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Micronovae are about 1 million times less bright than a classical nova, says Scaringi, lasting just half a day, compared with several weeks for novae.

The brevity of the events meant they had previously been missed, but TESS was able to spot them during its around-the-clock observations of the galaxy in search of exoplanets. Three were seen up to 5,000 light years from Earth, with the white dwarfs brightening temporarily before dimming again.

The exact mechanism behind the explosions isn’t clear, but it is thought they may be caused by hydrogen accumulating at the poles of the star – perhaps as much as the mass of an asteroid in just 100 days. Eventually, the hydrogen reaches sufficient temperatures and pressures to ignite fusion and cause a localised thermonuclear explosion that releases as much energy as the sun would in a day.

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A 3D printer that uses lasers to build up an object in any order, rather than layer by layer, could produce more advanced designs than is currently possible.

Existing 3D printers work by depositing layers of a plastic filament from a nozzle or by curing layers of resin with UV light. In both cases objects are built up one layer at a time, meaning that overhanging parts of a structure – the outstretched arms of a model human, say – must be propped up by temporary supports until printing is complete. These supports must then be carefully removed manually.

To get around this, Dan Congreve at Stanford University in California and his colleagues created a 3D-printing system that involves focusing a red laser at a particular point in a pool of resin. The resin is impregnated with particles 80 nanometres wide that convert red light into blue once the light hits a certain energy threshold, which only occurs at the point where the red laser is precisely focused.

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NASA’s Perseverance Mars rover used its Mastcam-Z camera system to shoot video of Phobos, one of Mars’ two moons, eclipsing the Sun. It’s the most zoomed-in, highest frame-rate observation of a Phobos solar eclipse ever taken from the Martian surface.

Several Mars rovers have observed Phobos crossing in front of the Sun over the past 18 years. Spirit and Opportunity made the first observations back in 2004; Curiosity in 2019 was the first to record video of the event. Each time these eclipses are observed, they allow scientists to measure subtle shifts in Phobos’ orbit over time. The moon’s tidal forces pull on the deep interior of the Red Planet, as well as its crust and mantle; studying how much Phobos shifts over time reveals something about how resistant the crust and mantle are, and thus what kinds of materials they’re made of.

The Mars 2020 Perseverance mission is part of NASA’s Moon to Mars exploration approach, which includes Artemis missions to the Moon that will help prepare for human exploration of the Red Planet.

Credit: NASA/JPL-Caltech/ASU/MSSS/SSI

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