Watch a massive cold spot grow and travel across the sun’s surface

Watch a massive cold spot grow and travel across the sun’s surface
A few sunspots pepper an otherwise calm star in 2013. NASA/SDO
A few sunspots pepper an otherwise calm star in 2013. NASA/SDO

From Earth, the sun looks small and calm. Up close, it’s anything but. Fortunately, NASA has an excellent view of the sun’s surface through its Solar Dynamics Observatory, equipped with three different devices for measuring the sun’s activity.

Between July 5 and July 11, that orbiter caught this incredible footage:

Source: NASA’s Goddard Space Flight Center/SDO/Joy Ng, producer

What you’re watching is a fast-growing tangle of magnetic fields on the sun’s surface. The spot looks dark because all the magnetic activity blocks some heat from rising to the sun’s surface — it’s about 2,300 degrees Kelvin cooler in the sunspot.

Sunspots are pretty common, although just how common they are changes over a cycle that lasts about 11 years. Right now, we’re approaching the low point of that cycle, which is why most of the sun’s surface looks so smooth. This sunspot is right about where the phenomenon most often occurs — in two strips on either side of the sun’s equator.

While they feel distant, sunspots can actually affect life here on Earth. They often lead to what’s called space weather, when the sun’s behavior sends streams of particles towards Earth that can cause auroras near the poles, tangle GPS signals, or even affect the power grid.