The paper suggests the presence of the carbon chain C_5_ molecule in translucent, interstellar HI clouds. This species, the only five atom interstellar molecule, observable in dark, translucent clouds, seems to be observable in reasonably dense clouds, causing also rather high reddening. The paper shows two likely discovered spectral features of C_5_, A^1^{Pi}u-X^1^{Sigma}g^+^ bands near 4975 and 5109{AA}. The attempt to discover the 3789{AA} C_4_ feature gave the negative result.