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Tribune News Service
DWARF galaxies orbiting the much larger galaxy Centaurus A appear to be moving along the same plane as one another. If this coordinated dance around a galactic hub is common in the cosmos, we may have to rethink our ideas about how galaxies form. But that is a big if.
Dwarf galaxies are thought to be captured by larger galaxies into random orbits based on the direction they came from. In this view, large galaxies are like hoarders, snatching up satellite galaxies and tossing them wherever. With Centaurus A, however, it is more like a collector has put them in a row on a shelf.
The coordinated dwarf galaxies were spotted by Oliver M'fcller at the University of Basel, Switzerland, and his colleagues, who found that 14 out of 16 known satellite galaxies circle Centaurus A on the same plane, suggesting that this may be common. To locate them, the team relied on velocity measurements based on redshift and blueshift: how an object's light changes colour as it moves away from or towards an observer.
To be sure of their alignment, we need an accurate 3D model of the satellite galaxies' positions around Centaurus A, says Rachael Beaton at the Carnegie Observatories in California. She says uncertainty in these new measurements means the orbits of these dwarf galaxies may not be as nicely aligned as they seem.
