Phys.org
Glossary · The Sun & Space Weather
Sunspot
A patch of the Sun where the magnetic field is strong enough to hold the heat back.
A sunspot is a region where the magnetic field breaks through the surface strongly enough to suppress the convection carrying heat up from below. The area cools to around 4,000 K against a 5,800 K background, which is why it looks black — it is not, it is merely dimmer, and a sunspot removed to the night sky would be blinding. They come in pairs of opposite polarity, last days to months, and are the visible bookkeeping of where the energy for flares is stored.
Where it has come up lately
Phys.org
Astronomy Magazine
Astronomy Magazine
Phys.org
ScienceDaily
Related terms
Coronal mass ejection
A billion tonnes of solar atmosphere thrown into space, and the cause of most serious aurorae.
Solar flare classes
A, B, C, M, X — a logarithmic scale for how hard the Sun just flashed in X-rays.
Kp index
A 0–9 scale of how disturbed Earth's magnetic field is right now.
The solar cycle
An eleven-year rhythm in sunspots, flares and the Sun's entire magnetic field.
Questions
What is Sunspot?
A patch of the Sun where the magnetic field is strong enough to hold the heat back.
Why does it matter?
The area cools to around 4,000 K against a 5,800 K background, which is why it looks black — it is not, it is merely dimmer, and a sunspot removed to the night sky would be blinding. They come in pairs of opposite polarity, last days to months, and are the visible bookkeeping of where the energy for flares is stored.