C/2011 L4 (PanSTARRS), also known as Comet PANSTARRS, is a non-periodic

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 ...

discovered in June 2011 that became visible to the

naked eye Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception unaided by a magnifying, light-collecting optical instrument, such as a telescope or microscope, or eye protection. Vision corrected to normal ...

when it was near

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 ...

in March 2013. It was discovered using the

Pan-STARRS The Panoramic Survey Telescope and Rapid Response System (Pan-STARRS1; obs. code: F51 and Pan-STARRS2 obs. code: F52) located at Haleakala Observatory, Hawaii, US, consists of astronomical cameras, telescopes and a computing facility that is ...

telescope located near the summit of

Haleakalā Haleakalā (; Hawaiian: ), or the East Maui Volcano, is a massive shield volcano that forms more than 75% of the Hawaiian Island of Maui. The western 25% of the island is formed by another volcano, Mauna Kahalawai, also referred to as the West ...

, on the island of Maui in Hawaii. Comet C/2011 L4 probably took millions of years to come from the

Oort cloud The Oort cloud (), sometimes called the Öpik–Oort cloud, first described in 1950 by the Dutch astronomer Jan Oort, is a theoretical concept of a cloud of predominantly icy planetesimals proposed to surround the Sun at distances ranging from ...

. After leaving the planetary region of the Solar System, the post-perihelion

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 planets ...

(

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 by ...

2050) is estimated to be roughly

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 ...

. Dust and gas production suggests the

comet nucleus The nucleus is the solid, central part of a comet, once termed a ''dirty snowball'' or an ''icy dirtball''. A cometary nucleus is composed of rock, dust, and frozen gases. When heated by the Sun, the gases sublime and produce an atmosphere ...

is roughly in diameter.

Observational history

Comet C/2011 L4 was still 7.9 AU from the Sun with 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 ...

of 19 when it was discovered in June 2011. By early May 2012, it had brightened to magnitude 13.5, and could be seen visually when using a large amateur telescope from a dark site. In October 2012, the coma (expanding tenuous dust atmosphere) was estimated to be about in diameter. C/2011 L4 was spotted without optical aid on 7 February 2013 at a magnitude of ~6. Comet PANSTARRS was visible from both hemispheres in the first weeks of March, and passed closest to Earth on 5 March 2013 at a distance of 1.09 AU. It came to

(closest approach to the Sun) on 10 March 2013. Original estimates predicted that C/2011 L4 would brighten to roughly

0 (roughly the brightness of

Alpha Centauri A Alpha Centauri (Latinisation of names, Latinized from α Centauri and often abbreviated Alpha Cen or α Cen) is a Star System, triple star system in the constellation of Centaurus (constellation), Centaurus. It consists of 3 stars: ...

Vega Vega is the brightest star in the northern constellation of Lyra. It has the Bayer designation α Lyrae, which is Latinised to Alpha Lyrae and abbreviated Alpha Lyr or α Lyr. This star is relatively close at only from the Sun, a ...

). An estimate in October 2012 predicted that it might brighten to magnitude −4 (roughly equivalent to

Venus Venus is the second planet from the Sun. It is sometimes called Earth's "sister" or "twin" planet as it is almost as large and has a similar composition. As an interior planet to Earth, Venus (like Mercury) appears in Earth's sky never f ...

). In January 2013 there was a noticeable brightening slowdown that suggested that it may only brighten to magnitude +1. During February the brightness curve showed a further slowdown suggesting a

magnitude of around +2. However, a study using the

secular Secularity, also the secular or secularness (from Latin ''saeculum'', "worldly" or "of a generation"), is the state of being unrelated or neutral in regards to religion. Anything that does not have an explicit reference to religion, either negativ ...

light curve In astronomy, a light curve is a graph of light intensity of a celestial object or region as a function of time, typically with the magnitude of light received on the y axis and with time on the x axis. The light is usually in a particular frequ ...

indicates that C/2011 L4 had a "slowdown event" when it was 3.6 AU from the Sun at a magnitude 5.6. The brightness increase rate decreased and the estimated magnitude at perihelion was predicted as +3.5.

