Giant cosmic tails point to a recent marriage
ICRAR astronomers Jonathan Diaz (left) and Dr Kenji Bekki (right) have created a new explanation for how a giant stream of gas came to trail behind the Magellanic Clouds.
New models show that our nearest galactic neighbours became entangled in a cosmic dance over the past few billion years, with a dramatic close encounter around 1.2 billion years ago.
In a paper to be published in the Monthly Notices of the Royal Astronomical Society, International Centre for Radio Astronomy Research (UWA) astronomers Jonathan Diaz and Dr Kenji Bekki have modelled the movement of the Large and Small Magellanic Clouds around the Milky Way and the structure of the gas that surrounds them.
“An enormous stream of hydrogen gas trails behind the Magellanic Clouds as they orbit the Milky Way,” says ICRAR student Jonathan Diaz.
“Previous explanations for the oversized tail had it being stripped away from the Magellanic Clouds during a close approach of the Milky Way around 2 billion years ago.”
However, recent observations made by the Hubble Space Telescope have cast doubt on whether that close approach actually occurred. The new data from Hubble shows that the Magellanic Clouds are moving differently than originally thought.
“We have found a solution to the question raised by the Hubble data, explains Diaz. Weve shown that its possible for the gas stream to form through a violent interaction between the two small galaxies around 1.2 billion years ago, without the need for a strong interaction with the much larger Milky Way.”
“Past models have assumed that the Magellanic Clouds have been cosmic companions since birth, but our work demonstrates a recent and quite dramatic coupling between the Clouds.”
“Our model shows the Magellanic Clouds have been drifting around the Milky Way for many billions of years, but have only just recently found each other,” says Dr Kenji Bekki, supervisor of the project.
“Were going to conduct further simulations and refine our model but this result shows us we still have more to learn about our galaxy and its neighbourhood.”
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Diaz J. and Bekki K, Monthly Notices of the Royal Astronomical Society. Available online at:http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2966.2011.18289.x/abstract