Saturday 7 November 2020

Sunspot Activity in Solar Cycle 25

With the skies being cloudy at night for sometime now and, with the recent development of some decent solar activity, my thoughts turned to the sun this afternoon. I didn't give myself much time as it was rapidly going down behind the neighbouring houses, but I did manage to get a couple of shots of the current active region known as AR 2781

Sunspots are temporary solar phenomena which are regions of reduced surface temperature caused by concentrations of magnetic field flux that inhibit convection. They are darker than the surrounding areas and occur in a region called the photosphere. Whereas the photosphere has a temperature of 5,800 degrees Kelvin, sunspots have temperatures of about 3,800 degrees K. They look dark only in comparison with the brighter and hotter regions of the photosphere around them and they usually appear in pairs of opposite magnetic polarity as well as moving across the sun's surface.


The designation AR stands for Active Region and the sunspots shown in these photos are part of the current Solar Cycle 25. NASA had this to say on their website:

Solar Cycle 25 has begun. 

The Solar Cycle 25 Prediction Panel, an international group of experts co-sponsored by NASA and NOAA, announced that solar minimum occurred in December 2019, marking the start of a new solar cycle. Because our Sun is so variable, it can take months after the fact to declare this event. Scientists use sunspots to track solar cycle progress; the dark blotches on the Sun are associated with solar activity, often as the origins for giant explosions – such as solar flares or coronal mass ejections – which can spew light, energy, and solar material into space.

Here's a cropped version of the above photo to show the sunspots in a little more detail:


To take these shots I had to dig out the solar filter I made for the Transit of Mercury back in November 2019 when I began to take my interest in astronomy a lot more seriously. 

It's really important to never look at the sun without proper protection - this doesn't mean just wearing sunglasses or even using a welding mask.  It's very dangerous to look directly at the sun through binoculars, telescopes and cameras and solar filters are made of a very complex layered material which offers great protection.  Even then, I only ever view the sun by looking at an image on the back of my camera, never through the eyepiece.

The Baader AstroSolar Safety Film I used to make the filter renders the image as more or less white, and indeed, this is the true colour of the light coming from the sun.  The orange hues we see by eye are mainly due to dust in the atmosphere, although some specialised filters do give the images a deeper orange colour.  Here's a simulation of that created by simply increasing my camera's white balance control.

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