Astronomers studying stars like our sun that are known to generate powerful "superflares" have also discovered that these superflares are likely associated with monster "starspots."
ANALYSIS: Superflares Found on Sun-like Stars
When our sun sees an uptick in magnetic activity, sunspots erupt all over the solar surface, acting as a warning sign that a storm is brewing. Every 11 years or so (a period known as the solar cycle), the sun will wax and wane in magnetic activity and the number of sunspots will also rise and fall. This relationship between the innermost magnetic dynamo of the sun and sunspot number is used by space weather forecasters to predict when and where the next solar flare may erupt.
Solar flares can have dramatic impacts on Earth - they bathe our upper atmosphere in powerful radiation, blocking global communications and they can irradiate in-space assets like satellites and even give harmful doses of radiation to unprotected astronauts. Flares are often triggered in regions of intense magnetic activity and it just so happens that sunspots are also created by intense regions of magnetic activity forcing through the sun's photosphere.
PHOTOS: The Psychedelic Anatomy of a Solar Flare
Although solar flares may be dramatic, like the X2-class solar flare that caused a radio blackout on May 5, they are nothing when compared with the superflares other stars in our galaxy have been seen to kick out.
In 2012, using Kepler Space Telescope data - which is usually associated with the detection of exoplanets as they drift (or transit) in front of their host stars - astronomers were able to identify several hundred superflare events on a number of sun-like stars. These gargantuan events kicked out flares 10-10,000 times more energy than our sun is able to muster.
Keeping in mind that these stars are sun-like stars, what makes them such superflare powerhouses? Why is our sun such a featherweight in comparison?
ANALYSIS: Large Flares from Small Stars
In an effort to understand the dynamics of superflare stars and perhaps answer these questions, astronomers from Kyoto University, University of Hyogo, the National Astronomical Observatory of Japan (NAOJ) and Nagoya University turned to the High Dispersion Spectrograph on the Subaru Telescope, located atop Mauna Kea in Hawaii, to carry out spectroscopic measurements of 50 of Kepler's superflare targets.
Through these spectroscopic observations, the researchers found that all of the stars selected for study possessed periodic changes in brightness. In all cases, these variations were caused by starspots (not exoplanets) rotating across the stars' surfaces. Some of the superflare stars even rotated as slowly as our sun, which has an equatorial rotation period of nearly 24.5 days.
Also, through analysis of the Ca II 854.2 nm (ionized Calcium) absorption line, the researchers realized that the periodic dimming of the stars' brightness was being caused by vast starspots that would dwarf even the biggest sunspot our sun can produce.
ANALYSIS: Life Under a Tiny, Red, Angry Sun
Therefore, the researchers conclude that sun-like stars can trigger superflares if they possess large sunspots, but further work is needed to understand the intricacies of this relationship.
But this research poses a quandary. If our sun is so similar to these sun-like superflare stars, why are their magnetic dynamics so radically different? We're pretty sure our sun isn't capable of generating superflares (as it seems unlikely that life would have been able to evolve in such a radiation-drenched solar system), so these oddities are unlikely to be "just a phase" in the life of a sun-like star.
It just goes to prove that just because a star may look like the sun from afar, up close, the reality can be radically different.
Source: Subaru Telescope