 Comet Lemmon inTucana on 16 February 2013 | |
| Discovery | |
|---|---|
| Discovered by | A. R. Gibbs Mt. Lemmon Survey (G96)[1] |
| Discovery date | 23 March 2012 |
| Orbital characteristics | |
| Epoch | 28 October 2012 (JD 2456228.5) |
| Aphelion | 973.47895 AU (Q) |
| Perihelion | 0.73126 AU (q) |
| Semi-major axis | 487.1051AU (a) |
| Eccentricity | 0.99850 (e) |
| Orbital period | ~8000yr (Barycentric solution forepoch 2050)[2] |
| Inclination | 82.60839° (i) |
| Last perihelion | 2013-03-24.516 |
| Physical characteristics[3][4] | |
Mean radius | 2.151±0.133 km |
Meandensity | 460±60 kg/m3 |
| 9.52±0.05 hours | |
C/2012 F6 (Lemmon) is along-period comet discovered inLeo on 23 March 2012, by A. R. Gibbs[1] using the 1.5-m reflector at theMt. Lemmon Survey, located at the summit of Mount Lemmon in theSanta Catalina Mountains north ofTucson, Arizona, USA. Initially, the object was considered to be of asteroidal nature before later observations confirmed its cometary appearance. Comet Lemmon has a highlyeccentric orbit, bringing it as close to 0.73 AU from the Sun atperihelion and as far as 973 AU from the Sun ataphelion. This also leads to the comet's long-period nature with anorbital period of approximately 8,000 years based onepoch 2050. The comet last reached perihelion on 24 March 2013.
For much of 2012, observation of Lemmon remained limited toCCD imagery, but steadily brightened throughout the course of the year. In late-November 2012, the comet became bright enough for telescopic viewing, and had anapparent magnitude estimated at +9 by the year's end. Brightening continued into the early months of 2013 before peaking at an apparent magnitude of +5 in late March, though viewing was mostly limited to theSouthern Hemisphere. On 24 March 2013, Lemmon reached its orbital perihelion and afterwards began to dim. On 20 April 2013, Lemmon crossed thecelestial equator and became primarily viewable in theNorthern Hemisphere, though by this time the comet was significantly dimmer relative to its peak brightness.[5]
A.R. Gibbs of theMount Lemmon Observatory inArizona discovered the comet based on images acquired by thesky survey's 1.5-m reflecting telescope on 23 March 2012.[6] However, Gibbs did not recognize its cometary appearance and was listed as an asteroid on theMinor Planet Center'sNear-Earth Object Confirmation Page.[7] At the time, theapparent magnitude of the comet was estimated between +20.6 and +20.8. Shortly after initial discovery, amateur astronomer Peter Birtwhistle inGreat Shefford observed the comet using a 40-cm refracting telescope andCCD images, estimating an apparent magnitude of +20.1 and a diameter stretching 5 arc seconds across.[6]
Following discovery, Lemmon remained a dim object but steadily brightened over the next few months. The comet was last sighted on 14 June 2012 with an apparent magnitude estimated at +19.0 before it was lost in the Sun's glare. On 25 August, the comet was analyzed to have passed an apparent 0.7 degrees from the Sun. The comet was re-sighted on 14 October utilizing theRAS (Remote Astronomical Society) Observatory of New Mexico inMayhill, with an apparent magnitude estimated to have brightened to +15.3. The first confirmed visual observation of the comet without the use of CCD imagery was conducted by Juan Jose Gonzalez Suarez inCantabria, Spain using a 20-cm reflector on 22 November. Several other visual confirmations were made throughout the rest of the year. By the end of 2012, the comet had acoma 5-7arc minutes across and an apparent magnitude estimated at +9.[6]
It was well placed for viewing in theSouthern Hemisphere in January 2013 to observe it brightening, crossingCentaurus,Crux andChamaeleon, and into February when it was circumpolar inOctans. By the end of February it set early evening situated inPhoenix, was observable well into March. After perihelion the comet should be reasonably well placed in the morning sky to observe as it fades.[8] The comet was visible in theSTEREO heliospheric imager HI-2A starting on 17 April.[9] C/2012 F6 crossed thecelestial equator on 20 April 2013 becoming aNorthern Hemisphere object. On 9 May 2013 the comet was nearGamma Pegasi and from a dark sky was visible inbinoculars before sunrise low in the eastern sky.[10]
On 11 August 2014, astronomers released studies, using theAtacama Large Millimeter/Submillimeter Array (ALMA) for the first time, that detailed the distribution ofHCN,HNC,H2CO, anddust inside thecomae ofcomets C/2012 F6 (Lemmon) andC/2012 S1 (ISON).[11][12]
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2013 in space | ||||||
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Space probe launches |
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| Impact events | ||||||
| SelectedNEOs | ||||||
| Exoplanets | ||||||
| Discoveries | ||||||
| Novae | ||||||
| Comets | ||||||
| Space exploration |
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