The Sun is the star at the centre of our solar system, a massive sphere of hot plasma primarily composed of hydrogen (about 75%) and helium (about 24%), with trace amounts of other elements. It provides the energy necessary for life on Earth through radiation, particularly in the form of light and heat, maintaining the planets temperature, driving weather patterns and supporting photosynthesis. Its energy is generated by nuclear fusion, a process in which hydrogen atoms combine to form helium, releasing immense amounts of energy. The Sun’s gravity holds the solar system together, influencing the orbits of planets, dwarf planets, moons, comets, meteoroids, asteroids and all other objects in its vicinity. Its life cycle places it in the “main sequence” stage, where it will remain for billions more years before transitioning into a red giant and eventually shedding its outer layers to form a white dwarf.

1. 1. Key facts about the sun

• • • Diameter: Approximately 1.39 million kilometres (about 109 times that of Earth).
    • Age: About 4.6 billion years.
    • Surface Temperature: Roughly 5,500 °C (9,932°F).
    • Core Temperature: Around 15 million °C (27 million °F).

 

1. 2. Structure of the Sun

• • • Core: This is where nuclear fusion occurs, producing the Sun’s energy. The core makes up about 20-25% of the Sun’s radius.
    • Radiative Zone: Above the core, energy moves outward through this zone by radiation. It can take millions of years for energy to travel through this layer due to the dense plasma that constantly absorbs and re-emits the energy.
    • Convective Zone: In this outer layer, energy is transported by convection, where hot plasma rises, cools, and sinks back down in a cyclic process.
    • Photosphere: This is the visible “surface” of the Sun, where sunlight escapes into space. It’s from this layer that most of the light and heat we feel comes from.
    • Chromosphere: This layer lies just above the photosphere and can be seen during solar eclipses. It’s a bit cooler than the photosphere, and it often appears as a reddish glow.
    • Corona: The outermost layer, extending millions of kilometres into space, the corona is much hotter than the photosphere, reaching temperatures up to 2 million degrees Celsius. It’s visible during total solar eclipses as a bright halo around the Sun.

 

1. 3. Solar phenomena’s due to the Sun’s magnetic field

• • • Sunspots: These are dark, cooler regions on the Sun’s surface caused by magnetic activity. They often occur in pairs or groups and can last for days or weeks.
    • Solar Flares: These are sudden bursts of energy caused by changes in the Sun’s magnetic field. Flares release massive amounts of radiation and can affect Earth’s magnetic field, causing geomagnetic storms.
    • Coronal Mass Ejections (CMEs): These are large clouds of solar plasma and magnetic fields ejected from the Sun’s corona. When directed towards Earth, they can disrupt satellite communications, GPS, and power grids.

 

1. 4. The Sun’s Influence on Earth

• • • Solar Radiation: This drives the water cycle, winds, and ocean currents, shaping our planet’s climate and supporting ecosystems.
    • Auroras: Solar wind (streams of charged particles from the Sun) interacts with Earth’s magnetic field, creating spectacular light displays known as the auroras (northern and southern lights).
    • Solar Cycle: The Sun goes through an approximately 11-year cycle of magnetic activity. At the peak of the cycle, solar activity (sunspots, flares) is highest, influencing space weather and sometimes causing disruptions to satellites and power systems on Earth.

 

1. 5. The Sun’s Lifecycle

• • • Current Stage (Main Sequence): The Sun is in the main sequence stage of its life cycle, where it burns hydrogen in its core. This phase is stable and will last for about 10 billion years in total.
    • Future Evolution: After about 5 billion more years, the Sun will exhaust the hydrogen in its core. It will then expand into a Red Giant, engulfing the inner planets, including possibly Earth.
    • End of the Sun: After the red giant phase, the Sun will shed its outer layers, forming a planetary nebula, leaving behind a dense core called a white dwarf. Over billions of years, this white dwarf will cool and fade away.

 

1. 6. The Sun’s role in space exploration and Astronomy

• • • Space Weather: Understanding the Sun’s activity is critical for space exploration, as solar radiation and storms can endanger astronauts and spacecraft.
    • Solar Observatories: Various space missions (like NASA’s Parker Solar Probe) are studying the Sun closely to understand its magnetic field, solar wind, and internal dynamics.
    • Solar Power: Harnessing solar energy is a key area of focus for renewable energy, using sunlight to generate electricity through photovoltaic cells.