Free Astronomy Magazine March-April 2024

39 MARCH-APRIL 2024 ASTRO PUBLISHING exocomets, and two im- aged exoplanets,” said Rebollido, lead author of the study. “While there have been previ- ous observations from the ground in this wave- length range, they did not have the sensitivity and the spatial resolu- tion that we now have with Webb, so they did- n’t detect this feature.” Even with Webb, or JWST, peering at Beta Pic in the right wave- length range — in this case, the mid-infrared — was crucial to detect the cat’s tail, as it only ap- peared in the MIRI data. Webb’s mid-infrared data also re- vealed differences in temperature between Beta Pic’s two disks, which likely is due to differences in com- position. “We didn’t expect Webb to reveal that there are two different types of material around Beta Pic, but MIRI clearly showed us that the material of the secondary disk and cat’s tail is hotter than the main disk,” said Christopher Stark, a co-author of the study at NASA’s Goddard Space Flight Center in Greenbelt, Mary- land. “The dust that forms that disk and tail must be very dark, so we don’t easily see it at visible wave- lengths — but in the mid-infrared, it’s glowing.” To explain the hotter temperature, the team deduced that the dust may be highly porous “organic refrac- tory material,” similar to the matter found on the surfaces of comets and asteroids in our solar system. For ex- ample, a preliminary analysis of ma- terial sampled from asteroid Bennu by NASA’s OSIRIS-REx mission found it to be very dark and carbon-rich, much like what MIRI detected at Beta Pic. difficult,” explained Stark. “Our model re- quires dust that can be pushed out of the sys- tem extremely rapidly, which again suggests it’s made of organic re- fractory material.” The team’s preferred model explains the sharp angle of the tail away from the disk as a simple op- tical illusion. Our per- spective combined with the curved shape of the tail creates the observed angle of the tail, while in fact, the arc of mate- rial is only departing from the disk at a five- degree incline. Taking into consideration the tail’s bright- ness, the team estimates the amount of dust within the cat’s tail to be equivalent to a large main belt asteroid spread out across 10 billion miles. A recent dust production event within Beta Pic’s debris disks could also explain a newly-seen asymmet- ric extension of the inclined inner disk, as shown in the MIRI data and seen only on the side opposite of the tail. Recent collisional dust pro- duction could also account for a fea- ture previously spotted by the Atacama Large Millimeter/submil- limeter Array in 2014: a clump of carbon monoxide (CO) located near the cat’s tail. Since the star’s radia- tion should break down CO within roughly one hundred years, this still- present concentration of gas could be lingering evidence of the same event. “Our research suggests that Beta Pic may be even more active and chaotic than we had previously thought,” said Stark. “JWST contin- ues to surprise us, even when look- ing at the most well-studied objects. We have a completely new window into these planetary systems.” T his is an animation portraying the creation of the cat’s tail, as hypothesized by a team of astronomers. This structure, which is seen in the southwest portion of Beta Pic’s secondary debris disk, is estimated to span 10 billion miles. [NASA, ESA, CSA, STScI, Ralf Crawford (STScI)] ! However, a major lingering question remains: What could explain the shape of the cat’s tail, a uniquely curved feature unlike what is seen in disks around other stars? Rebollido and the team modeled various scenarios in an attempt to emulate the cat’s tail and unravel its origins. Though further research and testing is required, the team presents a strong hypothesis that the cat’s tail is the result of a dust production event that occurred a mere one hundred years ago. “Something happens — like a colli- sion — and a lot of dust is pro- duced,” shared Marshall Perrin, a co-author of the study at the Space Telescope Science Institute in Balti- more, Maryland. “At first, the dust goes in the same orbital direction as its source, but then it also starts to spread out. The light from the star pushes the smallest, fluffiest dust particles away from the star faster, while the bigger grains do not move as much, creating a long tendril of dust.” “The cat’s tail feature is highly un- usual, and reproducing the curva- ture with a dynamical model was