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Dancing galaxies may shake up our ideas of galaxy formation

New Scientist

The dwarf galaxies orbiting the much larger galaxy Centaurus A appear to be moving along the same plane as one another. If this surprisingly coordinated dance around a galactic hub is common across the cosmos, we may have to go back to the drawing board on galaxy formation theory. But that's a big, big if. Theories on galaxy formation suggest that dwarf galaxies should be captured by larger galaxies into random orbits based on the direction they came from. In this view, …


Dancing galaxies may shake up our ideas of galaxy formation

New Scientist

The dwarf galaxies orbiting the much larger galaxy Centaurus A appear to be moving along the same plane as one another. If this surprisingly coordinated dance around a galactic hub is common across the cosmos, we may have to go back to the drawing board on galaxy formation theory. Theories on galaxy formation suggest that dwarf galaxies should be captured by larger galaxies into random orbits based on the direction they came from.


Dancing galaxies may shake up our ideas of galaxy formation

New Scientist

The dwarf galaxies orbiting the much larger galaxy Centaurus A appear to be moving along the same plane as one another. If this surprisingly coordinated dance around a galactic hub is common across the cosmos, we may have to go back to the drawing board on galaxy formation theory. Theories on galaxy formation suggest that dwarf galaxies should 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. In Centaurus A, however, it is more like a collector has neatly put them in a row on a shelf.


Space Photos of the Week: A Galaxy Takes a Punch Like a Pro

WIRED

Caption: This image shows the Vela ring galaxy, visible as a bright core surrounded by a baby blue halo. As the name suggests, this ring galaxy -- located in the southern constellation of Vela (The Sails) -- is notable due to its compact core and large circular belt of gas and stars. It is thought that ring galaxies like this are created when larger galaxies are punctured by a smaller galactic aggressor, which, passing through the heart of its more sizable victim, triggers a shock wave that spreads outwards. This pushes gas to the galaxy's periphery, where it begins to collapse and form new stars. The Vela ring galaxy is unusual in that it actually exhibits at least two rings, suggesting that the collision was not a recent one.ESO


Dark matter took its time to wrap around early galaxies

New Scientist

Darkness gathers – but it can take time. About 10 billion years ago, massive star-forming galaxies were dominated by normal matter, not the dark matter that's so influential in galaxies today. If spiral galaxies were only made up of the matter that we can see, stars at the outer edge should orbit the centre slower than those closer in. But in the 1970s, American astronomers Vera Rubin and Kent Ford noticed that this was not the case: all the stars in the Andromeda galaxy move at similar speeds, regardless of their distance from the galactic center. This study constituted some of the first evidence for dark matter, matter that doesn't interact with light and which we can only observe via its gravitational effects.