Astronomers have clearly imaged a moon-forming disk encircling a planet outside of our solar system for the first time, and it looks like something from the Lord of the Rings.
The disk is surrounding an exoplanet known as PDS 70c which orbits a star that is nearly 400 light-years away with its neighboring planet, PDS 70b. It's a circumplanetary disk, which the National Radio Astronomy Observatory defines as a belt that encircles planets, made up of dust and gas that is theorized to create planets and moons through collisions. Circumplanetary disks also control their growth by regulating the particles and materials that pass through them.
Scientists first found evidence of the disk in 2019, but this is the first time they have been able to confirm its existence with the help of the Atacama Large Millimetre/submillimetre Array (ALMA). These new findings were published on Thursday in The Astrophysical Journal Letters.
“PDS 70b and PDS 70c, which form a system reminiscent of the Jupiter-Saturn pair, are the only two exoplanets detected so far that are still in the process of being formed,” researcher Miriam Keppler of the Max Planck Institute for Astronomy in Germany wrote in the study.
Despite this comparison, the study’s press release notes that the circumplanetary disk surrounding PDS 70c is about 500 times larger than Saturn’s rings.
Scientists concluded that the disk has the same diameter as the distance from the Sun to Earth and has enough mass to form up to three satellites close to the size of Earth’s moon. Their research also found that PDS 70b did not have its own circumplanetary disk because PDS 70c was starving it of dust.
They are hoping to use the European Southern Observatory’s Extremely Large Telescope, which is currently under construction in Chile, to further observe the planetary system. Though it’s still unclear when the moons will begin forming, astronomers involved with the study note that this could be a unique opportunity to observe planet and moon formation in young stellar systems for the first time.