Astrophotography by Anthony Ayiomamitis

Solar Image Gallery - Sunspots

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 AR10501 (Zurich class: Dki, 02 N, 18 W) and AR10507 (Zurich class: Dki, 07 N, 49 E) are quite visible against the solar disk and have the potential for strong X-class flares and, in particular, AR10501 (or AR10484) was responsible for the auroral activity of Nov 20/2003 (see here). Of lesser importance is the sunspot group AR10506 (Zurich class: Dki, 23 S, 44 E) immediately to the south of AR10507 and which is characterized with an impressive plage. Further details for these active regions are available here. Similarly, for images of these particular sunspot groups by the author, please click here.

Note: There is some confusion as to the numbering/renumbering of these active regions which are making their second pass around the sun. Sunspot group AR10484 is also known as AR10501; sunspot group AR10486 is also known as AR10507; and, finally, AR10488 is also known as AR10506. Some SOHO imagery is currently using the original numbering scheme whereas other SOHO imagery is based on the renumbered sequence.

Note: When looking at the sun before it crosses the meridian, East is always to the left and West is always to the right and vice versa when the sun does cross the meridian.



Image Details
Solar Active Regions 10501 - 10507
Imaging Details
Body:
Sun

Mass:
332,900 x Earth

Mean Eq Diameter:
109.1 x Earth

Distance:
152 million km

RA / Dec:
15h 41m 41s /
-19 382' 52"


Diameter:
32.37'

Magnitude:
-26.8

Light Time:
0h 8m 21.6s
Date:
Nov 21, 2003
12:41:27 - 12:52:02 UT+2


Location:
Athens, Greece

Equipment:
TeleVue Pronto
TeleVue 3x Barlow
Celestron CG-3 GEM
Nikon Coolpix 995
ScopeTronix STWA14 Adapter
Baader ND-5 (full-aperture)


Exposures:
1 x 1/225 sec @ f5.5
3 x 1/31 sec @ f4.1
ISO Auto
JPG RGB Fine image format
2048x1536 image size
Autodark subtraction


Software:
Photoshop V6

Processing:
Unsharp Masking
Grayscale
Brightness/Contrast
Resampling (30%)
Cropping
JPG Compression