C/2012 F6 (Lemmon) is a

long-period comet A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena are ...

discovered in Leo on 23 March 2012, by A. R. Gibbs using the 1.5-m reflector at the Mt. Lemmon Survey, located at the summit of Mount Lemmon in the

Santa Catalina Mountains The Santa Catalina Mountains, commonly referred to as the Catalina Mountains or the Catalinas, are north and northeast of Tucson in Arizona, United States, on Tucson's north perimeter. The mountain range is the most prominent in the Tucson area, w ...

north of

Tucson, Arizona , "(at the) base of the black ill , nicknames = "The Old Pueblo", "Optics Valley", "America's biggest small town" , image_map = , mapsize = 260px , map_caption = Interactive map ...

, USA. Initially, the object was considered to be of asteroidal nature before later observations confirmed its cometary appearance. Comet Lemmon has a highly

eccentric orbit In astrodynamics, the orbital eccentricity of an astronomical object is a dimensionless parameter that determines the amount by which its orbit around another body deviates from a perfect circle. A value of 0 is a circular orbit, values betwee ...

, bringing it as close to 0.73 AU from the sun at

perihelion An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any elli ...

and as far as 973 AU from the sun at

aphelion An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any ell ...

. This also leads to the comet's long-period nature with an

orbital period The orbital period (also revolution period) is the amount of time a given astronomical object takes to complete one orbit around another object. In astronomy, it usually applies to planets or asteroids orbiting the Sun, moons orbiting pla ...

of approximately 8,000

years A year or annus is the orbital period of a planetary body, for example, the Earth, moving in its orbit around the Sun. Due to the Earth's axial tilt, the course of a year sees the passing of the seasons, marked by change in weather, the hou ...

based on

epoch In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured. The moment of epoch is usually decided ...

2050. The comet last reached perihelion on 24 March 2013. For much of 2012, observation of Lemmon remained limited to CCD imagery, but steadily brightened throughout the course of the year. In late-November 2012, the comet became bright enough for telescopic viewing, and had an

apparent magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's ...

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 the Southern Hemisphere. On 24 March 2013, Lemmon reached its orbital perihelion and afterwards began to dim. On 20 April 2013, Lemmon crossed the

celestial equator The celestial equator is the great circle of the imaginary celestial sphere on the same plane as the equator of Earth. This plane of reference bases the equatorial coordinate system. In other words, the celestial equator is an abstract proj ...

and became primarily viewable in the

Northern Hemisphere The Northern Hemisphere is the half of Earth that is north of the Equator. For other planets in the Solar System, north is defined as being in the same celestial hemisphere relative to the invariable plane of the solar system as Earth's Nort ...

, though by this time the comet was significantly dimmer relative to its peak brightness.

Discovery

A.R. Gibbs of the

Mount Lemmon Observatory Mount Lemmon Observatory (MLO), also known as the Mount Lemmon Infrared Observatory, is an astronomical observatory located on Mount Lemmon in the Santa Catalina Mountains approximately northeast of Tucson, Arizona (US). The site in the Corona ...

Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...

discovered the comet based on images acquired by the

sky survey An astronomical survey is a general map or image of a region of the sky (or of the whole sky) that lacks a specific observational target. Alternatively, an astronomical survey may comprise a set of images, spectra, or other observations of obje ...

's 1.5-m reflecting telescope on 23 March 2012. However, Gibbs did not recognize its cometary appearance and was listed as an asteroid on the

Minor Planet Center The Minor Planet Center (MPC) is the official body for observing and reporting on minor planets under the auspices of the International Astronomical Union (IAU). Founded in 1947, it operates at the Smithsonian Astrophysical Observatory. Function T ...

Near-Earth Object Confirmation Page The Near-Earth Object Confirmation Page (NEOCP) is a web service listing recently-submitted observations of objects that may be near-Earth objects (NEOs). It is a service of the Minor Planet Center (MPC), which is the official international archive ...

. At the time, the

of the comet was estimated between +20.6 and +20.8. Shortly after initial discovery, amateur astronomer Peter Birtwhistle in

Great Shefford Great Shefford (or West Shefford) is an English village and civil parish on the River Lambourn in the West Berkshire district of Berkshire. The present civil parish includes the historical parish of Little or East Shefford, a small, reduced co ...

observed the comet using a 40-cm refracting telescope and CCD images, estimating an apparent magnitude of +20.1 and a diameter stretching 5

arc second A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of one degree. Since one degree is of a turn (or complete rotation), one minute of arc is of a turn. The n ...

s across.

