Scientific Discoveries: Spectacular galactic collision spawns cosmic tadpole

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Spectacular galactic collision spawns cosmic tadpole

by Valerie Jamieson
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(Image: NASA, Holland Ford (JHU), the ACS Science Team and ESA)

Galaxy catalogues call it UGC 10214, but to everyone else this is the tadpole. Located 420 million light years away in the constellation Draco, its most dramatic feature is its 280,000-light-year-long tail.

The tadpole spawned its tail of debris when two galaxies collided, ripping each other apart over the achingly slow span of cosmic time. The smaller of the two galaxies is still visible on the upper left side of the larger one, which forms the tadpole’s head. Material torn from the larger galaxy spreads out into the tail, which swarms with young blue stars formed from collapsing gas and dust, older stars clumped together in clusters and new-born dwarf galaxies.

The tadpole and other galaxies like it might help to explain an outstanding mystery about our own galaxy, the Milky Way. Cosmology predicts there should be thousands of dwarf galaxies sprinkled randomly all around it. Yet observations show that just 26 dwarf galaxy companions orbit the Milky Way in a thin disc. Collisions like this one in our galaxy’s distant past might be an alternative mechanism that explains the discrepancies.

Just like the real thing, the tadpole galaxy will lose its tail. Eventually all the debris will be mopped up into satellite galaxies orbiting the grand giant.

Journal reference: arXiv:1406.1799

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