NASA’s SDO Catches a Lunar Transit

On Oct. 30, 2016, NASA’s Solar Dynamics Observatory, or SDO, experienced a partial solar eclipse in space when it caught the moon passing in front of the sun. The lunar transit lasted one hour, between 3:56 p.m. and 4:56 p.m. EDT, with the moon covering about 59 percent of the sun at the peak of its journey across the face of the sun.

On Oct. 30, 2016, NASA’s Solar Dynamics Observatory, or SDO, experienced a partial solar eclipse in space when it caught the moon passing in front of the sun. The lunar transit lasted one hour, between 3:56 p.m. and 4:56 p.m. EDT, with the moon covering about 59 percent of the sun at the peak of its journey across the face of the sun. The moon’s shadow obstructs SDO’s otherwise constant view of the sun, and the shadow’s edge is sharp and distinct, since the moon has no atmosphere which would distort sunlight.

From SDO’s point of view, the sun appears to be shaking slightly – but not because the solar observatory was spooked by this near-Halloween sight. Instead, the shaking results from slight adjustments in SDO’s guidance system, which normally relies upon viewing the entire sun to center the images between exposures. SDO captured these images in extreme ultraviolet light, a type of light invisible to human eyes. The imagery here is colorized in red.

Something New On the Sun: SDO Spots a Late Phase in Solar Flares

The sun's surface dances. Giant loops of magnetized solar material burst up, twist, and fall back down. Some erupt, shooting radiation flares and particles out into space. Forced to observe this dance from afar, scientists use all the tools at their disposal to look for patterns and connections to discover what causes these great explosions. Mapping these patterns could help scientists predict the onset of space weather that bursts toward Earth from the sun, interfering with communications and Global Positioning System (GPS) signals.

Analysis of 191 solar flares since May 2010 by NASA's Solar Dynamics Observatory (SDO) has recently shown a new piece in the pattern: some 15 percent of the flares have a distinct "late phase flare" some minutes to hours later that has never before been fully observed. This late phase of the flare pumps much more energy out into space than previously realized.

"We're starting to see all sorts of new things," says Phil Chamberlin, deputy project scientist for SDO at NASA's Goddard Space Flight Center in Greenbelt, Md. "We see a large increase in emissions a half-hour to several hours later, that is sometimes even larger than the original, traditional phases of the flare. In one case on November 3, 2010, measuring only the effects of the main flare would mean underestimating the amount of energy shooting into Earth's atmosphere by 70 percent."