From Earth, about 149 million kilometers away, the Sun appears as a radiant and glowing "disk" suspended in the sky. But beneath its radiant surface, the Sun is constantly shifting with turbulent flows, twisted magnetic fields, and explosive energy that continuously reshape its surface behavior.
Observing activity on the Sun's surface holds great scientific significance. It not only enhances our understanding of solar dynamics but also plays a vital role in forecasting and mitigating space weather disasters, protecting spacecraft, and supporting long-term research into Earth's climate changes.
In this article, we'll delve into a high-resolution image of sunspot AR4079 captured by a user of the ToupTek camera system. Through this image, we'll explore the features of the Sun's photosphere, including sunspots, penumbral filaments and granules to uncover how these solar phenomena influence our daily lives here on Earth.
Image: On May 3, the Shenzhen Astronomical Observatory (SZAO/Delai) captured active region sunspot AR4079 using a 0.51-meter RCOS telescope and a ToupTek IUA1700KMB high-frame-rate industrial camera (210 fps @ 1600×1100 resolution).
The Sun's Layered Structure
First, let's look at the layer structure of the Sun.
The Sun is structured in layers from the inside out: the core, the radiative zone, the convective zone, the photosphere, the chromosphere, and the corona. Each layer has a unique role in how energy is generated, transported, and released into space as heat, light and high-energy particles. Understanding these layers helps scientists trace how solar activity affects our planet from geomagnetic storms to fluctuations in satellite communication and power systems.
At the center, the core is the source of the Sun's energy, reaching temperatures around 15 million ℃, where hydrogen nuclei undergo nuclear fusion to release energy.
This energy is first transported outward through radiation in the radiative zone, then carried via convection in the convective zone to the surface.
Image: Layers of the Sun. Credit: NASA
The photosphere is the layer where visible sunlight is emitted and where we observe phenomena such as sunspots and granulation.
Above it lie the chromosphere and corona, the outer layers of the Sun’s atmosphere, where intense activity such as solar flares and coronal mass ejections (CMEs) often occurs.
Sunspots: Magnetically Active Regions
Sunspots are relatively dark areas on the Sun's photosphere, closely tied to the Sun's complex magnetic field activity.
Because the Sun's equator rotates faster than its poles, magnetic field lines become stretched, twisted, and tangled over time. These tangled magnetic fields build up areas of intense magnetic activity within the Sun's interior.
When magnetic flux tubes emerge from these regions due to buoyancy, they rise through the convective zone and pierce the photosphere, creating sunspots.
Inside these tubes, the intense magnetic field suppresses convective heat transfer, causing the temperature to drop compared to the surrounding area. As a result, sunspots appear darker in visible light, which is seen as a visible marker of intense magnetic activity and a warning sign for potential solar storms that can disrupt communications, satellites, and power systems on Earth.
Image: The location of Sunspots. Credit: SpaceWeatherLive
Penumbral Filaments: Traces of Twisted Magnetism
Surrounding the darker core of a sunspot is the penumbra, characterized by alternating light and dark filamentary structures. These penumbral filaments arise as magnetic field lines transition from vertical to inclined orientations.
Also found in the penumbra are bright penumbral grains, which are small, dot-like features created by localized pockets of rising and sinking plasma, known as small-scale convection. These grains often move inward toward the sunspot's center along the filaments, revealing how magnetic forces interact with plasma flows in and around sunspots.
Image: Solar WL AR4079. Credit: Shenzhen Astronomical Observatory (SZAO/Delai)
Granules: The Sun's Boiling Surface
Aside from sunspots, the photosphere is also covered with granules that are bright, cell-like patches that resemble a bubbling honeycomb surface. These granulation patterns are convection cells, formed as hot gases rise from the convective zone, cool at the surface, and sink back down.
Each granule spans about 1,000 kilometers in diameter and has a lifespan of roughly 8 to 20 minutes. They're constantly bubbling and evolving like a pot of boiling water on the solar surface.
Image: Dynamic simulation of solar granulation. Source: Internet
Granules not only show how hot plasma rises and cools but also help scientists map the Sun's magnetic field, which is critical for forecasting space weather and protecting Earth’s technology from solar disruptions.
Why It Matters?
From sunspots and penumbral filaments to the ever-changing granulation, every solar feature plays a role in shaping space weather. The dynamics can interface with GPS signals, affect satellite trajectories, overload electrical grids, and even long-term climate trends. These make solar observation more crucial than ever.