Hubble and JWST observations point to collision behind Beta Pictoris 'Cat's Tail'

The Cat's Tail, first detected by the James Webb Space Telescope (JWST) in 2024, extends roughly 1,000 astronomical units. Until now, it had only been observed in infrared light, puzzling researchers who could not see it in visible wavelengths.

Beta Pictoris, a star about 63 light-years away, is the subject of extensive research because of its youth, around 23 million years old, its proximity, and its debris disk, whose geometry allows detailed side views and which includes three directly imaged exoplanets.

New observations from the Hubble Space Telescope, collected across six epochs between 2012 and 2025, have now captured the Cat's Tail in scattered visible light. The data reveal that the feature consists almost entirely of organic refractory material: a carbon-rich substance that absorbs visible light, making it appear black.

"We think the Cat's Tail has eluded our observations in visible light until now because of what it's made of," said lead author Arin Avsar, a PhD candidate at the University of Arizona's Lunar and Planetary Laboratory. "It consists almost entirely of what we call organic refractory material, which is heavily carbon-based. These long chains of carbon atoms absorb visible light, so they're quite black."

The team modelled the amount of organic material needed to produce the tail and calculated that the colliding parent bodies each had a mass of roughly 1–3 × 10²¹ kilograms, equivalent to one to three times the mass of the dwarf planet Ceres, or a few percent of Earth's Moon. Assuming densities in line with those of dwarf planets in our Solar System, the objects had estimated radii between 600 and 800 kilometres, similar to Kuiper Belt dwarf planets such as Charon and Makemake.

"This invites the question: do dwarf planets in exo-Kuiper Belts (like that of β Pic) contain enough organic material to create the Cat's Tail?" the researchers write in the paper.

A separate finding in the new Hubble images is a warp in the outer halo of Beta Pictoris' dust disk, which the authors suggest may be caused by interactions with the giant planet Beta Pictoris B, a world about ten times Jupiter's mass. They caution that dedicated dynamical modelling is needed to confirm the link.

Co-author Kevin Wagner, an assistant research professor at the University of Arizona's Steward Observatory, noted a puzzle about the dust grains themselves. "How you can get dust grains that small that are as porous as we see here, no one really understands, and that's part of why we study this feature," he said. The team speculates that high-velocity collision impacts may have vaporized carbon, which then recondensed into highly porous micron-sized grains.

Because Beta Pictoris is so much younger than our 4.6-billion-year-old Solar System, the system offers a window into our own Solar System's chaotic past, when collisions were much more common.

"The Cat's Tail is thought to be the aftermath of a collision between large bodies – think something like Pluto," Avsar said. "Oddly, this feature had previously only been seen with the James Webb Space Telescope, which detects infrared light, but remained invisible at shorter wavelengths, which has puzzled the community for a while."