Week 5: The Sun and the stars

Introduction

In the first half of the course you familiarised yourself with the Stellarium software and started to learn your way around the night sky. You also discovered how telescopes work and how to use the magnitude scale for measuring and comparing the brightness of stars. And last week you took your first image with COAST.

Having used COAST to image some Messier objects, this second half of the course looks in more detail at the stars – how they work, what makes them shine and how they live out their life cycles. Over the next three weeks we will be looking at exactly what stars are, and the physics involved in producing their light and heat. You will also learn about how and why some stars vary over time and the implications of this behaviour. In the final week you will finish the course by making your own observations of variable stars.

This week starts with our own Sun, which is in fact a typical star. We won’t be imaging the Sun using COAST, but as you work through the next two or three weeks you can continue to use COAST to take further images of Messier objects and refine your images (as Alan explains):

Download this video clip.Video player: boc_aot_1_video_week5_intro.mp4

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Transcript

INSTRUCTOR:

By now, you'll have your first images back from Coast And we hope you're happy with them. Of course, we're not expecting them to look like this straightaway. And indeed it took me quite a lot of work to get this image of M27 that we looked at last time to get it looking like this, the way that I was completely happy with. There was quite a lot of repetition and experimentation involved until I got it to this stage.

There are certain adjustments you can make. So within Coast, you can adjust the contrast of your images. You can adjust the colour balance. And in a colour image, you can make adjustments of the alignment between the red, green, and blue frames to get the image looking the best that it can.

Now, you'll have the opportunity to go back and collect more images this week. And now you'll have the benefit of what you've learned from the images that you've already got. So you might want to try some different exposures. And you can use the images you already have to decide what exposures to use, maybe to decide which filters you want to try.

And what you'll find, just as I found in processing this image, is that each stage, as you use the information you've already got from the images you've already taken to repeat and refine and practise, that your images will get better and better, and they'll improve. So as you go through this week, keep taking images. Keep using what you've learned to improve them. And we'll look forward to seeing the results at the end of this week.

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By the end of this week you will be able to:

• describe the basic physical properties of the Sun
• describe the physical process that causes stars to shine
• compare our nearest star – the Sun – to other stars.