Mundane wayward space snowball, or extraterrestrial visitor?
Astronomers believe that our solar system's latest and only third ever confirmed interstellar visitor, 3I/ATLAS, is almost certainly a comet.
But lingering questions about the object means it's not yet an open and shut case. Amid that uncertainty, famed Harvard astronomer Avi Loeb is pushing the possibility that the interstellar interloper is an "extraterrestrial artifact" — perhaps even an "alien mothership" — here to menace or observe us. Which, though it sounds scary, could be interpreted as a good thing.
"The discovery of an extraterrestrial artifact would reset our priorities to explore the real estate beyond Earth instead of just focusing on terrestrial conflicts," Loeb wrote in a recent blog post. "Humanity desperately needs a wakeup call."
Loeb acknowledges that the odds aren't in his favor — but only slightly. Presently, on his detailed scale of one to ten for classifying the likelihood of interstellar objects representing a piece of alien technology, he gives 3I/Atlas a "four" — an "anomaly meeting potential technosignature criteria."
"Having a 40 percent chance for an accident while crossing the street, argues in favor of keeping our eyes open and monitoring an approaching car," he argues in the post.
The claims are controversial, but this isn't new territory for Loeb. He has long argued that 'Oumuamua, the first detected interstellar object in history, may have actually been an alien probe. The nearly quarter-mile object's unusual acceleration could have been a sign that it was being propelled with a solar sail, he argued.
In early July, astronomers confirmed that 3I/ATLAS, named after the telescope in Chile which first spotted it, came from interstellar space, making it the third detection ever of such an object. It followed the discovery of 2I/Borisov in 2019, which was also believed to be a comet.
The main giveaway was its blistering speed. Traveling at over 130,000 miles per hour, it vastly outpaces anything in our solar system, and would have had to reach its incredible speed outside the speed limit imposed by the Sun. The prevailing theory is that 3I/ATLAS originated in a star system near the center of our galaxy, and was propelled our way after being ejected from its home by a gravitational disturbance like a passing star.
The suspicion from the get-go has been that 3I/ATLAS is a comet. Images taken with the Hubble Space Telescope, for example, show evidence of a coma, the luminous halo of gas and dust that gives comets their flashy appearance, which form when the Sun warms the ice in the comet's solid core, leading to "outgassing." Loeb acknowledges the coma on his own blog.
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