Webb peers into exomoon forming disk for first time
While astronomers have studied circumstellar discs where planets are being assembled, the first observations of a moon-forming disk has now been conducted. Webb has investigated the chemical inventory and physical properties of such a disk.
For the first time, astronomers have peered into potential exomoon forming disk. The carbon-rich disk surrounds a giant exoplanet designated as CT Cha b, located at a distance of 625 lightyears from the Earth. No moons have been detected by Webb. Scientists know of no confirmed exomoons despite detecting over 6,000 exoplanets, although a few candidates have been identified. The exoplanet is in orbit around a star that is only two million years old, and is still accumulating material from the surrounding disk of gas and dust. The planets are assembled in the material leftover from the formation of the star in the circumstellar disk, with moons formed from circumplanetary disks.
The circumplanetary disk discovered by Webb is not part of the larger accretion disk around the newborn star. The exoplanet is at a distance of 495 AU from the star, with each AU or astronomical unit being the distance between the Earth and the Sun. The observations provide scientists with a valuable opportunity for understanding exoplanet and exomoon formation and the evolution of planetary systems across the galaxy. Moons are likely to outnumber planets by a wide margin, even though no confirmed exomoons have been spotted, and might actually offer the most habitable surfaces for life as we know it.
A window to the past
The newborn star system is similar to our own Solar System in its infancy, about 4.6 billion years ago. A paper describing the findings has been published in The Astrophysical Journal Letters. Co-lead author of the paper Sierra Grant says, "We can see evidence of the disk around the companion, and we can study the chemistry for the first time. We're not just witnessing moon formation — we're also witnessing this planet’s formation." Webb has been able to discover seven carbon-bearing molecules in the circumplanetary disk, including acetylene and benzene. The carbon-rich chemistry is in stark contrast to the chemistry in the circumstellar disk, which is rich in water, but not in carbon.