So, how’s this for a scenario? Not two, not three, but seven Earth-like planets circle a small, cooling star in a system a mere 39 light years from Sol. The rocky planets, all of a size to match our blue-green home, orbit tightly around their dim star, packed so closely together the sky of the outermost planets are filled with the faces of their sisters. The huge disk of their sun floods the landscape of each planet with reddish light, just warm enough for liquid water—and, perhaps, some outrageous lifeforms.
|Artist's conception of a planet in the TRAPPIST-1 system (NASA/CalTech)|
Well, yes, I’m a creative goddess, we know, but I didn’t make this up. I’m describing a newly discovered system referred to as TRAPPIST-1 after the European Southern Observatory's Transiting Planets and Planetesimals Small Telescope (TRAPPIST) in Chile that was used to find it. Michaël Gillon, an exoplanet researcher at the University of Liege in Belgium, and his team found and named the fascinating collection of planets that outdoes our own solar system, at least in terms of number of possible candidates for study. After all, our familiar yellow star can only claim three planets of the “terrestrial” or rocky, Earth-sized variety: Mercury, Venus, Earth and Mars).
Gillon explains the excitement the discovery caused: “Before this, if you wanted to study terrestrial planets, we had only four of them and they were all in our solar system. Now we have seven Earth-sized planets to expand our understanding. Yes, we have the possibility to find water and life. But even if we don't, whatever we find will be super-interesting.”
Of course, studying them from 39 light years out won’t be easy. Gillon and his fellow researchers determined the number of planets in the TRAPPIST-1 system and their relative orbits by noting the impact the bodies had on the red dwarf star they were observing in the constellation Aquarius. They refined their initial discoveries with observations with the Very Large Telescope array in the Atacama desert in South America and others. But closer observations to detect atmospheric components and thermal emissions from the planets (using telescopes like the James Webb Space Telescope after it launches in 2018) will be needed to tell us what conditions are like on the planet surfaces.
After all, alien observers from afar might assume that three of the four of our terrestrial planets in the Sol system would fall into the “Goldilocks” zone that could harbor liquid water, and, thus, life. Mercury, of course, is too close to the sun to sustain atmosphere and is fried to a crisp. But Venus is the cloud-covered victim of global warming run amuck and Mars is dead and cold, having suffered a loss of its dynamic inner core. In the TRAPPIST-1 system, three of the seven possible candidates fall into the Goldilocks zone—where the dim sun might provide enough warmth, but not too much—but scientists simply don’t know enough to speculate whether conditions might favor life as we know it.
It’s no doubt those scientists will be working overtime to find out more about our neighbors in TRAPPIST-1, as well as Proxima b, the planet circling our nearest star neighbor, Proxima Centauri. Meanwhile, the current planetary count (confirmed to a 99 percent probability) is 1284, according to NASA’s Kepler orbiting telescope. That extrapolates to nearly 10 billion possible Earth-like planets in the galaxy. Lots of fodder for space adventures there!
**Information for this post taken from, “Scientists Discover 7 ‘Earth-like’ Planets Orbiting a Nearby Star,” by Sarah Kaplan, Speaking of Science, The Washington Post, February 22, 2017. https://www.washingtonpost.com/news/speaking-of-science/wp/2017/02/22/scientists-discover-seven-earthlike-planets-orbiting-a-nearby-star/?utm_term=.84a891c29377