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The Galaxy May Be Way Bigger Than We Thought

New data analysis suggests that the Milky Way may be 50-percent larger than previously believed

A view of the center of the Milky Way Galaxy. (Martin Rietze/moodboard/Corbis)
smithsonian.com

Compared to the relative pinprick scale of our humble solar system, the Milky Way is huge. NASA previously estimated that the galaxy spans about 100,000 light-years across, and at 6 trillion miles a light-year, we’re talking virtually unimaginable breadth. But try to stretch your mind just a little bit further—new research suggesting that the galaxy may be 50,000 light-years bigger than once theorized.

This new insight all comes down to a thin strand of stars called the Monoceros Ring, which scientists discovered in 2002 surrounding the outer-reaches of the Milky Way, reports Irene Klotz over at Discovery News. At first, the identifying team suspected that the ring to be “a tidal debris stream” left over from the remnants of a neighboring dwarf galaxy. But a debate soon emerged over whether it is in fact a part of our galaxy’s disk.

New analysis of data collected by the Sloan Digital Sky Survey measuring the brightness and distance of stars on the edge of the Milky Way is sure to add more fuel to the dispute. It showed, according to Klotz, “that the fringe of the disk is puckered into ridges and grooves of stars, like corrugated cardboard.”

“It looks to me like maybe these patterns are following the spiral structure of the Milky Way, so they may be related,” astronomer Heidi Newberg told Discovery News.

She and colleagues suspect that a dwarf galaxy may have plunged through the disk of the Milky Way, setting off ripples, like a pebble falling into a pond.

Intruder galaxies also may have set up spiral wave patterns that later trigger star formation in the gas along waves, leading to spiral arms in galaxies.

Newberg, who was also involved in the discovery of the Monoceros Ring, came upon the new information while searching for evidence that the star stream is actually not part of the galaxy. Finding evidence to the opposite surprised her—and means that, if the theory she reached along with her colleagues is right, the scale of the Milky Way may be 50 percent bigger than current estimates.

The research is set to be published this week in the Astrophysical Journal, but astronomers are already hoping that 3D, higher-resolution images of the ring of stars will provide further and more conclusive information. Using Europe’s Gaia telescope, they’ll also be investigating another string of stars beyond the Monoceros filiment. Should that ring also belong to our galaxy, the Milky Way’s measurements will grow even larger.

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