Considered as a gedanken experiment are the conditions under which the relativistic Doppler shifting of visible electromagnetic radiation to beyond the human ocular range could reduce the
incident radiance of the source, and render a luminous astrophysical body (LAB) invisible to a naked eye. This paper determines the proper distance as a function of relativistic velocity
at which a luminous object attains ocular invisibility.

Black Sun: Ocular Invisibility of Relativistic Luminous Astrophysical Bodies.

Lee, J.S. and Cleaver, G.B. (2016)

Journal of High Energy Physics, Gravitation and Cosmology, 2, 562-570.

http://dx.doi.org/10.4236/jhepgc.2016.24048