Evgenij Zubko of Far Eastern Federal University (FEFU) in collaboration with other international team members has developed a comprehensive model to explain the results of a photometric study of the Comet Schwassmann-Wachmann 1 (29P) which was successfully accomplished recently. The findings came as a real surprise revealed that the dust environment of 29P predominantly consists of only one type of material - magnesium-rich silicate particles with presumably a small amount of iron (Fe-Mg silicates).
The observation of Comet 29P - the so-called Centaur object - was carried out in the course of the Comet activity when the brightness of the celestial body increases for hundreds of times. This was resulting from sudden and barely understood outburst activity of the comet. The observation results published in Icarus journal.
Except for 29P, there is the only sole example of a comet with a single-component dust coma - this is the comet 17P/Holmes. Like 29P, Holmes periodically experiences outbursts presumably as a result of the inner CO and CO 2 outgassing.
To perform the 29P study scientists measured the color of the sunlight reflected from its coma, using broadband filters adjusted to blue (B), green (V), red (R) and infrared (I) bands. Typically, such measurements undergo very little, mainly qualitative analysis, since quantitative analysis and retrievals of the microphysical properties of cometary species is a highly time-consuming problem. It should be based on comprehensive modeling of light scattering by cometary dust particles having various shapes, size distributions, and refractive indices. On the other hand, information about the color of comets is clearly insufficient for their classification. The point is that with the same chemical composition that is described in terms of the refractive index, the color of a comet may vary significantly during a short time period due to temporary variations in the size distribution of cometary dust particles. Evgenij Zubko, says that this time the team made a breakthrough moving from contemplating the comet to retrieving chemical composition of its dust.
What emerged from the whole-team efforts is an important constraint on the chemical composition of the 29P coma. The findings surprised the scientists due to the fact that the dust environment of 29P consists of only one type of material. Two-component mixtures are more usual.
Astronomers have assigned comet 29P to a special class of objects, the so-called "Centaurs". The name of this kind of comets was given by analogy with the mythological creatures. Like centaurs, comets like 29P have a dual nature: being comets, they move in a nearly circular orbit, atypical for comets. Such orbits are usual for large asteroids and planets.
Further study of the chemical composition of the 29P nucleus is aimed to determine more accurately which part of the Solar System the comet originates from.
Commenting on the importance of comets observation, Evgenij Zubko, emphasizes that comets are among the oldest objects in the Solar System. Some of them get formed when the Sun had not yet become a star, which means they should have very much primordial composition; whereas, billions of years spent by comets in very distant and cold Oort Cloud may help preserve their ancient composition. With comets we get a chance to have a look into the history of our Solar System. Currently, there are several known groups of comets with significantly different properties. Explaining of these differences is aimed to help scientists better understand how the Solar System evolved and which processes took place in it 4-5 billion years ago.
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A team of scientists from Russia, Slovakia, Brazil, France, Ukraine, and the United States observed Comet Schwassmann-Wachmann 1 (29P) during one night using the Southern Astrophysical Research (SOAR) Telescope with an aperture (primary mirror diameter) of 4.1 meters, located in Serra Pachon, Chile.
Original article: https://www.sciencedirect.com/science/article/pii/S0019103517307777
Universidade de São Paulo, Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Departamento de Astronomia, Rua do Matão, 1226, Cidade Universitária, São Paulo CEP 05508-900, SP, Brasil.
Astronomical Observatory, Taras Shevchenko National University of Kyiv, Observatorna str. 3, Kyiv 04053, Ukraine.
Astronomical Institute of the Slovak Academy of Sciences, Tatranská Lomnica, SK-05960, Slovak Republic.
Main Astronomical Observatory, National Academy of Sciences of Ukraine, Goloseevo, Kyiv 03680, Ukraine.
School of Natural Sciences, Far Eastern Federal University, 8 Sukhanova Street, Vladivostok 690950, Russia.
Instituto de Física e Química, Universidade Federal de Itajubá, Av. BPS, 1303, Pinheirinho, Itajubá CEP 37500-903, BRASIL.
US Army Research Laboratory, RDRL-CIE-S, 2800 Powder Mill Road, Adelphi MD 20783, USA.
Space Science Institute, 4750 Walnut Street, Boulder Suite 205, CO 80301, USA.
Department of Astronomy and Astronomical Observatory, Odessa National University, Shevchenko Park, Odessa 65014, Ukraine.
GEPI, Observatoire de Paris, PSL Research University, CNRS, Place Jules Janssen, Meudon 92195, France.
Icarus