C/2012 F6 (Lemmon)

Lore & Background

The comet was first detected in CCD images on 23 March 2012, with an apparent magnitude between +20.6 and +20.8, and was initially listed as an asteroid on the Minor Planet Center's Near-Earth Object Confirmation Page. Amateur astronomer Peter Birtwhistle later observed it with a 40-cm refracting telescope, estimating a magnitude of +20.1 and a diameter of 5 arc seconds. After being lost in the Sun's glare in June 2012, it was re-sighted on 14 October at magnitude +15.3 using the RAS Observatory of New Mexico. The first visual observation without CCD imagery was made by Juan Jose Gonzalez Suarez on 22 November using a 20-cm reflector. By the end of 2012, the comet had brightened to magnitude +9 with a coma 5–7 arc minutes across.

In early 2013, Lemmon was well placed for Southern Hemisphere viewing, crossing Centaurus, Crux, and Chamaeleon, and became circumpolar in Octans in February. It peaked at magnitude +5 in late March 2013, around the time of perihelion, though viewing was mostly limited to the Southern Hemisphere. After crossing the celestial equator on 20 April 2013, it became visible in the Northern Hemisphere but had dimmed significantly. On 9 May 2013, it was near Gamma Pegasi and visible in binoculars before sunrise. On 11 August 2014, studies using the Atacama Large Millimeter/Submillimeter Array (ALMA) detailed the distribution of HCN, HNC, H2CO, and dust inside the comet's coma.

Reader's Guide

C/2012 F6 (Lemmon) is notable for its long orbital period of about 8,000 years, reflecting a highly eccentric orbit that ranges from 0.73 AU at perihelion to 973 AU at aphelion. Its discovery by the Mount Lemmon Survey highlights the role of automated sky surveys in detecting comets, even when initially misidentified as asteroids. The comet's steady brightening over 2012 and into 2013 allowed both CCD and visual observations, with the first visual confirmation by an amateur astronomer in November 2012. Its peak brightness of magnitude +5 made it a binocular object for Southern Hemisphere observers in early 2013, though Northern Hemisphere viewers saw it only after it had faded. The comet's significance extends to scientific studies: in August 2014, ALMA observations provided the first detailed maps of molecular gas and dust in its coma, contributing to understanding of cometary composition. Lemmon's trajectory and visibility patterns—from Southern Hemisphere circumpolar status to a Northern Hemisphere morning object—illustrate the changing observational opportunities as a long-period comet moves through the inner solar system.

Did You Know?

• The comet was initially classified as an asteroid before cometary features were confirmed.
• Its orbital period is approximately 8,000 years based on epoch 2050.
• ALMA observations in August 2014 mapped HCN, HNC, H2CO, and dust in the comet's coma.