Detailed 3D Milky Way map reveals warped Galaxy

Katie Ramirez
August 2, 2019

The Milky Way's Cepheid stars are plotted in three dimensions, revealing the galaxy's warped shape.

Building an accurate map of the Milky Way is not easy. The galaxy has a bar-shaped core region surrounded by a flat disc of gas, dust, and stars. The difference between these can tell us how far away a star might be from our sun. This new map was created by mapping over 2,400 cepheids that are scattered throughout the galaxy. These Cepheid stars were identified by the Optical Gravitational Lensing Experiment (OGLE), and by determining the 3D coordinates of each distant pulsing star relative to our Sun, Skowron et al has built a large-scale 3D model of the Milky Way. Better yet, the stars used in this sample would belong to a specific, well-studied type to ensure observational accuracy.

Richard de Grijs, an astronomer at Macquarie University and co-author on the Nature Astronomy study, said that both the previous study and the new study rely on Cepheids that sit on our side of the Milky Way. And that map shows that the edges of the Milky Way bend slightly, giving it a warped S shape.

Our home galaxy is even more twisted than we thought. A team from the University of Warsaw used stars called cepheid variables to plot a map of the galactic disc, defining its structure.

The two studies show very similar results, particularly in regard to the unusual nature of the Milky Way's warped edges.

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'The internal structure and history of the Milky Way is still far from being understood, in part because it is extremely hard to measure distances to stars at the outer regions of our galaxy, ' she said. "This is a big percentage". Warping may have happened through past interactions with satellite galaxies, intergalactic gas or dark matter- invisible material present in galaxies about which little in known'.

But a new study in Science this week uses an old reliable method for building a 3D map of our half of the Milky Way. The are can young the Giant, the 100 to 10,000 Times as bright as our own sun and, therefore, often across the whole galaxy, are visible.

Cepheid variables are stars that vary naturally in their size and brightness, expanding in diameter as they brighten up, and contracting and dimming later on in regular periods. In total, the researchers observed the galactic disk for six years, taking 206,726 images of the sky.

The cosmologists followed the Cepheids utilizing the Warsaw Telescope situated in the Chilean Andes. These observations, however, have been limited, and the resulting maps of our galaxy, therefore, restricted, stressed "Science". These elderly stars are from a time much earlier in the Milky Way's life cycle, so they would provide another method to map the galaxy. "So this is the most "real" map of the Milky Way". Brighter colors represent Cepheids closer to the warped plane of the galaxy, indicated by the grid.

Each colored point relates to a star in the Milky Way.

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