By News Editor Aislinn Cottell
Astronomers are over the moon about a recent announcement that brings humanity another step closer to answering the tantalizing question—are we alone in the universe?
Not too long ago, that inquiry may have been relegated to the tin-hat territory of X-Files fanatics. However, for the last decade, that question has become less of a spooky subject, particularly since the launch of the Keppler Spacecraft in 2009. Designed specifically to search for exoplanets—planets in star systems other than our own—the Keppler telescope was set to observe a single piece of sky near the constellation Cygnus. In only a few years, Keppler detected not a handful, but thousands of planetary systems in this small region of space.
The astounding success of Keppler illuminated an equally astounding fact: that planets in general are much more common than expected, with perhaps every star system sporting at least one.
“If you just look at the Milky Way, we have a hundred billion, to two hundred billion stars,” says Gregory Arkos, professor of Astronomy, Physics, and Engineering at VIU. “A crazy number—absolutely enormous number. Even if every one of those has a handful of planets, which seems likely, and if even a small fraction of those have rocky planets, and some of those rocky planets are in their habitable zones, even with small, small fractions—if one in ten has a rocky world, and one in a hundred of those is in the habitable zone, and one in however many of those has an atmosphere—what you end up with is non-trivial numbers of Earth-type worlds.”
The interesting thing is that the building blocks of life—organic molecules, minerals—have been found widely distributed throughout the universe. What we don’t know is how these elements come together to form the ‘spark’—a living organism that can evolve and reproduce on its own. We don’t know if it’s some miraculous set of circumstances, or a relatively common occurrence.
“If we could find at least a signature of life on one of these worlds, what that means is the potential is there that life could be everywhere,” says Arkos. “Then you flip the question—what is the likelihood that nothing would happen out there, given all those chances?”
Which brings us to today. On February 22, NASA announced the discovery of four new planets located within the constellation Aquarius, in a star system currently named TRAPPIST-1. The name comes from the Belgian TRAnsiting Planets and Planetesimals Small Telescope, located in Chile, which first discovered the system in 2010. These new worlds are, in fact, only the most recent addition to the TRAPPIST-1 family; they join three other previously discovered planets orbiting the same star.
Now, seven planets, you may scoff—what’s so special about that? Our system boasts a whopping eight (nine, according to some). Well, yes, but let out the gas from your ego balloon a little—because that’s all that most of our celestial siblings are: gas. In the TRAPPIST-1 system, on the other hand, every single one of the seven are terrestrial.
What?
Terrestrial. As in terra—earth. According to estimates of the planet densities, every single one of the TRAPPIST-1 seven are rocky planets, made out of solid minerals and metals: the first qualification for a world to support life as it exists on Earth. It’s the largest number of terrestrial planets ever found in a single system. We ourselves only have four—Earth, Mercury, Venus, and Mars.
And, that’s not all. Three of the TRAPPIST-1 seven have been calculated to be orbiting in what is known as the “habitable” or “goldilocks” zone—the range of space around a star in which conditions are “just right” to support the formation of liquid water. The three—all seven, in fact—are close in diameter to Earth, ranging between three quarters to one times our size, and masses ranging from only 50 – 150 percent of ours.
According to Arkos, the TRAPPIST-1 system is like a wish come true for astronomers, something akin to a celestial goldmine.
“It’s like you were looking for life here and there, and then someone hands you a solar system that not only might have habitable worlds, but a whole bunch, in one place.”
Now, before you get too excited, existence within the habitable zone is only the second in a long list of qualities a planet must have in order to support life as we know it. In our own solar system, Venus and Mars also exist within the zone, along with Earth, and both are, as far as we know, completely barren. There are already many differences between the TRAPPIST-1 seven and Earth.
One of the biggest differences is that the TRAPPIST-1 seven are “tidally locked”, meaning they don’t spin, and have a permanent day and night side. The side facing their sun would live in constant, scorching heat, whereas the side facing away would be in permanent icy darkness. The weather effects of these temperature extremes could possibly strip the planet of its water and collapse the atmosphere. Even if it didn’t, only around the equator is it theorized that a relatively balanced climate might exist, in a kind of perpetual twilight zone.
Life on a tidally locked world would have to be structured significantly different to that of Earth, but it’s still by no means impossible. Many forms of life have been found in extreme conditions that defy expectations of what is or isn’t “habitable”. For example, deep sea creatures live at extreme depths and pressures where no daylight reaches, conditions which might resemble the “dark side” of a tidally locked planet.
“It’s so easy to find life everywhere on Earth; you turn over a rock in Antarctica and you find life, you find water bears that can survive these incredible things. You can put them in a vacuum, irradiate them, and they still survive—if life can do that, I find it really hard to imagine that if the chance is there, that somewhere else, it wouldn’t at least have a chance.”
Even if the presence of life there is still debatable, the TRAPPIST-1 system is a significant find, largely because we can observe it so easily. If there is life, we are much more likely to find it there than we might in other places.
Part of the reason for this is its relative proximity. TRAPPIST-1 is only 39 light-years from Earth, so travelling at the speed of light it would take approximately 39 years to get there. Using current rocket technology, it would take around 11,250 years, but this is still much closer than many of the other exoplanet systems currently under study.
Secondly, the type of system is one of the best kinds for our instrumets to detect. The TRAPPIST-1 sun is a type of star known as a “red dwarf”, which are much smaller and dimmer than yellow dwarfs like our own sun. This star in particular is 12 times less massive than our sun and only slightly larger than Jupiter in size.
