The distinctive blue bubble appearing to encircle WR 31a is a Wolf–Rayet nebula — an interstellar cloud of dust, hydrogen, helium and other gases. Created when speedy stellar winds interact with the outer layers of hydrogen ejected by Wolf–Rayet stars, these nebulae are frequently ring-shaped or spherical. via NASA

NASA research mathematician Katherine Johnson is photographed at her desk at Langley Research Center in 1966. Johnson made critical technical contributions during her career of 33 years, which included calculating the trajectory of the 1961 flight of Alan Shepard. She was awarded the Presidential Medal of Freedom on Nov. 24, 2015. via NASA

Expedition 46 crew member Tim Peake of the European Space Agency (ESA) shared a stunning image of a glowing aurora taken on Feb. 23, 2016, from the International Space Station. Peake wrote, "The @Space_Station just passed straight through a thick green fog of #aurora…eerie but very beautiful. #Principia" via NASA

This image, acquired by the Operational Land Imager (OLI) on Landsat 8, shows the glaciers of Sierra de Sangra on Jan. 14, 2015. Snow and ice are blue in these false-color images, which use different wavelengths to better differentiate areas of ice, rock, and vegetation. via NASA

Before the NSA deletes this post, we’ll be clear: We’re talking about a model of a nuclear reactor, not the real thing. Using Legos, [wgurecky] built a point kinetic reactor model that interfaces with the reactor simulator, pyReactor.

Even without the Lego, the Python code demonstrates reactor control in several modes. In power control mode, the user sets a power output, and the reactor attempts to maintain it. In control rod mode, the user can adjust the position of the control rods and see the results.

If things get out of hand, there’s a SCRAM button to shut the reactor …read more

from Hackaday