The Sciences

SDO opens its eyes and sees our star like never before

Bad AstronomyBy Phil PlaitApr 30, 2010 11:01 AM


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Last week, NASA presented the first images and videos from its latest and greatest eye on the Sun: the Solar Dynamics Observatory. SDO has been in the works for a long, long time, and I've been anxiously awaiting data from it for years... so of course I was away from my computer when the images were released. Still, it was worth a few extra days to see something as back-of-the-neck-hair-raising as this:

Holy Haleakala! Click to emprominate. As if on cue, just days after SDO's Atmospheric Imaging Assembly (AIA) was switched on, the Sun threw an epic fit, blasting out an arcing prominence perfectly positioned for us to see. A prominence is a loop of gas that erupts from the surface of the Sun. This gas follows the Sun's magnetic field lines; complicated interplay between the energy stored in the field lines versus their tension causes them to leap up from the Sun, anchored in two spots that represent where the north and south poles of the lines punch through the Sun's surface. A prominence might have as much as a hundred billion tons of matter in it, and can be hundreds of thousands of kilometers across. To give you an idea of this, here's a video made from images from AIA: Kaboom! Interestingly, the gas isn't as hot as you might think, and can be cooler than the surface of the Sun. When we see a prominence edge-on, silhouetted against the surface of the Sun, it actually appears dark! When that happens, we call it a filament. I've been a big fan of the Solar and Heliospheric Observatory (SOHO) for a long time, and SDO is like the Son of SOHO. It has technology that is more current, and has very high resolution cameras. SDO can take spectra of the Sun to look in detail at its composition, temperature, motion, and magnetic strength. It can also measure the seismology of the surface of the Sun, the way waves travel across it and make it pulse; this tells us about the interior of the Sun that is otherwise totally invisible. Combining all this data together yields a vast amount of knowledge waiting to be learned about our nearest star. It also produces stunning full-Sun imagery:

This image is amazing; it shows very hot helium and iron ranging in temperature from 60,000 Kelvin (100,000+° F) to well over a million Kelvins (1.8 million degrees F)! You can see the big prominence to the left, as well as several others around the disk. All the twisting and writhing on the surface is due to the bubbling convection of hot material from the Sun's interior rising to the surface coupled with the fiercely complex solar magnetic field. The physics involved is incredibly complex, but with SDO's help scientists will soon have a much firmer grasp on what's going on. Of course, they'll also have a pile of new mysteries to ponder as well. The Sun is the closest star to the Earth, and closer than most planets. We know a lot about it, but there's so much left to understand: what's the root cause of the 5.5 year long solar magnetic cycle? How is that tied to Earth's climate? What effect do sunspots have on the Sun and Earth? How exactly does the Sun influence space weather; the flood of subatomic particles streaming from the solar surface and interacting with our own magnetic field, affecting satellites and even our power grid? Science is like a tapestry with no edge, and with holes located here and there in the fabric. We can fill those holes ever more, and explore the edges, pushing them back with each new discovery. Along with many other observatories like it, SDO is our loom that helps us create and follow that weave. Credit: NASA/SDO/AIA, NASA/GSFC/SDO/AIA

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