ACTIVITY OF 50 LONG-PERIOD COMETS BEYOND 5.2 au

Abstract

Remote investigations of the ancient solar system matter has been traditionally carried out through the observations of long-period (LP) comets that are less affected by solar irradiation than the short-period counterparts orbiting much closer to the Sun. Here we summarize the results of our decade-long survey of the distant activity of LP comets. We found that the most important separation in the dataset is based on the dynamical nature of the objects. Dynamically new comets are characterized by a higher level of activity on average: the most active new comets in our sample can be characterized by Af ρ values >3-4 higher than that of our most active returning comets. New comets develop more symmetric comae, suggesting a generally isotropic outflow. Contrary to this, the coma of recurrent comets can be less symmetrical, ocassionally exhibiting negative slope parameters, suggesting sudden variations in matter production. The morphological appearance of the observed comets is rather diverse. A surprisingly large fraction of the comets have long, teniouos tails, but the presence of impressive tails does not show a clear correlation with the brightness of the comets.

Physical activity of the selected nearly isotropic comets with perihelia at large heliocentric distance

“…observations with A f ρ parameters surpassing 3000 cm, meanwhile the calculated A f ρ for three returning comets were less than 260 cm. The lower level of the physical activity of returning comets at large distances from the Sun has been mentioned in the literature and explained as a result of loosing volatiles during previous revolutions and developing a crust mantle on the surfaces (Lowry et al 1999;Lowry & Fitzsimmons 2001;Mazzotta Epifani et al 2007;Meech et al 2009;Mazzotta Epifani et al 2014;Sárneczky et al 2016). Eight comets from our sample have been previously characterized with the A f ρ (Mazzotta Epifani et al 2014;Sárneczky et al 2016).…”

“…The lower level of the physical activity of returning comets at large distances from the Sun has been mentioned in the literature and explained as a result of loosing volatiles during previous revolutions and developing a crust mantle on the surfaces (Lowry et al 1999;Lowry & Fitzsimmons 2001;Mazzotta Epifani et al 2007;Meech et al 2009;Mazzotta Epifani et al 2014;Sárneczky et al 2016). Eight comets from our sample have been previously characterized with the A f ρ (Mazzotta Epifani et al 2014;Sárneczky et al 2016). The estimates of the activity from literature for these comets are in reasonable agreement with the A f ρ values derived in this work, taking into account the different geometrical circumstances of observations and different reference radii used for the A f ρ calculation.…”

“…Comet C/2010 U3 (Boattini), which was observed at a heliocentric distance of 12.7 au (the largest distance among the investigated targets) on its inbound part of the orbit, has probably represented a different pattern of activity. According to the literature and our yet unpublished observations, the comet has been dimming and becoming more diffuse approaching the Sun as if it had experienced an outburst at a very large heliocentric distance (Jewitt 2015;Sárneczky et al 2016).…”

Oort spike comets with large perihelion distances

“…Later, prediscovery detections by Siding Spring Survey were found (16 July and 16 August 2004), extending the period of data to 8.7 yrs in a range of heliocentric distances: 10.3 au -5.593 au (perihelion) -13.4 au. C/2005 L3 and C/2006 S3 were among the brightest comets beyond 5 au from the Sun, and sizes of their nuclei can be expected to lie somewhere between size of comet 1P/Halley and comet C/1995 O1 Hale Bopp (Sárneczky et al 2016).…”

“…From its discovery, C/2010 S1 was followed during 4.8 years through its perihelion (5.9 au) up to 8.02 au from the Sun, and more than 8.5 thousands of positional measurements were obtained. Together with C/2005 L3 and C/2006 S3, this comet nucleus is expected to be large in size (Sárneczky et al 2016). Such a rich data material covering several years allows to determine the orbit of the highest quality class of 1a+.…”