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The Oldest Worlds    


Old As Dirt

Maybe there are alien civilizations in the galaxy that are billions of years older than us. Think about it: Earth is five billion years old, but that's young by comparison with our galaxy, which astronomers think is 13 billion years old.

Well, it is true that there are planets much older than Earth. In early 2015 an international team of scientists discovered Earth‑sized planets orbiting a star more than 11 billion years old, using data from the Kepler Space Telescope. This wasn't the first time that planets were found around a very old star.

That system was already older than our solar system is today, back when our sun was born.

Earth-sized, Mercury-hot

The astronomers found five planets orbiting a star somewhat smaller and dimmer than our sun. All five were actually a bit smaller than Earth, and about the size of Mercury or Venus in our solar system.

None were habitable, though. They were all closer to their star than Mercury is to our sun, and much too hot for life as we know it.

Still, if there are lots of these systems, some might have habitable planets. It took five billion years for intelligent life to evolve on Earth. Even if it took just as long on the oldest Earth‑like planets, alien civilizations might have already been building starships back when there was nothing but microbes on Earth.

Read More:

"Habitable Exoplanets Catalog" (Planetary Habitability Lab)

"Planet Quest, The Search for Another Earth" (NASA Jet Propulsion Laboratory)

"Alien Planets Revealed" (Nova, PBS)

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