On Wednesday NASA made headlines by announcing that researchers had detected seven exoplanets orbiting a dim dwarf star. These exoplanets are determined, based on measurements, to be approximately Earth-sized solid planets and three happen to fall in the “Goldilocks Zone” where water could exist in liquid form; not too hot, not too cold. Lots of people started speculating that in a few years we’ll find out if one of those planets harbors life. However that is just plain crazy-talk. The importance of this discover is that complex exoplanet systems do exist; the Solar System is not an exception, and that life is also not an exception.
The TRAPPIST-1 system contains a total of seven planets, all around the size of Earth. Three of them — TRAPPIST-1e, f and g — dwell in their star’s so-called “habitable zone.” [NASA/JPL]
0.60m Ritchey-Chrétien Reflector [TRAnsiting Planets and PlanetesImals Small Telescope–South / ESO]
The TRAnsiting Planets and PlanetesImals Small Telescope–South
made the discovery back in May 2016 of three exoplanets around the small star. But it was with the help of larger telescopes and the space-based Spitzer telescope that the count increased to seven and their orbits could be confirmed. What I find interesting is the initial discover was done by a relatively “small” 0.60m telescope. OK not your typical backyard astronomy gear, but scale that down by 1/3 and you have equivalent optics for about $3000. Add a mount and CCD and for $10,000 you could probably have your very own exoplanet hunter!
Back to the crazy-talk of finding life in this exoplanet system… Anyone who has studied the history and formation of the Solar System knows that there have been a series of unlikely events that have led to where we are today. Starting with the Sun, probably a 3rd generation star, where heavy elements like Calcium and Iron necessary for life as we know it were produced by previous stars and supernovas that used to exist in this spot of the galaxy we now occupy. All elements beyond Hydrogen are produced by stars, either through fusion or when they dramatically explode as supernovas. The atoms making up the air, the trees, the oceans, ourselves were not created in our Solar System during its formation. The Sun is currently only generating Helium and Lithium out of Hydrogen through the wonders of fusion. All the heavier atoms within us were created by previous stars that no longer exist. Hence for solid Earth-like exoplanets to exists there needs to have been one to two previous generation of stars in the region.
An alien race observing our Solar System would surely first spot Jupiter. One could almost say that it characterizes our home in this part of the galaxy. With its strong gravity this gas giant plays the vital role of neighborhood vacuum cleaner. It is either mopping up or launching away asteroids and comets that would otherwise impact Earth, bringing relative calm to the inner Solar System. If Earth was constantly bombarded by solar objects, there is no way that life could suitably evolve from slimy unicellular organisms. It took 3 billion years for multi-cellular organisms to show up once life appeared on Earth. If cataclysmic comet and asteroid impacts are a frequent occurrences, then there is little chance that complex organisms would come to be.
Looking at another element, TRAPPIST-1 is described as an ultra-cool dwarf star just shy of 40 light years from Earth in the constellation Aquarius. If we forget that it’s a fraction of our Sun’s size and brightness (hence heat generation), it is relatively young at 1 billion years old. So while there may be three planets that could be habitable, life may not have even begun yet. Our own Sun is 4.3 billion years old, and the animals we see around us have only been around for the last 14-16 million years. So what could be in a 1 billion year old planetary system? Assuming all the ingredients are there for life to exist, you probably only have bacterial soup.
Now, my article was getting long, and I wanted to cover many more subjects, too many for a single article. Hence I’ve decided to break them out into the EXOPLANET SERIES and will publish them over time.