>>11131781for the q in the pic it is not really massless
If a photon were orbiting a black hole as in moving tangent to the event horizon said black hole would measure as being the energy equivalent of said photon converted to rest mass heavier (immeasurably small difference)
the issue is that when space isn't bent so much that the photon could never escape it doesn't cause a gradient in the gravitational field except as a gravitational wave far too small in magnitude and fast moving to ever be detected because it is radiating uncontained in all directions in space so you can't localize it as a point mass and it only has a point like interaction when it interacts with a particle
essentially regular restmass comes from folded dimensions holding light into some geometry creating what we call mass. Photons as a simpler or more primitive configuration of energy are still energy but you would have no way of measuring their effect on space/time without trapping them in a potential well first to concentrate said effect. It would still be too small to measure then as relative to the object holding it it would be like looking for one hydrogen atoms difference in the observable universes mass. All energy is the same by the way. hope this help/confuses you because the concern over the topic would be more simply handled by saying all energy is just energy and photons just aren't much energy therefore their gravity is real but also irrelevant except cosmologically/collectively
