Hubble Spots a Dark ‘Cat’s Tail’ Long Enough to Loop the Sun 500 Times

Astronomers using the Hubble Space Telescope have captured in visible light a long trail of dust called the Cat's Tail, which they think is the wreckage of a collision between two Pluto-sized bodies. According to Space.com, the feature is so long that it could curl around the sun-Earth system about 500 times.

The tail extends from the debris disk around Beta Pictoris, a young planetary system 63 light-years away. Until now it had been seen only by the James Webb Space Telescope, which detects infrared light. The new work, published last month in The Astrophysical Journal Letters, helps explain why it stayed hidden at shorter wavelengths.

Why the Cat's Tail was so hard to see

The study was led by Arin Avsar of the University of Arizona. The team used 14 years of Hubble observations to work out how the structure formed and why it was invisible in visible light for so long.

Avsar said the tail is made almost entirely of what scientists call organic refractory material, which is heavily carbon-based. According to him, long chains of carbon atoms absorb visible light, which makes the material very dark. That would explain why it did not show up in earlier visible-light observations.

A fluffy tail with a puzzling texture

Hubble's data also suggest that the dust grains in the tail are extremely porous, which makes the tail, in the article's phrase, pleasingly fluffy. Avsar said nobody fully understands how grains this small could be so porous, and that this is part of the reason for studying the feature.

Team member Kevin Wagner, also of the University of Arizona, offered one possibility. The collision may have been so violent that the carbon grains vaporized into gas and then recondensed as they cooled, which could have left them full of tiny gaps. This is a suggestion, not a confirmed explanation.

A warp that points to a giant planet

The researchers also found a previously unknown warp in the tail. It appears to result from an interaction between the trail of material and Beta Pictoris b, a gas giant planet 10 times more massive than Jupiter.

Avsar said this offers another line of evidence for how giant planets shape comets and other material through their gravity. He said such planets influence dust and icy bodies out to hundreds of astronomical units, with one astronomical unit being the distance between Earth and the sun.

Why it matters: a look at a young solar system

Our solar system is about 4.6 billion years old and is relatively orderly. Most space rocks sit in the main asteroid belt between Mars and Jupiter or in the Kuiper belt beyond Neptune's orbit. Early on, it was far more chaotic, with frequent collisions among planetesimals, the building blocks of planets.

Astronomers cannot look back at that era directly, so they study young systems elsewhere. Beta Pictoris is no more than a few million years old and still sees collisions between planetary bodies, which makes it a useful stand-in for our own system's youth. For general readers, the finding does not affect daily life, but it adds detail to the picture of how planets and their surroundings are assembled and reshaped.

The explanation that two Pluto-sized bodies collided is the team's leading interpretation. Avsar described the tail as thought to be the aftermath of such a collision, and open questions remain, including how the grains became so porous.

Around Prague, based on reporting by Space.com