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Be Grateful the Sun Can’t Produce Flares Like This

Artist’s impression of the a massive flare — called a superflare — observed on one of the stars in the V1355 Orionis binary star system. The binary companion star is visible in the background on the right. (Credit: NAOJ)

Okay, so we all know that the Sun is heading into solar maximum. That means it’s quite a bit more active, with sunspots, coronal mass ejections, and flares aplenty. But, luckily for us, the Sun isn’t as active as the members of the binary star system V1355 Orionis. One of its stars periodically releases superflares. These are ten times more extensive than the largest solar flare ever recorded on the Sun.

On Earth, flares from the Sun often kick up geomagnetic storms (often referred to as “space weather”). In the worst cases, those storms can interfere with our technology. They can disrupt communications, shut down power grids, and damage satellites. Really powerful flares, like the ones at V1355 Orionis, could have even worse effects. That includes affecting the evolution of any nearby planets and their atmospheres. Certainly, if they’re strong enough, such flares could wipe out any life on those worlds. So, understanding flares on stars, and why they occur, is important.

A team of astronomers led by Shun Inoue at Kyoto University in Japan monitored this binary system using the 3.8-meter Seimei Telescope and the Transiting Exoplanet Survey Satellite (TESS). They managed to catch a superflare that began with a massive, high-velocity prominence. It was one of the most powerful ejections from a star. The velocity of the eruption was at least 990 kilometers per second—which is well over the star’s 347 km/sec escape velocity. It developed into a coronal mass ejection that carried trillions of tons of material away into space.

Understanding Flares from V1355 Orionis

The measurements made by the team are aimed at helping astronomers understand how superflares and eruptions begin. The V1355 Orionis system is classified as an RS CVn-type star. The classification comes from the RS Canum Venaticorum system, which is a variable containing close binary stars. These stars are typically magnetically active, with large superflares bursting out from their surfaces. They also often have large starspots. There are various subgroups of these systems, including flare stars like V1355 Orionis. Some are quite bright in X-rays and radio frequencies.

V1355 Orionis has both a K- and G-type star. The K star is a subgiant and the source of the superflare. The results of these observations show the need for more modeling and simulation of prominences on this type of star, particularly in a binary system. Among other things, it’s important to get a better idea of how much mass the star loses through its prominences and associated coronal mass ejections.

The superflare V13555 Orionis is useful to understand not just how they happen there, but the mechanism that causes prominences and flares on our Sun. Further observations should help nail down just what’s going on at the surface and with the magnetic fields on both types of stars.


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