World's Largest Solar Telescope Captures The Sun In Mind-Blowing Detail
The world's most powerful solar telescope, the U.S. National Science Foundation (NSF) Daniel K. Inouye Solar Telescope (Editor note: Try saying that one time fast!), is beginning to prove the potential of a new add-on with its first close-up image of the Sun. Located near the summit of Haleakalā in Maui, Hawai'i, the telescope utilized the most advanced instrument in its arsenal—the Visible Tunable Filter (VTF) imaging spectro-polarimter—to capture a narrow-band image of sunspots on our closest star in unprecedented detail. Inouye's architects and handlers believe that there's more to come as they've only just barely tapped into VTF's vast capabilities.
Last December, teams from Institut für Sonnenphysik (KIS) in Freiburg, Germany, National Solar Observatory, and NSF came together to complete an initial instrumentation build of the new Visible Tunable Filter for the NSF Daniel K. Inouye Solar Telescope. Perched near the top of the largest volcano in Hawai'i that benefits from high altitude and clear skies, Inouye isn't just the most powerful with some of the latest generation hardware, but also the largest of its kind (at four meters in diameter).
Impressively, the image of our Sun above comes from technical testing during the VTF's first light (i.e. the first time a telescope lens is exposed to the night sky for viewing). The image—with a spatial sampling of 6.2 miles (10 km) per pixel—shows off intense magnetic activity around a cluster of sunspots. To give you a better idea of the kind of imaging resolution we're talking about here, the image covers 241 million square miles. The land mass of the United States, in comparison, covers 3.5 million square miles.
Moreover, the VTF isn't technically operational yet, which means there's plenty of untapped potential for years to come. What makes the VTF unique among spectrographs is that it can capture specific light wavelengths rather than capturing the full electromagnetic spectrum. When peering at the Sun, Inouye can precisely peel away at each layer of the star's surface to observe what's happening between them. Essentially, this is achieved via the largest etalons (a pair of reflecting glass plates spaced tens of microns apart) ever made for solar research; Inouye scans each wavelength by adjusting the spacing of the glass plates at the nanometer scale.
And this is only scratching the surface—among other things, Inouye is expected to have a second etalon installed by the end of 2025. According to Dr. Stacey Sueoka, Senior Optical Engineer at NSO, "Even with just one etalon in place, we’re already seeing the instrument’s potential. This is only the beginning, and I’m excited to see what’s possible as we complete the system, integrate the second etalon, and move toward science verification and commissioning."
Photo credits: NSF/NSO/AURA
