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News  Flies in a spider’s web: galaxy caught in the making
New Hubble images have provided a dramatic glimpse of a large massive galaxy under assembly as smaller galaxies merge. This provides the best demonstration so far that large massive galaxies form by merging smaller ones. This formation process has commonly been thought to be the way galaxies grew in the young Universe. New Hubble observations of the radio galaxy MRC 1138-262, nicknamed the 'Spiderweb Galaxy', have shown dozens of star-forming satellite galaxies in the actual process of merging.
In nature spiders earn our respect by constructing fascinating, well-organised webs in all shapes and sizes. But the beauty masks a cruel, fatal trap. Analogously, the NASA/ESA Hubble Space Telescope has found a large galaxy 10.6 thousand million light-years away from Earth that is stuffing itself with smaller galaxies caught like flies in a web of gravity. The galaxy is so far away that astronomers are seeing it as it looked in the early formative years of the Universe, only 2 thousand million years after the Big Bang.
Team leader George Miley from Leiden Observatory in the Netherlands explains: "The new Hubble image is the best demonstration so far that large massive galaxies are built up by merging smaller ones." The image reaches much deeper than previous ones and shows the merging process in unprecedented detail. Galaxies can be seen as they are sucked into the Spiderweb at speeds of several hundred kilometres per second, from distances of more than a hundred thousand light years around it.
The new Hubble image provides a unique example for testing theoretical models of massive galaxy formation. The complexity of the Spiderweb is qualitatively consistent with the predictions of such models, but the Spiderweb Galaxy shows the surprising presence of several faint small linear galaxies within the merging structure.
The Spiderweb Galaxy is located in the southern constellation of Hydra (the water snake) and is one of the most massive galaxies known.
Notes for editors This result is published in the 10 October 2006 issue of the Astrophysical Journal Letters. The Hubble Space Telescope is a project of international cooperation between ESA and NASA.
Acknowledgement: The ACS Science Team and Davide de Martin
For more information George K. Miley, Leiden Observatory, Leiden, The Netherlands Email: miley @ strw.leidenuniv.nl
Lars Lindberg Christensen, Hubble/ESA, Garching, Germany
Ray Villard, Space Telescope Science Institute, Baltimore, USA
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