On 5 June 2026, scientists reported that more than 100 years of continuous data from the Kodaikanal Solar Observatory had helped explain how the giant convection patterns on the Sun's surface respond to solar activity — improving the ability to predict the solar cycle. The research, by the Indian Institute of Astrophysics (IIA), draws on the oldest continuous series of solar observations in India. For NDA and CDS aspirants, it is a perfect launch-point to revise solar physics, space weather and India's solar science programme — all high-yield topics.
What the study found
- Researchers at the Indian Institute of Astrophysics (IIA), Bengaluru used 100+ years of data from the Kodaikanal Solar Observatory (Tamil Nadu).
- They studied convection cells on the Sun — small-scale granules and larger supergranules — and how these relate to the Sun's 11-year activity cycle.
- Understanding this behaviour helps in predicting future solar cycles, which matters for protecting satellites, communications and power grids.
The Sun — basic facts
The Sun is a G-type main-sequence star (a yellow dwarf) at the centre of our Solar System, made up mostly of hydrogen (~74%) and helium (~24%). It contains about 99.8% of the Solar System's mass, and its gravity holds all the planets in orbit. Light from the Sun takes about 8 minutes 20 seconds to reach Earth.
Internal structure (from the centre outwards)
- Core — where energy is generated by nuclear fusion at temperatures of around 15 million °C.
- Radiative zone — energy travels outward slowly as radiation.
- Convective zone — energy is carried by convection, like a boiling pot of water; hot plasma rises, cools and sinks.
- Photosphere — the visible surface (~5,500 °C), where sunspots appear.
- Chromosphere — a reddish layer above the surface.
- Corona — the Sun's vast, extremely hot outer atmosphere (millions of degrees), visible during a total solar eclipse.
How the Sun shines — nuclear fusion
The Sun produces energy through nuclear fusion, mainly the proton–proton (p-p) chain, in which hydrogen nuclei fuse to form helium, releasing enormous energy (in line with Einstein's E = mc²). This is fundamentally different from nuclear fission (the splitting of heavy nuclei) used in current nuclear power plants. Fusion is the holy grail of clean energy on Earth, which is why projects like ITER are significant.
The solar (sunspot) cycle
The Sun's magnetic activity rises and falls over an approximately 11-year cycle, known as the Schwabe cycle, tracked by counting sunspots:
- Sunspots are cooler, darker patches on the photosphere caused by intense, concentrated magnetic fields that temporarily suppress convection (so they are cooler, hence darker).
- At solar maximum, sunspots are numerous and the Sun is very active; at solar minimum, they are few.
- A famous historical period of very low activity, the Maunder Minimum (1645–1715), coincided with the "Little Ice Age" — a popular exam linkage between solar activity and climate.
- The full magnetic cycle (in which the Sun's poles flip and return) is about 22 years (the Hale cycle).
The IIA study examined how supergranules — convective network cells roughly 30,000 km across with lifetimes of about 24 hours — change in size and behaviour across this cycle, which is a long-standing puzzle in solar physics.
Solar phenomena and "space weather"
Magnetic activity on the Sun drives dramatic events:
- Solar flares — sudden, intense bursts of radiation.
- Coronal Mass Ejections (CMEs) — huge clouds of charged plasma hurled into space.
- Solar wind — a continuous stream of charged particles flowing from the corona.
- Prominences and filaments — loops of plasma anchored to the surface by magnetic fields.
When these particles reach Earth they cause "space weather", which can:
- Disrupt satellites, GPS and radio communications;
- Induce currents that can damage power grids;
- Endanger astronauts and high-altitude aircraft;
- Produce beautiful auroras (Northern and Southern Lights).
The most powerful recorded solar storm, the Carrington Event of 1859, set telegraph systems on fire — a reminder of why forecasting the solar cycle is now strategically important.
India's solar science — Kodaikanal and Aditya-L1
- The Kodaikanal Solar Observatory, in the Palani Hills of Tamil Nadu, was established in 1899 and is run by the Indian Institute of Astrophysics (IIA), Bengaluru. Its century-plus archive of daily solar images (sunspots, plages, prominences) is one of the most valuable historical datasets in the world for studying long-term solar behaviour.
- India's first dedicated solar mission, Aditya-L1, launched by ISRO in September 2023, was placed in a halo orbit around the Lagrange Point 1 (L1), about 1.5 million km from Earth towards the Sun. From L1, it continuously observes the Sun without eclipses or occultations, studying the corona, solar wind and CMEs — complementing the long historical record from Kodaikanal.
