The team reconstructed Apollo's shape and determined its rotational state using brightness measurements from several years. They found that Apollo's rotation speed steadily increases, and showed that this is due to the re-radiation of solar energy from its surface. The study was published in Nature online on 7 March.
Apollo's rotation period is slightly over three hours, and it decreases only by four thousandths of a second per year, so the analysis required accurate mathematical methods. Because of the acceleration, Apollo is likely to break apart or radically change its figure in the future. It may already have done so earlier, and its present moonlet may be a remnant of such a breakup.
The study confirms that non-gravitational forces are important in the dynamical evolution of asteroids. Re-radiation of solar energy acts as a propulsion engine on the asteroid's surface. There are two coupled manifestations of this phenomenon: the one changing the orbit (the Yarkovsky effect), and the one changing the spin state (the Yarkovsky-Radzievskii-O'Keefe-Paddack or YORP effect). The study confirmed the latter, and the former was detected by radar in 2003. Non-gravitational orbital and spin changes can be significant or even critical over long time intervals. They affect the motion of asteroids that may collide with the Earth. The phenomenon can also be used to estimate the masses of asteroids. Apollo is now the first object larger than one kilometre across for which the propulsion effect has been detected.
Academy Research Fellow Mikko Kaasalainen works in the Centre of Excellence in Inverse Problem Research of the Academy of Finland at the Department of Mathematics and Statistics of the University of Helsinki. The CoE develops and applies mathematical methods in data analysis in various fields from biology to space research. Dr. Kaasalainen coordinates an international solar system research and observation network with researchers from Europe, America, Asia, and Australia. The study published in Nature was carried out by scientists from Finland, Czech Republic, the United States, and Ukraine.
Niko Rinta | alfa
Tracing aromatic molecules in the early universe
23.03.2017 | University of California - Riverside
New study maps space dust in 3-D
23.03.2017 | DOE/Lawrence Berkeley National Laboratory
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
23.03.2017 | Life Sciences
23.03.2017 | Power and Electrical Engineering
23.03.2017 | Earth Sciences