Mars-sized 'Light-bridge' on Surface of Sun Appears to Signal Break-up of Vast Sunspot

A vast sunspot on our star may be decaying, the discovery of a 5,000 mile-long bridge of light suggests.

Amateur astronomer and Florida resident Howard Eskildsen snapped an image of the "light bridge"—which has a length that's roughly equal to the diameter of Mars—in a recently formed sunspot dubbed AR2770, reported.

Sunspots are dark spots that temporarily appear on the solar surface, which are cooler than the surrounding areas.

These phenomena are caused by strong magnetic field concentrations, which inhibit convection—the transfer of heat from one place to another within gases and liquids. This process heats the solar surface.

Hot "bubbles" of plasma—charged particles that are one of the four fundamental states of matter—are transported from deeper, hotter layers to the surface, whereas cooler plasma is transported back to the interior, according to Tobias Felipe from the Instituto de Astrofísica de Canarias in Spain.

"It is a similar phenomenon to water boiling in a cooking pot. The point is that the strong magnetic fields of sunspots inhibit convection and, thus, this magnetized region has a lower temperature than the surroundings," Felipe told Newsweek. "Consequently, sunspots look darker than the surrounding regions."

According to Felipe, light bridges are bright, elongated structures that are commonly present in sunspots, which connect regions across the cooler, darker abyss of the sunspot.

They are created by the intrusion of plasma where the magnetic fields are weak into the strongly magnetized sunspot. In the light bridges, convection can still take place, which is why they are hotter than the rest of the sunspot and, thus, look brighter.

While there is still much we don't know about light bridges, they usually herald the break-up of the sunspot in question.

"Light bridges usually appear during the fragmentation of a decaying sunspot or in the assembling process of magnetized regions that leads to the formation of a new spot.

the sun
File photo: The sun emitting a mid-level solar flare on October 1, 2015. NASA/SDO

"[AR2770] seems that it is decaying. When it appeared around August 4, 2020, it was a round sunspot with an umbra (the inner darker part) and penumbra (the not-so-dark part). Currently, it has lost the penumbra and the umbra is 'broken' in two parts, divided by the light bridge."

Complex magnetic field configurations, like those exhibited by light bridges, can lead to solar flares—sudden explosions of energy at the sun's surface—according to Felipe. In fact, the sunspot in question already produced a small flare over the weekend.

"However, this does not mean that the sunspot will disappear in an explosion. It progressively falls apart," he said.

Currently there is not much activity on the sun and AR2770 is one of the most interesting features on our star at this time, according to Felipe. In fact, AR2770 is one of the first sunspots from the next 11 year solar cycle that scientists think is starting around now.

"The main manifestation of solar activity is the presence of sunspots, but it affects other solar phenomena, such as flares and coronal mass ejections—and even auroras on the Earth, since they are a result of solar activity," Felipe said.

"During this 11-year cycle, solar activity changes from very low activity (known as a solar minimum when few sunspots are observed) to the solar maximum (activity is higher and more sunspots are observed). We are currently at the end of the solar minimum, so it is expected that during the following years solar activity will increase and sunspots will appear more frequently."