First Observations Of Moon-Forming Planetary Disc Reported

Astronomers have used the most powerful radio telescopes on Earth to observe a circumplanetary disk of gas and dust believed to be similar to one that circled Jupiter and created its moons. The disk surrounds planet PDS 70 c, which is a still-growing gas giant that is 370 light years from Earth and was revealed for the first time last month in visible light images.

The astronomers used the ALMA radio telescope in Chile to identify dust grains in the star system where PDS 70 c and its sister planet PDS 70 b are forming. Most planet formation models show that circumplanetary disks disappear within about 10 million years of forming meaning it has been about 4 billion years since a disk of that sort was in our solar system.

This has sent astronomers looking elsewhere for this sort of disk to prove theories on planet and moon formation. The search for disks of this sort is why the discovery of PDS 70 C is a big deal to astronomers. The PDS 70 star is a dwarf star only three-quarters of the mass of the sun. Both of the planets that orbit that star are 5-10 times larger than Jupiter and the innermost planet orbits very far from the star, about the distance of Uranus from the sun.

Scientists say that the planets orbiting the star are still drawing in dust and gas and growing. The team says that the data gathered by ALMA was complementary to the optical data and provided independent confirmation that there is something there.

The data that the team is gathering will help to answer questions about how our solar system formed and how other planets might form The team plans additional observations in the future to continue studying the star and its planets.