Milky Way ‘X’ Shape Discovery Via Twitter: Light Years Of Stars Mark The Center Of The Galaxy

There’s a huge “X” made of stars marking the center of the Milky Way galaxy, just as if it were the spot on a galactic treasure map. The massive star structure had been predicted for years, but scientists were unable to prove its existence. Until now, that is. And all it took was a Twitter photo and the right person to recognize what was there.

CNN reported July 21 that Dustin Lang, a research associate for the Dunlap Institute for Astronomy & Astrophysics at the University of Toronto, was showing off — Lang’s own words — after he created an interactive website,, with maps of selected galaxies and then decided to share some of his work on Twitter. He said he did not expect to get the response he did.

Melissa Ness, who does research at the Max Planck Institute for Astronomy in Heidelberg, Germany, saw the “zoomed-out, whole-sky view” posted to Twitter and quickly recognized that there was an X-shaped bulge of stars at the galactic center of the Milky Way. That “bulge” is a common feature in spiral galaxies and, although it had been predicted to exist at the Milky Way’s center, it had yet to be proven.

She recalls, “It was simply the most fantastic image of the Milky Way bulge that I had seen. I studied the bulge for my Ph.D. and so was well aware that there are numerous works and data that demonstrate that there is an underlying X-shape in the bulge, and in fact it had been modeled in detail from these prior works, but with that image that Dustin had made, we were clearly seeing this X-shape directly in a real image of the inner region of the galaxy, for the first time.”

She wasted no time in contacting Lang to apprise him of the importance of the image. They soon began collaborating on a study to analyze the “X” shape at the galactic center, with Lang providing the photographic data and Ness contributing the scientific analysis.

The study was conducted with a re-analysis by Lang of previously released data from the Wide-field Infrared Survey Explorer (WISE) space telescope. In its original mission, the WISE space telescope captured the entire Milky Way in infrared, and it was the infrared data that provided the researchers with the clearest view of the X-shaped structure.

Lang said of the duo’s work, according to a Dunlap Institute press release, “There was controversy about whether the X-shaped structure existed. But our paper gives a good view of the core of our own galaxy. I think it has provided pretty good evidence for the existence of the X-shaped structure.”

What the study did was support the scientific view that the bulge was created as an extension of the bar structure of the galaxy (because the Milky Way is a barred spiral galaxy, meaning it has spiral arms emanating from a central bar of stars) that formed without external influences. The bar itself was created in the aftermath of the original galactic disk. A second view of how the bulge may have been created, that the Milky Way merged with other galaxies, was, of course, not supported by Lang and Ness’ work.

Ness noted in the press release that “the bulge is a key signature of formation of the Milky Way Galaxy,” suggesting that understanding it would lead to understanding “the key processes that have formed and shaped our galaxy.”

She continued, “The shape of the bulge tells us about how it has formed. We see the X-shape and boxy morphology so clearly in the WISE image and this demonstrates that internal formation processes have been the ones driving the bulge formation.”

Both Ness and Lang are proponents of the open science. And Lang is quick to note that open science led to the duo’s collaboration, kicked off, of course, by Ness realizing the importance of Lang’s Twitter photo.

“I really like the fact that this study happened at all — to me, it’s an example of the interesting, serendipitous science that can happen when people publicly release their data and try to communicate their results to the public and other scientists,” he said, according to CNN. “I don’t normally study Milky Way structure, so it was fun to learn how the WISE data could be used to answer a question I didn’t even know existed! This study wouldn’t have happened if the WISE team had not gone to great effort to create a very high-quality public data release.”

[Image via Shutterstock]