Understanding ‘Aditya’

The word 'Aditya' roughly translates to 'Sun' in Sanskrit. The Indian Space Research Organisation (ISRO) has recently, barely two weeks after its southern lunar adventure on the Moon's south pole, launched its first observation mission to study Aditya, the Sun. Hence the name Aditya-L1.

Why L1? We'll get to that in a minute.

Destined to be positioned in a halo orbit 1.5 million km away from the earth, with seven payloads on board designed to study primarily the outermost layer of the Sun (solar Corona), ISRO launched a solar observatory named Aditya-L1 on Saturday last week.

After being injected towards the path of the Sun, Aditya-L1 will take roughly four months (135 days according to the ISRO chief) to traverse it's 1.5 million km distance to reach Lagrange Point 1 (L1), which will provide an unhindered 24/7 view of the star. Despite having a five-year mission lifespan, Aditya-L1 will probably continue to observe the Sun for a much longer time.

Lagrange points

There are locations in space known as Lagrange points where the gravitational pull of two celestial bodies will balance out. Between the Sun and the Earth, there are actually five.

These are the points where, if a spacecraft is sent, the gravitational pull of the Earth and the Sun will cancel out the centrifugal force and gravitational force.

The stability it brings, together with fuel conservation and uninterrupted Sun observation, is the main advantage. Lagrange 1 (L1) and Lagrange 2 (L2) are the best options because they are nearer to Earth than the other points.

Layers of the Sun

Somewhat of a mystery exists regarding the outermost layer of the Sun. Apart from multiple theories lacking unanimous agreement, scientists still ponder over the fact as to why the Sun's Corona layer is exponentially hotter in temperature than some of its preceding layers.

Corona contains extremely high temperature plasma ranging from one to three million degrees Celsius.

The Photosphere layer is typically visible when we look at the sun from the ground.

When there is a solar eclipse, though, we notice a reddish glow around the eclipse. That layer is called the chromosphere.

Only the Corona layer is visible during the total solar eclipse. A hazy halo surrounds the sun.

Aditya- L1's mission includes studying these very three topmost layers of the Sun — Photosphere(6,000°C), Chromosphere (4,000-10,000°C) and the Corona layer.

Sunny emissions

Apart from the obvious 'things' emitted by the Sun, such as your heat and light and every sort of radiation from the electromagnetic spectrum, the Sun also emits solar wind and solar flares.

The studies from Aditya-L1 will help scientists understand such solar activities, and their effect on Earth and near-space weather in real time.

According to Mylswamy Annadurai, a former scientist of ISRO, the Sun constantly affects Earth's weather through radiation, heat, the movement of particles, and magnetic fields. He claims that it also affects the space weather at the same time.

"Knowing the activities of the Sun such as solar wind or a solar eruption a couple of days ahead will help us move satellites out of harm's way. This will help increase the longevity of satellites in space," he said in an interview with the BBC.

In essence, solar wind is a massive wave of charged protons and electrons. We witness phenomena like the Northern Lights when the solar wind interacts with the magnetic field of the Earth.

Coronal Mass Ejections (CMEs), which are large bursts of solar wind and magnetic fields, are also released from the Sun.

For reading, studying and measuring such activities, the Indian solar observatory has some equipment on it.

The payloads

The seven instruments or payloads on board Aditya-L1, are Visible Emission Line CoronaGraph (VELC), Solar UltraViolet Imaging Telescope(SUIT), Solar Low Energy X-Ray.

Spectrometer (SOLEXS), High Energy L1 Orbiting X-Ray Spectrometer (HEL1OS), Aditya Solar Wind Particle Experiment(ASPEX), Plasma Analyser Package for Aditya (PAPA)and last but not the least, a Magnetometer (MAG).

While SUIT is charged with imaging the sun's photosphere and chromosphere in the near UV range, VELC is built to investigate the dynamics of coronal mass ejections and the solar corona.

Both SOLEXS and HEL1OS  are designed to study the X-ray flares from the sun over a wide X-Ray energy range. ASPEX and PAPA will study the solar winds in depth and the MAG will measure the low intensity interplanetary magnetic field in space.

So, what it means is that four of the seven instruments will directly study the sun whereas the rest of the payloads will continuously take measurements around L1.

India will join an exclusive group of nations that are already researching the Sun if Aditya-L1 is a success.