The Sun, the whole Sun and nothing but the Sun
Has it really been over four years since I watched the STEREO spacecraft rocket into the sky over Florida? The two spacecraft used lunar swing-bys to put them into Earth-like orbits, one drifting away ahead of the Earth and one behind, each retreating from the Earth at an angle (with respect to the Sun) of 22.5 degrees per year.
On Sunday February 6th 2011, just after 17:08 GMT the two spacecraft will have drifted to the point where they are on exactly opposite sides of the Sun from each other. This is a momentous moment as it will be the first time we have been able to see the entire Sun. All very interesting you may think, but why is that important? Well, it is true that the the Sun rotates just like a planet, taking around 27 days to complete one rotation so we could just wait for it to roll past. Unlike a planet however, the Sun is a continuously churning magnetic fluid that rotates at different rates at different locations. The up-shot of all this motion is that the magnetic fields get stretched, tangled and knotted, causing the vast eruptions that solar stormwatch has been designed to study. These magnetic fields connect different regions of the Sun and, while we have been able to image the Earth side of the Sun since the start of the space-age, we have never been able to image changes on the far side that may trigger eruptions towards Earth.
While the two STEREO spacecraft will image the whole sun for a fleeting moment, as they continue on their paths towards the far side of the Sun from the Earth, Earth-orbiting spacecraft like the Solar Dynamic Observatory will fill in the gap and allow at least 8 years of observations of the entire Sun.
It’s going to be a fascinating time and, by participating in Solar Stormwatch, you will be helping us to understand the complex and mysterious life of the Sun, which in turn will help us to understand the many millions of stars that adorn the night’s sky.
Thanks again for all your time, effort and enthusiasm.