James Webb Space Telescope finds never-before-seen changes in a planet-forming disk around a twin star

Two stars shine in the sky of the planet Tattoine, known from the Star Wars movies. Such planetary systems exist not only in science fiction, but are also known to astronomers in real life. However, it is a mystery how these planets can form in the dynamic environment of two stars orbiting each other. The international research team led by Ágnes Kóspál (Konkoly Observatory, HUN-REN CSFK) has now come one step closer to solving this problem. 

The researchers studied the twin star DQ Tauri in the constellation Taurus using data from the James Webb Space Telescope. “We had the opportunity to conduct a very special experiment: we measured the infrared spectrum of DQ Tauri several times, a few weeks apart,” explains Ágnes Kóspál. Less than 8% of applications to the space telescope are accepted, and it is even rarer for an object to be targeted more than once. 

The DQ Tauri system consists of two identical young stars orbiting each other every two weeks on very elongated orbits. The stars are still actively accreting material from the disk of dust and gas that surrounds them. Such disks are the birthplaces of exoplanetary systems. The orbit of the binary determines how much material falls onto the stars: mass infall is always most intense when the two stars are closest to each other. At such times, the system regularly brightens for a few days every two weeks, like a cosmic lighthouse.

The repeated measurements revealed previously unseen changes in the structure and physical properties of the circumstellar disk. The inner rim of the disk pulsates in line with the binary star's orbit: sometimes it is farther from the stars and cooler, other times it gets closer to the stars and hotter. At this time, the inner part of the disk puffs up and casts an ever changing shadow on the outer parts of the disk. The researchers were also able to detect gas molecules (water, carbon monoxide, carbon dioxide, and hydrogen cyanide) in the disk, whose temperature is also always changing. 

“Although DQ Tauri is a very special system with its periodicity, similar changes can also occur in other young disks, albeit irregularly. From this experiment we learned that circumstellar disks, where planets are born, are much more variable than we previously thought,” concludes Ágnes Kóspál.