A team of Polish astronomers has created the most accurate three-dimensional map of the Milky Way to date, revealing surprising distortions and irregularities along the galactic disk.
Building an accurate map of the Milky Way is not easy.
Our location deep inside the gigantic structure means we can’t observe our galaxy externally, forcing us to envision its form from within. Dense expanses of stars, gas, and dust complicate our view even further. Despite these limitations, we know that the Milky Way is a spiral galaxy measuring around 120,000 light-years across, and that we’re located around 27,000 light-years from the galactic core.
team of scientists from the Astronomical Observatory at the University of Warsaw has compiled the most accurate 3D map of the Milky Way to date. Astronomer Dorota Skowron led the study, which was published today in Science.
Among several other new findings, the updated 3D map shows the S-shaped structure of our galaxy’s distorted stellar disk. The Milky Way is not flat like a pancake, and is instead “warped and twisted,” in the words of co-author Przemek Mroz, who described his team’s work in a related video. That our galaxy is warped was already known, but the new research further characterizes the surprising extent of these distortions. As the new research shows, this warp starts at ranges greater than 25,000 light-years from the galactic core, and it gets more severe with distance.
The new research also showed that the thickness of the Milky Way is variable throughout. Our galaxy gets thicker with distance from the core. At our location, for example, the galactic disk is about 500 light-years thick, but at the outer edges it’s as much as 3,000 light-years thick.
To create the 3D map, Skowron and her colleagues charted the location of Cepheid variable stars. These young, pulsating supergiants are ideal for this research because their brightness changes in a very regular pattern. Ultimately, the location of Cepheid stars within the Milky Way can be more accurately pinned down than other kinds of stars, which is precisely what was needed for this mapping project.
A sample of over 2,400 Cepheids was used to create the new map, the majority of which were identified with the Optical Gravitational Lensing Experiment (OGLE) survey, which monitors the brightness of nearly 2 billion stars. In total, the researchers observed the galactic disk for six years, taking 206,726 images of the sky.
If this work sounds familiar, it’s because research published earlier this year in Nature Astronomy employed a similar technique, in which scientists from the Chinese Academy of Sciences reached similar conclusions, using a different group of Cepheids for their map. One of the scientists behind the previous research, Xiaodian Chen from the National Astronomical Observatories at the Chinese Academy of Sciences, took issue with the fact that the authors of the new paper did not cite his team’s work. Nonetheless, he still liked the new science.