Scientists Discover Dwarf Galaxies Don't Swarm: They Dance

Astronomers are learning more about our universe each day. Now, they've taken a closer look at dwarf galaxies and have found that they don't "swarm" around larger ones like bees, but actually "dance" in orderly, disc-shaped orbits.

The universe is home to billions of galaxies. While some are immense, though, others are small. In fact, most galaxies are dwarf galaxies, which only house a few billion stars. For decades, scientists have tried to predict how these dwarf galaxies should orbit larger galaxies; most concluded that these orbits should be somewhat random. Yet a recent discovery indicated that the models weren't correct.

"Early in 2013 we announced our startling discovery that half of the dwarf galaxies surrounding the Andromeda Galaxy are orbiting it in an immense plane," said Geraint Lewis, one of the researchers, in a news release. "This plane is more than a million light years in diameter, but is very thin, with a width of only 300,000 light years. Our Andromeda discovery did not agree with expectations, and we felt compelled to explore if it was true of other galaxies throughout the universe."

In order to learn a bit more about galaxy orbits, the researchers dissected the properties of thousands of nearby galaxies by using data from the Sloan Digital Sky Survey. In the end, they found that a large proportion of pairs of satellite galaxies have oppositely directly velocities if they are situated on opposite sides of their giant galaxy hosts.

"Everywhere we looked we saw this strangely coherent coordinated motion of dwarf galaxies," said Lewis. "From this we can extrapolate that these circular planes of dancing dwarfs are universal, seen in about 50 percent of galaxies. This is a big problem that contradicts our standard cosmological models. IT challenges our understanding of how the universe works including the nature of dark matter."

The findings reveal a bit more about the physics of the universe and pave the way for future investigations when it comes to learning a bit more about galaxies.

The findings are published in the journal Nature.