Gigantic cosmic cataclysm in Stephan's Quintet of galaxies
The central region of Stephan's Quintet, showing the complex web of galaxy-galaxy and galaxy-intergalactic medium interactions. The intergalactic shock wave, triggered by the 1000 km/s infall velocity of the intruder galaxy NGC7319b, is delineated by the ridge of Hydrogen emission (shown in green) which runs vertically through this image. NGC7319b is the compact blob, seen both in optical light (coded blue) and in infrared continuum (coded red) immediately to the right of this ridge. Image: NASA/JPL-Caltech
Recent infrared observations made with NASA's Spitzer Space Telescope have revealed the presence of a huge intergalactic shock wave, or "sonic boom" in the middle of Stephan's Quintet, a group of galaxies which is now the scene of a gigantic cosmic cataclysm. This discovery, made by an international research team including scientists from the Max Planck Institute for Nuclear Physics (MPIK) in Heidelberg, provides a local view of what might have been going on in the early universe, when vast mergers and collisions between galaxies were commonplace.
When astronomers using NASA's Spitzer Space Telescope turned their attention to a well-known group of galaxies called Stephan's Quintet, they were, quite simply, shocked at what they saw. There, sweeping through the group, lurks one of the biggest shock waves ever seen.
For decades, astronomers using optical telescopes have known that the galaxies in this group, located about 300 million light years away, have a very distorted distribution of visible light from stars, indicating that the galaxies have experienced encounters in the past, and are now engaged in further collisions. But this, as it turns out, is only part of the drama. Recently, astronomers have become able to measure what, apart from the stars, is present in Stephan's Quintet. By looking in the radio and X-rays they discovered huge quantities of gas - about 100,000 million solar masses, mainly composed of hydrogen and helium - in the space between the galaxies, more than all the gas inside the galaxies themselves.
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