keeping up

counting single electrons

“[...] the most sensitive ammeter to date -- allows currents to be measured in the attoampere range for the first time. Dubbed a bi-directional single-electron ammeter, the device could be used for a wide variety of applications, including nanoelectronics, calibration devices, quantum computation and biology [...]”
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“ [...] the researchers can precisely count single electrons in both directions. Moreover, they can obtain a value for the average current by counting the net electron flow -- by subtracting the number of electrons travelling backwards from the number travelling forwards.”

new computer simulation of gas planet satellite development give fair match to reality

“Each of our Solar System's outer gaseous planets hosts a system of multiple satellites, and these objects include Jupiter's volcanic Io and Europa with its believed subsurface ocean, as well as Titan with its dense and organic-rich atmosphere at Saturn. While individual satellite properties vary, the systems all share a striking similarity: the total mass of each satellite system compared to the mass of its host planet is very nearly a constant ratio, roughly 1:10,000.”
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“[...] The team [Canup and Ward] proposes that the balance of two processes -- the ongoing inflow of material to the satellites during their growth and the loss of satellites to collision with the planet -- implies a maximum size for a gas planet satellite consistent with observations.” [Quoted from physorg.com]

“The [Canup and Ward] model also solves another problem. Previous models had moons forming too quickly and too violently, making them too hot to contain the ice observed today. In the new model, the moons take about a million years to form.”
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“Solid planets like Earth and Pluto have relatively large satellites with up to 10% of their mass. These were probably formed by cataclysmic impacts that threw up material into orbit. Since it is the gas that causes the moons of giant planets to spiral in to their death, there is no equivalent upper size limit for the moons of rocky planets.” [Quoted from newscientistspace.com]