Many scientists currently searching for traces of extraterrestrial life focus on planets orbiting within the habitable zones of their stars, where liquid water might exist. Now, a researcher has proposed a mind-boggling alternative that turns this convention on its head: What if alien civilizations learn to use free-floating “rogue” planets, which are not bound to any star, to traverse across interstellar distances? And how might we try to spot these extraterrestrials wandering across the dark patches of the galaxy, if they do exist?
This concept of “cosmic hitchhikers” is the brainchild of Irina Romanovskaya, a professor of physics and astronomy at Houston Community College who outlines how “extraterrestrial civilizations may travel from their home worlds to free-floating planets, and how they may transfer from their free-floating planets to other planetary systems” in her recent study published in the International Journal of Astrobiology.
“Almost 10 years ago, when reading about discoveries of free-floating planets, I thought of a hypothetical scenario of a free-floating planet approaching the Solar System,” Romanovskaya said in an email to Motherboard. “There are no traffic lights in the Galaxy. If the Solar System happens to be in the way of some free-floating planet, the planet will not stop at the red light. It will fly right through the Solar System. The probability of such an event would depend on how many free-floating planets exist in our Galaxy, which at that time remained to be estimated.”
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