A composite of images of the sun taken by NASA's Solar Dynamics Observatory. (Image: NASA/SDO/AIA/S. Wiessinger) At any given moment, the sun features material leaping off the surface in arcs, flares and ejections. That's dynamic enough, as previous posts here at ImaGeo have illustrated. (Check out this this one, for example.) But what would a composite of many snapshots of the sun's surface taken over a long time look like? Imagine no more. The picture above is a composite of 25 images of the sun taken from April 16, 2012 to April 15, 2013 by NASA's Solar Dynamics Observatory, or SDO. (And for a movie of several years of solar images, keep reading toward the end...) The sun is a giant cauldron of charged particles, a "plasma" made up of electrons, and atoms that have lost electrons, laced with magnetic fields. If you look closely at the edge of the sun in this image, some magnetic field lines have become manifest as gargantuan glowing loops. (Click the image for a larger version.) Following those lines, plasma is accelerating and leaping from the surface into the sun's outer atmosphere, called the corona. These coronal arcs can last from seconds to days, and sometimes they are a precursor to solar flares and coronal mass ejections — gigantic explosions of matter and radiation out into space. This material can race toward Earth, but luckily, we're protected by a shield — our planet's magnetic field. Even so, if a solar ejection is energetic enough, it can cause a geomagnetic storm. This in turn can damage satellites and cause disruption to electrical grids and communication and navigation systems. Because the picture at top is a composite of many images, you are seeing more coronal arcs than would be apparent at the surface at any given time. As a still image, it helps dramatize the incredibly violent nature of the sun's surface. But what if you could watch a movie of the sun, and not just over the course of a few days but a span of entire years? Once again, imagine no longer.
A screenshot of an animation of SDO images covering three years. Click on the image to watch the movie. (Animation: NASA Goddard Space Flight Center) Click on the image above to watch a mesmerizing animation of SDO images taken over the course of three years, at a rate of two images every day. From NASA:
SDO’s Atmospheric Imaging Assembly captures a shot of the sun every 12 seconds in 10 different wavelengths. The images shown here are based on a wavelength of 171 angstroms, which is in the extreme ultraviolet range and shows solar material at around 600,000 kelvins (about 1.08 million F). In this wavelength it is easy to see the sun’s 25-day rotation as well as how solar activity has increased over three years.
And this is amazing: Even as the SDO satellite orbits the Earth at 6,876 miles per hour, and the Earth in turn orbits the sun at 67,062 mph, the image is astonishingly stable.