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Have we found the edges of our galaxy?
Current affairs | 25 March 2020
Text Finn Blythe

Until this point, measuring the Milky Way has been like trying to catch smoke with your bare hands. Made up primarily of dark matter, invisible particles that are virtually undetectable to current telescopes, and spanning many millions of light-years, establishing its beginning and end has, understandably, perplexed scientists for decades.

Mystery surrounds not only the brightest part of the galaxy, and the exact location of our sun, but the vast disk of gas that lies beyond it. Now astronomers led by Alis Deacon have performed a study to measure dark matter distribution and locate the peripheries of our universe.

In order to locate the Milky Way’s edge, the team used computer simulations of giant galaxies similar to our own. By observing the many galaxies that orbit the Milky Way, they were able to establish the point at which the smallest neighbouring galaxies dropped off in their orbiting speed, and by measuring back to the centre of our galaxy, around 950,000 light-years away, they claim the Milky Way could extend nearly two million light-years. This may prove an important first step for additional research on our galaxy to build upon.

“There is great hope that future data will provide a more robust and accurate measurement of the edge of the Milky Way and nearby Milky Way-mass galaxies than the one we have presented here,” the researchers write.

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