Remember, NASA already has a solar probe, named Parker, providing incredible insights about the outer layer of the Sun. Launched in August 2018, Parker is now the closest spacecraft to the Sun. Now, the Indian Space Research Organisation (ISRO) has planned its solar mission, Aditya – L1, to be launched by the end of 2020. Looking at the scientific focus on the Sun across the globe, one may wonder why it is important to study this yellow dwarf star.
To answer this and understand more about ISRO's solar mission, we spoke to Dr. Abhay Deshpande, a Senior Scientist (Physicist) working for the Government of India as well as the Honorary Secretary of Khagol Mandal, a non-profit collective of astronomy enthusiasts who organise various sky observation programmes, lectures and study tours.
Apart from the heat and light that makes life possible on Earth, what are a few lesser-known impacts of the Sun on our daily life?
Although our parent star, the Sun, seems the brightest object for us, it is an average star in the astronomical sense. It is moderate in size and not one of the brightest stars in our galaxy. Moreover, it is at the edge of the galaxy and not the centre. All these features of the Sun make life possible on our planet Earth.
The Sun also shields us from several Gigantic Comets that may have the potential to hit Earth. The tremendous gravity of the Sun attracts all big incoming objects and thus keeps Earth safe.
Life on Earth depends on the energy that we get from the Sun. The Sun emits a large number of particles every second. The luminosity is 0.4 Billion Billion Billion (4 followed by twenty-six zeroes) Watts! Compare this common 10 Watt LED light we use at our homes. We receive such massive amounts of light consistently free of cost.
However, this figure also may vary. The Sun is a magnetically active object, and the magnetic field varies to follow an 11-year cycle of solar minima and maxima. The energy and charged particles released during these phases vary considerably and can have a wide range of impacts from weather to our modern-day communication.
What are solar maxima and minima?
Before we proceed, let us get familiar with Sun Spots, Sun Flare and Solar Wind.
On Sun, due to intense magnetic interactions, some regions get relatively cooled. These are the regions where Solar Plasma is trapped, and the temperature is around 4000°C as against the average temperature of 6000°C. Hence these regions appear darker and are called Sun Spots.
Near such intense magnetic regions, usually, there are sudden eruptions of Solar Flares. As the name suggests, these are bright flares coming out of the surface of the Sun known as photosphere. This results in the release of charged particles in space and some of such highly energised particles can travel and reach Earth. Such particles can heat up and change the weather patterns on Earth.
Fortunately, we have a magnetic field which is like a shield and this special shield divert most of the particles towards North or South Poles. These particles then ionise the upper layers and cause Arora Borealis in North and Arora Australis in the South region.
As mentioned earlier, the Sun exhibits a unique 11-year magnetic variation cycle. In this time the Magnetic Field changes and attends maxima and minima—due to the gradual flipping of magnetic axis of Sun in this period. The North and South Pole of the Sun flips in this time.
During maxima, Sun is very active and emits more charges particles. These particles can have severe effects on Earth! The minima are times when the Sun is "quiet" which means not much activity is there on Sun. The Sun Spots are rare or not seen at all. The emission of Solar Wind is minimum.
Tell us more about ISRO's Aditya-L1. What are the scientific objectives behind the mission?
Aditya-1 is India's first attempt to have Solar Observatory in space. Originally it was planned to place Aditya at 800 km height above Earth. But then an ambitious proposal was made, and now, the plan is to place Aditya near the Lagrangian Point L1. Hence we call this mission as Aditya-L1. The main objective of the mission is to observe the solar corona.