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Canadian astro tweet leads to amazing Milky Way discovery

The galactic core of the Milky Way is framed by a large X in this image produced by UofT researcher Dustin Lang. Credit: NASA/JPL-Caltech/D. Lang

Scott Sutherland
Meteorologist/Science Writer

Saturday, July 23, 2016, 3:55 PM - Astronomers have just discovered a giant X that crisscrosses the core of the Milky Way galaxy, which has revealed new details about our home in the universe, and it's all thanks to an innocent astronomy tweet sent out by a University of Toronto researcher.

Imagine this.

It's May 2015. You've just posted an image to Twitter. It took a very long time to produce, as a computer program you've written crawled through an immense survey of the known universe, taken by a telescope circling Earth up in space. You even put a 150 gigapixel interactive version of it up on the web, so that anyone could go and look at it, zoom in on the amazing features and simply be in awe of the billions of stars in our Milky Way galaxy.

A colleague responds to your Tweet, asking for a simple re-orienting of the image. Rather than seeing the galaxy the way NASA's WISE satellite saw it from orbit, he'd like to see a more "natural" view of it, like he'd see it standing on the deck of a spacecraft looking along the galactic disk. That's easy enough, as it just takes the computer a little bit of time to adjust from WISE's "ecliptic" view to a "galactic" view, and voila:

It's a truly incredible image, but this is also where it starts to get interesting, as an astronomer an ocean away spots an interesting feature in the picture. There is a large X shape framing the galactic core, and this is a very important find for astronomers who study our galaxy and its structure.

The galactic core of the Milky Way is framed by a large X in this image produced by UofT researcher Dustin Lang. Credit: NASA/JPL-Caltech/D. Lang

For something that was simply an ongoing project to make the incredible data from the WISE mission more widely available, this came as quite the surprise to Dustin Lang, a researcher at the University of Toronto's Dunlap Institute for Astronomy & Astrophysics.

"I had no idea this image would catch the attention of Milky Way researchers to this extent," Lang wrote in an email to The Weather Network. He explained that, normally, the images he generates with WISE data are meant for studying galaxies outside of our own, and the surveys he draws from to make them typically avoid aiming at the Milky Way because the stars and dust of the galaxy block the light from galaxies they want to see.

"That's one of the things I really like about this project -- it's a case where releasing data publicly and communicating our results to other scientists and the world (in this case via Twitter) generated a scientific result that I hadn't even remotely foreseen."

According to NASA:

The Milky Way is an example of a disk galaxy -- a collection of stars and gas in a rotating disk. In these kinds of galaxies, when the thin disk of gas and stars is sufficiently massive, a "stellar bar" may form, consisting of stars moving in a box-shaped orbit around the center. Our own Milky Way has a bar, as do nearly two-thirds of all nearby disk galaxies.
Over time, the bar may become unstable and buckle in the center. The resulting "bulge" would contain stars that move around the galactic center, perpendicular to the plane of the galaxy, and in and out radially. When viewed from the side, the stars would appear distributed in a box-like or peanut-like shape as they orbit. Within that structure, according to the new study, there is a giant X-shaped structure of stars crossing at the center of the galaxy.
A bulge can also form when galaxies merge, but the Milky Way has not merged with any large galaxy in at least 9 billion years.

"We see the boxy shape, and the X within it, clearly in the WISE image, which demonstrates that internal formation processes have driven the bulge formation," Melissa Ness, the postdoc researcher at the Max Planck Institute for Astronomy in Heidelberg, Germany, who contacted Dustin Lang after recognizing the X, explained in the NASA statement. "This also reinforces the idea that our galaxy has led a fairly quiet life, without major merging events since the bulge was formed, as this shape would have been disrupted if we had any major interactions with other galaxies."

This processing of images of the Milky Way's core, performed by subtracting computer simulation of the core structure from what is actually observed there, revealed an even clearer image of the giant X that frames the central bulge. Credit: NASA/JPL-Caltech/D. Lang

The paper that resulted from their meeting - led by Ness and co-written by Lang - was published in the Astronomical Journal this week.

Source: NASA

Watch Below: Hundreds of galaxies hidden behind the Milky Way?

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