[mhluongo]

Publicly verifiable randomness is possible without relying on astronomical events. Check out threshold relay by the Dfinity team (which we're porting to Ethereum), or RandHound and RandHerd [1].

1 - https://eprint.iacr.org/2016/1067.pdf

[barbegal]

That paper assumes that at most f out of at least 3f+1 participants are dishonest. In practice one can't make that assumption since sybil attacks are easy.

[mhluongo]

You can bootstrap a Sybil-resistant system using PoW or some other method. This is one building block.