The seeing was ≈1 9, mostly because of the airmass of 1.9 − 2.1, which was caused by the comet’s unfavourable celestial position close to the Southern pole. We took 26 × 180 s exposures with an image scale of 0 24/pixel. We performed new R C filtered observations with the 2.2 m ESO telescope at the La Silla site in Chile, on December 4, 2010, with sidereal tracking. In this paper, we present a photometrical and morphological analysis of these observations. In late 2010, the comet exhibited evidence of the cessation of the matter production.

Here we present new observations of Hale-Bopp at a 30.7 AU solar distance. Lacking photometric data of the bare nucleus, its size, one of the most important input parameters in activity models remained uncertain. The coma obscured the nucleus, which was not observed directly. Observing Hale-Bopp in a completely frozen state would also be extremely important because a thick coma was constantly present during the entire apparition. This surprising observation raised the question of when this activity will cease.

( 2008), we demonstrated that C/1995 O1 (Hale-Bopp) was the most distant active comet ever observed, with a prominent coma at 25.7 AU solar distance. The exact location of the snow line is very important in understanding the water reservoirs in the Solar System, hence also the structure and evolution of extrasolar systems, too. 2011) and Centaur objects (e.g. Meech et al. There are known examples of active long-period comets (Szabó et al. 1999 Lowry & Fitzsimmons 2001, 2005 Lowry & Wiessman 2003 Snodgrass et al. A few exceptional comets, however, have displayed activity far beyond 3 AU (e.g. Lowry et al. Key words: comets: individual: Hale-Bopp / techniques: photometricĪccording to the accepted paradigm of cometary activity, matter production decreases rapidly after the significant decrease of water sublimation at 3 AU (Fernández 2005). With this observation, Hale-Bopp has become the most distant comet ever observed, far beyond the orbit of Neptune. Alternatively, if the nucleus is already dormant, the albedo should be as high as 13%, assuming a radius of 35 km. We propose that the comet may still be in a low level of activity, despite the lack of a prominent coma. This size estimate contradicts significantly the previous results scattering around 35 km.Ĭonclusions. The calculated a R C value would imply a nucleus with 60−65 km radius assuming 4% albedo. The measured total brightness corresponds to a relative total reflecting surface, a R C, of 485 km 2, nine times less than three years before.

The profile of the coma was star-like at a seeing of 1 9, without any evidence of a coma or tail extending farther than 2 5 (=55 000 km in projection) and exceeding 26.5 mag/arcs 2 surface brightness. The comet was detected in R and had a total brightness of 23ṃ3 ± 0ṃ2, which corresponds to an absolute brightness of R(1,1,0) = 8ṃ3. On, 26 CCD images were taken with 180 s exposure times for photometry and morphology. We present new observations with the ESO 2.2 m telescope at La Silla to monitor the activity of Hale-Bopp at 30.7 AU solar distance. It is unclear when and how this activity will finally cease.Īims. Comet Hale-Bopp (C/1995 O1) has been the most interesting comet ever encountered by modern astronomy, which continued to display significant activity at a solar distance of 25.7 AU. Physics & Astronomical Observatory, University of Szeged, 6720 Szeged, HungaryĤ Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2006, AustraliaĬontext. Konkoly Observatory, Konkoly-Thege Miklós út 15-17, 1121 Budapest, HungaryĮ-mail: Eötvös Fellow at the Astronomy Dept., University of Texas at Austin, 78712 TX, USAĭept.

Astronomical objects: linking to databases.

Including author names using non-Roman alphabets.

Suggested resources for more tips on language editing in the sciences Punctuation and style concerns regarding equations, figures, tables, and footnotes

Hale bopp comet