Gaia Reveals How Sun-like Stars Turn Solid after They Die
Author: A Millisecond of Eternity On January 9, 2019, data captured by Gaia, the European Space Agency’s Milky Way–mapping spacecraft, revealed for the first time how white dwarfs—the dead remnants of stars such as our Sun—turn into solid spheres as the heat sources within them cool. The solidification, or crystallization, of matter inside white dwarfs was predicted 50 years ago. Only with Gaia, however, have astronomers been able to observe enough white dwarfs with sufficient precision to see the pattern that reveals the process. “Before Gaia, we had distances for only a few hundred white dwarfs, and many of them were in clusters where they all had the same age,” said Pierre-Emmanuel Tremblay of the University of Warwick in the United Kingdom, lead author of the study published in ...
A Stunning Animation of a Solar Flare
Author: 一毫秒的永恒 In this visualization of a solar flare, purple represents plasma cooler than one million kelvins, red represents temperatures between one and ten million kelvins, and green represents temperatures above ten million kelvins. This animated snapshot models the life cycle of a solar flare in three dimensions, using different colors to show the range of temperatures reached during the eruption. The dancing magnetic-field lines first surge, then erupt, and finally settle down. The simulation does more than produce a striking picture of a solar flare: it also lays important groundwork for predicting flare activity in space weather. Solar flares are the most powerful explosions in our solar system, and they are spectacular events. They form near sunspots—the dark patches on t ...
How Long Is a Day on Saturn? Scientists Finally Have a Precise Answer
Author: 一毫秒的永恒 An image taken by NASA's Cassini spacecraft shows Saturn's northern hemisphere approaching the summer solstice in 2016. A year on Saturn lasts 29 Earth years; according to the latest analysis of Cassini data, a day lasts only 10:33:38. Using new data from NASA’s Cassini spacecraft, researchers believe they have solved a long-standing mystery in Solar System science: the length of a day on Saturn. The answer is 10 hours, 33 minutes, and 38 seconds. Planetary scientists spent decades trying to obtain that figure because the rotating gas giant has no fixed surface features to track, while its unusual magnetic field conceals its rotation rate. The answer, it turns out, was hidden in Saturn’s rings. While Cassini orbited Saturn, its instruments examined the icy, rocky ri ...
The Mathematician's Beauty—Penrose Tilings
Author: Martin Gardner Translator: Tu Hong Excerpted from Fractals, Take-Away Games, and Penrose Tilings, Shanghai Scientific and Technological Education Publishing House Text and images selected from the WeChat account Fun Mathematics (ID: mathfun) Sir Roger Penrose (1931– ) is a British mathematical physicist who has made major contributions to general relativity and cosmology, as well as important contributions to recreational mathematics and philosophy. This article is excerpted from Fractals, Take-Away Games, and Penrose Tilings, part of a classic collection of Martin Gardner’s recreational mathematics writing. In 1957, Scientific American ran a column about tiling the plane periodically with congruent convex polygons. It was later reprinted in Time Travel and Other Mathematica ...