A large audience turned out to hear an extremely well presented lecture by Prof Lucie Green about solar research and the impact the Sun has on conditions on Earth.
She started by summarising the achievements of the twelve instruments aboard the SOHO solar observatory which provided an uninterrupted view of the Sun for over two solar cycles between 1996 and 2013. A new subject of helioseismology emerged, allowing sounds from the Sun to be used to determine what is happening inside the Sun. Professor Green showed spectacular videos of solar activity including dramatic coronal mass ejections, and it became clear that the planets of the solar system are at the mercy of the Sun’s “atmosphere”.
SOHO’s success arose primarily from the position at which it was placed – namely between the Earth and the Sun, orbiting Lagrange Point L1, thereby affording an uninterrupted view of the Sun.
Lagrange Points, Prof Green explained, are points near two large bodies in orbit (for example the Sun and the Earth) where a smaller object (such as a space telescope) will largely maintain its position relative to the large orbiting bodies.
Lagrange points L1, L2 and L3, which are a little unstable, lie along the line connecting the two large masses. The more stable Lagrange points - L4 and L5 - form the apex of two equilateral triangles that have the large masses at their vertices. L4 leads the orbit of earth, L5 follows.
These Lagrange points potentially have uses. L2, for example, would be a great place to do astrophysics or comet science, with the Sun out of sight.
Prof Green concluded her talk with a discussion of Magnetic Flux Ropes. These are bundles of magnetic fields that are twisted about each other and wrap around a common axis. From above they form an S-shape but they are probably helical in nature. They are believed to constitute the key component of coronal mass ejections.
And this is why Lagrange Point L5 may hold a special place for space weather forecasting. The impact of space weather on the Earth is already clear: in 2003, for example, forty-seven satellites were temporarily blacked out because of solar activity, power outages affected many on Earth and there was some disruption to GPS. A weather station at L5 would allow us to see “round the corner” of the Sun to see what’s coming and could provide an early-warning system for adverse space weather.
Wycombe Astronomical Society was very privileged to have Prof Green as a guest speaker. Let’s hope it won’t be too long before we see her again!
Sandy Giles
