by Ann » Sat May 11, 2024 5:48 am
So this thing is really big. And active, too.
It always bothered me that sunspots are dark because they are cooler than their surroundings, and yet they are so active. Why would cooler things be more active than hotter things?
Then again, the sunspots are about the same temperature as a red dwarf star (or at least about the same temperature as orange dwarfs of spectral class K), and red dwarfs (at least those of spectral class M) are known to be extremely active and spit stuff into the surroundings:
The red dwarf in the illustration appears to be peppered with dark spots near its poles, and the flares seem to be coming from the same general regions. Are red dwarfs particularly rich in sunspots, and is that why they are so active? I could google, but I'm too lazy.
But I found something else when I googled, namely a sunspots as seen in different wavelengths. And it is hugely interesting to compare a sunspot in visible light and in very near ultraviolet light:
The point here is that sunspots are indeed darker and cooler than their surroundings, but they are also brighter and hotter than the rest of the photosphere! But we don't see the bright parts of the sunspots, because our eyes are quite insensitive to these very near ultraviolet wavelengths.
And it's all caused by magnetism.
Sorry! I'll leave that to the rest of you to discuss.
APOD Robot wrote:
When impacting Earth's upper atmosphere, these particles can produce beautiful auroras, with some auroras already being reported unusually far south.
Yes. Last night, auroras could be seen over my hometown of Malmö.
Did I see this aurora? Heck no. I was fast asleep.
Ann
[img3="AR 3664: Giant Sunspot Group.
Image Credit & Copyright: Franco Fantasia & Guiseppe Conzo (Gruppo Astrofili Palidoro)"]https://apod.nasa.gov/apod/image/2405/SunAr3664_Fantasia_960.jpg[/img3]
So this thing is really big. And active, too.
It always bothered me that sunspots are dark because they are cooler than their surroundings, and yet they are so active. Why would cooler things be more active than hotter things?
Then again, the sunspots are about the same temperature as a red dwarf star (or at least about the same temperature as orange dwarfs of spectral class K), and red dwarfs (at least those of spectral class M) are known to be extremely active and spit stuff into the surroundings:
[img3="An artist’s impression of a flaring red dwarf and its exoplanet. Credit: AIP / J. Fohlmeister"]https://dq0hsqwjhea1.cloudfront.net/Mdwarfs_feat-600x400.jpg[/img3]
The red dwarf in the illustration appears to be peppered with dark spots near its poles, and the flares seem to be coming from the same general regions. Are red dwarfs particularly rich in sunspots, and is that why they are so active? I could google, but I'm too lazy.
But I found something else when I googled, namely a sunspots as seen in different wavelengths. And it is hugely interesting to compare a sunspot in visible light and in very near ultraviolet light:
[img3="A sunspot seen in the visible G band, 4305 Å." ]https://www.lmsal.com/solarsoft/hinode/movies/voevent_movies_sot/2007/04/30/20070430_0000_20070501_0000_prog_14/FG_G_band_4305_1024_1024_20070430_001456_j_micon.gif[/img3]
[img3="The same sunspot in the very near ultraviolet Ca II H line, 3968 Å. "]https://www.lmsal.com/solarsoft/hinode/movies/voevent_movies_sot/2007/04/30/20070430_0000_20070501_0000_prog_14/FG_Ca_II_H_line_1024_1024_20070430_001453_j_micon.gif[/img3]
The point here is that sunspots are indeed darker and cooler than their surroundings, but they are also brighter and hotter than the rest of the photosphere! But we don't see the bright parts of the sunspots, because our eyes are quite insensitive to these very near ultraviolet wavelengths.
And it's all caused by magnetism. 🥱 Sorry! I'll leave that to the rest of you to discuss.
[quote]APOD Robot wrote:
When impacting Earth's upper atmosphere, these particles can produce beautiful auroras, with some auroras already being reported unusually far south.[/quote]
Yes. Last night, auroras could be seen over my hometown of Malmö.
[img3="An aurora over my hometown of Malmö, on the night between the 10th and the 11th of May, 2024. Credit: Gunilla Hartsmar"]https://static.bonniernews.se/bildix/api/images/384dd98e-593d-44b1-a2b0-04150cdfd163.jpeg?fit=crop&w=960&h=1329[/img3]
Did I see this aurora? Heck no. I was fast asleep.
Ann