Four massive galaxies are colliding in the largest galactic merger ever seen, new observations reveal. The smash-up is shedding light on how the biggest galaxies in the universe form – and why many of them stopped giving birth to stars billions of years ago.
Astronomers classify mergers according to the relative sizes of the galaxies involved. Now, researchers led by Kenneth Rines of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, US, have found the largest major merger ever seen. It involves a quartet of galaxies at the centre of a galactic cluster known as CL0958+4702, which lies about 5 billion light years from Earth.Three of the merging galaxies are the size of the Milky Way, while the other is about three times as massive
Star plume
Using infrared observations by the Spitzer Space Telescope and optical images from the WIYN Observatory in Arizona, US, the team also discovered a colossal, fan-shaped 'plume' of old, red stars trailing about 360,000 light years from the merger, apparently tossed out of the galaxies as they spiralled towards each other. "That's the other fairly amazing thing – the number of stars in the plume is about three Milky Ways' worth. Eventually, about half of those stars will likely fall into the merged galaxies – which are expected to coalesce into a single mammoth galaxy in about 100 million years – while the other half will float freely outside it, he says. That suggests other free-floating stars previously found within galaxy clusters were also ejected from their birth galaxies during major mergers. This answers the question of how you form the most massive galaxies in the universe." That is because the most massive galaxies yet observed – weighing about 10 times the Milky Way – are found at the centres of nearby galaxy clusters, which are seen as they are now, 13.7 billion years after the big bang. Interestingly, the four merging galaxies are made of old, red stars, suggesting each had lost the gas necessary to form new stars long beforehand, within 5 billion years of the big bang. That agrees with other recent observations showing that galaxies within clusters – which typically contain hundreds of galaxies – contain fewer young stars than those lying outside clusters. The four newly discovered merging galaxies lie 5 billion light years away, meaning astronomers see them as they were 5 billion years ago!!!
Astronomers classify mergers according to the relative sizes of the galaxies involved. Now, researchers led by Kenneth Rines of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, US, have found the largest major merger ever seen. It involves a quartet of galaxies at the centre of a galactic cluster known as CL0958+4702, which lies about 5 billion light years from Earth.Three of the merging galaxies are the size of the Milky Way, while the other is about three times as massive
Star plume
Using infrared observations by the Spitzer Space Telescope and optical images from the WIYN Observatory in Arizona, US, the team also discovered a colossal, fan-shaped 'plume' of old, red stars trailing about 360,000 light years from the merger, apparently tossed out of the galaxies as they spiralled towards each other. "That's the other fairly amazing thing – the number of stars in the plume is about three Milky Ways' worth. Eventually, about half of those stars will likely fall into the merged galaxies – which are expected to coalesce into a single mammoth galaxy in about 100 million years – while the other half will float freely outside it, he says. That suggests other free-floating stars previously found within galaxy clusters were also ejected from their birth galaxies during major mergers. This answers the question of how you form the most massive galaxies in the universe." That is because the most massive galaxies yet observed – weighing about 10 times the Milky Way – are found at the centres of nearby galaxy clusters, which are seen as they are now, 13.7 billion years after the big bang. Interestingly, the four merging galaxies are made of old, red stars, suggesting each had lost the gas necessary to form new stars long beforehand, within 5 billion years of the big bang. That agrees with other recent observations showing that galaxies within clusters – which typically contain hundreds of galaxies – contain fewer young stars than those lying outside clusters. The four newly discovered merging galaxies lie 5 billion light years away, meaning astronomers see them as they were 5 billion years ago!!!
1 comment:
The collision of galaxies!!! Great!!!
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