In late October people around the world saw an unusually brilliant round of auroras, including blood-red northern lights that reached as far south as Alabama in the U.S.
The sky show was the product of what’s called a coronal mass ejection, or CME—a cloud of charged particles that came bursting off the sun on October 22.
It took a couple days for the cloud to reach Earth, slam into our atmosphere, and generate the auroral display.
Now, recently released video from one of NASA’s twin STEREO satellites shows the actual CME in action. Earth is out of the frame, but roughly to the left.
To give you a sense of scale, the white circle in the center of the video represents the sun, which is blocked by a mask so that the satellite can capture fainter structures in the bright star’s upper atmosphere.
Watch the video again—full screen in HD—and ponder this: The sun has a mean circumference of about 2.7 million miles (4.3 million kilometers)—and that massive cloud of material it ejected was aimed at Earth.
The sun goes through 11-year-long cycles of activity, and we’re currently in what’s known as Cycle 24. Sun experts expect a peak in this solar-activity cycle around May 2013.
Recent increases in solar activity—sunspots, flares, and CMEs—prompted NASA to raise its prediction for the level of activity we’ll see when the sun reaches that peak.
Our active sun, seen in September in UV light by NASA’s Solar Dynamics Observatory.
However, the predictions still call for this to be the smallest sunspot cycle in more than 80 years, according to experts at NASA’s Marshall Space Flight Center.
And some solar physicists are seeing signs that the sun is headed into what’s known as a grand minimum—an almost totally quiet period—during Cycle 25.
Still, it only takes one strong CME on the right trajectory to wreak havoc on Earth, scrambling satellites and maybe even burning out transformers in the electric grid.
And in the meantime, we’ll be sure to enjoy all the excellent auroras we can expect from Cycle 24, as well as the jaw-dropping videos from sun-orbiting satellites.