NASA’s Solar Dynamics Observatory (SDO) recently imaged a sunspot that appeared tiny but actually had a core larger than Earth.

The sunspot, classified as Active Region 12665, is the only sunspot cluster present on the sun right now. It seems to be growing over time, although it is difficult to tell how massive it could get or when it will disperse.

But what are sunspots and how do they form?

Sunspots Defined

A sunspot is a dark, cool area on the sun’s surface in a region known as the photosphere, Space.com reported. It looks dark in comparison with the brighter, hotter regions of the photosphere, which maintains a temperature of 5,800 degrees Kelvin, around it.

Sunspots can get quite humungous, or up to 50,000 kilometers (31,069 miles) in diameter.

How do they form anyway? Interestingly, they are produced by interactions with the magnetic field of the sun, which are yet to be fully understood. They take place in regions where there is intense magnetic action, where solar flares and coronal mass ejections (CMEs) erupt once such energy is released.

Since the early 20th century, sunspots are known to be bundles of vast magnetic field lines or the lines along which a magnet’s forces move. They can approximate the size of planets as well.

“Sunspots are one of the most important pieces of the sun,” said Shin Toriumi of the National Astronomical Observatory of Japan in a Popular Science report.

How They Form

Toriumi’s team probed sunspots further, feeding observations from two telescopes to NASA’s Pleiades supercomputer to run numerical models simulating sunspot formation. The findings allowed them to observe interactions between the solar surface and its chromosphere, the gassy middle layer of its atmosphere, for the first time.

Based on the data, the sun’s magnetic field lines emerge at the surface as pores or small bundles. When two of those approach each other, they sandwich the plasma between them into a long system dubbed a light bridge. As that action continues, the bridges merge into a sunspot.

Magnetic fields also induce much larger solar flares or the biggest explosions in the solar system that can get so powerful they can destroy Earth’s tech and communications infrastructure.

Recently, images from the Atacama Large Millimeter/submillimeter Array (ALMA) radio telescope in Chile exposed a turtle-shaped object on the surface of the sun, noting a sunspot in the making with a size double that of our planet.