The globular cluster Messier 4 (NGC 6121) in Scorpius, shown from a 15-second V-band exposure with a Tektronix 2048x2048 CCD at the prime focus of the 4-meter Mayall telescope of Kitt Peak National Observatory. North is at the top and east to the left, for direct comparison with a chart or eyepiece view. The image has been block-averaged to 512x512 for this presentation, which uses a logarithmic intensity transformation to preserve information across a wide dynamic range. The field is 14.3 arcminutes square; pixels were averaged 4x4 for this display.
M4 is among the closest globular clusters, as seen from its large apparent size. However, it suffers substantial dust obscuration, lying in a direction close to the huge Rho Ophiuchi dust complex. HST images have identified white dwarfs in M4, potentially important as an age indicator completely independent of the uncertainties in modelling evolution of main-sequence and giant stars.
Last changes: 4/2001 © 2001