Earlier this week, two NASA-affiliated teams announced the discovery of 715 new planets around other stars. I have to pause on that number for a moment. From the dawn of Mesopotamian astronomy around 2000 BC until 1992 AD, astronomers discovered a grand total of three planets: Uranus, Neptune, and Pluto. (I’m still counting Pluto as a planet. So sue me.) Now, in a single data release, scientists have found 715, bringing the total number of known alien worlds to 1,750.
And the news is even more amazing than the raw numbers convey. Through almost all of history, our solar system contained the only real estate that we knew about. Yes, astronomers studied other stars and nebulae, but they knew nothing of planets–the only places where life can exist, so far as we know, the only places where humans might set down and explore. Now we know that other planets exist, and that they come in a wide variety of exotic forms never before imagined.
Extrapolating from the latest statistics, our galaxy must contain at least 5 billion Earth-size planets, and perhaps ten times that many, orbiting in locations that could be hospitable for life. We have truly entered a new era in the human relationship to the cosmos–one that I would call the 4th Great Era of Discovery.
What were the other 3? I’ll have a lot more to say about that in my next post.
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