Observations and Orbits of Comets

Proceedings of The International Astronomical Union, 2009

We present the results of astrometric and photometric observations of comets and minor planets obtained at the Kiev comet station (Code MPC 585) of the Astronomical Observatory of Kyiv Shevchenko National University in 2006-2009. The 2318 position observations of 176 comets, 302 observations of 57 numbered minor planets, and 220 observations of 30 unnumbered minor planets were obtained. The accuracy of the astrometric observations of the comets is analyzed.

Proceedings of the International Astronomical Union, 2015

Commission 15 of the International Astronomical Union (IAU), entitled Physical Study of Comets and Minor Planets, was founded in 1935 and dissolved in 2015, following the reorganization of IAU. In 80 years of Commission 15, tremendous progress has been made on the knowledge of these objets, thanks to the combined efforts of ground- and space-based observations, space mission rendezvous and flybys, laboratory simulation and analyses of returned samples, and theoretical and numerical modeling. Together with dynamical studies of the Solar System, this discipline has provided a much deeper understanding of how the Solar System formed and evolved. We present a legacy report of Commission 15, which highlights key milestones in the exploration and knowledge of the small bodies of the Solar System.

Icarus, 2015

Photometric and spectroscopic observations of five nearly parabolic comets with eccentricity larger than 0.99 at heliocentric distances greater than 4 AU were performed. No molecular emission was observed for any studied comet and the entire cometary activity in all cases was attributed to dust production. Upper limits of the gas production rates for the main neutral molecules in the cometary comae were calculated. The derived values of dust apparent magnitudes were used to estimate the upper limit of the geometric cross-section of cometary nuclei (upper limits of radii range from 2 km to 28 km). Due to the poor sublimation of water ice at these distances from the Sun, other mechanisms triggering activity in comets are discussed.

Proceedings of the International Astronomical Union, 2005

Astronomy & Astrophysics, 2006

Aims. We have started a program of spectroscopic and photometric investigations of distant active comets in the optical domain. The comets with a significant level of activity-in particular, extended tails-are the objects of our observations. Methods. The observations were made at the 6-m telescope BTA (SAO RAS, Russia), with the focal reducer SCORPIO attached to the prime focus of the telescope. Long-slit and photometry modes were turned to perform our first observations. The spectral resolution in the spectroscopy mode was 10 Å. Results. The result of the spectrum analysis of comet C/2002 VQ94 (LINEAR) is of particular interest. The comet observed at the heliocentric distance of 6.8 AU clearly shows a rich molecular spectrum. We identified 14 vibrational bands of CO + (Comet Tail system), emissions of C 3 , and some tentatively assigned to N + 2 and CN. It should be emphasized that, for now, CO + and tentatively assigned N + 2 emissions are detected at a record heliocentric distance.

Proceedings of the …, 2005

Proceedings of The International Astronomical Union, 2010

Advances in Space Research, 2007

We explore how nuclear rotation and activity can be used as effective probes of the gross nuclear structure and therefore of the interior of comets. We present a model of nuclear activity and discuss that in the context of how activity and rotation can control the present day size distribution of active short period comets. We argue that there is a real paucity of sub-km comets when compared with what one expects based on the size distribution of the known Kuiper Belt Objects.

Solar System Research, 2009

We present an analysis of the results of photometric investigations of two distant comets, C/2002 VQ94 (LINEAR) and 29P/Schwassmann-Wachmann-1, obtained with the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. The comets under study demonstrate sufficient activity out of the zone of water ice sublimation (at heliocentric distances longer than 5 AU). In the spectra of the investigated comets, we found the CO + and N 2 + emission. The presence of this emission may say that the comets were formed in the outer parts of the Solar System, in a protoplanetary cloud at a temperature ≤25 K. We found that the photometric maximum of the ionosphere (in the CO + filter) of the comet C/2002 VQ94 (LINEAR) is shifted relative to the photometric center of the dust coma by 1.4′′ (7.44 × 10 3 km) in the direction deflected by 63° from the direction to the Sun. Using special filters to process the images, we picked out active structures (jets) in the dust coma of the 29P/Schwassmann-Wachmann-1 comet.

Icarus, 2000

CCD photometry of 18 Jupiter family comets, observed at medium and large heliocentric distances, was carried out between April 1990 and July 1995. This is part of a long-term observational program designed to obtain their nuclear magnitudes. The observations were made with the 1.54-m Danish Telescope at ESO La Silla, the 2.5-m Nordic Optical Telescope (NOT) at Observatorio del Roque de los Muchachos (La Palma), the 2.0-m telescope at Pic du Midi, and the 2.15-m telescope at CASLEO, Argentina. Our estimates of the absolute nuclear magnitudes are discussed in comparison with previous determinations. Estimates (sometimes upper limits) for the effective radius (R) of the nuclei are computed considering a typical geometric albedo pv=0.04. The lowest radius found is the one of 37P/Forbes (R=1.0 km) while the largest corresponds to 65P/Gunn (R=11.0 km), but in this case the comet was observed very active.Wherever possible, cometary image profiles are compared with stellar profiles, in order to determine the existence of a faint coma. Seven of the comets were active, six of them at heliocentric distances larger than 4 AU. This unexpected activity is also discussed. We find a strong correlation between activity at large heliocentric distances and recent downward jumps in perihelion distance.