NASA’s James Webb Space Telescope has provided the first direct measurements of the chemical and physical properties of a potential moon-forming disk encircling a large exoplanet.
Why it matters: Observing planet and moon formation is fundamental to understanding the evolution of planetary systems across our galaxy. Moons likely outnumber planets, and some might be habitats for life as we know it.
The details:
- The carbon-rich disk surrounds the exoplanet CT Cha b, located 625 light-years from Earth.
- The young star that CT Cha b orbits is only 2 million years old and is still accreting circumstellar material.
- The circumplanetary disk discovered by Webb is not part of the larger accretion disk around the central star.
- Webb’s data is invaluable for making comparisons to our solar system’s birth over 4 billion years ago.
What they’re saying:
- “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,” said co-lead author Sierra Grant of the Carnegie Institution for Science in Washington.
- “We are seeing what material is accreting to build the planet and moons,” added main lead author Gabriele Cugno of the University of Zürich and member of the National Center of Competence in Research PlanetS.
The team discovered seven carbon-bearing molecules within the planet’s disk, including acetylene and benzene. This carbon-rich chemistry is in stark contrast to the chemistry seen in the disk around the host star, where the researchers found water but no carbon.
The background: A circumplanetary disk has long been hypothesized as the birthplace of Jupiter’s four major moons. These Galilean satellites are believed to have condensed out of such a flattened disk billions of years ago, as evident in their co-planar orbits about Jupiter.
What’s next: In the coming year, the team will use Webb to study similar objects to better understand the diversity of physical and chemical properties in the disks around young planets. The findings will deepen our comprehension of planetary system formation and evolution.
