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Chandrayaan-2 peeks at distant Sun, helps unravel solar mystery

 Chandrayaan-2, which was lost during the hard landing on the dark side of the Moon, is still functioning in the form of its orbiter hovering over lunar surface.

A bright light of a solar flare on the rightside of the Sun. (Photo: Nasa)

From studies around nuclear fusion to deadly ejections from the surface, the Sun has always been a source of research for astrophysicists across the world. Chandrayaan-2, hovering over the Moon, has now found new developments on the hot outermost layer of the bright star known as Corona.

A team of scientists from the Physical Research Laboratory (PRL) found abundances of magnesium, aluminium and silicon in the solar corona and observed around 100 microflares, providing new insights about coronal mass heating. The research was published in two companion papers in the Astrophysical Journal Letters.

The corona emits ultraviolet, X-rays and consists of ionised gas at temperatures exceeding 2 million degrees Fahrenheit, while just 1,000 miles below, the surface known as the photosphere simmers at just 10,000 degrees Fahrenheit. This mysterious difference in temperatures is called the coronal heating problem. The new observations state that the high temperatures, when moving away from the surface could be due to strong magnetic fields present above the Sunspots (dark patches seen in visible images of the Sun).

Another puzzling observation about the corona is the presence of certain elements in abundances, nearly three to four times higher in the corona than in the photosphere.

On July 19, 2012, million-degree plasma in the sun's atmosphere began to cool and fall to the surface, resulting in a dazzling magnetic display known as coronal rain. (Photo: Nasa)

"Though we have a fairly good understanding of the origin of energy and other various aspects of the Sun, several potentially life-changing phenomena still remain a mystery. Being the nearest star, understanding the Sun also allows us to learn about other distant stars better," Isro said in a statement.

The Chandrayaan-2 mission, which was lost after it hard landed on the dark side of the Moon, remains active in the form of its orbiter hovering over the Moon. Scientists used the Solar X-ray Monitor (XSM) onboard Chandrayaan-2 in September 2019 to study the Sun. During the period the Sun was in solar minimum when typically, there were very few sunspots and active regions on the Sun. The solar minimum was characterised by an extremely quiet sun as its activity was at the lowest level over the past century.

"This provided a unique opportunity for XSM to observe the quiet corona without active regions for long periods," Isro added.

The Sun blew out a coronal mass ejection along with part of a solar filament over a three-hour period on February 24, 2015. (Photo: Nasa)

During the observation, scientists detected a large number of extremely small flares in the quiet corona, so small that their intensity is well below the standard scale to classify solar flares. This was the first observation and study of such a large sample of microflares in the quiet Sun, supporting the hypothesis of the presence of even smaller scale flares everywhere on the solar corona that could be responsible for the coronal heating.

The X-Ray observations that lasted over 76 days provided the measurement of abundances of various elements like aluminium and silicon, which were estimated to be lower than those seen in the active corona region but higher than that in the photosphere.

Isro stating that the orbiter was functioning smoothly said, "Both the Chandrayaan-2 orbiter and the XSM instrument are performing extremely well, and expected to provide many more exciting and new results."

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