An international team of scientists including two Bengaluru astrophysicists on Friday gave a new light to the 142-year-old mystery of the sun and in the process opened a new window to see one of the greatest puzzles associated with the Sun.
The team of researchers from the Indian Institute of Astrophysics discovered how, solar spicules – small-scale plasma jets of about one million of which are present on the Sun at all times – are born and die in stars.
This discovery could help uncover one of the biggest unsolved mysteries in astrophysics – how temperatures in the solar corona rise.
Corona is the outer atmosphere of the Sun, which extends outward for several million kilometers outside the surface of the sun. Although the temperature in the Sun's core is close to 15 million degrees Celsius, it drops to 5,700 degrees on the sun's surface (photosphere).
However, above the photosphere, the temperature begins to rise again with height, reaching one million degrees or more in the corona. What causes temperature increases in the corona even though it moves away from the core remains a mystery.
Tanmoy Samanta, who earned a PhD at IIA, his supervisor and senior IIA scientist Dipankar Banerjee and their colleagues from China, the US and Europe, believed that solar spicules gave them the opportunity to solve the puzzle.
Discovered by Pastor Secchi in 1877, small-scale solar spicules (3000-5000 km long and 200-500 km wide) magnetized like geysers geysers found everywhere on the chromosphere, the interface between photosphere and corona.
"Studying them is difficult because each spicula – from formation to collapse – only lasts a few minutes even though at any time there are about one million of them on the Sun," Samanta told DH.
Old-generation solar telescopes aren't sophisticated enough to study these features. The breakthrough occurred when the team made observations with the 1.6m Goode Solar Telescope at Big Bear Solar Observatory, California, the largest solar telescope in the world that is currently operational.
Telescopes not only observe excessive spicules in great detail but also measure magnetic fields in photospheres with high spatial resolution.
"Spicules are produced from two opposite polarity magnetic fields, which destroy each other which produces kinetic energy and heat. This leads to the manufacture of plasma jets, which in turn might contribute to an increase in corona temperature. But we need to learn more to be sure, "explained Samanta. These findings have been published in journals Science on Friday.
Scientists must now carry out sophisticated computer simulations and theoretical investigations based on the results of these new observations to solve the long-standing problem of coronal heating.