[Spacetectonics (OP)]

 binary orbits are inherently unstable, and will eventually spiral in towards one another and eventually triggering a Type Ia supernova ,it gets radiated away, but in gravitational radiation .

My question is :What happens to light when crosses gravitational radiation zone(binary orbit)?

[evan_au]

If the two objects are very massive (like a white dwarf and a neutron star) and in fairly close proximity, then a significant amount of energy will be radiated away as gravitational waves, causing the two objects to spiral inwards. This effect has been detected in the case where one of the objects is a pulsar.

If the two objects are close enough for matter to be pulled off the larger object onto the more compact object, then a light ray passing between them will be absorbed by the cloud of matter being pulled between them.

If the two objects are distant enough for each object to be self-contained, then a light ray passing between them will be deflected by the intense gravitational field of each object, but will continue onwards, providing it doesn't strike the atmosphere of either object.

Note: In other cases where the objects are not so massive, like a planet and a normal star, or where they are well-separated, such as the Earth and the Sun, the amount of gravitational radiation will be negligible, and a binary orbit will be quite stable. Other effects like the solar wind will have more effect than gravitational radiation.