3I/ATLAS Is Bleeding Matter In A Way No Comet Should

According to calculations outlined by Harvard astrophysicist Avi Loeb, the anti-tail observed in 3I/ATLAS cannot be formed by the ultra-fine dust grains typically seen in cometary comae. Those particles would be blown away almost instantly by sunlight. Nor can the jet be composed of larger grains or pebbles, which gas drag could not accelerate to the observed speeds. The math forces an uncomfortable middle ground: dust grains roughly ten microns in size, clustered in extraordinary numbers.

This is where the mass-loss story becomes far more interesting — and far less discussed.

To account for the observed brightness, the glow around 3I/ATLAS reflects sunlight as if it were a single mirror roughly ten kilometers in radius. That sounds poetic, but physically it means something stark. Because brightness scales with surface area, and surface area scales with the square of size, achieving that glow requires on the order of 10¹⁸ individual dust particles. Each particle is tiny. Collectively, they represent a massive, organized outflow.