A loopy look at sunspots

Tangled nests of magnetic fields burst from sunspots on the solar surface. The spots appear blue and yellow in this false color composite photograph, which was taken in October by NASA’s Solar Dynamics Observatory and released in May. The pale streaks trace magnetic field lines, which stretch up to 200,000 kilometers above the surface (black).

In visible light, sunspots look like dark blotches that often expel flares of searing plasma. The orbiting observatory provides a different perspective, aided by the equivalent of ultraviolet goggles and polarized sunglasses. Iron atoms stripped of electrons glow in ultraviolet as they are propelled into the sun’s atmosphere, providing a sharp view of the magnetic field lines. Many lines form loops, as seen at the center of the image, that link pairs of sunspots with opposite magnetic polarity.

By watching how these magnetic knots arise and disperse, researchers hope to better understand what drives flares expelled by the sun and other stars. “It’s the only star where we can see any of this in detail,” says Karel Schrijver, a solar physicist at the Lockheed Martin Solar and Astrophysics Laboratory in Palo Alto, Calif. “It’s a great example of what happens elsewhere in the universe.”