September 27, 2014

ANU-ASTRO2x Exoplanets

Tags: EdX, MOOC, Astronomy

The previous astronomy MOOC I completed, ANU-ASTRO1x Greatest Unsolved Mysteries of the Universe, was merely the first of a series. In total, the 4 courses in the series supposedly comprise the first year course in astronomy at the Australian National University. I just completed the second course of the series, ANU-ASTRO2x Exoplanets.

Exoplanets is a 9-week course on the science behind detecting planets beyond our solar system. The format is the same as the previous 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 again based on a “mystery” universe, so prior knowledge of exoplanets (or wikipedia) won’t help - students just have to do the maths themselves. 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).

As for difficulty, this course is easy. Easier than the previous ANU course. Basic algebra is all the maths ability required. No assignment took me more than 30 minutes, most took much less. I read an article suggesting that the “MOOC revolution” is failing for many reasons, one of which is that the courses are getting easier and certainly are no where near as testing as the original university courses. I can’t help but think that must be true for this course. The material is interesting, but I would find it hard to believe that first year science students at a respected university like ANU (one of the top tier universities in Australia) are gifted with such an easy course where a mark of 100% can be obtained with barely an hour of work each week.

Starting with the first exoplanet discovered, surprisingly around a pulsar, the course goes through the methods used to find exoplanets. The pulsar planet was found through reflex motion - a wiggle in a star’s movement caused by a planet’s mass. Most exoplanets have been found through transits, that is the periodic dimming of a star as a planet passes between it and us. It is also possible to find exoplanets with gravitational micro-lensing, which is when a planet passes in front of a star and focuses its light on us. This method is has the benefit of finding planets that are not orbiting stars but are instead free floating. The downside is that such planets can only be observed once (as they pass the star). Still, the number of discovered micro-lensing events suggests there are a large number of such free-floating planets in existence. Lastly it is becoming possible to directly observe exoplanets with modern adaptive optics technology applied to telescopes. The course also addresses what is known about the exoplanets discovered - calculating their mass, temperature and thus the composition of both their atmosphere and surface.

An easy and interesting discussion of the current state of detecting exoplanets. However, the field of exoplanet detection is very active and fast moving. I’m not sure how quickly this course will age.