17 September 2010

Are Sunspots Disappearing? New Paper Rocks Solar Physics World!

Posted by Dan Satterfield

The Sun today 17 September. Three sunspots are visible in the lower half of the image. Could we be seeing no sunspots at all soon? Read on.. (IMAGE FROM NASA SDO)

Two scientists at the National Solar Observatory in Tuscon, Arizona have published a paper that has literally rocked the world of solar physics.

Their paper says that sunspots may disappear from the sun by 2016 and stay gone for decades!


This has actually happened before. From 1645 to about 1715 there were virtually no sunspots seen on the sun. This period is called the Maunder Minimum and it also happens to be a period of unusually cool weather on Earth.

It might seem at first glance that sunspots would mean the Earth gets less solar radiation since a part of the sun is black instead of bright white. In reality, an active sun with sunspots is putting out more energy than a quiet spot free sun. It’s quite likely that the chilly years of 1645 to 1715 are at least in part related to the quiet sun.

Along come Matt Penn and Bill Livingston. They looked at the magnetic field around sunspots using a technique that involves something called Zeeman Splitting. The magnetic field of the sunspots causes the spectral lines of iron atoms to split when looked at in a spectograph. The wider the lines are apart, the more intense the magnetic field.

Declining magnetic field on the sun. From Penn and Livingston's paper. Image ctsy NASA Sci. Now.

Penn and Livingston’s data shows the magnetism is declining and if you extrapolate into the future, the magnetism drops to a point where there will be no sunspots by 2016.

This would be a BIG deal.


Now before you run screaming into the streets, you should know that the authors of the paper themselves have serious doubts about whether a new Maunder Minimum is about to start. The time period of their data is just 17 years. They very well could be just seeing a normal downward trend that will start back up soon.

NASA has one of the world’s top experts on solar physics right here in Huntsville. His name is David Hathaway. I’ve emailed him with some questions but I suspect his inbox is full of similar questions from every corner of the globe!

Hathaway IS quoted in NASA Science News as saying “The drop in magnetic fields could be a normal aspect of the solar cycle and not a sign that sunspots are permanently vanishing.” He also adds “the sun is behaving in an interesting way and I believe we’re about to learn something new.”

Scientists had expected the new solar cycle to be well underway now, but the sun remains very quiet.

The solar cycles are numbered and the one that everyone is waiting to start will be cycle 25. No doubt about it, it is way overdue.


You might be wondering by the way if a new Maunder Minimum would cancel out the effects of increasing greenhouse gases.

The answer is no.

Dr. James Hansen did the math and says that even a new maunder event would be cancelled out within 7  years by the rising greenhouse gases. It would slow the warming temporarily though…

One last thing. I just wrote a blog about something really interesting in astronomy before Phil Plait on BAD ASTRONOMY.