♪ The Sun has got its spots on … ♫

It has been a whole year since I last posted. I’m sure that this is in part one of many diverse legacies of SARS-COV2, but it’s also related to the fact that my primary focus for the blog was always to reflect on living life as a scientist.* I have in the meantime continued to write about topics in science elsewhere: using my u3a local branch’s social media group example. However, the point is that I intended only to write on this blog as and when my week involved me in rolling up my metaphorical scientists’ sleeves and getting directly involved. You can perhaps see where this is headed …

Last week I visited Year 5 of The Churchill School; one of the two classes is taught by my talented daughter-in-law, and it was she who invited me. I’ve been to the school many times before, but less often as a visiting scientist (e.g. here). I freely confess that school classrooms unnerve me. I (mostly) loved school when I was part of the whole thing as a child and I have the deepest of respect for excellent teachers like my daughter-in-law. However, nowadays, the thought of standing in front of a class of children – let alone two 30+ classes combined – with the aim of leading them into some new knowledge and understanding renders me a little weak at the knees. It was truly lovely, then, to get a warm welcome by the four staff members involved – but it was the eagerness of the 9/10 year-olds that completely blew me away.

I turned up while they were still in a school assembly so that I could get everything set up in peace. I had brought with me my newly acquired second-hand 72 mm refractor, the lightest of my two equatorial mounts and a tray of bits and pieces which included a homemade solar filter. The neutral filter material, which removes 99.999% of the incident light, is of the highest standard, but I can’t say the same thing about the cardboard and duct tape assembly that holds it in place in front of the telescope’s objective lens. In order for the equatorial mount’s tiny battery-driven motors to keep the telescope pointing towards the Sun over time, it has to be tilted to the correct latitude, levelled and compass-aligned. The telescope itself also needs to be balanced (both front to back and side to side). Once the Sun had been located and its image focused I have to say that I was more than relieved to see several sunspot clusters clearly visible; passing clouds were, as ever, less predictable. (By the way, the images taken at the school were carefully checked by them before they were released for my use; faces have been covered/blurred as necessary.)

I was given a generous introduction inside the school before we all trooped out to the school’s expansive playing field and the children sat in a semi-circle on the summer-dry grass. I kept my own introduction to the telescope very simple; no-one needed to know about focal lengths and lenses in order to observe the Sun. What did need to be shared at the outset though was the standard but ever-vital warning not to look directly at the Sun for fear of damaging the eyes. In this instance it was important to go much further, making the point that looking at the Sun through binoculars or a telescope is likely to cause blindness without the appropriate safety measures in place. You also have now been warned 😉

I had given them a rough idea where the sunspot clusters were by describing the Sun’s disk as a clock face: two and eight o’clock got them to the most obvious, although it was a busy day on the Sun and there was a lot to choose from. This is an image captured by a talented amateur astronomer, Roger Hyman ( find him here or here) on that same day; the image is used with his permission. The orientation isn’t exactly as we saw it – the angle of the camera he was using and other factors will affect that, but it’s close enough. All clusters of sunspots are given a unique identifying number and on Friday 15th July 2022 they were, beginning at the 2:30 position and moving clockwise: 3057, 3056, 3055 and 3053 (see here).

In between the slowly drifting clouds, everyone got a chance to look through the telescope – even the adults. All but a handful said they’d seen the sunspots: some after a bit of coaching in terms of how to use an eyepiece. It took a while, and given the need for a lot of patience they did astonishingly well.

Every time a cloud came over we used it as an opportunity for questions, which came thick and fast. Indeed, the flow of questions continued when everyone had had the opportunity to take a peek and we had moved back inside the building. These were exceptionally wide-ranging, and varied from the scientifically and philosophically challenging to the more speculative ‘what if’ (the Sun disappeared, you went into a black hole, …) and ‘would you’ (like to go into space, live on Mars, …) type of question. All of them deserved to be taken seriously and given the best response I could muster. I can only say that I was genuinely impressed; it was uplifting to see so much evidence of the potential on display within that classroom. A few of them were obviously highly clued up, and several made a point of telling me that they wanted to be a scientist. Perhaps what I should have said in response, but for some reason didn’t, is that in a sense they already were – just as much as I was at their age.

I was at the school for almost 2½ hours in total, although it felt far briefer than that.

I promised this blog post in order to provide a reminder of what we did, and to offer a little information in a more coherent way than I fear I managed on the day. Perhaps one might start by saying that sunspots are associated with a localised increase in the Sun’s magnetic field. They appear darker than their surroundings simply because they are a little cooler, with their central region (the umbra) at about 3000-4000ºC compared to the average of 6000ºC. Their sizes vary a great deal, with the largest being several times the diameter of the Earth. (If you are able to see the above image of the Sun on a reasonably large screen then you might notice the small blue dot I inserted to the left hand side: that is approximately the size of the Earth on the same scale.) Sunspots can last for days, but eventually disappear. The number of sunspots visible at any one time varies over the eleven years of the solar activity cycle; we’ll be at the next maximum in this cycle in 2024. You can find lots more information here, here and here; a recent BBC ‘Sky at Night’ programme covered some of this ground also.

Perhaps a fitting way to close this post would be to offer a couple of suggestions for useful astronomy apps and to share a small number of my own images. The first app I downloaded when picking up after retiring the hobby of my youth (from Android Play Store) was ‘Sky Map’, which I still use as a simple interactive guide to the sky; for a little more sophistication one might go for ‘Stellarium’. The choice is yours. In addition, and especially if you want to pursue this further, I’d recommend joining your nearest amateur astronomy group. Unfortunately, the one I’m in – Ashford Amateur Astronomy Society – is an hour’s drive from my home; maybe there’s one closer to where you live.

The above were taken at different dates, through different telescopes and with different cameras. The result is that we have a fairly recent image of the whole disc of the Sun together with a more highly magnified image of one part of the solar disc, and a close-up of two particular sunspot clusters taken in 2021 which bring out a bit more detail in terms of their structure. You’ll notice that each sunspot comprises a dark central region (the umbra) and a somewhat bright outer region (the penumbra); as you might anticipate, the penumbra has a temperature which is intermediate between the umbra’s and the Sun’s average surface temperature.

Happy observing.


* I retired from my paid employment as an academic and multidisciplinary materials research team leader about seven years ago, but I’m still a scientist – just as I was as far back into childhood as I can remember; I’ve covered this ground in earlier posts (e.g. here).