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Dwarf Galaxies That Dance? Andromeda Observations Reveal A Larger Cosmic Mystery

Astrophoto: Andromeda Galaxy by Fabio Bortoli

Andromeda Galaxy. Credit: Fabio Bortoli

What is up with these dwarf galaxies? A survey of thousands of galaxies using the Sloan Digital Sky Survey reveals something interesting, which was first revealed by looking at the massive Andromeda Galaxy nearby Earth: dwarf galaxies orbiting larger ones are often in disc-shaped orbits and not distributed randomly, as astronomers expected.

The finding follows on from research in 2013 that showed that 50% of Andromeda’s dwarf galaxies are in a single plane about a million light-years in diameter, but only 300,000 light-years thick. Now with the larger discovery, scientists suspect that perhaps there is a yet-to-be found process that is controlling gas flow in the cosmos.

“We were surprised to find that a large proportion of pairs of satellite galaxies have oppositely directed velocities if they are situated on opposite sides of their giant galaxy hosts,” stated lead author Neil Ibata of Lycée International in France.

“Everywhere we looked, we saw this strangely coherent coordinated motion of dwarf galaxies,” added Geraint Lewis, a University of Sydney physicist. “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 astronomers also speculated this could show something unexpected in the laws of physics, such as motion and gravity, but added it would take far more investigation to figure that out.

The findings were published in the journal Nature.

Source: University of Sydney

About 

Elizabeth Howell is the senior writer at Universe Today. She also works for Space.com, Space Exploration Network, the NASA Lunar Science Institute, NASA Astrobiology Magazine and LiveScience, among others. Career highlights include watching three shuttle launches, and going on a two-week simulated Mars expedition in rural Utah. You can follow her on Twitter @howellspace or contact her at her website.

Comments on this entry are closed.

  • john kulick July 22, 2014, 10:31 AM

    The matter that makes up Galaxies enters the Universe as jets that are spatially separated with the Universe having an initial spatial size.
    (All the matter in every atom, in every star, in every galaxy, do not enter the Universe at a singularity)
    The jets tend to align matter along the axis, hence the shared orientation of matter on the same plane and the opposite spin on opposite sides of the galaxy.
    There is no Dark Matter, but there is an additional accelerative field effect that draws matter inwards, besides gravity.

  • Zoutsteen July 22, 2014, 4:42 PM

    Try give the Galaxy some velocity in any direction and see what kind of velocity is needed for Gas or Dwarf Galaxies to keep up.

    My guess:
    at least a velocity in about the same direction as the Galaxy, which would reduce the angle of any captured Dwarf Galaxy (or Gas) to within a single plane.

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