The Cat’s Tail is a dusty feature in the debris disk around the star Beta Pictoris. A study published October 7, 2026, reports the first Hubble detection of its visible and near-infrared scattered light: the signal reaches a projected separation of about 230 astronomical units (AU). Earlier modeling of the feature in mid-infrared light places its tip beyond 1,000 AU, tracing a different part of the picture. The study in The Astrophysical Journal Letters also models the dust’s properties and discusses possible explanations for the tail and the surrounding halo.
Hubble catches starlight scattered by dust; Webb’s MIRI traces the dust’s thermal emission. Each reveals a different part of the structure.
What Hubble detected
The Hubble Space Telescope’s STIS instrument detected the tail in scattered light, meaning starlight reflected by dust. The signal-to-noise ratio, a measure of how clearly a signal stands out from background noise, is about 5–10. The study combines six observing epochs collected between 2012 and 2025.
The measured surface brightness falls from about 0.03 millijanskys per square arcsecond at the tail’s base to 0.01 at its tip. The detected feature fades into the surrounding halo; its maximum projected separation is about 230 AU. “Projected” means measured on the sky image, rather than a direct measure of the structure’s full three-dimensional distance.
Why the infrared observations trace farther
JWST’s MIRI instrument detects mid-infrared light emitted by warm dust. The study cites earlier MIRI modeling that places the tail’s tip beyond 1,000 AU. That modeled reach and Hubble’s roughly 230 AU projected detection are not measurements of the same light: STIS detects reflected visible and near-infrared light, while MIRI detects thermal emission.
Under a model that assumes a matched shape for the feature, the study estimates that the STIS scattered-light flux is 0.1%–0.4% of the flux measured in MIRI’s F1550C band. The earlier Webb discovery and possible origins of the structure are discussed in this 2024 video:
What the dust model suggests
The study’s grain model favors dust made mostly of organic refractory material, a class of carbon-rich solids, with a smaller silicate component. Its modeled ranges are 85%–99% organic refractory material and 1%–15% astronomical silicates by solid fraction. The model also gives the grains a porosity of 0.55–0.93, meaning they contain substantial empty space.
A collision between large bodies is one proposed explanation for the tail. Under assumptions about the bodies’ composition, collision and fragment sizes, and density, the study estimates a lower-limit mass of roughly 1–3 × 10²¹ kilograms for each hypothetical progenitor. At an assumed density of 1.5 grams per cubic centimeter, that corresponds to estimated radii of 600–800 kilometers. These are model-based estimates, not measurements of identified parent bodies.
The outer halo’s asymmetric shape
Hubble’s images also show a convex-and-concave asymmetry in the outer dust halo, beginning at projected separations of about 130 AU. Interactions among planets could help explain that shape, according to the study, which calls for further dynamical modeling that accounts for the planetary system and radiation pressure.
