The sun wakes again

January 31, 2010


The astronomy department of the University of Amsterdam recently moved to a new building which will eventually house all science research of the UvA. One of the best things out of this is that the institute now has two brand new telescopes for educational purposes, one of which for looking at the sun. Last Monday the astronomy professor in charge of the two observation domes finished mounting the solar telescope and I took some pictures with my mobile phone of the image that it projects (it took me a while to get them off the phone and on the computer, I had some troubles with the Bluetooth settings of the phone)

The pictures show the image from the telescope as it is projected on a white screen mounted directly behind the telescope, taken on January 22nd. The white spot is the sun shining directly on the screen, the grey / yellow disc is the projection. The blurry edge around the disc is caused by the atmosphere in Amsterdam. The little black dot and the baby dots on the right in the disc are sunspots – the only visible sunspots on the entire sun! The professor was ecstatic that there was at least one proper sunspot, for he had set up an elaborate astronomy class elsewhere a week before and the students ended up disappointed because there wasn’t a single sunspot to be seen.

The sun has been extraordinarily quiescent the past years, even beyond the normal solar cycle. Which may be boring for astronomers, but from the perspective of climate science has been a relief. Although not much of a relief, for the past decade nevertheless still is the warmest decade on record. This record is likely to be broken by the following decade as the sun becomes active again. To quote p. 37 of my copy of The New Solar system (4th edition) which I bought approximately one solar cycle ago for an introductory astronomy class:

The sun becomes brighter overall as the number of sunspots on its surface increases, and vice versa. This seems counterintuitive, since sunspots are cooler than their surroundings. However, the sunspot cycle is accompanied by variations in magnetic activity, which create an increase in luminous output that exceeds the cooling effects of sunspots. Indeed, the entire spectrum of the Sun’s radiation varies in step with the 11-year cycle of solar magnetic activity.