This image is a close-up view from the NASA/ESA Hubble Space Telescope of NGC 4755, or the Jewel Box cluster. Several bright, pale blue supergiant stars, a solitary ruby-red supergiant, and a variety of other brilliantly colored stars are visible in the image, as well as many fainter ones, often with intriguing colors. The huge variety in brightness exists because the brighter stars are 15 to 20 times the mass of the Sun, while the dimmest stars are less than half the mass of the Sun. This is the first image of an open galactic cluster with imaging extending from the far ultraviolet to the near-infrared.
NASA/ESA/Jesús Maíz Apellániz (Instituto de Astrofísica de Andalucía, Spain)