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article imageLow solar outputs puzzling astronomers

By Paul Wallis     Apr 22, 2009 in Science
The Sun has entered a period of what seems to be relative inactivity. The usual 11-year cycle of activity isn’t repeating as usual. The solar wind is at a 50 year low, and radio emissions at a 55-year low, and 100-year low in sunspot activity.
This slowdown in solar activity isn’t the end of the world, but previous solar events, like the “Maunder Minimum” in the 17th century, led to the “mini Ice Age”. The Earth catches cold easily.
One thing that needs to be understood is that our Sun is what’s called a Yellow Dwarf, a G class star pretty much bang in the middle of the stellar range of sizes, colors and behaviors. The Sun is actually a pretty well behaved G class star. Some others in our neighborhood shoot out bolts of plasma which would incinerate any Earth like planets orbiting them, so we’re actually lucky to have a nice, stable, workaday gigantic nuclear fusion reactor to play with.
On the other hand there’s such a thing as too quiet. The Sun is in its late middle age. It has burned 70% of its hydrogen. The expected cycle for a star of this kind is that it starts burning helium, it expands, it contracts, it becomes a white dwarf surrounded by asteroids.
There’s some evidence to suggest the Sun is actually operating according to a longer cycle, a “solar oscillation” from high to low activity over centuries. It has just come through a peak energy cycle, and is now reducing its output. The evidence of this cycle has been found in tree rings and ice cores. The Sun’s slight dimming, as far as anyone knows at this point, won’t affect temperatures on Earth.
It’s not clear, nor is there a lot of verifiable information, about the possibility of any larger cycle of Solar behavior, or other causes, in relation to this reduction in the Sun’s activity. A repeat of the mini Ice Age isn’t being realistically suggested. Nor is there any evidence of external forces affecting the Sun, like gravity anomalies.
However- The 17th century, by astronomical standards, was two breaths ago. The Sun is on the way to entering its dotage, in terms of its life cycle.
I wrote a story some years ago on the subject of the Sun not waiting to burn the last hydrogen atom before starting to burn helium. Obviously, one of the basic questions was “How do you know when your friendly local star is about to turn feral?”
Answer: When it starts behaving abnormally.
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