NASA’s announcement has captivated people’s imaginations. The web is alive with questions and curiosity. People want to know more about the largest collection of small, rocky worlds ever discovered. But some might be feeling a little underwhelmed by the hyped-up announcement. Whenever NASA calls a press conference, news agencies immediately begin speculating about alien life. Most people are mature enough to understand the likelihood of “the” announcement happening tomorrow is still low, yet it can still be disappointing for many people.
What hurts more is that at the 40-light-year distance, there is little chance that in our lifetimes we will be able to confirm living things on these worlds. That just makes the headline teasing all the more annoying. Put that distance into perspective. The sun is 93 million miles from Earth. A light year consists of 63,000 of those 93-million-mile distances. Multiply 63,000 by 93 million, and you get 5.859 trillion miles. Forty of those is 234.36 trillion miles. The septet of planets NASA announced Wednesday, named TRAPPIST-1 after the TRAPPIST exoplanet survey, is absurdly far away.
Why should anyone give a damn? Astronomers have discovered literally 3,583 exoplanets in the last 30 years. But why make any issue out of this? We must know that in our universe, our galaxy let alone, there are bound to be planets rotating other stars. Why is it news every time NASA confirms they exist?
As much as I am a space enthusiast and feel humanity is in debt to the fantastical ambitions of science fiction writers, rocket scientists and imaginative entrepreneurs like Elon Musk, I have to admit these are extremely valid questions.
We are no closer to the holy grail of scientific discoveries: life on another planet. We know these planets are out there. We can continue cataloging them. The technology we use for detection (besides telescopes) will continue to improve and we will be able to literally map tens of thousands in the next few years. But that will not help us pinpoint an alien satellite orbiting a distant planet, nor detect gravitational anomalies caused by fleets of starships traveling between worlds.
Well, Mr. Devil’s Advocate, that’s partially the point. We might not have to. The now rather predictable, continued discovery of exoplanets is allowing astronomy to move beyond simply detecting planets. Now we are finding patterns of how solar systems are laid out that give us more reason than ever to fairly assume life has evolved rather consistently in our galaxy.
Three rocky, atmospheric planets in the habitable zone
Until recently, we could only confirm the existence of
nine eight planets in the whole universe (Pluto lives!). Based on that limited knowledge of planetary science, we had one model for how a star system worked: rocky inner planets close to the star, a ring of rocky debris (the Asteroid Belt), several large gas giants like Uranus (couldn’t resist), and only very recently a far-out region of rocky and icy debris (the Kuiper Belt). But among all the exoplanets found so far, none have come this close to resembling our own neighborhood.
“The seven wonders of TRAPPIST-1 are the first Earth-size planets that have been found orbiting this kind of star,” said Michael Gillon, who led the study and leads the TRAPPIST exoplanet survey at Belgium’s University of Liege. “It is also the best target yet for studying the atmospheres of potentially habitable, Earth-size worlds.”
The Hubble Space Telescope is screening four of the seven planets for atmospheric readings, including three which the study estimates are in the star’s habitable zone. The habitable zone, a.k.a. the Goldilocks Zone, is a region around a star that is not too hot nor too cold, and is just rightly placed to give rise to species. Even though all seven planets are actually closer to their star than Mercury is to the Sun (the seventh planet is actually six times closer to its star than Mercury), the cooler nature of TRAPPIST-1 means they can keep a closer orbit and still be at a safe distance. They can retain life-supporting conditions.
The proximity of the planets makes scientists think they are tidally locked — i.e., just as the same side of the Moon constantly faces Earth and never rotates in its orbit, so too would the seven planets of TRAPPIST-1. That normally would depress scientists, because only a few parts of the planet would have a comfortable temperature between the blazing side facing the star and the freezing side facing away from it. Given those circumstances and the extreme proximity of the planets, which are so close together that their geological features would be visible from one globe to another, how could it have such a specific habitable zone, let alone one at all?
“The habitable zone is estimated based on the luminosity of the star and recognizing how far away can you be from it such that water can exist in it’s liquid form on the surface of a terrestrial planet like the Earth,” wrote Farisa Morales, exoplanet scientist at the NASA Jet Propulsion Laboratory, in a Reddit AMA Wednesday night. “Too close and the water evaporates; too far and the water freezes solid. Thus, the habitable zone is independent of whether the planets are tidally locked or not.”
The tantalizing possibility would be for those three planets might host life. It is perhaps a cosmic coincidence that a trio of worlds relatively close to one another, considering our own planetary triad of rocky, atmospheric planets close to the Sun. What some might not realize is that plenty of theories exist about the former habitability of Earth’s immediate neighbors: the frozen desert of Mars and the hellacious Venus.
“Many of the same tools we use to model climate change on Earth can be adapted to study climates on other planets, both past and present,” said Michael Way, a researcher at the Institute for Space Studies (GISS) who co-authored research in 2016 that found evidence Venus was once a cooler planet with a liquid water ocean. “These results show ancient Venus may have been a very different place than it is today.”
Today, Venus has temperatures that climb as high 864°F/462°C with an asphyxiating atmosphere of carbon dioxide. When the Soviet Union somehow managed to land probes on the surface they would stop transmitting data within two hours because their instruments would melt. Plenty of studies have concluded Mars once held more livable conditions, including its own Martian ocean. With those studies in mind, it becomes feasible that a foreign star system might also have planets passing by each other which all meet the conditions to host lifeforms.
So, does the discovery of TRAPPIST-1 constitute a pattern for life-forming star systems parallel to our own?
There haven’t been enough discoveries like this one to know just yet. Of the stars discovered with planets in their Goldilocks regions, only the Sun (when including Mars and Venus from a historical perspective), TRAPPIST-1, and Gliese 180 could have more than one life-bearing world. Both these foreign stars are red dwarfs with planets discovered extremely close to the star itself. Every other candidate planet to match Earth’s habitability are single. It’s far from a foregone conclusion that multiple planets in a star system need to meet a certain standard in order for us to find an Earth-like one.
The next step will be analyzing what kind of atmospheres these places have, and yes we can do that. The James Webb Space Telescope (JWST) that will deploy in 2018 will be the most capable astronomical tool yet to finding indications of water, methane, oxygen, ozone in foreign atmospheres.
“It’s going to be awhile before we find an oxygen rich atmosphere,” wrote MIT’s Sara Seager on Reddit, pointing to the JWST. Still, Seager warned it would be wrong to assume oxygen meant we would confirm the unthinkable. “It turns out some oxygen-rich atmospheres might exist that are not created by life, so to associate oxygen will require care.”
And just in case you don’t trust NASA will let us know if they find ultimate proof of aliens, JPL social media lead Stephanie L. Smith answered one Redditor’s skepticism with reassurance.
“It’s part of our charter that NASA ‘provide for the widest practicable and appropriate dissemination of information concerning its activities and the results thereof,’ so, yes, we would inform the public.”