Sunspots form on the sun's surface as magnetic fields rearrange and realign.
Beginning Tuesday, instruments on the solar observatory detected a sunspot that grew to giant proportions in just under 48 hours, the space agency said Wednesday.
The spot has quickly grown into what astronomers call a delta region, in which the lighter areas around the sunspot, known as the penumbra, exhibit magnetic fields that point in the opposite direction of those fields in the center, dark area, NASA said.
This is a fairly unstable configuration that scientists have confirmed can lead to eruptions of radiation on the sun called solar flares, it said.
N.J. man wakes up from 10-hour sleep with knife in back
Campus cop fatally shoots Texas student during traffic stop