A square hole in the sun is causing astronomers to question what caused the unusual formation. This odd feature seems to flicker and emit sparks.
This square hole on the surface of the sun is seen in ultraviolet light, giving a glimpse into a coronal hole. These features of the sun give rise to high-speed solar wind, which races away from the sun to the depths of the solar system.
NASA released a video of the mysterious-looking dark square, as it traveled across the surface of our companion star. The film was shot over the course of two days, which are compressed to 14 seconds.
Coronal holes are not actually holes - they are areas of the sun which are cooler and less dense than surrounding area.
"[The hole] appears dark in extreme ultraviolet light, as there is less material to emit in these wavelengths. Inside the coronal hole you can see bright loops where the hot plasma outlines little pieces of the solar magnetic field sticking above the surface," astronomers from NASA wrote on YouTube.
Our sun experiences cycles of sunspots, which cycle every 22 years, in two 11-year segments. Coronal holes can form during any part of this process, but are most prevalent when sunspots are dying down. The current cycle began six years ago, in January 2008.
The video was taken by the Solar Dynamics Observatory (SDO), which launched in 2010. When the film was complete, space agency officials announced the news on Twitter.
"A coronal hole, almost a square, is a noticeable feature on the sun of late," NASA researchers tweeted.
The magnetic field of the sun plays a central role in the formation of these cool areas. When these lines of force open up into open space, coronal holes can form at their bases. This pushes the solar wind from our sun at tremendous velocities. Lines of magnetism that arch back to the surface create hotter, brighter regions.
Coronal holes come in a wide variety of shapes and sizes, including this square example. There is no single reason why this feature formed in this particular shape.
The coronal hole formed in the far southern region of the sun, and charged particles streaming from the source are not headed to the Earth. When particles like these travel near the Earth, they can be deflected by the magnetic field of our planet and drawn into the upper atmosphere. There, they can create the northern and southern lights.
There are few space-based observatories studying the sun today, making observations of such events especially valuable when they are recorded.
