On May 1, 2013, NASA's Solar Dynamics Observatory (SDO) watched as an active region just around the East limb (left edge) of the sun erupted with a huge cloud of solar material—a heated, charged gas called plasma. This eruption, called a coronal mass ejection, or CME, sent the plasma streaming out through the solar system. Viewing the sun in the extreme ultraviolet wavelength of 304 angstroms, SDO provided a beautiful view of the initial arc as it left the solar surface.
Such eruptions soon leave SDO's field of view, but other satellites in NASA's Heliophysics fleet can pick them up, tracking such space weather to determine if they are headed toward Earth or spacecraft near other planets. With advance warning, many space assets can be put into safe mode and protect themselves from the effects of such particle radiation.
In addition to the images captured by SDO, the May 1, 2013 CME was also observed by the ESA/NASA Solar and Heliospheric Observatory (SOHO). SOHO houses two overlapping coronagraphs—telescopes where the bright sun is blocked by a disk so it doesn't overpower the fainter solar atmosphere—and they both saw the CME continue outward. The LASCO C2 coronagraph shows the region out to about 2.5 million miles. The LASCO C3 coronagraph expands even farther out to around 13.5 million miles. Both of these instruments show the CME as it expands and becomes fainter on its trip away from the sun.
NASA's Solar Terrestrial Relations Observatory (STEREO) Ahead satellite saw the eruption from a very different angle. It, along with its twin STEREO Behind, is orbiting at a similar distance as Earth. STEREO-A orbits slightly faster than Earth and STEREO-B orbits slightly slower. Currently, STEREO-A is more than two-thirds of the way to being directly behind the sun, and has a view of the far side of the sun. From this perspective, the CME came off the right side of the sun. STEREO has an extreme ultraviolet camera similar to SDO's, but it also has coronagraphs like SOHO. As a result, using its two inner coronagraphs, it was able to track the CME from the solar surface out to 6.3 million miles.
Working together, such missions provide excellent coverage of a wide variety of solar events, a wealth of scientific data—and lots of beautiful imagery.
Watch this video on YouTube.