A NASA space telescope has spotted surprising ‘magnetic braids’ of super-hot matter in the Sun’s outer atmosphere, a finding that scientists claim may explain the star’s mysteriously hot corona.
The discovery, made by NASA’s High-Resolution Coronal Imager, or Hi-C, also may lead to better space weather forecasts, the scientists added.
Jonathan Cirtain, a solar astrophysicist at NASA’s Marshall Space Flight Center, Huntsville and his team launched the 9.5-inch (24 centimetres) telescope last July on a 10-minute flight just beyond Earth’s atmosphere to study the corona, the Sun’s million-degree outer atmosphere.
The telescope snapped 165 photos in stunning detail before parachuting back to Earth, Space.com reported.
The surface of the Sun is unsurprisingly hot, up to 6,125 degrees Celsius. Bizarrely, however, the corona – the outer atmosphere far above the Sun’s surface – is hotter by a thousand fold, even in the absence of solar flares.
Scientists recently found that powerful magnetic waves rippling from below the Sun’s surface may heat the corona by 1.5 million degrees Celsius. However, that alone would not account for the corona’s ultra-hot temperatures.
Now high-resolution images of the Sun’s corona support the idea of magnetic braids generating tremendous amounts of heat, possibly enough to explain the readings of up to 6 million degrees Celsius.
“What we have observed is a bundle of magnetic fields, wrapped about several other bundles to form a magnetic bundle ensemble. The magnetic fields in this ensemble have varying lengths, and the rate of curvature along individual field lines may also vary such that some fields are very highly curved while others are less so,” Cirtain said.
These magnetic fields are physically manifested within the super-hot plasma making up the Sun. For instance, very highly curved magnetic fields can take the form of coronal loops, giant arches rising from the Sun.
Eventually these magnetic braids can grow unstable enough for individual magnetic field lines of force to interact within them. This phenomenon, known as reconnection, decreases the curvature of the magnetic field, releasing potentially vast amounts of energy that can heat plasma or accelerate solar flares and other massive outbursts.
While astronomers have seen magnetic braids on the surface of the Sun, until now they had little way to see how common the braids were in the corona.
Researchers said it is possible the braids they saw were not bundles of magnetic fields but sets of many nested magnetic loops overlying and underlying each other.
If so, they would store less energy than estimated. Even so, however, the corona would still hold 100 times the energy needed to be super-heated.
The findings were published in the journal Nature.