Planet formation is a complicated, complex process. Despite the influx of data on exoplanets, there are still only two known planets that are not yet fully formed. Known as PDS 70b and PDS 70c, the two planets originally found by the Very Large Telescope are some of the best objects we have for concretizing our planet formation models. And now it has been confirmed that one of them has a moon-forming disk around it.
This additional finding arose from observations made by ALMA. Astronomers had long predicted that the planet PDS 70c was surrounded by such a disk, but the images they had previously taken did not confirm its existence. Now it is physically confirmed beyond any doubt.
UT video about the formation of our own moon.
At this point in time, the formation of the moon is even less well understood than the formation of planets. Even the origins of our own moon are still up for debate. But the discovery of the PDS 70c has the potential to shed light on the making of at least one as we observe it. In fact, there is enough material in the disk to create three moons the size of our own around the Jupiter-like planet.
The lunar formation process also plays a key role in planet formation, with circumplanetary disks that can form moons also affecting the formation of the planet itself. Watching this disk evolve will aid scientists in their models of both lunar and planetary formation.
UT video about exomoons with Dr. David Kipping
This development will certainly take millions of years, but so far PDS 70c is the only known planet with some kind of circumplanetary disk. The same dataset that confirmed its existence showed that its Saturn-like twin, PDS 70b, does not have a disk that some scientists had previously suggested. Others could be found with more powerful telescopes, but until then this system is the best we have.
Because of its uniqueness, the PDS 70 system will remain a focal point for much observation fire power. Now there is one more important detail to consider with these instruments – hopefully there are even more details to be discovered.
Max Planck Institute for Astronomy – Astronomers clearly identify a moon-forming disk around an exoplanet for the first time
Astrophysical Journal Letters – A circumplanetary disk around PDS70c
NYT – Astronomers see moons form in a disk around a distant exoplanet
Space.com – Astronomers discover the first moon-forming disk around an alien world
ALMA image of the PDS 70 system, with a close-up of the circumplanetary disk around PDS 70c.
Credit- ALMA (ESO / NAOJ / NRAO) / Benisty et al.