The Sun is the most influential celestial object for life as we know it. Understanding and predicting its behavior is essential for our existence. Plants are green because our Sun is a red star. However in the early days of life this relationship was quite different. The young Earth was spinning much faster and the days were 8 hours long. The Sun was less bright and cooler. The early photosynthesizing organisms were purple to maximize light harvesting in liquid environment. These organisms did not yet evolved the powerful water splitting photosynthesis that transformed our planet into an oxygen rich place.
Life giving powers of the Sun can also be deadly. Solar wind can blow the fragile atmosphere away like in Mars. Thanks to the Earth’s magnetosphere life is shielded from such exterminating effects. Coronal mass ejections however are still a pending threat. Like from a nuclear cannon if the Earth takes a direct hit from a coronal ejection our magnetospheric shield may not be sufficient to protect.
NASA’s Solar Dynamics Observatory (SDO) was launched on Feb. 11, 2010. The spacecraft keeps an unblinking eye on the entire disk of the sun visible from Earth. It watches activity of solar material coursing through the sun’s atmosphere, the corona. The following video by NASA provides a good explanation for some of the observations made in SDO’s 6th year (explanation starts at 2 minutes 50 seconds into the video):
SDO’s Atmospheric Imaging Assembly (AIA) instrument captures a picture 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. The instrument displays solar material at around 600,000 kelvins (about 1,079,540 degrees F). In this wavelength it is easy to see the sun’s 25-day rotation.
During the course of the video, the sun slowly increases and decreases in size. This is because the distance between the SDO spacecraft and the sun varies over time. The transmitted images are remarkably consistent despite the fact that SDO orbits Earth at 6,876 mph, and Earth orbits the sun at 67,062 mph.
SDO data is archived for studying the complex electromagnetic system causing the constant movement on the sun. Flares and solar explosions called coronal mass ejections can be powerful enough to disrupt technology. We must keep our guard on for the big one. Moreover, studying our closest star is one way of learning about other stars in the galaxy. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, built, operates and manages the SDO spacecraft for NASA’s Science Mission Directorate in Washington, D.C.
February 11, 2015 marked five years in space for SDO. Throughout this period SDO has provided detailed pictures of features on Sun’s surface that grow and erupt as coronal mass ejection (CME). Poetic movement of solar material through the sun’s atmosphere, the corona can also be captured through these imagery. In honor of SDO’s fifth anniversary, NASA has released a video showcasing highlights from the last five years of sun watching. Watch the movie to see giant clouds of solar material hurled out into space, the dance of giant loops hovering in the corona, and huge sunspots growing and shrinking on the sun’s surface.
The imagery is an example of the kind of data that SDO provides to scientists. By watching the sun in different wavelengths – and therefore different temperatures – scientists can watch how material courses through the corona, which holds clues to what causes eruptions on the sun, what heats the sun’s atmosphere up to 1,000 times hotter than its surface, and why the sun’s magnetic fields are constantly on the move.
Five years into its mission, SDO continues to send back tantalizing imagery to incite scientists’ curiosity. For example, in late 2014, SDO captured imagery of the largest
sunspots seen since 1995 as well as a torrent of intense solar flares. Solar flares are bursts of light, energy and X-rays. They can occur by themselves or can be accompanied by what’s called a coronal mass ejection, or CME, in which a giant cloud of solar material erupts off the sun, achieves escape velocity and heads off into space. In this case, the sun produced only flares and no CMEs, which, while not unheard of, is somewhat unusual for flares of that size. Scientists are looking at that data now to see if they can determine what circumstances might have led to flares eruptions alone.
The following video is a timelapse of one week of Solar activity between July 20 – 27th 2016 condensed into 28 seconds (4 seconds for each Earth day) from the eyes of SDO. These observations were recorded by 9 separate AIA instruments tuned to different wavelengths in Angstrom. You can see many features such as sunspots, filaments and CMEs annotated on the surface: