Dr. Jeff Hall
Dr. Jeff Hall Astronomer, Director, Lowell Observatory
There have been two longstanding programs in this area: one carried out at Mount Wilson Observatory starting in 1966, and then ours, which really got going in 1994. We've learned that other stars do have activity cycles like the sun's, that sometimes other stars stop cycling -- as the sun appears to do from time to time. Between about 1645 and 1715, a period known as the Maunder Minimum, the solar cycle pretty much ceased. And that coincides with a period of severe winters and regional climatic effects here on Earth.
Is that unique to the sun? Might the sun do it again? The stars can help give us that answer. It turns out that stars, indeed, stars like the sun do seem to cease cycles and go into periods of quiescence with about the frequency that we seem to observe in the solar record. What makes this area particularly interesting and timely right now is recent solar behavior suggests that it may well be going into a period of weaker or even near-absent cycles over the next several decades.
What might be the effects of such a change in solar behavior on climate? We don't know. That spurred climatologists to try to figure out as best they can, but the recent behavior of the sun does suggest we might be seeing a change from the way it's been cycling since about 1920.
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