Observational history

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 the

RAS (Remote Astronomical Society) Observatory of New Mexico The Remote Astronomical Society (RAS) Observatory, Mayhill, also known as the New Mexico Skies Observatory ( obs. code H06) is a remotely controlled observatory hosted by the New Mexico Skies astronomy hosting company. It is located 15 miles n ...

Mayhill Mayhill is a district of Swansea, Wales, at the top of a steep hill of the same name just north west of the city centre, partly separated from Townhill to the west. Mayhill Garden City started in 1914 as an experimental row of six houses that ...

, 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 in Cantabria, 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 a

coma A coma is a deep state of prolonged unconsciousness in which a person cannot be awakened, fails to respond normally to painful stimuli, light, or sound, lacks a normal wake-sleep cycle and does not initiate voluntary actions. Coma patients exhi ...

5-7

arc minute A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of one degree. Since one degree is of a turn (or complete rotation), one minute of arc is of a turn. The n ...

s across and an apparent magnitude estimated at +9. It was well placed for viewing in the southern hemisphere in January 2013 to observe it brightening, crossing

Centaurus Centaurus is a bright constellation in the southern sky. One of the largest constellations, Centaurus was included among the 48 constellations listed by the 2nd-century astronomer Ptolemy, and it remains one of the 88 modern constellations. ...

Crux Crux () is a constellation of the southern sky that is centred on four bright stars in a cross-shaped asterism commonly known as the Southern Cross. It lies on the southern end of the Milky Way's visible band. The name ''Crux'' is Latin f ...

and

Chamaeleon Chamaeleon () is a small constellation in the deep southern sky. It is named after the chameleon, a kind of lizard. It was first defined in the 16th century. History Chamaeleon was one of twelve constellations created by Petrus Plancius fr ...

, and into February when it was circumpolar in

Octans Octans () is a faint constellation located in the deep Southern Sky. Its name is Latin for the eighth part of a circle, but it is named after the octant, a navigational instrument. Devised by French astronomer Nicolas Louis de Lacaille in 1752 ...

. By the end of February it set early evening situated in

Phoenix Phoenix most often refers to: * Phoenix (mythology), a legendary bird from ancient Greek folklore * Phoenix, Arizona, a city in the United States Phoenix may also refer to: Mythology Greek mythological figures * Phoenix (son of Amyntor), a ...

, was observable well into March. After perihelion the comet should be reasonably well placed in the morning sky to observe as it fades. The comet was visible in the

STEREO Stereophonic sound, or more commonly stereo, is a method of sound reproduction that recreates a multi-directional, 3-dimensional audible perspective. This is usually achieved by using two independent audio channels through a configuration ...

heliospheric imager HI-2A starting on 17 April. C/2012 F6 crossed the

on 20 April 2013 becoming a

northern hemisphere The Northern Hemisphere is the half of Earth that is north of the Equator. For other planets in the Solar System, north is defined as being in the same celestial hemisphere relative to the invariable plane of the solar system as Earth's Nort ...

object. On 9 May 2013 the comet was near Gamma Pegasi and from a dark sky was visible in

binoculars Binoculars or field glasses are two refracting telescopes mounted side-by-side and aligned to point in the same direction, allowing the viewer to use both eyes (binocular vision) when viewing distant objects. Most binoculars are sized to be held ...

before sunrise low in the eastern sky. On 11 August 2014, astronomers released studies, using the Atacama Large Millimeter/Submillimeter Array (ALMA) for the first time, that detailed the distribution of HCN, HNC, H₂CO, and

dust Dust is made of fine particles of solid matter. On Earth, it generally consists of particles in the atmosphere that come from various sources such as soil lifted by wind (an aeolian process), volcanic eruptions, and pollution. Dust in ...

inside the comae of

comet A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena ...

s C/2012 F6 (Lemmon) and C/2012 S1 (ISON).

Gallery

Comet C2012 F6 (Lemmon) - 1 Mar 2013.jpg, Comet Lemmon on 1 March from Mount Burnett Observatory Comets and Shooting Stars Dance Over Paranal.jpg, Lemmon in conjunction with C/2011 L4 and a meteoroid trail from Paranal Observatory on 5 March

References

External links

South African photo gallery of C/2012 F6 ( Lemmon )
(@ psychohistorian.org)

- Seiichi Yoshida @ aerith.net

�
Shadow & Substance

(

APOD Astronomy Picture of the Day (APOD) is a website provided by NASA and Michigan Technological University (MTU). According to the website, "Each day a different image or photograph of our universe is featured, along with a brief explanation written ...

2013 May 6)
Comet Lemmon
(Damian Peach 2013 May 15) {{DEFAULTSORT:Lemmon, 2012 F6 20120323 20130324 Non-periodic comets