Serpens Caput contains many RR Lyrae variables, although most are too faint to be seen without professional photography. The brightest is VY Serpentis, only of 10th magnitude. This star's period has been increasing by approximately 1.2 seconds per century.[34] A variable star of a different kind is Tau4 Serpentis, a cool red giant that pulsates between magnitudes 5.89 and 7.07 in 87 days.[35] This star has been found to display an inverse P Cygni profile,[36] where cold infalling gas on to the star creates redshifted hydrogen absorption lines next to the normal emission lines.[37]