Solar Exploration

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.

Layered structure of sun’s atmosphere

image 108
  • 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).

Additional Information

  • 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.

Position of Aditya-L1

  • 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.
Online Counselling
Table of Contents
Today's Current Affairs
This is default text for notification bar