Eclipse 2001: STEREO mission

Nothing on earth is as awe-inspiring as an eclipse: our invincible sun, dying before our eyes, only to be reborn minutes later.

For scientists, eclipses are more than just breathtaking—they’re an opportunity to see things that can’t ordinarily be seen, subtle details that are usually drowned out by the sun’s brilliant light. One key feature of the sun that becomes especially clear during a solar eclipse is the sun’s atmosphere, or corona. If you’re fortunate enough to witness a solar eclipse, you’ll see the corona as a blazing halo around the sun.

Take an even closer look and you may notice blobs or bubbles in the corona. Scientists first discovered these irregularities during a solar eclipse a few decades ago. Today they have a name: coronal mass ejections.


Dr. Madhulika Guhathakurta describes the measurements she will be making during the 2001 African eclipse.

A coronal mass ejection (or CME) is an enormous eruption at the sun’s surface. During the eruption, as much as ten billion tons of the sun’s atmosphere can be ejected into interstellar space at speeds of up to 2000 km per second. This solar spew consists of high-energy particles—mostly protons and electrons—along with radiation such as X rays and gamma rays. When these reach earth, they can interfere with or destroy the sensitive electronics of satellites, not to mention damage spacecraft and harm unprotected astronauts.

Coronal mass ejections also cause geomagnetic storms on earth, disrupting communication and navigation systems, and causing power surges that can lead to equipment failure and blackouts. In 1989, a CME flare left parts of Quebec without power for nine hours. Yet for all the costly and even deadly damage CMEs can do, a lot remains unknown about them.

NASA's Solar-Terrestrial Relations Observatory (STEREO) Mission will send up two satellites to orbit the Sun. Like a pair of eyes, the satellites will provide three-dimensional images of the Sun's surface.

Solar Eclipse.

Coronal mass ejection.