Fastest star ever seen is moving at 8% the speed of light

An observer on earth?

A very Henry Kissinger thing to say.

It's relative to Sagittarius A* , the black hole at the center of our galaxy, which this star is orbiting. Or you could say relative to our galaxy, since Sagittarius A* appears to be stationary within it.

However, 8% of the speed of light (24000 km/s) is so fast that the orbital speed of the sun in the galaxy (200km/s) and the orbital speed of the Earth around the sun (30km/s) are negligible in comparison. So you might as well say that it is relative to Earth.

I don't know enough physics to give a proper answer, but I think this example is wrong. I don't think you can measure your speed relative to something moving at the speed of light, because there is no reference frame for the photon to be 'at rest'. Even in the photons own reference frame, it's still moving at c.

No, you are not. Photons do not experience time and so there is no such thing as photon frame of reference.

Moreover, photons (in vacuum) will always be observed to travel at the same speed regardless of the observer's frame of reference.