Planetary formation is a complicated, multilayered process. Even with 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, which were originally found by the Very Large Telescope, are some of the best objects we have to flesh out our planetary formation models. And now, one of them has been confirmed to have a moon-forming disk around it.
That additional insight came from observations conducted by ALMA. Astronomers had long predicted that planet PDS 70c was surrounded by such a disk, but with the images they had captured previously they were unable to confirm its existence. Now, it has been physically confirmed beyond the shadow of a doubt.
Moon formation is even less well understood than planetary formation at this point. Even the origins of our own Moon are still up for debate. But the PDS 70c discovery has the potential to illuminate the creation of at least one as we are watching. In fact, there is enough material in the disk to create three moons the size of our own around the Jupiter-like planet.
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The moon formation process also plays a key part in planetary formation, with circumplanetary disks that can form moons also influencing the creation of the planet itself. Watching that disk evolve will help scientists with their models of both moon and planetary formation.
That evolution is sure to take millions of years, but so far PDS 70c is the only known planet with any type of circumplanetary disk. The same data set confirming its existence showed that it’s Saturn-like twin, PDS 70b, does not have a disk that some scientists had previously suggested. Others might be found with more powerful telescopes, but until then this system is the best we have.
Given its uniqueness, the PDS 70 system will remain a focal point of plenty of observational firepower. Now there’s one more important detail to look into with those instruments – hopefully there will be more details to discover as well.
Max Planck Institute for Astronomy – Astronomers make first clear detection of a moon-forming disk around an exoplanet
Astrophysical Journal Letters – A Circumplanetary Disk around PDS70c
NYT – Astronomers See Moons Forming in Disk Around Distant Exoplanet
Space.com – Astronomers spot 1st 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.