orin stepanek wrote:It would have to be aimed precisely toward us;
Eta Carinae might not be so much of a direct thread to us. WR104 is more frightening.
You further wrote: besides it would have a narrow beam and still it is about 8000ly away.
The angle of the beam is ≅ 0.2 radian. The characteristic width of the bundle would be approx. 1500ly.
You further wrote: how long would a planet take to pass through the beam? Everything is moving along pretty fast through space.
That depends on the releative tangential motion between the source and recipient. Like on the highway: everybody is moving pretty fast, yet when a large truck takes over another truck, it takes some time, due to a small difference in their relative motion.
The speed of the sun around the center of galaxy is approx. 300 km/s, (or was it 200 km/s?) so 0.001 of the speed of light. To pass the bundle it would take an odd one million years, if eta Carinae isn't moving.
Regards,
Henk