World’s most powerful solar telescope is up and running

The Daniel K. Inouye Solar Telescope has produced the highest resolution image of the Sun’s surface ever taken.

This is the highest-resolution image of the Sun ever taken. Credit: NSO/NSF/AURA

The world’s most powerful solar telescope has opened its eyes.

Atop the Haleakala mountain in Hawaii, the 4-metre Daniel K. Inouye Solar Telescope is finally looking at the Sun. The US$344-million observatory, which has been two decades in the making, is scrutinizing the star in extraordinary detail. That includes probing how the Sun’s seething magnetic energy leads to solar eruptions that can affect life on Earth.

New images released on 29 January show patterns of superheated gas churning on the Sun’s surface. Bright ‘cells’ represent the plasma rising from deeper within the star, while darker borders between the cells indicate where plasma is cooling and sinking.

The Inouye Solar Telescope eclipses what had been the world’s largest solar telescope, a 1.6-metre facility at Big Bear Solar Observatory in southern California. Scientists say that the dramatic upgrade will transform solar physics for decades.

“It’s going to be such a revolution for understanding the Sun,” says Momchil Molnar, a solar physicist at the University of Colorado Boulder.

NSF's DKI Solar Telescope, Maui

The Daniel K. Inouye Solar Telescope has taken its first images of the Sun.Credit: National Solar Observatory/AURA/NSF

The Inouye Solar Telescope will make the most precise measurements of the Sun’s magnetic field, including the first-ever magnetic measurements in the Sun’s atmosphere, or corona. Understanding how magnetism arises and changes in the corona should help scientists to unravel many of the Sun’s biggest mysteries — such as why the corona is millions of degrees hotter than the Sun’s surface, and how magnetic fields can trigger eruptions of superheated gas that fly through space and sometimes slam into Earth, disrupting communications.

The telescope’s huge mirror can study objects as small as 35 kilometres across, from a distance of 150 million kilometres. “It acts as a microscope to resolve very small features on the Sun,” says Aparna Venkataramanasastry, a solar physicist at Georgia State University in Atlanta. “It’s very exciting.”

The telescope took its first-light images in December, but engineers are still working to finish construction in the dome. That’s scheduled to be completed by 30 June, with science studies beginning in earnest in July. “It’s not easy to stand up a facility like this overnight,” says Thomas Rimmele, the project’s director at the National Solar Observatory in Boulder, Colorado. “The fact that this complex machine delivered such images right out of the box is amazing.”

Here comes the Sun

Eventually, sunlight will stream into five instruments on the rotating platform beneath the telescope’s main mirror. Scientists can mix and match those instruments to address different questions in solar physics, says David Boboltz, programme director at the US National Science Foundation (NSF) in Alexandria, Virginia, which funded and built the telescope.

Sunlight hits the primary mirror and is focused to an intense point, which gets so hot that it could pop a bag of popcorn in three seconds. To prevent the heat from melting the telescope, engineers built a cooling system that makes the equivalent of a swimming pool full of ice every night.

Construction on the telescope, which is named after a former senator from Hawaii, began in 2012. To help pay for it, the NSF cut back on funding for two older solar telescopes in Arizona and New Mexico.

Stephanie Yardley, a solar physicist at the University of St. Andrews, UK, wants to use the telescope to probe how the Sun’s magnetic field rearranges itself before an eruption — information that could help researchers predict space-weather disruptions on Earth. And Lyndsay Fletcher, a solar physicist at the University of Glasgow, UK, plans to map the dramatic bursts known as solar flares that transport energy in the Sun’s atmosphere.

Eventually, solar physicists will combine telescope data with those coming from two new space missions: NASA’s Parker Solar Probe, which is whizzing through a series of close encounters with the Sun, and the European Space Agency’s Solar Orbiter, which is slated to launch next week. And European scientists are planning their own 4-metre solar telescope for the Canary Islands.

For now, the Hawaii telescope will keep researchers more than busy, says Shah Bahauddin, a solar physicist at the University of Colorado Boulder. “There will be so many people coming,” he says, “there will be a traffic jam.”

doi: https://doi.org/10.1038/d41586-020-00224-z


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