Comet McNaught (260P/2012 K2): spin axis orientation and rotation period (original) (raw)
Related papers
Coma morphology and constraints on the rotation of Comet HaleBopp (C/1995 O1)
Earth, Moon, and Planets, 1997
We present constraints on the spin state of comet Hale-Bopp based on coma morphology. Three cases of rotational states are compatible with near perihelion observations: (1) principal-axis rotation, (2) complex rotational state with a small precessional angle, or (3) complex rotational state with a large ratio between the component periods. For principal axis rotators, images from 1996 (pre-perihelion) are consistent with a rotational angular momentum vector, M, directed at ecliptic longitude and latitude (250 • , −5 • ) while images from late 1997 (post-perihelion) indicate (310 • , −40 • ). This may suggest a change in M. A complex rotational state with small precessional angle requires only a small or no change in M over the active orbital arc. In this case, M is directed near ecliptic longitude and latitude (270 • , −20 • ). A rotationally excited nucleus with a large ratio between component periods requires the nucleus to be nearly spherical. The transformation of dust coma morphology from near-radial jets to bright arcs and then again to near-radial jets is interpreted as a heliocentric and geocentric distance dependent evolutionary sequence. The spiral structures seen in CN filters near perihelion (in contrast to sunward side arcs seen in continuum) can be explained if the precursor of CN molecules (likely sub-micron grains) are emitted from the nucleus at low levels (≈ 10% of the peak daytime emission) during the nighttime. This may be indicative of a nucleus with a CO-rich active area(s).
Earth, Moon, and Planets, 2007
High quality CCD images obtained at two different observatories in North Italy allowed the identification of four morphological structures near the nuclear region of the comet Ikeya-Zhang (I-Z): haloes, jets, shells and spirals. The interpretation of the nature of these structures has been attempted by means of a comparison of different up-to-date image processing techniques, which led to a single common estimate of the rotation period (p=1.48±0.20 days).
Rotation of Cometary Nuclei [and Discussion]
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 1984
Asymmetric comas and repetitive appearances of structures in the heads and tails of comets are used to infer nuclei rotation periods. However, periodic behaviour of optically-thick expanding comas or of ion plasma production may contribute spurious results. The spin periods of comets are longer than those of asteroids, ranging generally over 10-100 h and above probable limits for gravitational escape. The periods show a flatter distribution, which may reflect an accretional rather than collisional fragmentation history. Arguments for spin-up with age due to sublimating gases are weak; the converse is possible and spin-down due to preferential escape of particles from equatorial regions appears likely.
Comet 81/P Wild 2: Changes in the spin axis orientation during the last five apparitions
Icarus, 2024
Comet 81P/Wild 2 is characterized by the presence of a prominent fan-shaped dust emission originating from an active source at high latitude on the nucleus, whose axis is assumed to coincide with the comet's rotation axis. Therefore, several authors estimated the spin axis orientation of 81P in past apparitions based on the polar jet model. By measuring the PAs of the fan on CCD images taken with different telescopes during the 2009-10 and 2022-23 apparitions, we estimated a position of the comet's spin axis at RA=295.0°±7.5°, Dec=14.5°±4.0° for the 2009-10 apparition and at RA=296.7±2.0°, Dec=17.3±2.5° for the 2022-23 apparition. Despite some degree of uncertainty of the estimate for the 2009-10 apparition, we interpolated the estimate for 2009-10 and 2022-23 with the published data of the previous apparition of 1997, to assess the presence and the extent of a drift of the pole since the 1997 passage. The analysis over a long time span of five consecutive apparitions confirms previous observations that the spin axis of comet 81P is subject to a slow drift with variable rate, probably connected to outgassing-induced jet forces and the related non-gravitational perturbations of its orbital period.
