Just as mysterious interstellar object 3I/ATLAS reemerged from behind the Sun last week, astronomers detected intriguing radio signals from it that give new clues about its chemical composition.
3I/ATLAS, which is widely believed to be a comet, has been soaring through the solar system at a breakneck speed, reaching its perihelion, or closest point to the Sun, on October 29. Days earlier, it reached its solar conjunction relative to Earth, or when the Sun was perfectly in line between us and the mysterious object, temporarily blocking it from view.
On October 24, astronomers at the South African Radio Astronomy Observatory used the MeerKAT radio telescope to once again probe the rare visitor.
Two previous attempts in September proved fruitless — but the third time was the charm. The team “detected radio absorption lines by hydroxyl radicals,” which are produced when water molecules are broken down by sunlight, in what Harvard astronomer and passionate 3I/ATLAS tracker Avi Loeb declared in a blog post to be the “first radio detection of 3I/ATLAS.”
The intriguing findings could once again support the theory that 3I/ATLAS is a comet with interstellar origins that’s shedding copious amounts of water as it passes by the Sun — not an enormous alien spacecraft measuring miles across, as Loeb has suggested numerous times.
Some previous observations by NASA’s James Webb Space Telescope had hinted that 3I/ATLAS is mostly made of carbon dioxide ice, and only a trace of water, accounting for four percent of its mass.
But astronomers already detected hydroxyl gas, a chemical fingerprint of water, in previous ultraviolet spectrum data collected by NASA’s Neil Gehrels Swift Observatory. The findings had the researchers excited, potentially allowing us to study the chemistry of planetary systems beyond the Sun, as the BBC reported last week.
“When we detect water — or even its faint ultraviolet echo, OH — from an interstellar comet, we’re reading a note from another planetary system,” Auburn University physics professor Dennis Bodewits told the broadcaster. “It tells us that the ingredients for life’s chemistry are not unique to our own.”
The astronomers noted a substantial water-loss rate despite the object being just under three times farther from the Sun than the Earth, a region where familiar comets from our solar system are typically far less active.
Fortunately, there will be even more opportunities to study 3I/ATLAS before it leaves the solar system for good.
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