Perhaps the most obvious feature of the sun is the sunspots that characterize the photosphere. The base temperature of
the 300-km deep photosphere is approximately 6400 °C whereas the sunspot regions are characterized with areas of
relatively lower temperature (around 4800 °C for the umbral regions and 5900 °C for the penumbral regions) and increased
magnetic activity (up to 3000 times the average magnetic field of the sun). Due to the differential rate of rotation of
the solar disk (26 days at the equator and 36 days at the poles), there is a "twisting" of the magnetic fields which
surface to the photosphere producing sunspots. Typically, these spots and groups are found to lie + 30° of the
solar equator and can physically be many-fold times larger than our planet! As the images below indicate, sunspots are
characterized with a dark core, the "umbra", where the temperature is about 1600 °C less than the surrounding temperature
of the photosphere whereas the less darker envelope which typically encompasses the umbral region, the "penumbra", is
about only 500 °C less than the surrounding photospheric temperature.
Studies have shown sunsplot activity to exhibit an eleven-yr cycle with virtually little sunspot activity during the minima of the cycle whereas frequent sunspots and associated groups dominate during the maximum of the same cycle, typically approximately 4.5 years after the minimum. During the solar maximum, we also have frequent filaments, flares and prominences (see here) which include ejected material from the sun's outermost "shell", the chromosphere, that reaches earth causing, for example, geomagnetic storms that produce the well-known and beautiful aurora borealis and australis.
Note: The sunspot groups AR10484 (Zurich class: Ekc, 03° N, 41° W) and AR10486 (Zurich class: Fkc, 15° S, 31° E) are each approximately the size of Jupiter and represent a most-impressive site through the eyepiece. Further details for these active regions are available here. Similarly, for a full-disk image of today's sun by the author which includes AR10485 and AR10487 (Zurich class: Dao, 14° N, 60° E) in the vicinity of AR10486, please click here.
332,900 x Earth
Mean Eq Diameter:
109.1 x Earth
152 million km
RA / Dec:
14h 05m 28s /
-12° 43' 09"
0h 8m 21.6s
Oct 27, 2003
Celestron CG-3 GEM
ScopeTronix STWA14 Adapter
Nikon Coolpix 995
Baader ND-5 (full-aperture)
1 x 1/320 sec @ f6.0
JPG RGB Fine image format
2048x1536 image size