How we found the Milky Way’s bar: This Week in Astronomy with Dave Eicher – Astronomy Magazine

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The Milky Way is no ordinary spiral galaxy, but instead features an elongated bar of stars at its center with mysteries that astronomers are still trying to unlock.

The Milky Way's central region has not just a spherical core but an elongated bar of stars. Credit: NASA/JPL-Caltech/R. Hurt (SSC/Caltech)

Its difficult to see the shape of something from inside of it and nowhere is that truer than in our own Milky Way Galaxy. It wasnt until 1923 that Edwin Hubble found definitive evidence that the Milky Way was just one of many other galaxies. And even after that, for decades, the shape of Milky Way was assumed to be a normal spiral galaxy.

But in 2005, a team led by astronomers from the University of Wisconsin-Whitewater found strong evidence that the Milky Way is in fact a barred spiral galaxy. The team used data from NASAs Spitzer Space Telescope, an infrared telescope that was a forerunner to the current James Webb Space Telescope. Observing in infrared light allowed Spitzer to peer through interstellar dust and survey 30 million stars in the plane of the Milky Way in a project named the Galactic Legacy Mid-Plane Survey Extraordinaire, or GLIMPSE. That survey indicated that there was a long bar of stars extending from the galactic core a feature seen in many other galaxies.

Today, we know that the Milky Way is indeed a barred spiral galaxy. But astronomers still havent gained a complete picture of the bar, making it difficult to know precisely how large it is. But the European Space Agencys Gaia spacecraft which is making the largest ever 3D map of the stars in the Milky Way is starting to directly measure the galactic bar for the first time.

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How we found the Milky Way's bar: This Week in Astronomy with Dave Eicher - Astronomy Magazine