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Posted Thu, 01/03/2013 - 09:00 in Science

Astrophysicists make stellar discovery about galaxies far, far away

Together with an international team of astrophysicists, Dal's Scott Chapman has shed new light on how galaxies formed in the early universe. The discovery suggests that the current model for galaxy formation and evolution needs to be reassessed.

Key Points:

  • Andromeda is the nearest 'large' galaxy to the Milky Way, at 2.5 million light years away. Its size and disc-like structure is similar to the Milky Way, and it's often referred to as our companion galaxy. The next closest large galaxy is 10 million light years away.

  • This new study observes 13 smaller satellite galaxies orbiting around the immense Andromeda galaxy in a way similar to how the planets in our solar system orbit around the sun. The galaxies are orbiting on a thin, pancake-like plane at a scale 900 million times larger than our own solar system.

  • The Lambda-Cold Dark Matter (Lambda-CDM) model struggles to explain the formation of these thirteen satellite galaxies orbiting around Andromeda. The Lambda-CDM is a standard model in astrophysics that assumes galaxies collide and merge with one another to grow mass.

  • The discovery also lends support to theories on how satellite galaxies are orbiting around the Milky Way, which is a much harder activity to observe given the earth's position within it—the galaxy itself blocks our view.

  • The researchers are working on a followup study that will explore how the orbital system formed the way that it did, working on the hypothesis that all thirteen galaxies must have formed at the same time within the same structure billions of years ago.

Pull Quotes:

  • "These dwarf galaxies appear to have formed together in the structure, and our analysis is showing their stars seem to have formed at a similar epoch in the early universe." – Peter Smith, graduate student, Department of Physics and Atmospheric Science.

  • "This tells us that this hierarchical buildup that gravitational simulations predict isn't quite right—as structures like this 'andromeda pancake' never happen in the simulations. We may not understand gravity as well as many would like to believe. It's very hard to test gravity in the very weak field limit." – Dr. Scott Chapman, co-author and professor in Department of Physics and Atmospheric Science.


The Andromeda galaxy is pictured on the cover of Nature (January 2, 2013)
Cover of Nature, January 3, 2013
The Andromeda galaxy is pictured on the cover of Nature (January 2, 2013)
Photo Credit: Nature
Download Hi-Res


Nature_animation_MediaCentre 300.flv
Animation detailing the satellite galaxies orbiting around Andromeda
Download high resolution version (broadcast ready).

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