Solar Exploration - Rau's IAS

About Sun

The Sun is an ordinary star with a radiating surface area that emits a tremendous amount of radiation, mainly at visible wavelengths, due to its high temperature of 5800 K.
Its luminosity, which is the total amount of energy emitted per second, is about 3.9*10^26 watts.
The Sun’s core is where the thermonuclear reaction occurs, which is the fundamental source of the Sun’s tremendous energies that it radiates into space.
In the Sun’s core, atomic nuclei fuse together to form larger nuclei at extremely high temperatures exceeding 10^7 K.
The energy produced in the core is transported via radiative diffusion to a distance of about 0.71 R (radius) and by convection between 0.71 R and 1.00 R.

The three layers of the Sun’s atmosphere are the photosphere, chromosphere, and corona.

Layer from which the Sun’s visible light is emitted and is heated from below by energy streaming outward from the solar interior.
It shines like a nearly perfect blackbody with an average temperature of about 5800 K and is primarily made of hydrogen and helium.

Transparent to visible light
Revealed during a total solar eclipse as a glowing, pinkish layer of gas above the photosphere.

Sun’s outermost layer which least dense, but most dynamic in nature.
It can only be viewed when the light from the photosphere is blocked out during a total eclipse.
It is the source of dynamic activities including solar wind, solar flares, coronal mass ejections etc.
Interesting thing about Corona is it has high temperatures of more than 1-million-degree Kelvin far higher than the photosphere (6000 degrees Kelvin). The reason for this is still unknown and this is what Aditya L-1 will aim to understand. (NASA’s Parker probe is currently exploring this aspect).

Solar Wind: Corona ejects millions of tonnes of high-speed solar wind that engulfs the entire solar system including earth.
These solar winds are basically composed of electrons and nuclei of hydrogen and helium atoms.
Significance: Earth’s magnetic field acts as a protective shield against the solar wind.
However, these solar winds can be harmful to space-based instruments like satellites and thus to our communication networks, GPS etc.

India’s 1st first mission to sun to be launched in mid-2023
Its main objective is to study the upper atmosphere of sun including solar corona and chromosphere.
As a result, it observes solar activities including coronal heating, coronal mass ejection, solar winds, solar flares etc. and their influence on space weather.

Placed in a halo orbit around the first Lagrange (L1) point, about 1.5 million Km from earth.
It enables to study sun continuously without any obstruction due to occultation or eclipse.