Astronomy Day (Spring)
"The most accessible field in science, from the point of view of language, is astrophysics. What do you call spots on the sun? Sunspots. Regions of space you fall into and you don’t come out of? Black holes. Big red stars? Red giants."
~ Astronomer Neil deGrasse Tyson
Sunspots are temporary phenomena on the Sun's photosphere that appear as visible dark freckling on the sun's surface. First noted by Chinese in 800 BC, sunspots occur as a result of reduced surface temperature caused by concentrations of magnetic field flux that inhibit convection. Sunspots usually appear in pairs of opposite magnetic polarity and occur in cycles of 11 years, half of a 22 year cycle of solar activity. The magnetic activity that accompanies the sunspots can produce dramatic changes in the ultraviolet and soft X-ray emission levels and are much studied to understand the effect on the earth's climate. Sunspots sometimes erupt into powerful solar storms that shoot streams of charged particles into space, occasionally in the direction of Earth, and can bombard the Earth's magnetic field and disrupt power grids or knock out satellites in orbit. However, the current solar cycle, Cycle 24, is declining and predicted to reach solar minimum - the period when the Sun is least active - late in 2019 or 2020.
This tartan, designed by Carol A.L. Martin was created in celebration of recently-emerging sunspots.
Sunspots are areas on the sun where the magnetic field is about 2,500 times stronger than Earth's, much higher than anywhere else on the Sun. Because of the strong magnetic field, the magnetic pressure increases while the surrounding atmospheric pressure decreases. This in turn lowers the temperature relative to its surroundings because the concentrated magnetic field inhibits the flow of hot, new gas from the Sun's interior to the surface. This area of lower temperature results in sunspots.
Sunspots tend to occur in pairs that have magnetic fields pointing in opposite directions. A typical spot consists of a dark region called the umbra, surrounded by a lighter region known as the penumbra. The surrounding surface of the Sun (the photosphere) is about 10,000 degrees F while the umbra is about 6,300 degrees F.
Sunspots tend to appear in cycles of 11 years. One period of history, The Maunder Minimum (1645-1715), also known as the "prolonged sunspot minimum", was a period during which sunspots became exceedingly rare, as noted by solar observers.
Sunspots sometimes erupt into powerful solar storms that shoot streams of charged particles into space, occasionally in the direction of Earth. Some powerful solar storms can bombard Earth's magnetic field and disrupt power grids or knock out satellites in orbit around the planet.
As the sun reaches the end of a cycle, new sunspots appear near the equator, and a new cycle begins with the production of sunspots at higher latitudes on the surface of the sun.
For more about Sunspots, click the sun's surface.