For nearly all of human history, there was only one way to observe a cosmic event: with your eyes. This was a bad thing if the event occurred on a cloudy day, and an even worse thing if it wasn’t cloudy but the event was a solar eclipse, which could wind up being, well, the last thing you’d ever see.
A lot has changed, and that fact was spectacularly in evidence this week, as Venus made one of its very rare transits of the sun—an event that won’t come again for 105 years. All over the world, skywatchers had telescopes and cameras pointed sunward as the black speck of Venus glided slowly across the solar disk. But 22,000 mi. (36,000 km) above the Earth, another set of eyes was watching the event. Those eyes belong to the Solar Dynamics Observatory (SDO), whose designers know a thing or two about looking at the sun.
SDO was launched in 2010, as part of NASA’s Living With a Star (LWS) program—a series of planned spacecraft launches to study the sun and its impact on the Earth. That’s worth doing for far more than just scientific reasons, since solar activity can affect communications satellites, the power grid, the global climate and human health. There are six spacecraft tentatively planned for launching in the LWS program over the next several years. The only one of those to make it to space so far is the SDO, but in the case of the Venus transit, it’s a good thing that one was at the front of the line.
SDO has multiple imaging systems on board: four telescopes with filters covering 10 wavelength bands to study the surface of the sun; another instrument measuring extreme ultraviolet variability; and still another measuring subsurface magnetic storms—a phenomenon wonderfully called helioseismology.
During a six-hr. stretch on June 5 and 6, multiple imagers sensitive to multiple wavelengths recorded extremely high-definition, time-lapse footage of Venus’s trip across the solar disk and transmitted it all home to NASA. The resulting video, which went live today, offers a perspective on the Venusian crossing that the ancients—and even the not-so-ancients—never had before. There’s no telling what the imaging technology will be in 2117 when Venus reprises this week’s performance, but judging by the new footage, what we’ve got in 2012 ain’t half bad.