The Sun is a star located at the center of our solar system. It plays a fundamental role in providing heat, light, and energy that sustains life on Earth. Read here the know in detail about the structure, composition, and features of the Sun.
Recently scientists have predicted that the Sun is expected to reach the peak of its activity in 2024, a year earlier than previous estimates.
This activity, known as “solar maximum”, in the current 11-year cycle will be between January and October 2024, according to the US National Oceanic and Atmospheric Administration (NOAA).
The 11-year activity cycle of the Sun is tied to the number of sunspots, which in turn are linked to the intensity of space weather, including solar flare activity from the star.
The solar cycle is the cycle that the Sun’s magnetic field goes through approximately every 11 years.
- Every 11 years or so, the Sun’s magnetic field completely flips. This means that the Sun’s north and south poles switch places.
- Then it takes about another 11 years for the Sun’s north and south poles to flip back again.
- The solar cycle affects activity on the surface of the Sun, such as sunspots which are caused by the Sun’s magnetic fields.
- As the magnetic fields change, so does the amount of activity on the Sun’s surface.
One way to track the solar cycle is by counting the number of sunspots.
- The beginning of a solar cycle is a solar minimum, or when the Sun has the least sunspots. Over time, solar activity and the number of sunspots increase.
- The middle of the solar cycle is the solar maximum, or when the Sun has the most sunspots. As the cycle ends, it fades back to the solar minimum, and then a new cycle begins.
Giant eruptions on the Sun, such as solar flares and coronal mass ejections, also increase during the solar cycle. These eruptions send powerful bursts of energy and material into space.
This activity can have effects on Earth. For example, eruptions can cause lights in the sky, called aurora, or impact radio communications. Extreme eruptions can even affect electricity grids on Earth.
What is space weather?
Activity on the Sun’s surface creates a type of weather called space weather. The Sun is about 93 million miles (150 million kilometers away from Earth. However, space weather can affect Earth and the rest of the solar system.
- The Sun is always spewing gas and particles into space. This stream of particles is known as the solar wind.
- The gas and particles come from the Sun’s hot outer atmosphere, called the corona.
- These particles from the corona are charged with electricity. The solar wind carries these particles toward Earth at up to a million miles per hour!
The Earth’s magnetic field and atmosphere act as a shield protecting it from the majority of solar wind blasts.
The Sun: structure
The Sun is located at the center of our solar system. It has a layered structure, consisting of several distinct regions or zones, moving from its core outward.
- Core: The core is the innermost region of the Sun, where nuclear fusion reactions take place. It is the hottest part, with temperatures exceeding 15 million degrees Celsius. These high temperatures and pressures cause hydrogen nuclei to fuse into helium, releasing a tremendous amount of energy in the form of light and heat.
- Radiative Zone: Surrounding the core is the radiative zone. In this region, energy generated in the core is transported outward primarily through the process of radiation. Photons of light are absorbed and re-emitted by charged particles, gradually making their way to the next layer.
- Convective Zone: Beyond the radiative zone is the convective zone. In this region, energy is transported by the physical motion of material. Hot, less dense plasma rises from the core to the surface, while cooler, denser material sinks back down in a process called convection.
- Photosphere: The photosphere is the visible surface of the Sun that emits the light we see. It has an average temperature of around 5,500 degrees Celsius. The photosphere contains various features like sunspots, granules, and supergranules, which are related to the Sun’s magnetic activity.
- Chromosphere: Above the photosphere is the chromosphere, a layer of the Sun’s atmosphere. During a solar eclipse, the chromosphere is visible as a reddish-pink ring around the dark disk of the Moon. This region is hotter than the photosphere.
- Transition Region: The transition region is a narrow layer between the chromosphere and the outer atmosphere, known as the corona. Temperatures in the transition region rise rapidly.
- Corona: The corona is the outermost layer, extending millions of kilometers into space. It is incredibly hot, with temperatures exceeding a million degrees Celsius. The corona is visible during a total solar eclipse as a halo of faint, white light radiating from the Sun’s disk.
The Sun is primarily composed of hydrogen (about 74% by mass) and helium (about 24% by mass).
- These two elements undergo nuclear fusion reactions in the core, primarily the fusion of hydrogen nuclei (protons) to form helium nuclei.
- In addition to hydrogen and helium, the Sun contains trace amounts of other elements, including carbon, nitrogen, oxygen, and heavier elements like iron.
Features of Sun
The giant star exhibits various features and phenomena:
- Sunspots: Sunspots are dark, cooler regions on the Sun’s surface caused by strong magnetic activity. They appear in cycles and are associated with the Sun’s magnetic field.
- Solar Flares: Solar flares are sudden and intense bursts of energy and radiation from the Sun’s surface, often associated with sunspots and magnetic activity.
- Prominences: Solar prominences are enormous, arching structures of hot, glowing gas that extend from the Sun’s surface into its outer atmosphere. They are often seen during total solar eclipses.
- Solar Wind: The Sun continually emits a stream of charged particles called the solar wind. It can affect Earth’s magnetic field and cause phenomena like the Northern and Southern Lights (Aurora Borealis and Aurora Australis).
- Coronal Mass Ejections (CMEs): CMEs are massive eruptions of solar material from the Sun’s corona. When directed toward Earth, they can disrupt satellites, power grids, and communication systems.
The Sun’s energy output, in the form of sunlight and solar radiation, is essential for life on Earth and has a profound influence on our planet’s climate and environment. Understanding the Sun’s structure, composition, and features is critical for studying solar physics, space weather, and the impact of solar activity on Earth.
-Article by Swathi Satish