. | . |
The Umov Effect: Space dust clouds and the mysteries of the universe by Staff Writers Vladivostok, Russia (SPX) Aug 10, 2018
FEFU scientists are developing a methodology to calculate the ratio of dust and gas in comas and tails of comets. This will help learn more about the history of the Solar System and its development, as well as understand the processes that took part on different stages of universal evolution. A team of scientists from the Far Eastern Federal University (FEFU) under the supervision of the astrophysicist Evgenij Zubko, Ph.D., a lead scientist of the School of Natural Sciences at FEFU is trying to solve a fundamental problem of modern astrophysics which is to assess the reflectivity of cosmic dust particles, their ability to scatter sunlight (or, more generally, star light). To do so, the scientists study the optic characteristics of dust particles in the comae and tails of comets. The methodology under development is based on the Umov effect - an inverse correlation between the reflectivity of a body and the degree of linear polarization of light scattered by it. The brighter is an object, the lower polarization it produces. This relation was first formulated by the Russian physicist Nikolay Umov in 1905. According to Evgenij Zubko, previously the Umov effect was studied only for surfaces, such as regolite (Moon surface) and the surfaces of asteroids. The explanation of this effect given in 1960-1970s, excluded its application to single dust particles that comprise the regolite. However, the team concluded that the Umov effect is almost equally applicable to individual particles and surfaces in general. Previously the researchers concluded that the Umov effect holds in a homogenous sparse cloud of space dust. In the article published in the July 11, 2018 print issue of Monthly Notices of the Royal Astronomical Society the scientists suggested that this physical effect could be also applicable to clouds consisting of two types of dust particles which is characteristic of comae and tails of comets. The Umov effect is also expected to be observed in a three-component clouds of cosmic dust that is more typical for protoplanetary disks. After studying the degree of linear polarization acquired by sunlight when it is scattered by cometary dust particles, scientists are able to give reliable estimation of the particles' albedo or reflectivity. This characteristic is an extremely important for retrieval the total volume of dust expelled from a comet. The latter parameter allows the scientists to improve the existing methods of estimation of the dust-to-gas volume ratio in cometary comae. This is one of the most important characteristic of a cometary evolution - for example, it could indicate the place in the Solar System in which the comet was formed. "Knowing the ratio between the volumes of ejected dust and gas, we can better understand the evolutionary stages passed by different comets and the circumstances of the Solar-System formation. However, while it is easy to calculate the volume of gas in a comet, in case of dust particles this is much more complicated," said Evgenij Zubko. "When we measure the sunlight reflected by the coma, we need to understand the number of dust particles that contribute to the sunlight scattering. Their albedo or reflectivity is the key data we require to answer this question. However, different dust particles also behave differently, and the difference in the reflectivity of dark and bright particles in comets may exceed ten times. This is a common issue nowadays that also arises in other areas of astrophysics, such as the evaluation of matter volumes in protoplanetary disks around other stars. We strive to understand the value of this albedo and use additional methods to do so - in particular, polarimetry to measure the degree of linear polarization and, thus, retrieve the reflectivity of cometary dust particles based on the Umov effect." There is still a lot to be discovered in the course of this work. "We are literally chasing a ghost," says the scientist. He also pointed out that to achieve a breakthrough in this area of studies, groups of astrophysicists from different parts of the world had to extensively collaborate. The analysis methodology based on the Umov effect may be further used in other areas besides the studies of comets. It may serve as a key to understanding the processes of formation and evolution of other planetary systems and therefore the Solar System as well. According to Evgenij Zubko, the value of the Umov effect for the science in general is as high as the importance of the spectral analysis method developed by Gustav Kirchhoff. While the spectral analysis helps us understand the chemical composition of distant bodies based on the light reflected from them, the Umov effect allows to evaluate their size even if they appear like a point to an observer.
Molecular oxygen in comet's atmosphere not created on its surface London, UK (SPX) Jul 04, 2018 Scientists have found that molecular oxygen around comet 67P is not produced on its surface, as some suggested, but may be from its body. The European Space Agency's Rosetta spacecraft escorted comet 67P/Churyumov-Gerasimenko on its journey round the sun from August 2014 - September 2016, dropping a probe and eventually crashing onto its surface. When the comet is close enough to the sun the ice on its surface 'sublimes' - transforms from solid to gas - forming a gas atmosphere called a coma ... read more
|
|
The content herein, unless otherwise known to be public domain, are Copyright 1995-2024 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. General Data Protection Regulation (GDPR) Statement Our advertisers use various cookies and the like to deliver the best ad banner available at one time. All network advertising suppliers have GDPR policies (Legitimate Interest) that conform with EU regulations for data collection. By using our websites you consent to cookie based advertising. If you do not agree with this then you must stop using the websites from May 25, 2018. Privacy Statement. Additional information can be found here at About Us. |