Officials of the National Astronomical Observatory of Japan and the Riken research foundation said on April 19 that the activity of sunspots appeared to resemble a 70-year period in the 17th century. Known as the Maunder Minimum, temperatures are estimated to have been about 2.5 degrees lower than in the second half of the 20th century. The researchers also found signs of unusual magnetic changes in the sun. Normally, the sunâ(TM)s magnetic field flips about once every 11 years. The solar observation satellite Hinode found that the north pole of the sun had started flipping about a year earlier than expected, with no noticeable change in the south pole. It's possible the north pole could complete its flip in May 2012 but create a four-pole magnetic structure in the sun, with two new poles created in the vicinity of the equator of our closest star.