C/2011 L4

      For the Hawaii telescope facility, see Pan-STARRS.
      C/2011 L4 (PANSTARRS)
      C 2011 L4 PanSTARRS.jpg
      Image of Comet PanSTARRS by Gingin Observatory
      Discovery
      Discovered by Pan-STARRS
      Discovery date 6 June 2011
      Orbital characteristics A
      Epoch 2012-Mar-20
      (JD 2456006.5)
      Aphelion Unknown
      Perihelion 0.30161 AU (q)
      Semi-major axis Unknown
      Eccentricity 1.000087
      Orbital period ~106000 yr
      (Barycentric solution for epoch 2050)[1]
      Inclination 84.199°
      Last perihelion 10 March 2013[2]
      Next perihelion Unknown

      Comet C/2011 L4 (PANSTARRS) is a non-periodic comet discovered in June 2011 that became visible to the naked eye when it was near perihelion in March 2013.[3][4] The comet was discovered using the Pan-STARRS telescope located near the summit of Haleakalā, on the island of Maui in Hawaii (U.S.).

      Comet C/2011 L4 was still 7.9 AU from the Sun[4] with an apparent magnitude of 19 when it was discovered in June 2011.[5] By early May 2012, the comet had brightened to magnitude 13.5,[6] and could be seen visually when using a large amateur telescope from a dark site. As of October 2012, the coma (expanding tenuous dust atmosphere) was estimated to be about 120,000 kilometers (75,000 miles) in diameter.[7] The comet was spotted without optical aid on 7 February 2013 at a magnitude of ~6.[8] Comet PANSTARRS was visible from both hemispheres in the first weeks of March,[9] and passed closest to Earth on 5 March 2013 at a distance of 1.09 AU.[4] It came to perihelion (closest approach to the Sun) on 10 March 2013.[2] Original estimates predicted the comet would brighten to roughly apparent magnitude 0 (roughly the brightness of Alpha Centauri A or Vega). An estimate in October 2012 predicted the comet might brighten to magnitude −4 (roughly equivalent to Venus).[10] In January 2013 there was a noticeable brightening slowdown that suggested the comet may only brighten to magnitude +1.[11] During February the brightness curve showed a further slowdown suggesting a perihelion magnitude of around +2.[12]

      However, a study using the secular light curve indicates that the comet had a "slowdown event" when it was 3.6 AU from the Sun at a magnitude 5.6.[13] The brightness increase rate decreased and the estimated magnitude at perihelion was predicted as +3.5. Comet Halley would be magnitude −1.0 at the same perihelion distance. The same study concluded that the comet is very young and belongs to the class of "baby comets" (i.e. those with a photometric age of less than 4 comet years).[13]

      When the comet reached perihelion in March 2013, the actual peak magnitude turned out to be around +1,[14] as estimated by various observers all over the planet. However, the low altitude of the comet 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 the brightness of twilight and low elevation in the sky, the comet was best seen in binoculars about 40 minutes after sunset.[15] On 17/18 March, the comet was near the magnitude 2.8 star Algenib (Gamma Pegasi).[16] On 22 April it was near Beta Cassiopeiae.[12] On 12–14 May it will be near Gamma Cephei.[17] The comet will continue moving North until 28 May.

      Comet C/2011 L4 probably took millions of years to come from the Oort cloud. After leaving the planetary region of the Solar System, the post-perihelion orbital period (epoch 2050) is estimated to be roughly 106000 years.[1] Dust and gas production suggests the comet nucleus is roughly 1 kilometer (0.62 mi) in diameter.[18]

      Gallery

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      See also

      • C/2012 S1 — may also be visible to the naked eye when it is near perihelion in late 2013.
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      References

      1. ^ a b Horizons output. "Barycentric Osculating Orbital Elements for Comet C/2011 L4 (PANSTARRS)". Retrieved 2012-07-17.  (Solution using the Solar System Barycenter and barycentric coordinates. Select Ephemeris Type:Elements and Center:@0)
      2. ^ a b "JPL Small-Body Database Browser: C/2011 L4 (PANSTARRS)". Jet Propulsion Laboratory. 2012-07-14 last obs (data arc=1.15 yr). Retrieved 2012-06-12. 
      3. ^ "Comet Pan-STARRS: Still on Track". Sky & Telescope. 2012-04-12. Retrieved 2012-04-12. 
      4. ^ a b c Kronk, Gary W. "C/2011 L4 (PANSTARRS)". Retrieved 2012-06-13.  (Cometography Home Page)
      5. ^ "MPEC 2011-L33 : COMET C/2011 L4 (PANSTARRS)". IAU Minor Planet Center. 2011-06-08. Retrieved 2012-05-17.  (CK11L040)
      6. ^ "MPEC 2012-J16 : OBSERVATIONS AND ORBITS OF COMETS". IAU Minor Planet Center. 2012-05-04. Retrieved 2012-05-17. 
      7. ^ Jakub Cerny (2012-10-07). "Watching comet Panstarrs activity". Robotic telescope FRAM. Retrieved 2012-10-08. 
      8. ^ David Seargent (2013-02-10). "L4 naked-eye and T5 faded". comets-ml · Comets Mailing List. Retrieved 2013-02-10. 
      9. ^ Geert Barentsen (2013-03-05). "Map: when can you see comet PanSTARRS". Retrieved 2013-03-05. 
      10. ^ J.P.Navarro Pina (2012-10-23). "UPDATE THE LIGHT VISUAL CURVE OF COMET C/2011 L4 PANSTARRS". COMETS & ASTROPHYSICAL. Retrieved 2012-10-23. 
      11. ^ Jakub Cerny (2013-01-12). "Comet Panstarrs brightening slowdown". comets-ml · Comets Mailing List. Retrieved 2013-01-12. 
      12. ^ a b Yoshida, Seiichi. "C/2011 L4 ( PanSTARRS )". www.aerith.net. Retrieved 25 February 2013. 
      13. ^ a b Ferrin, Ignacio (2013). Secular Light Curves of Comets C/2011 L4 Panstarrs and C/2012 S1 ISON. University of Antioquia. arXiv:1302.4621. 
      14. ^ "Recent Comet Brightness Estimates". Retrieved 2013-03-15. 
      15. ^ a b Stuart Atkinson (7 March 2013). "Comet PANSTARRS". Retrieved 2013-03-10. 
      16. ^ Deborah Byrd. "Everything you need to know: How to see Comet PANSTARRS". Earthsky. Retrieved 2013-03-17. 
      17. ^ King, Bob (2013-05-03). "Comet PANSTARRS for die-hards". Retrieved 2013-05-05. 
      18. ^ ScienceAtNASA (14 March 2013). "ScienceCasts: Sunset Comet". Retrieved 2013-03-17. 
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      External links

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      Last modified on 29 May 2013, at 19:25