Holz & Wheeler ( [ ] ) have recently proposed that a Schwarzschild black hole may act as a retro-lens which , if illuminated by a powerful light source , deflects light ray paths to large bending angles and a series of luminous arcs ( or rings in the case of aligned objects ) centered on the black hole may form .
Obviously , the most convenient geometry to get retro-lensing images would be that of a very bright star close to a massive black hole , say the putative \sim 4 \times 10 ^ { 6 } M _ { \odot } black hole at the galactic center .
Recent observations of the galactic center region in the K -band have revealed the presence of a very bright main sequence star ( labelled S2 ) with mass \sim 15 
M _ { \odot } orbiting at close distance ( 130 - 1900 AU ) from Sgr A ^ { * } .
The relatively vicinity of S2 to the central massive black hole may offer a unique laboratory to test the formation of retro-lensing images .
The next generation of space-based telescopes in the K -band ( like NGST ) may have high enough limiting magnitude necessary to observe such retro-lensing images .