Light year

[Zhibek]

Light year is the distance light travels in one year. What does mean light? Particles from which star? Are particles like photons differ from various stars ?

 

[Zhibek]

Gravitational lensing - when light encounetrs gravity well it follows the local curvature which bends light onto a new path.( internet) . It means that distances in light years from cosmic objects are not right

 

[billslugg]

All stars give off photons of all wavelengths. The intensities of each wavelength vary by the star.
Any two photons of the same wavelength have the same energy.
Gravitational lensing causes distances to vary. This is why a single supernova can be seen many times spread out over several years as the various images arrive here at Earth.