the Hunt for Comet C/2012 F6 Lemmon.

Comet Lemmon (arrowed) passes through

the Southern Cross on January 20th.

Photo by Luis Argerich. Used with permission.

Astronomy in 2013 already has one great thing going for it; the potential for several bright comets. While the astro-pundits debate the potential for comets C/2011 L4 PanSTARRS later this Spring and C/2012 S1 ISON later this year, we’d like to turn your attention southward to what could become the first naked eye comet of 2013.

Comet C/2012 F6 Lemmon is currently deep in the southern hemisphere, and may just be poised to become the very antithesis of its name. Discovered on March 23rd 2012 by the Mount Lemmon survey based in the Catalina Mountains north of Tucson Arizona, this icy interloper (we’ll refer to it simply as “Comet Lemmon” from here on out) is on an elliptical orbit with a calculated period of an extraordinary 11,164 years. (Comet Hyakutake, seen in the late 1990s, has one on the longest periods ever documented at +70,000 years). Think about that, and what our ancestors might’ve been up to over 11 millennia ago when this comet last graced our sky.

Comet Lemmon is also on a very high inclination orbit tilted 82.6° degrees relative to the ecliptic. This means that it finishes off January as a southern circumpolar object, tracing a near parallel path with the “0 Hour” in right ascension as it speeds northward from our point of view through February & March to become visible in the dawn sky for low to mid-northern latitude observers in early April. There’s already some indication that Comet Lemmon may be a solid performer; photographer Luis Argerich (@lrargerich on Twitter) based out of Buenos Aires Argentina noted that the comet was at about +7th magnitude at around January 17th-18th, displaying a bright cyan/green nucleus but no tail. Luis and also caught this outstanding animation of its passage through the constellation of the Southern Cross;

Animation of Comet Lemmon passing by Gacrux (Gamma Crucis).

on January 17th. (Animation courtesy of Luis Argerich. Used with permission).

If predictions hold, Comet Lemmon should reach greater than +6 magnitude visibility naked eye status and be visible from a good dark sky site from the period spanning January 26th to April 30th. Here’s a blow-by-blow of the springtime cometary action to be on the watch for from Comet Lemmon;

The path(*) of Comet Lemmon as seen from latitude -30 South from January 28th-February 28th around 9PM local.

(Note:  The orientation of the horizon for each graphic is set for the last day listed).

Comet Lemmon ends January as a circumpolar object and remains so until February 22nd for latitudes below -30° south. In fact, the comet passes within 1° degree of the +4.3 magnitude star Delta Octantis on February 2nd on its way to passing within 3° degrees of the South Celestial Pole on February 5th. Comet Lemmon also makes its closest approach of 0.98 astronomical units (A.U.s) from the Earth on the same date. The comet then begins its long trek northward through the southern sky moving about 4° degrees a day, passing within a degree of the +4.1 magnitude star Beta Octantis on February 9th.

A red letter date for deep sky photography occurs around February 14th-15th. On those evenings, Comet Lemmon will pass within 3° degrees of the +4.9 magnitude globular cluster 47 Tucanae and the Small Magellanic Cloud as it crosses into the constellation Tucana, making an inviting target. This also occurs only 4 days after New Moon, another bonus. Comet Lemmon will also pass within a degree of +4.5 magnitude Epsilon Tucanae on February 18th.

Comet Lemmon running parallel to the dawn horizon as seen from the equator through the month of March.

Observations of Comet Lemmon may become more difficult for observers based along the equator as it passes from dusk to dawn skies along the same right ascension as the Sun in mid-March. The comet will also cross the celestial meridian on February 23rd-24th, continuing its run northward through into the constellation Phoenix. Interestingly, Comet Lemon will be placed only 25° degrees from Comet PanSTARRS on February 27th. Comet PanSTARRS will be only 22° from the Sun at the time, and may shine at +1st magnitude. (More on that next month!)

Comet Lemmon then passes within a degree of +3.9 magnitude star Epsilon Phoenicis on March 5th on its way to a perihelion passage of 0.7 A.U.s from the Sun on March 24th as it crosses from the constellation Sculptor into Cetus. Comet Lemmon may also reach its peak predicted brightness just above magnitude +4 in the last half of March.

The path of Comet Lemmon as seen through the month of April from latitude 30 North at 6AM local.

In early April, mid-northern hemisphere viewers could get their first looks at Comet Lemmon as it vaults up into the dawn sky crossing into the constellation Pisces. It still should maintain a decent level of brightness from +4th to +5th magnitude, an easy naked eye object under dark skies. Note that we don’t pretend to make any predictions as to what cometary tails might do… comets are fickle beasts! Interestingly, Comet Lemmon will pass within 3° degrees of the planet Mercury on April 17th, and then cross the celestial equator on April 20th on its way back out of the solar system, not to return again for another… you guessed it; 11,000+ years.

Comet Lemmon will continue moving northward about a degree a day into the constellation Andromeda in mid-May and dipping back down below naked-eye brightness. Keep in mind, Comet PanSTARRS may also dazzle or fizzle during this March-April timeframe. Be sure to follow us on @Astroguyz as the situation evolves with these comets and much more. After a lengthy “comet drought,” 2013 may well become the Year of the Comet(s)!

(*All graphics created by the Author in Starry Night).


  1. Ronald Blay says:

    A very good well written article with lots of information,sadly I am in the Northern hemisphere but i will try to image it in April.
    Thank you Ron Blay

  2. David Dickinson says:

    Thanks… hopefully Comet Lemmon stays bright enough for us to track it in April, will keep monitoring reports from down south.


  1. [...] sur donde los observadores australes también pueden observar en estos momentos otro cometa, el  C/2012 F6 Lemmon. Y es que este año 2013 promete ser bastante interesante en cuanto a cometas, a la espera de ver [...]

  2. [...] Comet PanSTARRS is the first of three anticipated naked eye comets for 2013. The other two are Comet C/2012 F6 Lemmon set to grace morning skies for northern hemisphere viewers next month, and the sungrazer C/2102 S1 [...]

  3. [...] this is but Act One in a forecasted three act cometary saga for 2013. Comet C/2012 F6 Lemmon will grace early dawn skies in April for northern hemisphere observers, and then all eyes will be [...]

  4. [...] donde los observadores australes también pueden observar en estos momentos otro cometa, el  C/2012 F6 Lemmon. Y es que este año 2013 promete ser bastante interesante en cuanto a cometas, a la espera de ver [...]

Speak Your Mind