The mysterious interstellar object 3I/ATLAS is just weeks away from reaching its closest approach to Earth: It’s expected to pass within just 170 million miles of our planet on December 19, giving astronomers an unprecedented opportunity to see it up close as it roars by.
As Harvard astronomer Avi Loeb points out in a new blog post, they will build on interesting existing observations from ground-based telescopes, including a paper published in the journal Astronomy and Astrophysics In October, a team of researchers in Europe and Africa found signs that it was radiating a “heartbeat” of light pulses that repeated every 16.16 hours.
While this sounds like an interesting new twist in Loeb’s long-standing effort to support the theory that the object could be an alien spacecraft visiting the solar system, there may be a more mundane explanation: It’s spinning, pulsing us with light like an interstellar beacon.
“Overall, 3I shows typical characteristics of weakly active outer solar system comets, despite its interstellar origin,” the researchers wrote in the paper. “Continuous monitoring around perihelion is necessary to track changes in activity and color, which will provide insights into the evolution of interstellar material under solar radiation.”
If it is indeed spinning, 3I/ATLAS’s anti-tail, which scientists suspect is the result of a small portion of material less affected by solar radiation pressure, could cause a stream of particles to pour into its coma, the fuzzy atmosphere of ice and dust that forms around its core.
“In the context of natural comets, this could be caused by a sunward ejection (reverse tail) that only kicks in when a chunk of ice on one side of the comet’s nucleus faces the Sun,” Loeb wrote. “Thus, the coma is being pumped out every time the ice pack faces the Sun.”
The activity, he added, is similar to “a heartbeat with a puff of gas and dust that periodically acts like a ‘blood’ through coma during a 16.16-hour spin cycle.”
Although most scientists believe the object may be a natural comet, Loeb remains hopeful that 3I/ATLAS’s jets will be technological in nature.
“For technical objects, the direction of the pulse jet can be arbitrary and does not necessarily point toward the sun,” he wrote.
Regardless, a better understanding of how these pulses change over time could provide more clues to solving this problem. For one, its rotation may have changed since it reached perihelion, the point closest to the sun, in late October.
“This heartbeat pattern should be evident in a series of carefully calibrated coma snapshots over several days, but none has been systematically studied in the published literature,” Loeb wrote. “A movie showing the periodic brightening of the jet around 3I/ATLAS over several days could reveal whether the jet is natural or technological based on the direction of the heartbeat pattern relative to the sun.”
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