Solar System Research, 2012
The results of the photometric observations of comet 29P/Schwassmann-Wachmann 1 are ana lyzed. The comet demonstrates substantial activity at heliocentric distances larger than 5 AU, i.e., outside the water ice sublimation zone. The CCD images of the comet were obtained in wideband R filters at the 6 meter telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAS) and at the 2 meter Zeiss 2000 telescope of the Peak Terskol Observatory. The processing of the images with special digital filters allowed the active structures (jets) to be distinguished in the dust coma of the comet. With the cross correlation method, the rotation period of the cometary nucleus was determined as 12.1 ± 1.2 and 11.7 ± 1.5 days for the observations taken in December 2008, and February 2009, respectively. The probable causes of the difference in the estimates of the rotation period of the cometary nucleus obtained by different authors are discussed.
Rotation of comet 46P/Wirtanen
Abstract. We have observed comet 46P/Wirtanen during 1996 June, August and November using the University of Hawai‘i 2.2m telescope. At the time of the observations, the comet was atheliocentricdistances,r =2.99,2.53and1.83AU.Duringthe August run observations were made in order to search for light curve variations due to rotational modulation,of the nucleus. The comet was active for all runs, and during 1996 August the comaextended>16, km at the distance of the comet) at PA 75. Thesurfacebrightnessproleexhibitedagradientslopeof,1:6 and 1:4 in August and November, respectively, only slightly steeperthanthatexpectedbyradiationpressureandphaseangle effectsalone.Usingaphase-dispersionminimizationtechnique, we,nd a possible rotation period near 7.6 hours. The color of the nucleus plus dust is B V =0 :756 0:009, V R = 0:456 0:009 and R,I =0 :366 0:009 averaged over the three runs. Key words: comets: 46P/Wirtanen { space vehicles
Rotation of the nucleus of comet p/Arend-Rigaux
Icarus, 1985
Time-resolved charge-coupled device photometry of Comet p/Arend-Rigaux shows a cyclic variation in cometary brightness consistent with the periods T~ = 574 + 5 min (9.58-+ 0.08 hr) and /'2 = 407-5 rain (6.78-0.08 hr). The variation has a 30% range and is confined to the inner coma. The relative photometric stability of the outer coma indicates that the variations in the inner coma are associated with the nucleus and probably result from its rotation at, or at a multiple of, one of the above periods.
Rotation of Comet 103P/HARTLEY 2 from Structures in the Coma
The Astrophysical Journal, 2011
The CN coma structure of the EPOXI mission target, comet 103P/Hartley 2, was observed during twenty nights from September to December 2010. These CN images probe the rotational state of the comet's nucleus and provide a ground-based observational context to complement the EPOXI observations. A dynamically excited cometary nucleus with a changing rotational rate is observed, a characteristic not seen in any comet in the past. The lack of rotational damping during the four-month observing interval places constraints on the interior structure of the nucleus.
Further Investigation of Changes in Cometary Rotation
The Astronomical Journal, 2018
Samarasinha & Mueller (2013) related changes of cometary rotation to other physical parameters for four Jupiter family comets defining a parameter X, which is approximately constant within a factor of two irrespective of the active fraction of a comet. Two additional comets are added to this sample in this paper and the claim of a nearly constant parameter X for these six comets is confirmed, albeit with a larger scatter. Taking the geometric mean of X for all the comets above excluding 2P/Encke (as X for each comet was determined with respect to that of 2P/Encke), the expected changes in the rotation periods for a sample of 24 periodic comets are derived. We identify comets from this sample that are most likely to show observationally detectable changes in their rotation periods. Using this sample and including the six comets used to determine X, we find a correlation between the parameter ζ (i.e. the total water production per unit surface area per orbit approximated by that inside of 4 au) and the perihelion distance q; specifically we derive ζ ∝ q −0.8 and provide a theoretical basis for this in Appendix A. This relationship between ζ and q enables ready comparisons of activity due to insolation between comets. Additionally, a relationship between the nuclear radius R and the rotation period P is found. Specifically, we find that on average smaller nuclei have smaller rotation periods compared to the rotation periods of larger nuclei. This is consistent with expectations for rotational evolution and spin-up of comet nuclei, providing strong observational evidence for sublimation-driven rotational changes in comets.