“It’s Massive!” –Our Milky Way Galaxy May Be Twice as Big as Previously Thought


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It’s no secret that the Milky Way is huge, long thought to be about 100,000 light-years end to end with about 200 billion stars and their orbiting planets, but new research shows that it may be much bigger than we ever imagined –a vast rotating disk of stars spans at least 170,000 light-years, and possibly up to 200,000 light-years.


Researchers at the Canary Islands Institute of Astrophysics and the National Astronomical Observatories of Beijing turned to a pair of star atlases and studied the chemical composition of thousands of stars in the outermost parts of the galactic plane — the plane that extends through the center of the disk using a statistical analysis to confirm that the far-flung stars are chemically similar to the stars in the galactic disk and thus should be considered part of it.


The colored region is the previously known galactic disk. The new research has extended its limits much farther away: there is a probability 99.7% or 95.4% respectively that there are disk stars in the regions outside the dashed/dotted circles. Yellow dot is the position of the sun. Background Milky Way image from “A Roadmap to the Milky Way.”R. Hurt / SSC-Caltech, NASA/JPL-Caltech


The research also gives a new sense of the sun’s position within the Milky Way, which previously thought that the sun orbits the center of our galaxy at about half the galactic radius. But astronomers now know that some stars are more than three times that distance from the galaxy’s center possibly more than four times which means that our sun it’s much closer to the center of the galaxy than thought.

The Daily Galaxy via Astronomy & Astrophysics

Image credit top of page: With thanks to National Geographic


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