The Solar and Heliospheric Observatory (aka SOHO) spacecraft is a joint mission between ESA and NASA. Launched in 1995 with a planned 2 year lifetime, it has now been operational for over 25 years. The Solar Dynamics Observatory (aka SDO) spacecraft is a NASA mission launched in 2010.

The NASA websites for the two observatories publish a massive amount of data, but of particular interest to amateur astronomers is the daily sunspots image which gives a indication of what to expect when solar observing/imaging. By chance one day I wondered if they left the images for previous days available for download and indeed they do, going back to early 2006. The early images are from the SOHO MDI instrument, but from March 2011 they switched source to publish from the SDO HMI instrument (notice the instrument name on the top of each image).

One of the many great things about NASA is that the majority of information and data they publish is free from copyright restrictions, allowing the opportunity to reuse and remix. With that in mind I downloaded the full set of published sunspot images dating back to 2006. I felt it could be interesting to see how the intensity and number of sunspots evolved over the course of the solar cycle, so I set about animating them into a video. A solar cycle is 11 years, so with 16 years of data we’re coming up to having 1 & 1/2 solar cycles worth of sunspot images. Out of 5750 images downloaded, I found that 60 had significant corruption/glitching/processing errors and needed to be discarded, but the rest made it into the video as-is.

For whirlwind tour of the data I encoded at 30 frames per second, giving an animation covering about 5 years per minute of running time.

For a more majestic tour of the data I then re-encoded at 5 frames, giving an animation covering about 1 year per minute of running time.

The National Oceanic and Atmospheric Administration website has a space weather section giving a graphic illustration of the solar cycles vs observed sunspots. From that we can see that the start of the video in 2006 coincides with a low point of the solar cycle and indeed there are not many sunspots visible initially. Things start to pick up significantly in 2011 though and the next 5 years of the video show a lot of activity before heading down into the next dip in the cycle. After experiencing a good few years with hardly any sunspots visible, as an amateur astronomer wishing to do some more sunspot imaging, it is pleasing to see activity picking up once again in 2021. It should be a good few years ahead of us now…