It might not look like much relative to the rest of the sun's surface, but the sunspot pictured up top (dubbed AR1339 by the folks at NASA's Solar Dynamics Observatory) is positively massive — the biggest astronomers have observed in years.
According to SpaceWeather.com, AR1339 is about 50,000 miles long and 25,000 miles wide. As a point of reference, Earth has a diameter of just 8,000 miles.
Sunspots form when localized regions of intense magnetic activity interfere with an energy-transfer process known as convection. This interference causes areas of the Sun's surface to cool. When they do, they wind up appearing visibly dimmer than their immediate surroundings.
These same spikes in magnetic activity can also give rise to solar flares, hurtling billions of subatomic particles into space (lo and behold, SpaceWeather.com reported last night that the spot has released a class X2 solar flare). If these particles happen to be directed towards the Earth, results can range anywhere from infrastructural meltdown (in theory), to stunning northern lights.