![]() "In their early formative years, galaxies might have been pretty small and they bled stars pretty easily because of a weaker gravitational grasp." Current theories cannot explain our results, but somehow they were produced in large quantities in the early universe," said Jee. "We don't exactly know what made them homeless. But that is not the case in the new Hubble data, which show a constant fraction over billions of years. That's because the intracluster light fraction would increase over time to the present if stripping is the main player. However, based on the new Hubble survey, Jee rules out this mechanism as the primary cause for the intracluster star production. In the process, drag pushes gas and dust out of the galaxy. Stars can be scattered outside of their galactic birthplace when a galaxy moves through gaseous material in the space between galaxies, as it orbits the center of the cluster. His results are bei ng published in the January 5 issue of Nature magazine. "This means that these stars were already homeless in the early stages of the cluster's formation," said James Jee of Yonsei University in Seoul, South Korea. The survey reveals that the fraction of the intracluster light relative to the total light in the cluster remains constant, looking over billions of years back into time. These measurements must be made from space because the faint intracluster light is 10,000 times dimmer than the night sky as seen from the ground. The survey included 10 galaxy clusters as far away as nearly 10 billion light-years. ![]() The new Hubble observations suggest that these stars have been wandering around for billions of years, and are not a product of more recent dynamical activity inside a galaxy cluster that would strip them out of normal galaxies. The nagging question for astronomers has been: how did the stars get so scattered throughout the cluster in the first place? Several competing theories include the possibility that the stars were stripped out of a cluster's galaxies, or they were tossed around after mergers of galaxies, or they were present early in a cluster's formative years many billions of years ago.Ī recent infrared survey from NASA's Hubble Space Telescope, which looked for this so-called "intracluster light" sheds new light on the mystery. These stars are not gravitationally tied to any one galaxy in a cluster. In giant clusters of hundreds or thousands of galaxies, innumerable stars wander among the galaxies like lost souls, emitting a ghostly haze of light. Understanding the origin of intracluster light could give astronomers new insights into the assembly history of entire galaxy clusters. (The escape velocity from our Milky Way is over 1 million miles per hour). Billions of years ago galaxies would have been smaller than seen today, and they probably shed stars pretty easily because of a weaker gravitational pull. Although the first clues came in 1951, Hubble can easily detect this light even though it's 1/10,000th the glow of the night sky as seen from the ground-based telescopes. The nighttime sky would appear inky black and starless to any inhabitants orbiting their parent sun, save for the feeble soft glow of neighboring galaxies peppering the sky.Ĭollectively, the dim dispersed glow from these wayward stars forms a background called intracluster light that is evidence they are lurking around. But there are many stars wandering about inside giant clusters of hundreds or thousands of galaxies. We are nestled inside the sprawling Milky Way galaxy, an empire of stars. Thanks to Hubble, astronomers now know about entire families of stars – and presumably their planetary systems – that don't even have a galaxy to call home. But truth is stranger than fiction when it comes to Hubble Space Telescope discoveries. In the 1960s sci-fi television show "Lost in Space" a small family of would-be planetary colonists get off course and lost in our galaxy. Four Successful Women Behind the Hubble Space Telescope's Achievements.Characterizing Planets Around Other Stars.Measuring the Universe's Expansion Rate.
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