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NASA’s Advanced Solar Observatory Captured Mercury’s Transit for the First Time

Forget Instagram: The Solar Dynamics Observatory has all the best camera filters.
SDO Wavelength comparison. Image: NASA Goddard/YouTube

On Monday, Mercury spent a little over seven hours waltzing across the Sun from our perspective on Earth. It's a rare transit that occurs only about a dozen times per century, and it marked the first time that NASA was able to capture the entire crossing with the sophisticated new Solar Dynamics Observatory (SDO), which was launched into geocentric orbit in 2010.

This newly released timelapse video from NASA Goddard compiles the most stunning shots of Mercury's transit taken by the SDO, across a wide variety of angles and wavelengths. The visuals reinforce the colossal girth of the Sun compared to Mercury, the innermost planet, which, at only about a third of the diameter of Earth, is outranked in size by the solar system's two largest moons, Jupiter's Ganymede and Saturn's Titan.

On top of that, SDO's impressive suite of cameras imaged the transit with multiple wavelength filters to expose the Sun's dynamic appearance across the light spectrum.

The observatory's AIA 304 channel, for instance, shows the Sun as a deep scarlet inferno pockmarked with flares and cool dark spots, while the HMI Intensitygram displays the full solar disk at 6,173 angstroms—perfect for highlighting Mercury's stark silhouette as it traverses the star. The AIA 193 channel picks up the cooler, outer atmosphere of the Sun, revealing the magnetic perturbations of the star in gold. You can browse through a handy guide to each of these filters on SDO's main page.

The use of comparison shots and crossfades of various wavelengths enhances the mesmerizing effect of the timelapse even further, and attests to SDO's reputation as the most advanced and sophisticated solar observatory in orbit.