How Special is Our Solar System – July 2018
How Special is Our Solar System – July 2018

How Special is Our Solar System – July 2018

I’m going to jump right in here and say that before the talk began I thought about the title and decided ~ yes, it was! Was I going to be right on the night was worth the wait to find out?

Our speaker on the topic, Dhara Patel, is the Royal Observatory Greenwich Astronomy Education Officer, and it was clear from the start that Dhara is a communicator, with a punchy, enthusiastic style that makes you want to listen.

There was a slight downside to the presentation and that was that some of the animations on the presentation did not run well. However, I’ll put my hand up here to the mistake. We ran the presentation off the USB when we probably should have downloaded it, then run it. My computer, I was assisting her to present it properly and I didn’t; so my apologies to Dhara and to you all.

The good side was that this didn’t really make a difference as Dhara was little fazed and just described what we should be seeing and there were plenty of other PowerPoint slides to help out?

Dhara began by taking us through how our own solar system likely formed, a look at our Sun and then on to our Milky Way galaxy. This ran into how our planets formed and the impact of how the changing orbits of the major planets, Jupiter in particular, influenced how the other planets formed and settled into their current order. Why was Mars smaller than it should be ~ Jupiter again! Earth’s atmosphere certainly makes us special in the Solar System and is important for habitability.
This led us into the search for exoplanets (by definition, a planet which orbits a star outside the Solar System) which is now a major source of interest and scientific investigation. Are we alone as planets around a star? Certainly not from the number of exoplanets which have been found ~ 3,726 confirmed so far. Dhara took us through the range of sizes and orbits ~ many much larger, at least 40 like Neptune, with many of ‘Super Earth’ size.

There are a number of ways of finding these exoplanets ~ Light Dip, Radial Velocity, Micro-Lensing, Coronarography, Astrometry and Pulsar Timing being some of them. Dhara explained each method briefly and then took us through some of the protoplanetary discs found with Hubble.

Dhara reported many of the found exoplanets much closer in to their host star with many being uninhabitable. Star system ‘Trappist 1’ was interesting as it looks similar to our Solar System but all the planets are much closer to the star as it is cooler. But, it seems, many stars have only one exoplanet.

Does an Earth like exoplanet exist? Well, of some 150,000 stars found, 42 were Sun like with 603 exoplanets possible but only 10 were found to be ‘Earth like’; although this is a tenuous definition as these exoplanets are a long, long way away and scientific accuracy on the viability of these exoplanets is minimal at the moment.

Although some exoplanets have a relatively high ‘Earth Similarity Index’ number [a proposed characterization of how similar these exoplanets are to Earth], such as Kepler 438b with 0.88 and Ross 182b with 0.86 (the scale is zero to 1, with 1 being Earth like), under current standards, these results are VERY wide and, very importantly, give no indication of habitability. Also, the current methods to discover exoplanets are not yet able to discern planets of Earth size but only those much larger. Many of these are gaseous or simply not conducive to anything like human life.

So, is our Solar System special ~ well, probably yes! Of those found, the solar systems currently containing discovered exoplanets are widely different to our own with certain aspects of the history of our Solar System probably being unique; such as that part played by Jupiter (again) in the history of the current planetary positions.

Clearly, this is early days in the discovery of exoplanets science and a number of space telescopes have yet to be launched which will substantially enhance the accuracy of the exoplanet discoveries. We’ll look forward to a follow up from Dhara in due course on their progress.

Hugh Alford ~ Vice-Chair