India's wider space and solar programme
Aditya-L1 and Kodaikanal sit within a broader Indian space effort that aspirants should connect:
- Lagrange points are five positions in a two-body system (here Sun–Earth) where gravitational forces balance, letting a spacecraft hold a stable position with little fuel. L1, between the Sun and Earth, gives an uninterrupted view of the Sun — ideal for Aditya-L1.
- India's recent space milestones include Chandrayaan-3 (2023), which made India the first nation to land near the lunar south pole, and the upcoming human-spaceflight programme Gaganyaan.
- The Indian Institute of Astrophysics (IIA), which runs Kodaikanal, also operates observatories such as the one at Hanle, Ladakh — one of the world's highest, in a designated Dark Sky Reserve.
This combination of a century-old solar archive and cutting-edge missions makes India a serious player in both historical and frontier solar science.
Why it matters
- Space-weather preparedness: predicting the solar cycle protects satellites, navigation, communications and power grids.
- Indigenous science: a globally valuable Indian dataset and the Aditya-L1 mission showcase India's growing capability in astrophysics.
- Conceptual base: reinforces fundamentals — fusion, the structure of the Sun, sunspots — that recur in NDA/CDS science papers.
Solar eclipses and the corona
Studying the Sun connects naturally to solar eclipses, a favourite exam topic. A solar eclipse occurs at new moon, when the Moon passes between the Sun and Earth, casting its shadow on Earth — total, partial or annular depending on alignment and distance. During a total solar eclipse, the Sun's faint outer atmosphere, the corona, becomes visible — historically one of the few ways to study it from the ground (now done continuously from space by missions like Aditya-L1). The corona's puzzlingly high temperature (millions of degrees, far hotter than the surface) is one of solar physics' great unsolved questions.
The Sun as Earth's energy source
Finally, it is worth remembering that the Sun is the ultimate source of almost all energy on Earth. Photosynthesis captures solar energy into food chains; fossil fuels are ancient stored sunlight; wind, ocean currents and the water cycle are all driven by solar heating; and solar power harnesses it directly. India receives abundant solar radiation, which is why the country has invested so heavily in solar energy and co-founded the International Solar Alliance. Understanding the Sun, therefore, is not just astronomy — it underpins climate, agriculture and the energy transition.
Key facts for your exam
- What: 100+ years of Kodaikanal Solar Observatory data used to decode the Sun's 11-year cycle; by the Indian Institute of Astrophysics (IIA).
- Sun's energy: nuclear fusion (hydrogen → helium, p-p chain).
- Solar cycle: ~11 years (Schwabe); magnetic cycle ~22 years (Hale).
- Sunspots: cooler, darker areas of intense magnetic field on the photosphere.
- Aditya-L1: ISRO's first solar mission (2023), at Lagrange Point L1, ~1.5 million km from Earth.
- Kodaikanal Observatory: established 1899, run by IIA.
Previous-year & expected exam questions
Q1. The Sun produces its energy primarily through — Answer: Nuclear fusion of hydrogen into helium in its core.
Q2. The solar cycle, marked by the rise and fall of sunspots, has an average period of about — Answer: 11 years.
Q3. India's first dedicated solar observation mission, Aditya-L1, is positioned at — Answer: The Lagrange Point L1, about 1.5 million km from Earth toward the Sun.
Q4. Sunspots appear darker than the surrounding surface because they are — Answer: Cooler, due to strong magnetic fields suppressing convection at those spots.
FAQ
Q1. What are granules and supergranules? They are convection cells on the Sun's surface formed by rising hot plasma and sinking cooler plasma — granules are small (~1,000 km, minutes long) and supergranules are large (~30,000 km, ~24-hour lifetime).
Q2. Why does old solar data matter so much? A continuous century-long record (like Kodaikanal's) lets scientists study long-term patterns in solar activity that short modern datasets cannot reveal — essential for predicting the solar cycle.
Q3. What is "space weather"? Disturbances caused by solar flares and coronal mass ejections that can affect satellites, GPS, radio, power grids and astronauts, and produce auroras.
Q4. How is fusion different from fission? Fusion joins light nuclei (hydrogen → helium) and powers the Sun; fission splits heavy nuclei (like uranium) and powers today's nuclear reactors.