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065

sunspots

OLogy Series
astronomy
card
065

sunspots

OLogy Series
astronomy

The Sun is speckled with markings called sunspots that look darker than the rest of its surface. These spots show up where strong magnetic fields inside the Sun keep currents of hot gas from reaching the surface. Sunspots follow an 11-year cycle. The first spots appear near the poles; as years pass, more spots develop and move towards the equator.

Solar flares are explosions on the surface of the Sun that occur near sunspots. This type of solar activity causes:

Earth spots

rainbows

auroras

Are you right?

Correct!

As solar flares hit Earth's upper atmosphere, the particles glow in bright colors visible from Earth. You are more likely to see auroras when there are lots of sunspots.

Sunspots look dark in visible light because:

smoke comes out of them

their surroundings are so bright

the Sun's surface is burned

Are you right?

Correct!

The darker center is about 3,000 degrees F cooler than the rest of the sunspot. The center is called the umbra (Latin for "shadow"), and the lighter, hotter area around it is called the penumbra.

Mordecai-Mark MacLow, astrophysicist

Looking directly at the Sun for more than a fraction of a second can lead to blindness. The Sun and its spots can only be safely viewed with filters designed for the purpose.

Our Sun is the only star where sunspots appear.

Fact
or
Fiction
?

Fiction

Many stars get sunspots; only then we call them "starspots."

Size: groups can be as large as 50,000 miles in diameter
Temperature: 39,200 degrees F
Parts: the darker, cooler umbra and the hotter, brighter penumbra
Frequency: heaviest every 11 years
Characteristics: cooler areas on the surface of Sun, appear less bright in visible light, and are strong sources of ultraviolet and X-ray radiation
Significance: used to measure rotation of Sun

Image credits: courtesy of AURA/NOAO/NSF; Mordecai-Mark MacLow: AMNH.