Watch the Sun rotate for over a month brought to you by SDO. Since the Sun rotates once every 27 days on average, this movie presents more than an entire solar rotation. From March 30 through Apr. 29, 2011, the Sun sported quite a few active regions and magnetic loops. The movie shows the Sun in the 171 Angstrom wavelength of extreme ultraviolet light (capturing ionized iron heated to about 600,000 degrees), color coded to appear gold. The movie is based on a frame taken every 15 minutes being shown at 24 frames per second, with very few data gaps in this almost two-minute movie. Source Solar Dynamics Observatory
Another fresh reminder we owe our existence to the sun along with the climate in which we evolved and adapted. The Forbes article is Early Sun’s ‘Goldilocks’ Rotation Rate May Be Why We’re Here Excerpts in italics with my bolds.
Our early Sun’s rate of rotation may be one reason we’re here to talk about it, astrobiologists now say. The key likely lies in the fact that between the first hundred million to the first billion years of its life, our G-dwarf star likely had a ‘Goldilocks’ rotation rate; neither too slow nor too fast.
Instead, its hypothetical ‘intermediate’ few days rate of rotation guaranteed our Sun was active enough to rid our newly-formed Earth of its inhospitable, hydrogen-rich primary atmosphere. This would have enabled a more habitable, secondary atmosphere composed of nitrogen, carbon dioxide, hydrogen and oxygen to eventually form.
If it had been a ‘fast’ (less than one day rotator), our Sun might have continually stripped our young planet of its secondary atmosphere as well. However, if it took more than 10 days to rotate, it might not have been active enough to strip Earth of its hypothetical primary atmosphere.
Such ideas were recently bandied about in oral presentations at last month’s the General Assembly of the International Astronomical Union (IAU) in Vienna.
Earth’s very first atmosphere would have been too hot and too thick, more like Venus’ present-day atmosphere, Theresa Luftinger, an astrophysicist at the University of Vienna, told me. No known organisms could have evolved under such an atmosphere. A secondary atmosphere cannot evolve in the presence of a primordial atmosphere , says Luftinger.
It’s the star’s magnetic dynamo that drives its magnetic fields. And these magnetic fields, in turn, interact with the star itself, creating an interplay of extreme stellar activity.
“So, the quicker the star rotates, the higher the interaction between the magnetic field and the stellar body ,” said Luftinger.
Faster rotation means higher extreme ultra-violet and x-ray activity, Helmut Lammer, an astrophysicist at Austria’s Space Science Institute in Graz, told me. This would lead to atmospheric stripping and water loss on earthlike planets around an active young star, he says.
Our Sun is now a very slow rotator at 27 days. But that wasn’t always the case. As for why some stars seem to inherently rotate faster than others?
Astrophysicists suspect that initial conditions within star-forming clouds cause newborn stars to have different rotation rates.
Researchers are able to roughly pinpoint the Sun’s early rotation rates by studying the isotopic ratios of neon, argon, potassium, and uranium here in Earth’s crust. That is, elements which have atoms that have the same numbers of protons in their atomic nucleus, but different numbers of neutrons. The researchers also considered such isotopic ratios from decades’-old Venus surface samples taken by Soviet Venus lander missions.