Astronomy is often referred to as the most intellectually humbling academic subject. When you study astronomy you are confronted with scale, size, and time that is completely alien to the human mind. We evolved to understand spatial scales of kilometers, not light-years, and to understand temporal scales of decades, not billions of years.
Despite this, it is always important to contextualize the human experience with astronomical knowledge. And last year was a year of particularly insightful discoveries relevant to understanding our species place within the universe. In 2012, astronomers discovered: a) the first earth-sized planets, b) an earth-sized planet in the nearest star system to earth, and c) the first earth-sized planet within the habitable zone of its parents star. These discoveries represent major milestones in the development of human knowledge. They allow us to better-contextualize our planets relationship to the rest of the universe.
To me, these discoveries provide the first empirical evidence that earth-like planets are likely very common in the Milky Way galaxy (and probably in most other galaxies as well). As soon as astronomers had the technology and methods developed to detect planets as small as earth, they started detecting them. In the coming years I expect that we will become overwhelmed with headlines similar to: “another earth-like planet detected.”
Interestingly, a paper accepted yesterday in the Astrophysical Journal Letters provided a statistical analysis indicating that we should find some of those earth-like planets in our cosmic neighbourhood. Ravi Kopparapu, lead author of the study claims: “we now estimate that if we were to look at 10 of the nearest small stars we would find about four potentially habitable planets, give or take. That is a conservation estimate.” Since there are eight M-stars (small stars) within 10 light-years of Earth, we should conservatively expect to find three Earth-sized planets in the habitable zones of their parent star.
For me, these estimates are very surprising. Last decade we had no data on likely frequency of earth-like planets and relatively little data on frequency of exoplanets. I was someone who thought exoplanets would be very common (which they are), but I thought earth-like planets would be relatively rare. But it looks like that guess was off. And if current estimates are accurate, and there are three Earth-like planets within 10 light-years of Earth, we should expect some BIG discoveries in the next two decades.
Why? Because of the launch of the James Webb Space Telescope (JWST).
I remember a few years ago I went to a special presentation at McMaster University with my granddad and a friend about the first image ever recorded of an exoplanet. I was excited, but I knew before the presentation started that what we were going to be observing would be a grainy pixel on a dark black screen. Even our best telescopes are very poor at directly detecting exoplanets (which is why all exoplanet discoveries are made indirectly by either a) detecting the light they bend when they cross their parent star(s) or b) their gravitation effects on their parent star(s)).
However, when the JWST (successor to the Hubble Space Telescope) is launched in 2018, we will be able to directly detect exoplanets within 25 light-years of our star system. This means that if Kopparapu and others are correct we are going to be able to see images of other earth-like planets in the 2020s.
I’ll let that thought sink in a little bit.
But wait! It gets better. The JWST can also determine the chemical composition of planets. This means that not only will we get detailed images of other Earth-like planets soon but also we will likely be able to tell if those planets are home to life. This is because life creates, transforms, and regulates the biosphere, radically altering a planets chemical composition. Obviously we will not be able to identify species and get specific biological information, but we would likely be able to tell if they were carbon-based life forms that depended on oxygen and hydrogen for survival (for example).
If this doesn’t get you interested in scientific discovery and the future of human understanding, I don’t know what will. The discoveries of the past two years in astronomy definitely help us conceptualize our place within the Milky Way. However, these discoveries make me even more excited for what is just around the corner. We are on the technological edge of making the most profound discoveries in the history of science: finding another earth. And if you think about how much seeing a picture of our planet from space did to our understanding of life and our place within the universe, just wait until you see another Earth.