Free Astronomy Magazine May-June 2018

48 MAY-JUNE 2018 SPACE CHRONICLES Kepler solves the mystery of fast and furious explosions by NASA/ESA T his illustration shows a proposed model for a mysterious astronomical event called a Fast-Evolving Luminous Tran- sient (FELT). In the left panel, an aging red giant star loses mass via a stellar wind. This balloons into a huge gaseous shell around the star. In the center panel, the massive star’s core implodes to trigger a supernova explosion. In the right panel, the supernova shockwave plows into the outer shell, converting the kinetic energy from the explosion into a bril- liant burst of light. The flash of radiation lasts for only a few days — one-tenth the duration of a typical supernova ex- plosion. [NASA, ESA, and A. Feild (STScI)] T he universe is full of mysteri- ous exploding phenomena that go boom in the dark. One particular type of ephemeral event, called a Fast-Evolving Luminous Transient (FELT), has bewildered as- tronomers for a decade because of its very brief duration. Now, NASA’s Kepler Space Telescope — designed to go hunting for plan- ets across our galaxy — has also been used to catch FELTs in the act and determine their nature. They appear to be a new kind of super- nova that gets a brief turbo boost in brightness from its surroundings. Kepler’s ability to precisely sample sudden changes in starlight has al- lowed astronomers to quickly arrive at this model for explaining FELTs, and rule out alternative explana- tions. Researchers conclude that the source of the flash is from a star after it collapses to explode as a su- pernova. The big difference is that the star is cocooned inside one or more shells of gas and dust. When the tsunami of explosive energy from the blast slams into the shell, most of the kinetic energy is imme- diately converted to light. The burst of radiation lasts for only a few days