Red dwarf systems are valuable, research-wise, for a very simple reason—we can see them. Counterintuitively, perhaps, because red dwarfs burn at a much lower intensity and, therefore, give off much less light than other star types. However, the method that astronomers use to detect exoplanets is one that relies on both light and its absence. Called “transit photometry”, this method works by measuring the tiny change in light as a planet passes in front of its star. Consequently, for this to work the star needs to give off enough light that we can see it—but not too much light that it completely drowns out the small change caused by the transiting planet’s shadow.
As well as being easy to see, TRAPPIST-1 also has some very cool features. For one, the sun isn’t the only dwarf in the system. Although all seven planets are relatively close to Earth’s in size, the distance between them is much smaller than between us and our own planetary neighbours. In fact, the entire TRAPPIST-1 system is only 10 million km in length, and could fit easily within the 60 million km distance between Mercury and our own sun. The whole setup is actually closer in size to Jupiter and its moons than the entirety of our own far-flung family.
What this means is that for someone standing on one of the TRAPPIST-1 seven, the other planets could easily be seen with the naked eye, at two or three times the size of how the moon appears in our own sky. With a simple telescope, actual geological features could be observed. If life developed on one planet, it would be relatively easy for meteors to pass between them and populate the others. If intelligent life were achieved, interplanetary travel and/or colonization would be much easier than it is for us.
In addition, this cozy setup has resulted in an interesting effect on the planetary orbits. From our observations, the planets move in almost complete “resonance” with each other. That is, each of their orbits around their sun take a consistent fraction less time than the last. Astronomers theorize that this harmony resulted because the planetary bodies were so close when forming, and, with so many gravitational forces in play, they had a much higher chance and opportunity to ‘tug’ at each other and sync their orbits in the most favourable pattern.
Unfortunately, this closeness extends to the TRAPPIST-1 sun, as well—and that makes things a bit toasty, on a radioactive level. Because the star is a red dwarf, it can emit powerful bursts of X-ray and UV radiation, which could leave nearby planets too volatile to sustain life if their atmospheres aren’t thick enough to protect the surface below. An atmosphere like ours would be able to withstand the bursts, but it takes time for those gases to build up and, during that process, the close proximity to the star could cause this young atmosphere to be stripped away by violent solar flares.
However, there are other ways a planet could deal with the excess radiation. One possibility proposed is a world filled with corals, as here on Earth we know of some species which absorb UV light and emit it back at less harmful wavelengths. Another is that volcanic activity, resulting in high amounts of hydrogen gas in the atmosphere, could keep a colder planet warm. This could cause the habitable zone of a system to be ‘artificially’ extended to include planets further away from the volatile star.
Arkos reminds that our ideas of what is and isn’t possible can be limited by our experiences here on Earth. The red dwarf systems are the closest we can find to Earthlike conditions—what if there is life out there that doesn’t conform at all to our definitions?
“We’re limited by our imaginations and what we see on Earth, but life is very diverse here, and this is just one way of doing it. I think it would be very arrogant of us to assume that this is the only way to do it.”
Perhaps creatures have evolved in the swirling atmospheres of gas planets, or are not bound to planets at all, but somehow eke out an existence in the endless void between stars.
“I think that if, and when we, find life, it’ll be different from what we can imagine, it’ll be completely different—it won’t be some bulbous head, dangly armed creature. We are bound by what we see and know, and that’s maybe a very poor representation of what’s possible out there.”
At the moment, all we know is that life on the TRAPPIST-1 worlds is theoretically possible according to our rules.
As for detecting it, well, the SETI Institute used the Allen Telescope Array to scan the system for radio signals that might indicate the presence of artificial communication, but none have been so far detected—so we probably won’t be making first contact any time soon, at least not from that direction.
But the future is bright. Next year, NASA is launching the brand-new James Webb Telescope, which will be able to probe the seven using what are called “spectral techniques”. These rely on the way light from the system star interacts with certain molecules in the planet atmospheres, which then give off signals that astronomers can detect and identify—specifically, certain “fingerprint” molecules that would indicate life, or the possibility of life, such as oxygen or methane. If those are found, the probability of life existing there would increase significantly.
It may be on the TRAPPIST-1 seven, or in some other system, in a year, a decade, or a century, but as our technology advances, Arkos says the statistics for finding extraterrestrial life are only getting better.
“It wouldn’t surprise me if in our life-time, we not only find more earthlike worlds, but some more-than-a-hint of there being intelligent life somewhere—a signal, a sign in an atmosphere,” says Arkos.
As for those who might say these kinds of explorations are a waste of time, or money, Arkos says he thinks the benefits far outweigh the costs. For starters, in the future it could be intrinsic to our survival as a species. Whether due to changing conditions on Earth or the distant but inevitable expansion of our sun, spreading to other worlds could well be a matter of life or death to our descendants.
Arkos also believes that beyond mere necessity, it is part of human nature to push past the boundaries of our understanding, and that it’s an important part of how we cope with the sometimes overwhelming realities of our lives.
“The truth is, I think we are meant as a species to question, to push, and to boldly go. I think if we don’t do that, we do ourselves a disservice,” he contemplates. “The beauty and the majesty of everything that’s out there—there’s a lot of everyday ugliness in things that we see, but [astronomy] lets us remind ourselves that there is beauty in the universe, that there are things which transcend that. Even more so, it speaks to us as humans—at a core level, this need to be part of something bigger.”
“We really are connected to each other and this universe as a whole, in a very real way, and I think it behooves us to explore that and find our place.”
Who are we, and are we the only ones asking? It may be awhile before we know, but humanity has a well-documented history of bull-headed pursuit of our ambitions, for better or for worse.
In the meantime, keep looking up—the answer could be written in the stars.
Aislinn is a third year Bachelor of Arts and Science student majoring in creative writing and minoring in chemistry. New to The Nav team this year, she’s enjoying finding out about all the interesting things happening on campus. Her hobbies include reading, drawing, Netflix, and the copious consumption of coffee.
