December 14, 2014

ANU-ASTRO3x The Violent Universe

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The series of introductory astronomy courses from ANU at EdX continues with ANU-ASTRO3x The Violent Universe, covering high-energy events and the remnants of stellar explosions. The structure of the course is exactly the same as Part 1 on Great Unsolved Mysteries and Part 2 on Exoplanets. It is a 9-week course with about an hour per week of video lectures. There are also mini-tests and a homework assignment each week with a final exam. The exam is based on a “mystery” universe nullifying real-world knowledge and forcing the student to fall back on basic principles. The lectures are almost a conversational back-and-forth between the presenters Paul Francis and Brian Schmidt (with pictures and notes appearing projected behind them).

The course starts by looking at Sirius B. In the 1800’s it was determined that Sirius (the brightest star in the sky) was wobbling and must be orbiting another small body with a mass about the same of our Sun. This led to the discovery of white dwarf stars. These stars are about as heavy as the Sun, but only as large as the Earth. They also have a tendency to accrete disks of matter from any larger and less dense companions. This in turn can result in dwarf novae, where instability in the accretion disc causes a burst of energy; and, classical novae when hydrogen from the disc builds up on the white dwarf, eventually exploding. White dwarves can also cause the much large type Ia supernovae, where enough material accretes on the white dwarf to start carbon fusion and a runaway thermonuclear explosion. Other types of supernovae result from large stars (much larger than our Sun) reaching the end of their life and exploding after their core collapses. The remnant of such an event is a neutron star or maybe even a black hole.

The difficulty level of these courses only seems to decrease. It is now so easy I didn’t feel there was any value in spending the time to complete the assessments – just watching the videos seemed enough. The lectures still run through the basic maths at the algebraic level (no calculus), but the assignment is often a multiple choice question or much simpler maths question.

Entertaining and informative videos, not sure about the value of the assessment and resulting certification.


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