It’s funny… With all the crazy things to observe out there in the Universe, like galactic mergers, gravitational lenses, relativistic jets and extrasolar planets, a lot of people seem to forget about stars. Perhaps ironically, seeing as stars are essentially what we were looking at in the first place. A lot of people forget, perhaps. But not everyone.
Using a combination of Europe’s VLT and Newton X-ray satellite, a group of plucky astronomers have managed to achieve a high enough resolution view of another star that they can actually discern surface features like flares! The star in question bears the (perhaps slightly unfortunate) name of BO Microscopii and is around 150 light years away, and at only 30 million years old, it’s still barely a teenager by stellar standards. Bearing the nickname of “Speedy Mic” due to it’s fast rotation speed (once every 9 hours), it’s a star slightly smaller than ours (about 90% solar mass), and when it grows up, it’ll probably be a lot like it.
Imaging such detail is quite an accomplishment really, given how difficult the task actually is. The technique they used to image these flares is “doppler imaging”, measuring slight fluctuations in the star’s lights as it rotates. These fluctuations are then mapped to the surface of the rotating star (shown in the attached image). Across 142 observations, they managed to pick out several surface features, including starspots haphazardly dotted about the stars north and south hemispheres (and seeming to correlate quite nicely with where the star’s magnetic field lines should be) and a flare lasting around 4 hours.
The 4 hour flare was a puzzle though. It managed to kick out over 100 times as much energy as a solar flare generally would, as well as being significantly bigger than any solar coronal loop. Not too unusual, particularly for a highly convective young star — but the puzzle was that this flare did not actually correspond to any of the observed starspots. This seemingly contradicts what we know about solar flares, raising a few interesting questions…