Monday, June 28, 2021

Sunspots in pills

Sunspots are vast black regions of the solar photosphere, with typical sizes comparable to that of the Earth.

Sunspots are formed in those areas of the photosphere where the flux of the solar magnetic field is very high (therefore at the points where the magnetic field lines enter and exit). To put it in numerical terms, the magnetic field in sunspots is 1000 times stronger than the average solar magnetic field.

Such a concentrated magnetic field has the effect of modifying the convective mechanisms that transport energy inside the Sun, thus causing a decrease in the temperature of the surface gas.

The temperature of the solar photosphere is in fact about 6000 Kelvin, while within these regions it is 4200 Kelvin. The black color of sunspots is therefore only due to the fact that they are cooler and emit much less light than the surrounding regions!

In fact, if we imagined to rip a sunspot away from the Sun and move it somewhere in the sky at night, its brightness would be comparable to that of the full Moon and would appear orange.

.Credit: NASA, SDO.

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