Hello, Earthlings!

Viewer discretion advised: Before you start any solar observing program, make absolutely certain that you have safe filters and a safe set-up!

Sunspotting can be quite the sport, very similar to bird-watching, in that there are different classifications of sunspots!

Before we learn how to name them, let's look at what are sunspots...

Sunspots are temporary phenomena on the Sun's photosphere that appear as dark spots (noticeable in a solar telescope). They are regions of "relatively cooler" surface temperatures caused by concentrations of convecting magnetic fields.

So why do we need a classification system? Well, sunspots tend to be all sorts of shapes and sizes! By learning about the classification, solar astronomers use this as a tool for understanding our Sun's magnetic field and solar cycles!

There are two main sunspot classification systems:

Modified Zurich Sunspot Class: A seven class (A-F, H) system of describing a sunspot group, mainly by the size of the group and distribution 

McIntosh Sunspot Classification System: Adds classes for the type of the largest sunspot and sunspot distribution to the Modified Zurich Class by this three-letter system. (For example, a small lone sunspot with a penumbra might be coded as Hsx. A very large complex group might be Fkc.) 

Here's the diagram that solar astronomer's use for classifying:


One this to notice about sunspots is that sometimes they'll have a halo effect called the "penumbra". The dark sunspot is called the umbra. 

Here is an example of a sunspot group with a penumbra effect:

Notice the lighter gray halo around the darker sunspots? That's the penumbra!

Notice the lighter gray halo around the darker sunspots? That's the penumbra!

Would you like to classify sunspots? Take a look at completing the Sunspotter Observing Program by the Astronomical League:

Thank you for reading and come back next week on a segment about Devon Island!


Caitlin Ahrens