Tuesday, 6 June 2017
A researcher has designed a novel computing system made solely from carbon that might one day replace the silicon transistors that power today’s electronic devices.
via Science Daily
Solar flares and associated eruptions can trigger auroras on Earth or, more ominously, damage satellites and power grids. Could flares on cool, red dwarf stars cause even more havoc to orbiting planets, even rendering them uninhabitable? To help answer that question, astronomers sought to find out how many flares such stars typically unleash.
A new study of archival ultraviolet observations from the Galaxy Evolution Explorer (GALEX) spacecraft detected dozens of flares from red dwarf stars. Some flares were weaker than any previously detected. Since smaller flares tend to occur more frequently, these tiny flares might have big implications for planetary habitability.
via Hubble - News feed
What's happened to giant star N6946-BH1? It was there just a few years ago -- Hubble imaged it. Now there's only a faint glow. What's curiouser, no bright supernova occurred -- although the star did brightened significantly for a few months. The leading theory is that, at about 25 times the mass of our Sun, N6946-BH1's great gravity held much of the star together during its final tumultuous death throes, after which most the star sunk into a black hole of its own making. If so, then what remained outside of the black hole likely then formed an accretion disk that emits comparatively faint infrared light as it swirls around, before falling in. If this mode of star death is confirmed with other stars, it gives direct evidence that a very massive star can end its life with a whimper rather than a bang.
Zazzle Space Gifts for young and old
A graphene transistor that outperforms previous state-of-the-art has been developed by an international team of scientists gathered around the Graphene Flagship project. By utilizing a thin top gate insulator material, researchers from Italy, Sweden, the USA and Spain optimized transistor figures of merit such as maximum oscillation frequency, cutoff frequency, forward transmission coefficient, and open-circuit voltage gain, realizing devices that show prospect of using graphene in a wide range of electronic applications.
The use of graphene field effect transistors (GFETs) in digital electronics has been problematic due to the lack of a bandgap in graphene. The lack of bandgap results in the inability to switch the transistors off, effectively rendering the “0” state in digital logic inaccessible. For most analog applications, however, a bandgap is not necessary. The only undesired side-effect of using GFETs in analog circuits is a poor saturation of the drain current, which prevents high-gain operation. Researchers have now succeeded in improving saturation by optimizing the dielectric material (AlOx) that is used to electrically insulate the top gate of the GFET. An improved quality of gate dielectric resulted in strong control over carriers in the graphene channel, yielding overall performance benefits.
“Such GFETs could find applications in analog circuits, in which high gain and operating speed could be traded off against power consumption”, says Roman Sordan, leader of the group that performed the research. “Some examples include amplifiers, oscillators, and very simple mixed-signal circuits (e.g., for baseband processing)”, he adds.
Image: Graphene transistors (copyright Nature Publishing Group, Creative Commons)
The paper was published in the Nature Publishing Group journal Scientific Reports. As part of the project, the authors have identified critical technological parameters that could be optimized to further improve the maximum oscillation frequency, showing that the proposed improvements are of a technological nature, rather than a fundamental obstacle. The research suggests that a further improvement of CVD graphene quality, smoother substrates, reduced contact and gate resistances should yield devices with even higher real use potential.
This research is a result of the Graphene Flagship, a billion-euro ten-year project of the European Commission.
Atmospheres of Two Hot Jupiters: Cloudy and Clear
Astronomers once thought that the family of planets that orbit our sun were typical of what would eventually be found around other stars: a grouping of small rocky planets like Earth huddled close to their parent star, and an outer family of monstrous gaseous planets like Jupiter and Saturn.
But ever since the discovery of the first planet around another star (or exoplanet) the universe looks a bit more complicated — if not downright capricious. There is an entire class of exoplanets called "hot Jupiters." They formed like Jupiter did, in the frigid outer reaches of their planetary system, but then changed Zip code! They migrated inward to be so close to their star that temperatures are well over 1,000 degrees Fahrenheit.
Astronomers would like to understand the weather on these hot Jupiters and must tease out atmospheric conditions by analyzing how starlight filters through a planet's atmosphere. If the spectral fingerprint of water can be found, then astronomers conclude the planet must have relatively clear skies that lets them see deep into the atmosphere. If the spectrum doesn't have any such telltale fingerprints, then the planet is bland-looking with a high cloud deck.
Knowing the atmospheres on these distant worlds yields clues to how they formed and evolved around their parent star. In a unique experiment, astronomers aimed the Hubble Space Telescope at two "cousin" hot Jupiters that are similar in several respects. However, the researchers were surprised to learn that one planet is very cloudy, and the other has clear skies.
via Hubble - News feed