These images offer a dramatic look at a spiral galaxy like our Milky Way being ripped apart as it races at 4.5 million miles per hour through the heart of a distant cluster of galaxies. The images, taken over several wavelengths, provide evidence of the "galactic assault and battery," namely, gas being stripped from the doomed galaxy, called C153.
The composite photograph at left was made by combining the four images at right, taken in X-ray, radio, and visible wavelengths as well as the green light of oxygen gas. Astronomers studied the galaxy across several wavelengths to trace how stars, gas, and dust are being tossed around and torn from the fragile galaxy.
The composite image at left shows long streamers of gas flowing from the galaxy as it travels through the cluster, called Abell 2125. Hot gas from the cluster is stretching the galaxy's cooler gas into long streamers. Velocity measurements of several hundred galaxies in the cluster indicate that C153 is moving away from Earth within the cluster. The image, therefore, shows the streaking tail of "stripped gas." The image spans about 1 million light-years across. Abell 2125 is about 3 billion light-years away, on the boundary between the constellations Ursa Minor and Draco.
The visible-light image [above, right], taken by the Wide Field Planetary Camera 2 aboard NASA's Hubble Space Telescope, reveals intricate detail in the structure of stars and dust within C153. The galaxy exhibits evidence of a large-scale disturbance that has left its star-forming regions concentrated to one side of its disk and beyond. Dust features are twisted into chaotic patterns, obscuring any spiral pattern the galaxy once had.
X-ray emission [above, right], imaged by the Chandra X-ray Observatory, shows a gas tail extending from C153, which roughly matches the glowing gas tail observed in visible light. The temperature of the gas tail is cooler than the surrounding gas. This temperature difference is further evidence that gas is being "stripped" from the galaxy. The hotter gas is so diffuse that it cannot be seen in the image.
Radio observations [below, right] depict high-energy particles as they spiral through the galaxy's magnetic field, with some escaping in a perpendicular direction to the galaxy's disk. The particles probably came from an energetic black hole that was fueled by a collision between two galaxy clusters. This emission first marked C153 as unusual, leading scientists to conduct further observations.
The image [below, right], taken by the 4-meter Mayall telescope at Kitt Peak National Observatory, isolated the light from glowing oxygen gas. This view shows a tail forming as gas is pulled from the galaxy and stretched into long streamers that extends for about 200,000 light-years.
Credit: NASA, W. Keel (U Alabama), F. Owen (NRAO), M. Ledlow (Gemini Obs.), and D. Wang (U Mass.)