Only a hot stellar core remains in the form of a white dwarf; the rest of the star is dispersed into the interstellar medium, enriching it with chemically processed elements, such as carbon, that is found in all living organisms on Earth.
These elements were cooked in the stellar furnace during a stellar life span covering billions of years. The high-energy radiation from the hot white dwarf makes the blown gas to shine for a short period of time, and the result is one of the most colourful and beautiful astronomical objects: a planetary nebula.
The complex history of mass loss
Integral field spectroscopy to the rescue
Through the new technique of integral field spectroscopy it is possible to obtain hundreds of spectra across a relatively large area of the sky, and this opens new prospects for the analysis of extended objects, such as planetary nebulae. Calar Alto Observatory has one of the world's best integral field spectrographs, PMAS (Potsdam Multi-Aperture Spectrophotometer), attached to its 3.5 m telescope.
In a research article, that was just published in the journal Astronomy and Astrophysics, a research team from the Astrophysical Institute in Potsdam, lead by C. Sandin, has used PMAS to study the two-dimensional structure of a selected set of five planetary nebulae in our Galaxy: the Blue Snowball Nebula (NGC 7662), M2-2, IC 3568, the Blinking Planetary Nebula (NGC 6826) and the Owl Nebula (NGC 3587).
The halos of planetary nebulae revealed
For four of these objects the research team derived a temperature structure, which extended all the way from the central star and out into the halo, and found, in three cases, that the temperature increases steeply in the inner halo. According to Sandin, "The appearance of such hot halos can be readily explained as a transient phenomenon which occurs when the halo is being ionized." Another remarkable result of this study is that it has been possible, for the first time, to measure the mass loss history of the final evolution of the stars which produced the planetary nebulae.
Sandin says that "In comparison to other methods which measure mass loss rates, our estimates are made directly on the gas component of the stellar wind." The results allow important insights on how mass is lost in time, and the researchers found that "the mass loss rate increases by a factor of about 4-7 during the final, say, 10 000 years of mass loss."
The research team plans to continue with this study of the final evolutionary phases of low mass stars, and have observed planetary nebulae in the Magellanic Clouds. As the authors argue "on the theoretical side the results of our studies should provide a challenging basis for further improvement of models of stellar winds."
Beyond the brim, Sombrero Galaxy's halo suggests turbulent past
21.02.2020 | NASA/Goddard Space Flight Center
10,000 times faster calculations of many-body quantum dynamics possible
21.02.2020 | Christian-Albrechts-Universität zu Kiel
The operational speed of semiconductors in various electronic and optoelectronic devices is limited to several gigahertz (a billion oscillations per second). This constrains the upper limit of the operational speed of computing. Now researchers from the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg, Germany, and the Indian Institute of Technology in Bombay have explained how these processes can be sped up through the use of light waves and defected solid materials.
Light waves perform several hundred trillion oscillations per second. Hence, it is natural to envision employing light oscillations to drive the electronic...
Most natural and artificial surfaces are rough: metals and even glasses that appear smooth to the naked eye can look like jagged mountain ranges under the microscope. There is currently no uniform theory about the origin of this roughness despite it being observed on all scales, from the atomic to the tectonic. Scientists suspect that the rough surface is formed by irreversible plastic deformation that occurs in many processes of mechanical machining of components such as milling.
Prof. Dr. Lars Pastewka from the Simulation group at the Department of Microsystems Engineering at the University of Freiburg and his team have simulated such...
Investigation of the temperature dependence of the skyrmion Hall effect reveals further insights into possible new data storage devices
The joint research project of Johannes Gutenberg University Mainz (JGU) and the Massachusetts Institute of Technology (MIT) that had previously demonstrated...
Researchers at Chalmers University of Technology, Sweden, recently completed a 5-year research project looking at how to make fibre optic communications systems more energy efficient. Among their proposals are smart, error-correcting data chip circuits, which they refined to be 10 times less energy consumptive. The project has yielded several scientific articles, in publications including Nature Communications.
Streaming films and music, scrolling through social media, and using cloud-based storage services are everyday activities now.
After helping develop a new approach for organic synthesis -- carbon-hydrogen functionalization -- scientists at Emory University are now showing how this approach may apply to drug discovery. Nature Catalysis published their most recent work -- a streamlined process for making a three-dimensional scaffold of keen interest to the pharmaceutical industry.
"Our tools open up whole new chemical space for potential drug targets," says Huw Davies, Emory professor of organic chemistry and senior author of the paper.
12.02.2020 | Event News
16.01.2020 | Event News
15.01.2020 | Event News
24.02.2020 | Life Sciences
24.02.2020 | Materials Sciences
24.02.2020 | Earth Sciences