What are Sunspots?

A Magnetic Flare: What is the Science Behind Sunspots?

A sunspot is the result of intense magnetic activity on the sun's surface. This central star of our galaxy―the Milky Way―is as unique in its composition as it is in the provision of life. Its surface or the photosphere is a playground for activity that adds to its own temperature, and that of surrounding planets, including ours.
The sun is a star at the very center of the solar system. It is consistently orbited by planets, asteroids, meteoroids, and comets. It emits light and heat that not only supports all life forms on Earth, but also offers us climate and weather that is conducive to growth. This central star comprises hydrogen, helium, iron, nickel, silicon, sulfur, magnesium, neon, oxygen, carbon, chromium, and calcium. The sun has a surface temperature of approximately 5,500 °C. When seen from the Earth, it seems to emit a yellow glow, which is actually white and appears so on account of 'atmospheric scattering'. It is a 'main sequence star' that generates solar energy by a hydrogen-helium nuclear fusion. It completes one revolution within the Milky Way galaxy in approximately 250 million Earth years or one Galactic year.

Understanding Sunspots
The magnetic activity on the sun's surface inhibits convection. This results in the formation of surface areas that have reduced surface temperature. These surfaces are visible from the Earth even without a telescope, and are referred to as sunspots. They have temperatures of approximately 4,500 K, within the surrounding 5,800 K. This makes them appear as dark spots due to the heat variation. Interestingly, research reveals that if a sunspot is viewed isolated from the photosphere around, it would actually be very luminous. A sunspot cycle roughly comprises eleven Earth years. The cycle refers to the number of sunspots due to recent magnetic polarity that outnumber the previously generated polarity variants.

They are breeding grounds for secondary phenomena like sequenced reconnection events, coronal loops, solar flares, and ejections or emissions of coronal mass. The same phenomena observed on other stars is referred to as starspots. The sun is now observed to be at a heightened level, correlating to the intensity of solar radiation and radiative flux. Research suggests that an increase in sunspots could lead to lower solar radiation and solar constant or brightness of the sun. Scientists are now exploring the possible resonant gravitational link between photospheric and inter-planetary tidal forces.

The earliest references to sunspots were made as far back as 28 BC, by Chinese astronomers. History reveals that a large one was sighted at the time coinciding with the death of Charlemagne, in 813 AD. However, the most precise and well-interpreted explanations were not provided until 1612, by Galileo. The observations that Galileo Galilei worked on came from astronomers Thomas Harriot, Johannes and David Fabricius. They fuel the debate over the inherent nature of our solar system. The spots observed highlight the fact that the sun does change, and its appearance and generated radiation are subject to the motion of encompassed components.

They display cyclic variation of number and intensity. The relationship between sunspots and the Earth's weather remains a matter of continuous research and debate. Suggestions imply that:
  • Sunspots do influence crop yields, and hence, the economy.
  • The sun has changed modality from a period of little or no sunspots to regular cycles.
  • They are counterparts of tubes of magnetic flux in the sun's convective zone, caused by differential rotation.
  • The spots observed are sun-surface depressions, ranging from central umbra, to the surrounding penumbra.
  • Display a powerful downdraft, generating a rotating vortex.
  • They are self-perpetuating storms like the terrestrial hurricanes we observe on the planet.
They can be observed with the help of terrestrial solar telescopes as well as those fitted on orbiting satellites. The generated filtration techniques involve the use of special-filter cameras, spectroscopes, hydrogen-alpha narrow bandpass filters, aluminum coated glass attenuation filters, and spectrohelioscopes. Observation with the naked eye is known to cause permanent damage to vision.