IRIS Movie of the Day
At least once a week a movie of the Sun taken by NASA's Interface Region Imaging Spectrograph (IRIS) is posted by one of the scientists operating the instrument.
IRIS eclipse movie #1
Credit: IRIS, LMSAL/NASA
IRIS saw two eclipses on 21-Aug-2017. The first one happened around 16:16 UT, just after the eclipse started in Oregon. The movie shows the edge of the Sun (or limb) in light that is emitted by singly ionized Magnesium which, under solar conditions, means that we are looking at chromospheric gases that are at temperatures of about 10,000 K. The Moon appears in the upper right hand corner and goes on to obscure much of the solar disk for about 15 minutes. The eclipse as seen by IRIS occurs much faster than what we saw on Earth. The Moon's rapid apparent motion is caused by the orbital motion of IRIS. This movie was obtained at high cadence with very short exposure times (0.5 seconds) to "freeze" this rapid motion and create sharp pictures of the Moon's edge. When you freeze the movie while the Moon obscures part of the solar disk, you can see that the Moon's profile is irregular. This is caused by the mountains on the Moon. The high spatial resolution of IRIS means it can resolve details as small as 1 km on the Moon.