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This chart shows, on the top row, artist conceptions of the seven planets of TRAPPIST-1 with their orbital periods, distances from their star, and radii and masses as compared to those of Earth. The bottom row shows data about Mercury, Venus, Earth and Mars. (NASA/JPL-Caltech)
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http://sfexaminer.com/category/the-city/sf-news-columns/sally-stephens/

Within a decade, we could have an answer to one of the most fundamental questions in science: Are we alone in the universe?

Last week, astronomers announced that they had detected seven rocky, Earth-sized planets orbiting a small, ultra-cool dwarf star in the constellation Aquarius. At least three of the planets, and possibly all seven, could have liquid water on their surfaces, which is key to life as we know it.

The new planetary system is relatively nearby — about 40 light years (235 trillion miles) from the Sun. That’s close enough that astronomers will be able to study the atmospheres of the planets in detail. Over the next decade, they’ll be looking for the chemical fingerprints of water, methane, oxygen, ozone and other compounds produced by living things.

If astronomers find evidence of life in this new planetary system, it could indicate that life is fairly common throughout the galaxy. Given the right circumstances, especially liquid water, life will develop.

But, of course, what we really want to know is if there are intelligent beings and advanced civilizations — Vulcans or Klingons — out there. It’s unlikely we’ll get that answer soon; astronomers have been looking for radio signals from advanced civilizations for decades with, so far, negative results. That doesn’t necessarily mean they’re not there. Just that we haven’t detected any radio signals from them.

Radio astronomer Frank Drake devised an equation to estimate the number of technologically advanced civilizations in the Milky Way Galaxy that we could communicate with via radio transmissions. The number depends on things like the fraction of stars that have planets, the fraction of planets that develop life, and the fraction of planets with life that develop intelligent, technologically advanced civilizations. Most of the terms are speculative.

The final term in the Drake Equation is the length of time that technologically advanced civilizations send out radio signals. Earth has actually been unintentionally sending out signals for about 100 years, since the days of Marconi. But once you get more than a few light years away from Earth, the signals are so severely degraded they wouldn’t be recognizable as a radio or TV show.

Ultimately, the final term depends on how long technologically advanced civilizations last. Here on Earth, we’ve gotten to the point where we can destroy the planet — and ourselves — through environmental degradation, climate change or nuclear war. If our experience is common, and most civilizations destroy themselves within decades of becoming technologically advanced enough to send radio signals out into the cosmos, then there might not be many aliens out there to talk to. Or maybe they’ve figured out how to overcome similar problems. If so, we could learn a lot from them.

But the excitement about the announcement last week is that this is the first time astronomers have seen so many Earth-like planets in one system that could have liquid water and, therefore, could be habitable. And they’re close enough that we can study them in detail to look for evidence of life.

The star is called TRAPPIST-1, after the telescope that first detected some of the planets. The central star is small — about the size of Jupiter — and is so cool in temperature that it would appear salmon-colored. The seven planets all orbit closer to their central star than Mercury orbits the Sun. A year would take less than three weeks on all of the planets, and only 36 hours on the one closest to the star. The planets are so close together that, if you were standing on one, you could look up in the sky every now and then and see a neighboring planet, looming so large you could easily see its clouds and continents.

We may know within a few years whether or not any of TRAPPIST-1’s planets have life. Even if we only find microbes, that discovery would be the first proof of life elsewhere in the universe. On Earth, microbial life ultimately evolved into intelligent, technologically advanced creatures: us. Maybe the same thing is happening — or has already happened — on TRAPPIST-1. If life can develop in both places, then maybe it can happen anywhere. We may not be as alone as we fear.

Sally Stephens is an animal, park and neighborhood activist who lives in the West of Twin Peaks area.

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