It’s an exciting time to be a planetary scientist. Not only are we sending nuclear robots to Mars, checking out truly alien worlds in our backyard and pushing the outer limits of the solar system, but we are for the first time getting a glimpse at the number of potentially habitable planets.
Last month, astronomers announced that three Earth-like planets were found around star Gliese 667C, part of the Gliese 667 triple star system. Well, Earth-like might be a bit of a misnomer. The newly discovered planets appear to be rocky or watery, but are between four and eight times the mass of the Earth, a fact that earned them their title: Super-Earths. What is significant about these planets is that they are in their star’s habitable zone, which is basically the space in the orbit of a star where a planet can support liquid water.
We’ve been finding more and more of these extrasolar planets lately, thanks in large part to the now dead Kepler space observatory, which as of last month had discovered over 3,200 candidates for alien worlds. Kepler finds these planets by looking for transits, which is when a planet passes in front of the star. When a transit occurs, the brightness of the star goes down a tiny bit. Kepler measures those decreases, and when it finds one, voila: we have a possible alien planet.
However, these three new extoplanets were found using a different method. The method the researchers used is called the radial velocity method. Using this method, researchers look for the star to wobble slightly because, if a planet is there, its gravity will effect the star.
This is exciting stuff, but when we talk about potentially habitable planets, we need to put a big emphasis on “potential.” We don’t really know anything about these planets other than they exist and are rocky. We don’t know what the atmospheres of these planets are composed of. Frankly, we don’t even know what kind of life to look for. We know what has worked on Earth. We know that everything here needs water to survive. But one data point does not a trend make. It could be that any liquid would do. We have ideas, but we don’t know anything for sure.
I don’t mean to rain on the parade. Planetary scientists are doing amazing work. For thousands of years we thought that we — humans, Earthlings — held a special place in the universe. For a long time, we basically thought we were the universe. We know now that we aren’t.
Our planet, other than it being the only planet that we know of with life on it, is unspectacular. We’ve found dozens of rocky worlds similar to Earth; there are three in this Gliese system alone. But you know what is spectacular? We can sit on our tiny planet and see planets dozens and hundreds of light years away using methods we’ve developed with our big brains and ingenuity.
For me, that’s the takeaway from this. Sure, we’re narrowing down the areas at which we can look for potential life, which if we find it has the potential to change everything. But there is also a poetic beauty to this whole endeavor outside of the science.
Whenever I hear about the discovery of a new planet, I feel incredibly special and painfully insignificant, all at the same time — special because I am a member of a species that, through a quirk of chemistry millions of years ago, has managed to break free from the Earth’s surface to explore new worlds; insignificant because, with every new planet found, I realize a little more vividly how big the universe is compared to everything I love. It’s an exhilarating feeling. It intensifies the feeling of being alive and human and I look forward to more opportunities to feel that way.
Photo Credit: European Southern Observatory