You’ve never seen sunspots this close

The largest solar telescope in the world, the Daniel K. Inouye Solar Telescope (DKIST), sits on the 3,000-foot summit of Haleakala Volcano on the Hawaiian island of Maui. The powerful telescope, named after a former US senator, provides extremely detailed images of the solar surface – thanks to its high resolution, even objects up to 20 kilometers in size are visible.

A special cooling system protects the sensitive technology from the heat released when the four-metre-high mirror is pointed at the sun. The pipes for the coolant are a total of more than twelve kilometers long; the telescopic dome is equipped with special cooling plates with which the temperature can be regulated.

Three years ago, the device, built by the US National Solar Observatory (NSO) and operated by an Association of American Universities (AURA), provided the highest-resolution images of our central star to date. Now the NSO has released new spectacular images created with the Sensor Visible-Broadband Imager (VBI). In addition to relatively calm solar regions, they also show turbulent sunspots in unprecedented detail.

Sunspots are dark areas on the sun that are a few thousand degrees cooler than the rest of the solar surface (photosphere). They emit less light and appear black, but that’s only because they contrast with the sun’s otherwise extremely bright surface. The spots, which may be larger than Earth, are caused by disturbances in the sun’s strong magnetic field, which cause arcs. In the process, matter is expelled into the sun’s corona, cooling the exit and entry points of the field arcs. Sunspots therefore appear in pairs.

The number of sunspots varies in a cycle of about 11 years – the so-called Schwabe cycle – from one solar maximum to the next. During a maximum, the sun shows many more spots. While these are slightly cooler, the Sun will generally radiate a little more energy because it is very active and has more flares that are hotter than the rest of the photosphere. On the other hand, during a minimum, the sun is still and produces hardly any sunspots and flares.

The last maximum occurred in 2013/2014. After the last minimum in 2019, we are currently approaching a new solar maximum expected between 2024 and 2026. Therefore, the number of sunspots is currently high. And they are closely observed: Large sunspots or groups of them are associated with solar outbursts or even coronal mass ejections. Such mass ejections, in which energetic particles are flung into space, can cause solar storms on Earth. Such solar storms can not only create beautiful northern lights, but in extreme cases can also paralyze the electrical infrastructure. (i.e)