What this new study – spearheaded by Penn State doctoral student Alexander Richert – does is enhance this original model. As it turns out, aside from PeI, there’s another destructive artist at work here: the pressure of starlight.
Electromagnetic radiation of any kind causes pressure changes whenever it passes through a medium. As photons bounce off the surface of matter they encounter, they transfer their momentum to it, like a ghostly hand pushing down on a table. The pressure increase is incredibly small per photon, but if you have enough of them, it can add up.
Highly energetic stars near debris disks, then, also exert a not-insignificant radiation pressure on those clumps of gas and dust, which alters their shape. As the team explain in their study – not yet peer-reviewed, but available here as a pre-print – this can mold debris disks into spiral patterns.
Along with Pel, these two mechanisms neatly explain the unique forms of many disks spotted over the last few years, all without needing to invoke planetary action.
The story likely won’t end here. There are other ways to make debris disks unique, and the team suggest a few.
One rather marvelous idea, first discovered in 1959, is that gases containing free electrical charges can be influenced by regional magnetic fields. This “magnetorotational instability” or MRI can cause the disk to become somewhat unstable, and stretch out, creating endless new forms.
In any case, this new study reminds us that there’s so much we have yet to discover about the theatrics of the universe. In time, we’re sure that other cosmic ballets, hidden for billions of years, will be uncovered by work like this.