For the second time, Wycombe Astronomical Society held a lecture evening by Zoom – this time to welcome the return of Colin Stuart. His subject was the Sun, what we have learned about it from the time of Galileo onwards and just how much we still don’t understand, and really need to, because our modern world is very vulnerable to the extremes of unpredictable solar storms.
He covered the early work of Galileo on sunspots, Fraunhofer’s spectroscopy discoveries and Williamina Fleming’s designation system of stars. More recent knowledge comes from the Solar & Heliospheric Observatory (SOHO), which has been running continuously since 1995 to study the Sun from its deep core to the outer corona and the solar wind.
The Sun generates its energy by nuclear fusion of hydrogen nuclei into helium. In its core, every second the Sun fuses 620 million metric tons of hydrogen and makes 606 million metric tons of helium. And the “missing” 14 million tons? Well that’s sunlight. Interestingly whilst it takes 8 minutes for light to travel from the surface of the Sun to reach Earth, it’s a much slower process inside the Sun – indeed it is estimated that it takes 170,000 years for light generated in the centre of the Sun to escape to the surface.
But light is not the only thing produced by the Sun – also magnetism. Understanding this has allowed us to understand sunspots and solar flares. Sunspots are areas that appear dark because they are cooler than other parts of the Sun's surface. Solar flares are a sudden explosion of energy caused by tangling, crossing or reorganizing of magnetic field lines near sunspots.
And it is to understand (and possibly to better predict) these processes that ESA and NASA have sent the Solar Orbiter to the Sun. In fact today (16th July 2020) the first images from this orbiter are due to be released! Colin’s lecture took its title from a book he wrote about the Sun. As a new era of solar exploration dawns, “Rebel Star” takes an illuminating look at what we know so far and the vital mysteries still to be revealed about the powerhouse at the heart of our solar system.
If you were unable to join the meeting by Zoom, the lecture was recorded is available from a special Meeting Recordings page for a limited time. It is a password protected so users will need to enter a password to view it.
Sandy Giles
Find out more about Colin at https://www.colinstuart.net