X marks the spot at the center of the Milky Way galaxy
Two astronomers -- with the help of Twitter -- have uncovered the strongest evidence yet that an enormous X-shaped structure made of stars lies within the central bulge of the Milky Way Galaxy.
|WISE allsky map of the sky showing the Milky Way Galaxy. The central circle indicates the centre |
of the Galaxy and the inset shows an enhanced view of the x-shaped structure
[Credit: NASA/JPL-Caltech; D. Lang/Dunlap Institute]
"There was controversy about whether the X-shaped structure existed," says Dustin Lang, a Research Associate at the Dunlap Institute for Astronomy & Astrophysics, University of Toronto, and co-author of the paper describing the discovery. "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."
The results appear in the July issue of the Astronomical Journal. The lead author is Melissa Ness, a postdoctoral researcher at the Max Planck Institute for Astronomy in Heidelberg.
The Milky Way Galaxy is a barred spiral galaxy: a disk-shaped collection of dust, gas and billions of stars, 100,000 light-years in diameter. It is far from a simple disk structure, being composed of two spiral arms, a bar-shaped feature that runs through its centre, and a central bulge of stars. The central bulge, like other barred galaxy's bulges, resembles a rectangular box or peanut when viewed -- as we view it -- from within the plane of the galaxy. The X-shaped structure is an integral component of the bulge.
|An enhanced, close-up view centred on the Galaxy’s bulge and the blue-tinted “X” |
[Credit: D. Lang/Dunlap Institute]
This latest, clearest view of the bulge emerged when Lang re-analyzed previously released data from the Wide-field Infrared Survey Explorer (WISE), a space telescope launched by NASA in 2009. Before ending its initial mission in 2011, WISE surveyed the entire sky in infrared -- imaging three-quarters of a billion galaxies, stars and asteroids.
"The bulge is a key signature of formation of the Milky Way Galaxy," says Ness. "If we understand the bulge we will understand the key processes that have formed and shaped our galaxy."
"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."
Lang's analysis was originally intended to aid in his research in mapping the web of galaxies beyond the Milky Way Galaxy. To help explore the maps he'd developed from the WISE data, he created an interactive map-browsing website and tweeted an image of the entire sky.
"Ness saw the tweet and immediately recognized the importance of the X-shaped structure," says Lang. "We arranged to meet at an upcoming conference we were both attending. The paper was born from that meeting. That's the power of large surveys and open science!"
Source: Dunlap Institute for Astronomy & Astrophysics [July 19,2016]