Apart from India’s Aditya-L1, 5 missions are currently observing the sun

Vibha Sharma

Chandigarh, August 29

These are exciting times for India and space scientists.

After the moon mission Chandrayaan-3, the Indian Space Research Organisation (ISRO) is all set to study the sun, the star at the centre of our solar system.

Scientists of India’s premium space research will on September 2 launch the Aditya-L1 Solar Observatory spacecraft to explore its various activities in real time and study their influence on space weather.

By studying the nearest star, ISRO also hopes to learn more about the Milky Way and other stars in it.

Aditya-L1

Aditya-L1 will be the first space-based Indian observatory in a low earth orbit.

Subsequently, it will be launched towards the Lagrange point (L1).

The total travel time from the launch to L1 is expected to be around four months.

Aditya, which signifies ‘newly risen sun’ or lord Surya, will carry seven ‘made in India’ payloads to observe the photosphere, chromosphere and the outermost layers of the sun (corona) using electromagnetic and particle and magnetic field detectors.

Its four payloads will directly view the sun and the other three carry in-situ studies of particles and fields at L1.

L1 point of the earth-sun system gives an uninterrupted view of the sun and according to NASA is currently home to its Solar and Heliospheric Observatory Satellite SOHO.

Lagrange points

According to NASA’s solar system exploration, Lagrange points are positions in space where “objects sent there tend to stay put”.

“At Lagrange points, the gravitational pull of two large masses precisely equals the centripetal force required for a small object to move with them. These points in space can be used by spacecraft to reduce fuel consumption needed to remain in position.”

In other words, at Lagrange points in space, gravitational forces of the sun and the earth produce enhanced regions of attraction and repulsion which can be used by spacecraft to reduce fuel consumption needed to remain in position.

Lagrange points are named in honour of Italian-French mathematician Josephy-Louis Lagrange.

Of the five Lagrange points, three are unstable and two are stable.

The unstable Lagrange points (L1, L2 and L3) are along the line connecting the two large masses.

The stable Lagrange points (L4 and L5) form the apex of two equilateral triangles that have the large masses at their vertices.

L4 leads the orbit of earth and L5 follows.

Why sun

With the current technology as on date, it is not humanly possible to physically explore the sun—the celestial object crucial for our survival on earth. However, scientists hope to learn more about it to have a better understanding of earth’s future and other stats in our galaxy, the Milky Way.

The sun is basically a massive hot ball of plasma, inflated and heated by nuclear fusion reactions at its core. It radiates this energy—light, ultraviolet, and infrared radiation—the most important source of energy for life on the earth.

Its enormity and size vis-à-vis other celestial objects can be understood from the fact that it constitutes about 99.86% of the mass of the solar system.

Our sun may be one of at least 100 billion stars in the Milky Way but without it life on earth would have been impossible.

The sun is closer to us than any other star and also plays the role of an anchor, creating gravity that keeps earth and other planets in the space around it. Without it, earth would have flown off loose into the universe.

By studying the sun, scientists hope to explore and learn more about other stars. A better understanding of other stars will help them know about the Milky Way, other galaxies and the universe.

Solar observatories

Scientists at space agencies have designed and launched multiple solar observation probes to operate in heliocentric orbit or at one Lagrangian point.

In fact, NASA’S Pioneer 10 (of the Pioneer Spacecraft Missions series) “made valuable scientific investigations in the outer regions of our solar system until the end of its science mission on March 31, 1997,” according to the space agency.

Parker Solar Probe was developed as part of NASA’s ‘Living with a Star’ programme to explore aspects of the sun-earth system that directly affects life and society. According to NASA, Parker Solar Probe accomplished a “milestone on June 27, 2023 – its 16th orbit of the sun”.

“This included a close approach to the sun (known as perihelion) on June 22, 2023, where the spacecraft came within 5.3 million miles of the solar surface while moving at 3,64,610 miles per hour. The spacecraft emerged from the solar flyby healthy and operating normally,” it said.

Launched in 2018, NASA’s Parker Solar Probe is studying the sun’s atmosphere by being in it, the closest any spacecraft has ever ventured.

Ongoing missions  

According to the Planetary Society, five missions are currently observing the sun. Apart from Parker Solar Probe, they include the ESA-led Solar Orbiter mission in 2020 which is imaging the sun and huge swaths of its corona up close for the first time.

“Since 2010, NASA’s Solar Dynamics Observatory (SDO) has been comprehensively mapping the sun’s active regions to understand how solar flares develop and erupt.

“Since 2006, NASA’s STEREO-A spacecraft has been providing us insights on solar eruptions.

“The ESA-NASA SOHO spacecraft has been observing the sun since 1995, particularly using its coronagraph to block sunlight in order to better see the corona and track solar eruptions,” as per the website.

Happening soon

While India is launching Aditya-L1 in September, in 2024, ESA’s Proba-3 comprising two spacecraft will fly in formation to create a coronagraph that will study inner layers of the sun’s atmosphere, according to reports.