The Inouye Solar Telescope Can Now Visualize Eruptions on the Sun’s Surface

Learn how a new instrument will increase the telescope’s ability to spot sunspots in unprecedented detail.

By Paul Smaglik
Apr 24, 2025 8:45 PMApr 24, 2025 9:00 PM
Narrow-band image of the Sun as seen with VTF
A narrow-band image of the Sun at a wavelength of λ=588.9nm, that of a well known solar sodium line also known as the “NaD line.” The image was acquired during recent first light efforts with the VTF at the Inouye, and shows how precisely the structures within a sunspot are resolved. Each pixel in the original version of the image corresponds to 10 km (or 6.2 miles) on the Sun. (Image Credit: © VTF/KIS/NSF/NSO/AURA)

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The most powerful instrument of its kind has now taken its first picture of the sun. Although the Inouye Solar Telescope began operating from its perch on the Hawaiian volcano Haleakala in 2022, the addition of its latest key piece of equipment provides a major boost to its spatial, temporal, and spectral resolution to the most powerful telescope of its kind in the world.

This will increase its ability to visualize eruptions on the sun’s surface. Those storms hurl particles and radiation into space, producing spectacular auroras on Earth — but also can disrupt some technical infrastructure and satellites.

“The Inouye Solar Telescope was designed to study the underlying physics of the Sun as the driver of space weather,” Christoph Keller, director of the National Solar Observatory, which operates the Inouye Solar Telescope, said in a press release.

The Inouye Solar Telescope

The telescope employs a primary mirror about 13 feet wide. But to enhance its resolution, new instruments have been added since. The last, and most powerful one of its kind — called a spectro-polarimeter VTF — will up the telescope’s ability to examine individual wavelengths of light and different states of polarization, in turn allowing the telescope to peer more closely at the hot plasma flows and changing magnetic fields roiling the sun’s surface.

The VTF empowers the telescope to scan the sun’s spectra with an accuracy of a few picometers. It also selects individual polarization images, essentially snapping rapid pictures as the light changes directions. The instrument creates 2D images from each wavelength and oscillation state.

That composite picture helps visualize the temperature, pressure, speed, and magnetic field strength at different altitudes of the Sun. The end result is images with a spatial resolution of about 6 miles per pixel and a temporal resolution of hundreds of images per second.


Read More: The Dazzling Sun of 2024


Image of a Dark Sunspot

Creating an instrument to perform at that level was a massive undertaking. The VTF weighs 5.6 tons, rests on a garage-sized footprint, and reaches two stories. A team of physicists in Freiburg, Germany developed, built, then installed it over 15 years.

The first published image the VTF enabled shows a dark sunspot — including detailed shadows known as penumbra — on a section of the sun’s surface about 15,500 miles by 15,500 miles. Sunspots are associated with strong magnetic fields that prevent hot plasma from rising from within the sun.

“VTF enables images of unprecedented quality and thus heralds a new era in ground-based solar observation,” Sami K. Solanki, director at the Max Planck Institute for Solar System Research (MPS) in Göttingen, Germany, said in a press release.


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Before joining Discover Magazine, Paul Smaglik spent over 20 years as a science journalist, specializing in U.S. life science policy and global scientific career issues. He began his career in newspapers, but switched to scientific magazines. His work has appeared in publications including Science News, Science, Nature, and Scientific American.

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