Astrophysical blog of science cometaryAstrophysical blog of science cometary by J.P.Navarro Pina http://astrocometas.blogspot.com
Abstracts of articles in press or recently published. Limited to 3000 characters.
Results from the Worldwide Coma Morphology Campaign for Comet ISON (C/2012 S1)
- Planetary Science Institute, Tucson, AZ
We present the results of a global coma morphology campaign for comet C/2012 S1 (ISON), which was organized to involve both professional and amateur observers. In response to the campaign, many hundreds of images, from nearly two dozen groups were collected. Images were taken primarily in the continuum, which help to characterize the behavior of dust in the coma of comet ISON. The campaign received images from January 12 through November 22, 2013 (an interval over which the heliocentric distance decreased from 5.1 AU to 0.35 AU), allowing monitoring of the long-term evolution of coma morphology during comet ISON’s pre-perihelion leg. Data were contributed by observers spread around the world, resulting in particularly good temporal coverage during November when comet ISON was brightest but its visibility was limited from any one location due to the small solar elongation. We analyze the northwestern sunward continuum coma feature observed in comet ISON during the first half of 2013, finding that it was likely present from at least February through May and did not show variations on diurnal time scales. From these images we constrain the grain velocities to ~10 m s-1, and we find that the grains spent 2-4 weeks in the sunward side prior to merging with the dust tail. We present a rationale for the lack of continuum coma features from September until mid-November 2013, determining that if the feature from the first half of 2013 was present, it was likely too small to be clearly detected. We also analyze the continuum coma morphology observed subsequent to the November 12 outburst, and constrain the first appearance of new features in the continuum to later than November 13.99 UT.
Planetary and Space Science (Published)
DOI: 10.1016/j.pss.2015.10.006 arXiv: 1511.07592
Orbital and Physical Characteristics of Meter-scale Impactors from Airburst Observations
- Dept. of Physics and Astronomy, University of Western Ontario, London, Ontario, Canada N6A 3K7
- Centre for Planetary Science and Exploration, University of Western Ontario, London, Ontario, Canada N6A 5B8
- Dept of Earth Sciences, University of Western Ontario, London, Ontario, Canada N6A 5B7
- ET Space Systems, 5990 Worth Way, Camarillo, CA, 93012 USA
We have analysed the orbits and ablation characteristics in the atmosphere of 59 earth-impacting fireballs, produced by meteoroids one meter in diameter or larger, described here as meter-scale. Using heights at peak luminosity as a proxy for strength, we determine that there is roughly an order of magnitude spread in strengths of the population of meter-scale impactors at the Earth. We use fireballs producing recovered meteorites and well documented fireballs from ground-based camera networks to calibrate our ablation model interpretation of the observed peak height of luminosity as a function of speed. The orbits and physical strength of these objects are consistent with the majority being asteroidal bodies originating from the inner main asteroid belt. This is in contrast to earlier suggestions by Ceplecha (1994) that the majority of meter-tens of meter sized meteoroids are “…cometary bodies of the weakest known structure”. We find a lower limit of ~10-15% of our objects have a possible cometary (Jupiter-Family comet and/or Halley-type comet) origin based on orbital characteristics alone. Only half this number, however, also show evidence for weaker than average structure. Two events, Sumava and USG 20131121, have exceptionally high (relative to the remainder of the population) heights of peak brightness. These are physically most consistent with high microporosity objects, though both were on asteroidal-type orbits. We also find three events, including the Oct 8, 2009 airburst near Sulawesi, Indonesia, which display comparatively low heights of peak brightness, consistent with strong monolithic stones or iron meteoroids. Based on orbital similarity, we find a probable connection among several events in our population with the Taurid meteoroid complex; no other major meteoroid streams show probable linkages to the orbits of our meter-scale population. Our impactors cover almost four orders of magnitude in mass, but no trend in height of peak brightness as a function of mass is evident, suggesting no strong trend in strength with size for meter-scale impactors consistent with the results of Popova et al (2011).
Icarus (In press)
Nano-metric Dust Particles as a Hardly Detectable Component of the Interplanetary Dust Cloud
- Ilia State University, Cholokashvili str. 3/5, Tbilisi 0162, Georgia. e-mail: email@example.com
- Shamakhy Astrophysical Observatory, P.O. Box 153, Central Post Office, Baku AZ-1000, Azerbaijan.
- Qafqaz University, Khirdalan City, Hasan Aliyev str., 120, Baku, Absheron AZ-0101, Azerbaijan.
The present work introduces the hypothesis of existence of a hardly detectable component of the interplanetary dust cloud and demonstrates that such a component is a dust formation consisting of the dust particles of nano-metric dimensions. This work describes the main physical properties of such a kind of nano-dust, and its possible chemical and mineralogical peculiarities proposes new explanations related to reddening of the dynamically cold transneptunian objects on account of scattering their light by nano-dust of the hardly detectable component of the interplanetary dust cloud. We propose the relation for the coefficient of absorption by the nano-dust and provide results of the statistical analysis of the TNO color index–orbital inclinations. We also present a critical assessment of the proposed hypothesis.
J. Astrophys. Astr. (In press)