With the world’s largest solar telescope now conducting formal observations, scientists are eager to watch the sun’s increasing activity and better understand the threats of space weather.
The Daniel K. Inouye Solar Telescope (DKIST), located in Hawaii, began science observations earlier this year, joining a host of other sun watchers, most notably NASA’s Parker Solar Probe and the European Space Agency’s (ESA) Solar Orbiter. It’s perfect timing on two fronts: the sun’s activity is ramping up, and skywatchers will enjoy solar eclipses in both 2023 and 2024.
“We have a really exciting year and a half coming up,” Carrie Black, program director for the National Solar Observatory, which includes DKIST, said during a news conference held on Tuesday (Dec. 13) at the annual conference of the American Geophysical Union, held in Chicago and virtually last week.
Related: World’s largest solar telescope produces never-before-seen image of our star
DKIST, which is on the island of Maui, is owned by the U.S. National Science Foundation (NSF). The observatory was designed to focus on the upper parts of the solar atmosphere, or corona, and to specialize in observing the sun’s magnetic field.
“The Daniel K. Inouye Solar Telescope really excels at very small-scale features that are incredibly important,” Black said. “Now we’ll really be able to compare theory with reality on the surface of the sun, which is tremendously exciting and really going to propel the science forward.”
The telescope’s very first images — stunning views that spotlight the popcorn-like granules on the surface of the sun — were released in January 2020, although delays from the COVID-19 pandemic pushed the beginning of DKIST’s science observations to this year. DKIST released its first batch of data on Dec. 12, as well as new video based on the observations.
The video shows granules in the sun’s chromosphere, just above the visible surface. “You can see this fantastic dynamic motion that’s happening,” Black said. Within each granule, hot plasma is rising up in the center, cooling off and then falling back down into the star along the dark web connecting the granules.
Scientists think those granules play a key role in one of the biggest mysteries about the sun: why the corona is so hot. The visible surface of the sun, known as the photosphere, can reach scorching temperatures as high as 7,460 to 11,000 degrees Fahrenheit (4,125 to 6,125 degrees Celsius). But in the corona, temperatures can soar to 3.5 million F (2 million C).
“That’s like if you walked away from a fireplace and it got 100 times hotter,” Nicholeen Viall, an astrophysicist at NASA’s Goddard Space Flight Center in Maryland, said during the news conference.
That blazing-hot mystery is a key puzzle not only for DKIST but also for NASA’s Parker Solar Probe spacecraft, which launched in 2018, and the joint NASA/ESA Solar Orbiter spacecraft, which launched in 2020. The three missions are collaborating, and the new DKIST video comes from observations this summer coordinated with the Parker Solar Probe — specifically, a close flyby of the sun it performed on June 1.
The granules might play a role in a second mystery as well. The solar wind is a stream of charged particles that constantly flows off the sun and into space — at speeds of sometimes 1 million mph (1.6 million kph), Viall said, although scientists aren’t sure how the particles get so fast.
“So that plasma is constantly bombarding the Earth. And I haven’t even gotten yet to the big solar storms,” Viall said. “That’s just the regular sun and on a regular day.”
Weather from the sun
But understanding how the sun works isn’t just academic. Even from 93 million miles (150 million kilometers) away, the sun’s activity has consequences for life on Earth due to a collection of phenomena scientists call space weather.
Space weather can include huge bursts of electromagnetic radiation called solar flares, as well as coronal mass ejections (CMEs) that shoot massive blobs of plasma into space. Space weather events become more frequent and more severe toward the peak of the 11-year solar cycle; currently, the sun’s activity is generally increasing, with solar maximum predicted to occur in 2025.
Space weather can harm astronauts on the International Space Station, damage satellites in orbit and interfere with radio communications; particularly strong space weather events can even knock out power grids.
“Studying space weather is important to our global economy because solar storms can affect the advanced technology we’ve become so dependent upon in our everyday lives,” Talaat said.
As an example, he noted SpaceX’s experience in February, when 40 Starlink internet satellites burned up in the atmosphere soon after launch after a solar storm increased the density of Earth’s atmosphere at the satellites’ initial altitude. “Even mild space weather activity can have adverse effects because we are pushing the edges of technology with our infrastructure right now,” Talaat said.
That’s why scientists want to be able to predict space weather, just like traditional weather: If you know space weather is coming your way, you can prepare. But right now, scientists don’t know enough about the sun to make any predictions, he said.
“We basically are reactive right now when we see explosions on the sun,” Talaat said.
That’s not how any weather forecaster wants to be working. “What we would love to have is predictive capability of when these storms happen,” he said. “That would be just an incredible leap of knowledge.”
Scientists know that it takes about three days for material to travel from the sun to Earth, and they can get a sense of what activity might be headed in generally our direction. In addition, the U.S. National Oceanic and Atmospheric Administration (NOAA) operates the Deep Space Climate Observatory (DSCOVR) satellite, which launched in 2015. DSCOVR is parked about 1 million miles (1.5 million km) away from Earth toward the sun and can give 15 minutes or at most an hour of warning that something is coming.
That’s hardly forecasting. “We absolutely have a lot of science to do before we get there,” Talaat said.
Eclipsing the sun
Fortunately, the solar system is giving scientists two particularly intriguing opportunities in the coming years.
Skywatchers are getting ready for two upcoming solar eclipses: an annular eclipse in October 2023 that will pass over the Western U.S., and a total solar eclipse in April 2024, which will begin in Mexico and then be visible from the Southern U.S. to the Northeast.
Eclipses are a skywatching spectacle, but they’re also a rare science opportunity, since the moon blocks out the disk of the sun, allowing scientists to actually glimpse the wispy corona. DKIST is armed with a device that mimics this, called a coronagraph, but an artificial eclipse can’t quite live up to the real thing, according to Viall. “The moon just does a better job,” she said, noting that a total solar eclipse offers a better view of the middle corona in particular.
Observers in the U.S. last caught a glimpse of the corona during the total solar eclipse that crossed the country in August 2017. At the time, the sun was quiet, approaching the low point of its activity cycle, which came in late 2019.
“It’s going to be really cool timing that the 2024 eclipse will be on that approach to solar maximum, in contrast to the 2017 eclipse, which was a different part of the solar cycle,” Viall said. “That’s a cool thing, to see the sun in the same way but during a different phase of its cycle.”