SUNSPOTS
Sunspots are dark spots that appear on the photosphere, or visible "surface" of the Sun. They usually have a dark
core, called the umbra, surrounded by a lighter border, called the penumbra. They form when large disturbances in
the Sun's magnetic field cool portions of the photosphere. Sunspots are relatively cool, being only 6000°F (3300°C)
compared to the normal 10,000°F (5500°C) of the rest of the photosphere. Although these spots appear to be almost
black, they are actually quite bright. If it were possible to remove a sunspot from the Sun and put it in the night sky, it
would shine brighter than the full moon. They only appears to be "dark" when compared to the rest of the photosphere.
Sunspots can be big. Very big. They can range in size from 10 to 100,000 miles (16 to 160,000 km) in diameter. To put that
into perspective, the Earth is only 8,000 miles (12,800 km) in diameter! Compare sunspot sizes to the relative size of the
Earth in the image below in order to better grasp the immense size of the Sun and share that WOW factor with neighbors,
friends, and family.
Sunspots usually appear in pairs but can also appear in very large groups. They can last from a few days to several
weeks and can change their shape, size and number as they slowly rotate across the face of the Sun. It will take about two
weeks for a sunspot group to cross the Sun. Try looking at the Sun every day and draw a picture of what you see. At the
end of the week, compare your drawings and you'll see how sunspots evolve.
PLANETARY TRANSIT
Planetary transits occur when the planet Mercury or Venus pass between the Sun and Earth allowing observers on
Earth to track the planet's dark disk as it crosses the face of the Sun. This is an extremely rare event, occurring only four
times over the next 50 years.
LIMB DARKENING
When viewing the Sun's disk, look for a falloff of brightness as you look from the center of the disk to the edge, or limb.
This is caused by the thick solar corona, or outer atmosphere of the Sun. As you look at the center of the solar disk, you
are looking straight down through the least amount of atmosphere. As you look near the limb, you are looking through a
thicker layer, which dims the amount of light shining through.
ENGLISH |
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