The Kepler planet-hunting telescope. NASA

Finding the next Earth: The Ars guide to exoplanets

Have a faster-than-light colony ship? This is what you should know.

by John Timmer – Feb 17 2013, 7:00pm EST

Are we alone in the Universe? For years, people have been making predictions, many using the Drake equation. That involves the use of various educated guesses about the frequency of planets, how many are habitable, and so on. Until about a decade ago, most of the values in the equation remained just that, however: guesses.

In the last dozen years, we’ve witnessed an amazing transformation in science and appear to be on the verge of several more. The existence of planets orbiting other stars—exoplanets—has gone from a hypothetical to a reality. We’ve now got a catalog of thousands of potential planets. In many cases, we even have an idea about their size, composition, and temperature. Some of them orbit stars that are, in galactic terms, right next door.

The result has been an incredible buzz of information—over the course of this winter, there were a series of updated estimates on the number of planets in the galaxy (answer: lots) along with various ways of slicing and dicing the numbers. How many Earth-like planets? How many orbiting stars like our Sun? In every case, the numbers were staggeringly large, with the possibility Earth could be one of millions, if not billions, of similar planets in our galaxy alone.

Given all this information, it seems like we’re on the verge of finding Earth’s twin—a small, rocky, planet sitting at just the right distance from a star to play host to liquid water. But that poses a far more significant challenge than what might be apparent from the field’s most recent successes. An understanding of the challenges involved suggests a different time frame, one where we might still be decades away from getting a clear picture of what our galaxy’s planets look like.

Read more: Finding the next Earth: The Ars guide to exoplanets | Ars Technica.

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