Sunspots
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Regular sunspot observed with CHROMIS
Swedish 1-m Solar Telescope
A sunspot is a dark patch on the sun. It is associated with a strong magnetic field. The central part of the sunspot is the dark umbra. It is surrounded by the penumbra, which has a filamentary structure similar to the petals of a flower. Sunspots are darker than their surroundings because the magnetic field inhibits the convective motions under the surface that transports heat. But they are not completely dark and cold. It may sound strange, but one of many sunspot mysteries is why they are so bright! After all, the penumbra shines with about 75% of the ordinary solar output.
The image shows the main sunspot in AR 12585 as observed with CHROMIS through a wideband filter sampling the quasi-continuum of the Ca H and K lines at 3950 A. Note that the black line in the lower left measures 2500 km
Image credit: Luc Rouppe van der Voort, Shahin Jafarzadeh (ITA, University of Oslo)
Data reduction: Jaime de la Cruz Rodríguez (ISP/Stockholm)
Publication: Esteban Pozuelo et al., 2019, ApJ, 870