The wild, roiling activity of a sunspot can now be seen in mesmerising detail, thanks to a freshly released image from a brand new solar observatory.
In Hawaii, the Daniel K. Inouye Solar Telescope (DKIST) is still in the final stages of completion, but its first image of a sunspot, taken on 28 January 2020 (not the sunspots that appeared in late November), is already the most detailed we’ve seen.
“The sunspot image achieves a spatial resolution about 2.5 times higher than ever previously achieved, showing magnetic structures as small as 20 kilometres (12 miles) on the surface of the sun,” said astronomer Thomas Rimmerle of the NSF’s National Solar Observatory.
Sunspots are of great interest to us here on Earth. Most of the Sun’s surface looks like the popcorn-looking area around the sunspot. Each of those granules is a convection cell; hot plasma rises in the middle, moves out to the edges as it cools, and falls back down into the Sun. And they’re huge – a typical granule is about 1,500 kilometres (930 miles) across.
Sunspots are temporary patches where the Sun’s magnetic field becomes particularly strong, inhibiting the star’s normal convection activity. Because hot plasma is prevented by the magnetic field lines from rising from the interior, the sunspot is about one-third cooler than the area around it, and appears darker.
Those magnetic field lines are responsible for another phenomenon that affects us here on Earth. As they tangle, snap, and reconnect, they can release tremendous amounts of energy, unleashing solar flares and coronal mass ejections.
So scientists are very keen to learn more about sunspots and how they work – and DKIST, in this picture taken during its commissioning phase (basically testing everything is working correctly), has demonstrated just how powerful it will be in that context.
The image is about 16,000 kilometres (10,000 miles) across, and Earth, with its diameter of 12,742 kilometres, could fit comfortably inside the sunspot, the researchers said. As they imaged the region, they were able to track changes in the fine structure over short time scales – around 100 seconds. This can be seen in the gif above.
“For example, narrow dark lanes are observed consistently in both umbral dots (UD) and penumbral grains (PG). A few typical examples are pointed out with arrows,” the researchers wrote.
“Narrow, dark lanes within bright UDs and PGs have been predicted by numerical simulations of magneto-convection and are a consequence of strong upflow plumes in areas of lower magnetic-field strength. The dark lanes evolve significantly during 100 seconds giving the impression of small-scale, overturning convection occurring in these features. DKIST’s spectro-polarimeters will allow detailed analysis of these small-scale features and comparison to model predictions.”
Over the coming months and years, DKIST will likely prove invaluable. We’re moving into a period of heightened solar activity known as the solar maximum. These swing around every 11 years, and are characterised by a noticeable increase in sunspots and flares.
A better understanding of the physics behind solar activity is a tool that, scientists hope, will refine our ability to predict solar weather. And that starts with observations.
“With this solar cycle just beginning, we also enter the era of the Inouye Solar Telescope,” said astrophysicist Matt Mountain of the Association of Universities for Research in Astronomy, which manages DKIST.
“We can now point the world’s most advanced solar telescope at the Sun to capture and share incredibly detailed images and add to our scientific insights about the Sun’s activity.”
The team’s paper has been published in Solar Physics.