How Does Stellar Radiation Clear Dust from a Proto-Planetary Disc?

[RJ Emery]

How does radiation from a star clear dust from a proto-planetary disc, changing the area from one of opaqueness to one of transparency?

Please note that I am a retired engineer with an interest in astronomy, cosmology and particle physics but very much a layman..

 

[Drakkith]

Radiation pressure forces the dust outwards and away from the star.

 

[RJ Emery]

Thanks for answering my question.

 

[Drakkith]

Thanks for answering my question.

Thanks for asking your question.

 

[sophiecentaur]

How does radiation from a star clear dust from a proto-planetary disc,

I'd like to add to the contribution from @Drakkith . You might ask why the radiation affects just the dust and not all the bigger stuff. It's because the area that the radiation acts on an object (and hence the force) is proportional to the radius squared (A = πr²) BUT the gravitational force on an object is proportional to its Mass, which is proportional to the radius cubed. (Mass = density times 4πr³/3). For small objects the radiation pressure wind and for large (massive) objects, the gravitational force wind.
This is just an example of how things don't scale in a simple way - why fleas can jump much higher than elephants - in terms of the animals' own height - and why a mouse can jump of the Empire State Building and land safely but one of us . . . . . . . .