Space Weather: Solar Minimum is a Big Event

Our blank sun!

SPOTLESS SUNS: Yesterday, NASA announced that the sun has plunged into the deepest solar minimum in nearly a century. Sunspots have all but vanished and consequently the sun has become very quiet. In 2008, the sun had no spots 73% of the time, a 95-year low. In 2009, sunspots are even more scarce, with the "spotless rate" jumping to 87%. We are currently experiencing a stretch of 25 continuous days uninterrupted by sunspots--and there's no end in sight.

This is a big event, but it is not unprecedented. Similarly deep solar minima were common in the late-19th and early-20th centuries, and each time the sun recovered with a fairly robust solar maximum. That's probably what will happen in the present case, although no one can say for sure. This is the first deep solar minimum of the Space Age, and the first one we have been able to observe using modern technology. Is it like others of the past? Or does this solar minimum have its own unique characteristics that we will discover for the first time as the cycle unfolds? These questions are at the cutting edge of solar physics.

You can monitor the progress of solar minimum with a new "Spotless Days Counter" on spaceweather.com. Instead of counting sunspots, we're counting no sunspots. Daily updated totals tell you how many spotless days there have been in a row, in this year, and in the entire solar cycle. Comparisons to historical benchmarks put it all in perspective.

100 HOURS OF ASTRONOMY: This week, astronomers are celebrating the 400th anniversary of Galileo's original telescopic exploration of the sky with "100 Hours of Astronomy," a cornerstone project of the International Year of Astronomy. Running from April 2 through April 5, many different public programs are planned worldwide. Is one of them near you? Visit the 100 Hours web site to find out here. Note that the celebration ends on Sun Day, April 5th, a special date devoted to observations of the sun: http://solarastronomy2009.org/100-hours-sunday/ .


This is an exciting time in science. If you have a telescope, and your seeing is good, then join in the fun.