This week at BEA the topic under discussion was stellar evolution. After a brief discussion of why stars twinkle, we moved onto how astronomers measure the properties of stars (temperature and luminosity) before taking a look at the most important diagram in astrophysics: the Hertzsprung Russell diagram.
Then it was a brief tour of how stars shine; the competition between gravity and pressure which keeps a star in hydrostatic equilibrium during life on the Main Sequence of the HR diagram.
Finally we looked at stellar evolution for low mass and high mass stars. Low mass stars such as the Sun are destined to end up as white dwarf stars. High mass stars are heading for supernova and a more violent end.
Lecture notes can be downloaded here. (Warning: big powerpoint file; 19MB).
Wishing you clear skies!
The first session of my astronomy course went ahead at Berwick Educational Association this morning. I had some pretty bad technical issues right before the session, so I'm not able to post a Powerpoint right now.
However, much of what I discussed in the first part of the presentation - the history of geocentric and heliocentric theories, leading up to Kepler's laws and beyond - is covered in this earlier post.
The second part of my talk was a whistle-stop tour of the major planets and moons in the solar system. For an overview of the things I talked about in this part - visit the Nine Planets website (another casualty of Pluto's demotion from planethood!)
There wasn't time to show this video but I would have liked to given a bit more time (or less talking from me):
It's a scale model of the solar system constructed in the desert. You get a sense of not only how big and empty the solar system is but also how tiny the planets are in comparison to the distances between them!
Also in this session we had a brief discussion about the definition of a planet. All of these discussions in the astronomical community were brought about by astronomers figuring out the layout of the solar system in the past couple of centuries. Recent discoveries of Pluto-sized objects beyond Neptune finally brought the situation to a head in 2006. You can read some of the background to this in my presentation about Pluto here (warning: big PDF!)
The very last thing we looked at was the great gathering of the planets taking place in the morning sky this month. Here are how the planets are arranged this week.
Venus is the brightest - by some margin! Jupiter is the next brightest. It's quite close to Mars - not so bright and definitely orange in colour. The moon will be close to Mercury on Sunday morning. Mercury will be the most difficult planet to see because it's low near the horizon.
Dr Adrian Jannetta
Guitar strummin' explorer of the universe. Mild mannered maths teacher by day and astronomer by night.