Essentially located in what’s considered our solar system’s “backyard,” the three Earth-sized planets orbit an ultracool dwarf star that’s so cosmically close to them that the astronomers expect to discover each planet’s relative ozone, oxygen, and methane levels in future observations. The team’s findings were published Monday in the scientific journal Nature.
Using the Chilean Transiting Planets and Planetesimals Small Telescope (TRAPPIST), Gillon and his crew discovered the ultracool dwarf star, now dubbed TRAPPIST-1. After observing the star slightly fading at a regularly occurring interval, it was theorized that other objects were orbiting the star. Gillon peered closer and reported the existence of three Earth-sized planets orbiting TRAPPIST-1. Named TRAPPIST-1b, TRAPPIST-1c, and TRAPPIST-1d, each planet boasts slightly different orbital patterns and generates an equal amount of optimism in its ability to sustain life.
“With such short orbital periods, the planets are between 20 and 100 times closer to their star than the Earth to the sun,” says Gillon. “The structure of this planetary system is much more similar in scale to the system of Jupiter’s moons than to that of the solar system.”
Specifically, TRAPPIST-1b and TRAPPIST-1c orbit their host star every 1.51 and 2.42 days, respectively, which allows the planets to absorb roughly four times and two times the amount of solar radiation as Earth. Because of this, these two planets don’t necessarily reside in what’s considered the “Goldilocks” zone for habitable planets, however, Gillon and his team haven’t yet ruled out the possibility of life thriving in other areas of the planets. Furthermore, TRAPPIST-1d, the orbital pattern of which has yet to be determined, receives much less radiation than the other two, potentially putting it into the preferred habitable zone.
Despite the fact each planet is incredibly similar in size to Earth, all three orbit so close to TRAPPIST-1 that it’s reasonable for the astronomers to assume they’re tidal locked to the star, meaning the same side of the planet faces the host star at all times. While this seems like a disadvantage in terms of their relative habitability, Gillon tells Motherboard that tidal locking might actually be a “huge advantage for life.”
Whereas one face of the planet is likely super hot and the other supercold, winds generated on the daytime side of the planet could feasibly manifest livable conditions on the other side. Gillon elaborates on this point to Motherboard by saying “the western terminator could be colder than the dayside [face], enough to have conditions suitable for liquid water, and maybe life, even for a planet that is slightly (too close in) to be in the habitable zone.”
As of now, Gillon’s assessments are mere theories, with further research required to begin hacking away at what exactly TRAPPIST-1 and its nearby planets have to offer. In addition to the findings, the team did mention that roughly 15 percent of the stars near our sun are of the ultracool dwarf variety — meaning their effective temperature sits at roughly 4,400 degrees Fahrenheit as opposed to the sun’s effective temperature of 9,929 degrees Fahrenheit. Not only does this bode well for finding additional life-bearing planets, but it narrows the scope for astronomers continuing to search for exoplanets.
Moving forward, the team plans on making use of more powerful telescopes — like NASA’s James Webb Space Telescope and ESO’s E-ELT — in order to further research TRAPPIST-1 and the surrounding planets. The plan, according to co-author Julien de Wit, is to first study the atmospheric composition of each planet before searching for signs of water and assessing biological activity. Though this process will likely take years before any concrete evidence for or against life is discovered, the fact that Gillon and his team stumbled on such a discovery this close to Earth seems nothing short of extraordinary.
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