Hubble detects Beta Pictoris’s Cat’s Tail in visible light

Astronomers led by Arin Avsar, a planetary-science doctoral student at the University of Arizona, have detected Beta Pictoris’s Cat’s Tail in visible light for the first time. The team interprets the faint dust as possible debris from a collision between dwarf-planet-sized bodies. Its inferred composition helps the researchers estimate how large those bodies would have needed to be.

Beta Pictoris is a star about 23 million years old, roughly 63 light-years from Earth. Its surrounding disk of dust and gas is seen edge-on from Earth and contains three known planets.

A 2024 paper first revealed the Cat’s Tail in James Webb Space Telescope images as a curved extension of a secondary disk, bending away from the main disk’s plane. The feature may stretch about 1,000 astronomical units, with one astronomical unit equal to the average Earth–Sun distance.

The 2026 study, published in The Astrophysical Journal Letters, searched for the tail’s scattered starlight using Hubble’s Space Telescope Imaging Spectrograph. The analysis combined observations from six observing periods between 2012 and 2025.

Analysis

Why nearly black dust can still glow

The two telescopes measure different light from the dust. Hubble detects starlight scattered by the grains, while Webb’s Mid-Infrared Imager detects their infrared heat emission. Comparing the scattered light’s brightness and colour with the infrared observations helps constrain the grains’ composition, size and porosity—the amount of empty space within them.

Avsar said the team infers that the dust consists almost entirely of organic refractory material: carbon-rich solids containing long chains of carbon atoms. Those chains absorb visible light, making the grains nearly black. That explains why the tail can be faint in reflected starlight while remaining detectable through its heat emission.

The observations also support extremely porous grains about a micron—a millionth of a metre—in size. The tail appears shorter in Hubble’s images because grains farther from the star reflect less starlight, the University of Arizona said.

The combined images and modelling also revise the tail’s possible orientation. Avsar said it may extend mainly sideways across the sky, perhaps slightly behind the star, rather than stretching far behind it along our line of sight.

Analysis

Estimating the proposed parent bodies

The amount of carbon-rich dust matters to the collision explanation. The researchers argue that surface coatings like those on Pluto contain too little organic material to supply the tail. They instead point to material from inside disrupted bodies as the likely source.

To estimate how much organic material the bodies could have contained, the team examined abundances in nearby interstellar matter—the gas and dust between stars—and in comet 67P/Churyumov-Gerasimenko. Universe Today described how the researchers used those constraints to calculate the masses needed to supply the tail’s estimated organic debris.

The required mass is roughly one to three times that of the dwarf planet Ceres. The researchers compare the inferred mass and radius range with Pluto’s companion Charon and the dwarf planet Makemake. These estimates describe the bodies required by the proposed collision, rather than bodies directly seen in the images.

Porous grains and a warped halo

How such small grains became so porous remains unexplained, Avsar said. Co-author Kevin Wagner, a University of Arizona researcher, proposed one possibility: sufficiently fast collisions could have vaporised carbon grains, which then condensed again as they cooled into porous particles.

Avsar sees Beta Pictoris as a way to investigate the young Solar System. In the university’s account, the Kuiper Belt at about 20 million years old may have contained hundreds of Pluto-sized bodies, many later displaced or ejected by giant planets.

Hubble also revealed a warp in Beta Pictoris’s outer dust halo, with an outward-curving shape on one side and an inward-curving shape on the other. The researchers propose that an interaction with Beta Pictoris b, a gas giant about ten times Jupiter’s mass, could explain it. The authors say dedicated modelling of the dust’s motion under gravity is needed to test that explanation.