Comet Halley Halley's Comet or Comet Halley, officially designated 1P/Halley, is a short-period comet visible from Earth every 75–79 years. Halley is the only known short-period comet that is regularly visible to the naked eye from Earth, and thus the on ...

would be magnitude −1.0 at the same perihelion distance. The same study concluded that C/2011 L4 is very young and belongs to the class of "baby comets" (i.e. those with a photometric age of less than 4 comet years). When C/2011 L4 reached perihelion in March 2013, the actual peak magnitude turned out to be around +1, as estimated by various observers all over the planet. However, its low altitude over the horizon made these estimates difficult and subject to significant uncertainties, both because of the lack of suitable reference stars in the area and the need for differential atmospheric extinction corrections. As of mid-March 2013, due to the brightness of twilight and low elevation in the sky, C/2011 L4 was best seen in binoculars about 40 minutes after sunset. On 17–18 March, C/2011 L4 was near the 2.8-magnitude star Algenib (

Gamma Pegasi Gamma Pegasi is a star in the constellation of Pegasus, located at the southeast corner of the asterism known as the Great Square. It has the formal name Algenib ; the Bayer designation Gamma Pegasi is Latinized from γ Pegasi and abbre ...

). On 22 April, it was near Beta Cassiopeiae. On 12–14 May, it was near

Gamma Cephei Gamma Cephei (γ Cephei, abbreviated Gamma Cep, γ Cep) is a binary star system approximately 45 light-years away in the constellation of Cepheus. The primary (designated Gamma Cephei A, officially named Errai , the traditional name of ...

. C/2011 L4 continued moving North until 28 May. The comet may have had a sodium tail as

Comet Hale–Bopp Comet Hale–Bopp (formally designated C/1995 O1) is a comet that was one of the most widely observed of the 20th century and one of the brightest seen for many decades. Alan Hale and Thomas Bopp discovered Comet Hale–Bopp separately ...

had.Comet C/2011 L4 (PanSTARRS) with sodium tail - 15 March 2013
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Gallery

File:PanSTARRs And Moon.jpg, Comet PANSTARRS as observed from Southern California, USA, about 3° east of the new crescent Moon File:Comet C2011 L4 (PANSTARRS).png, Photo taken 12 March 2013 in

Woodland Hills, Los Angeles Woodland Hills is a neighborhood bordering the Santa Monica Mountains in the San Fernando Valley region of Los Angeles, California. Geography Woodland Hills is in the southwestern region of the San Fernando Valley, which is located east of Ca ...

, USA. File:Comet C2011L4 PanSTARRS 2013-03-24 in Russia.jpg, Comet C/2011 L4 (PanSTARRS) with a fan-shaped tail 2013-03-24 17:00UT in

Special Astrophysical Observatory of the Russian Academy of Science The Special Astrophysical Observatory of the Russian Academy of Science (SAO RAS; russian: Специальная Астрофизическая Обсерватория) is an astronomical observatory, set up in 1966 in the USSR, and now operat ...

near the village of Nizhny Arkhyz. File:Comet Pan-STARRS.JPG, Photo taken 18 March 2013, at

Orbetello Orbetello is a town and ''comune'' in the province of Grosseto (Tuscany), Italy. It is located about south of Grosseto, on the eponymous lagoon, which is home to an important Natural Reserve. History Orbetello was an ancient Etruscan settleme ...

, Italy). File:C-2011 Comet PanStarrs taken from the Norman Lockyer Observatory on 26th May 2013 by John Maclean.jpeg, Photo taken by John Maclean at the Norman Lockyer Observatory, Sidmouth, Devon.

References

External links

C/2011 L4 (PANSTARRS)
– Cometography.com by Gary W. Kronk

– Seiichi Yoshida @ aerith.net

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Shadow & Substance

Elements and Ephemeris for C/2011 L4 (PANSTARRS)
– Minor Planet Center
The complete guide to viewing Comet PANSTARR

The view STEREO-B will have of PanSTARRS in March
(Bill Thompson via Twitter account ''Sungrazing Comets'')
C/2011 L4 on 2013-March-09
(entering STEREO/SECCHI HI-1B field of view below the "2013")

– Remanzacco Observatory (18 May 2012)
Very quick high-resolution "first look" at PanSTARRS in STEREO HI-1B

2013-March-10 GIF animation

2013-March-12 up close
(Twitter account ''Sungrazing Comets'')
Video of Comet Panstarrs seen from Paris

Don’t let Comets PANSTARRS and Lemmon out of your sight … yet
– AstroBob (19 May 2013) {{DEFAULTSORT:C 2011 L4 Comets in 2013 20110606 Non-periodic comets Oort cloud Discoveries by Pan-STARRS

Observational history

Gallery

See also

References

External links