Astronomers spot a circumplanetary disk for the first time

A. Isella ESO

A. Isella ESO

This image taken from the ALMA observatory in Chile could show the birth of a moon for the first time.

During an earlier survey, scientists discovered two new Jupiter-like planets orbiting PDS 70 using the observational abilities of European Southern Observatory's Very Large Telescope.

Astronomers were able to register the presence of dust grains over the entire surface of the planet PDS 70 c. The work also explores the elusive nature of PDS 70 c a gas giant which is now forming at a distance of 370 light-years away from Earth, and whose existence surfaced last month in visible light images. The star is just 10 million years old, the planets barely formed.

"For the first time, we can conclusively see the telltale signs of a circumplanetary disk, which helps to support numerous current theories of planet formation", lead author Andrea Isella from Rice University says in a press release.

'Jupiter and its moons are a little planetary system within our solar system, for example, and it's believed Jupiter's moons formed from a circumplanetary disk when Jupiter was very young. It means circumplanetary disks haven't existed in our solar system for more than 4 billion years.

For the new study, astronomers used Atacama Large Millimeter/submillimeter Array, a collection of high-precision dish antennas in northern Chile, to measure the faint radio waves emitted by the tiny gas particles surrounding the outermost body in the PDS 70 system. In 2017, observations made by ALMA were analyzed and researched by Isella and his team.

PDS 70 is a small star around seventy five percent the mass of the sun. PDS 70 b and 70 c "are among the most robust because there have been independent observations with different instruments and techniques". The involved planets are about 5-10 times bigger than Jupiter, which is the biggest planet in our solar system.

Andrea Isella, Assistant Professor at Rice University in the USA, stated, "Planets structure plates of gas and residue around recently framing stars and if a planet is enormous enough, it can shape its very own circle as it assembles material in its circle around the star". By combining those new observations with the VLT data and optical telescope images, the team believes that a cloud of dust also surrounds the planet PDS 70c, and that it is now in the process of forming planet-sized moons. For instance, the ALMA results show a point that is planet PDS 70c in the middle of the dust disk, but when viewed in infrared wavelengths, PDS 70c becomes much less solid.

Isella said direct observation of planets with circumplanetary disks could allow astronomers to test theories of planet formation.

Isella is an assistant professor of astronomy and physics and Earth, environmental and planetary sciences at Rice.