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I’m not sure of the distinction between light ring and this, but probably a good place to read: Photon sphere https://en.wikipedia.org/wiki/Photon_sphere

It is a closed lightlike curve. There is no impact on causality, as time does not pass on a lightlike curve.

Thanks. I'd been dividing it between spacelike and timelike. I forgot there was a third option.

A light ring is not a closed timelike curve.