3I/ATLAS is pulsing every 16.16 hours — what this strange pattern could mean for Jupiter’s moon Callisto

Something strange has been occurring with the interstellar object 3I/ATLAS: The comet appears to be brightening and dimming in approximately a steady 16.16-hour heartbeat-like manner. 

This steady flicker has surprised scientists and created much online chatter. It came to the point that some even speculated whether this bizarre rhythm could have an impact on one of Jupiter's moons, Callisto.

However, scientists remain very clear: nothing dangerous is going on, and this pulse does not have any influence on Jupiter, Callisto, or any planet whatsoever; it is just a different way the comet reflects the sun. 

3I/ATLAS was first seen on July 1, and since then, telescopes around the world have been watching it carefully. Reports from Axy Media say the brightness rises and falls in a smooth, regular pattern, which made researchers curious.

Why is the comet pulsing?

Initially, it had been suspected that the brightness might change owing to the fact that the comet's core is rotating, something quite normal: many comets spin, and with different sides facing the Sun, the brightness shifts. 

But new images from NASA's Hubble Space Telescope showed something important: most of the light we see does not come from the solid surface of this comet. It actually emanates from a large cloud of gas and dust that surrounds the comet, called a coma. 

Hubble data show the nucleus is very small and faint, and therefore rotation alone cannot account for such huge brightness changes. 

Because of this, scientists have been looking at another explanation: jet activity. This means the comet has a spot on its surface with more frozen material. 

As that part turns toward the Sun, the Sun heats it up, and gas shoots out quickly, almost jet-like. This makes the coma expand and reflect more sunlight, so suddenly the comet appears way brighter. 

When that area is turned away from the Sun again, the brightness is gone. This cycle corresponds very nicely to the 16.16-hour pulse.

No danger to Callisto or Jupiter

Even though social media posts suggested the pulsing might “send energy” toward Jupiter or Callisto, scientists say this is not true at all. The comet’s pulse does not change its mass or path. It is not releasing dangerous radiation or pushing anything toward the planets.

The brightness change is only an optical effect, not a physical force. And current tracking shows the comet will not even come close to Jupiter.

​What scientists will study next

Researchers now want to watch 3I/ATLAS for many hours at a time to see if the brightening always happens when the same part of the comet faces the Sun. If yes, it will confirm the jet theory.

Since 3I/ATLAS is only the third interstellar object ever found, every small discovery helps scientists understand objects from other star systems better.

For now, the comet’s “heartbeat” remains a strange but harmless curiosity.