Transcript

NSTRUCTOR:

Well, the clouds have rolled in here on the Tenerife mountainside, so we've moved indoors for the moment. As we've seen from the Hertzsprung-Russell diagram, stellar evolution is generally a fairly slow process. Most stars spend a significant portion of their time on the main sequence, where their output is relatively stable. Our own sun is on the main sequence at the moment. And that's probably just as well for life here on Earth.

In other phases of a star's lifetime, things can change on much shorter timescales. And many professional and amateur astronomers are drawn to studying variable stars whose brightness varies on a regular basis. We’ve already mentioned the instability strip on the HR diagram, and we'll find that this is where pulsating stars vary their output as they expand and contract. This type of variability can be used for measuring interstellar distances or for mapping the scale of the galaxy.

Another type of variability is where one object passes in front of another, as with orbiting binary stars. And in recent years, exciting developments have enabled us to detect ever smaller changes, which leads us directly to the search for planets beyond our own solar system, which we'll find out more about this week.