A New 3D Map Shows How the Milky Way Is Warped and Twisted

Researchers in Poland have been able to chart our galaxy on a scale bigger than ever before by measuring the distance from our sun to thousands of individual pulsating stars scattered across the Milky Way.

A newly created three-dimensional map (see below), which provides a broad view of our location in the cosmos, reveals the S-like structure of the Milky Way’s warped stellar disc. The map was published on Thursday in the journal Science.

Dr. Dorota Skowron, co-author of the paper, tells Inverse that our galaxy, and all of its 200-400 billion stars, is a spiral of sorts.

“The structure of the Milky Way is very hard to assess, because our Solar System is located inside the plane of our galaxy structure,” Skowron says. “We know now that this is a spiral galaxy, and this has been inferred, among others, from our extrapolation of structures seen in other galaxies.”

“Our map shows the Milky Way disk is not flat. It is warped and twisted,” co-author Przemek Mroz said in a statement. “This is the first time we can use individual objects to show this in three dimensions.”

Much of the current understanding of the spiral shape and structure of our galaxy is built upon indirect measurements to celestial landmarks and inferences based on other galaxies in the universe. However, the galactic map drafted by those limited observations remains incomplete.

Like so many lighthouses on distant foggy shores, classical cepheid variable stars — massive young stellar bodies that burn hundreds, if not thousands of times brighter than our own sun — pulsate at regular intervals and are visible through the vast clouds of interstellar dust that often obscure dimmer stellar bodies.

"Our map shows the Milky Way disk is not flat. It is warped and twisted” — Przemek Mroz

“We could say that our observations of distant galaxies help us learn about our Milky Way,” says Skowron.

Using the periodic variations in their brightness, the distances to these stars can be precisely determined. Mroz, Skowron and their colleagues at the Warsaw University Astronomical Observatory charted the distance to more than 2,400 Cepheids throughout the Milky Way, most of which were identified by the Optical Gravitational Lensing Experiment (OGLE) – a project that more than doubled the number of known galactic classical cepheids. By determining the 3D coordinates of each distant pulsing star relative to our sun, the team built a large scale 3D model of the Milky Way. The new map illustrates and helps constrain the previously observed shape of the galaxy’s warped stellar disc.

“In order to collect such a complete and pure sample of classical cepheids, one has to regularly observe the whole Milky Way for a long period of time. This requires a dedicated survey. To give some numbers: we had observed the galactic disk for six years, took 206,726 images of the sky – which contain 1,055,030,021 stars – resulting in 153,704,543,662 individual observations,” says Skowron.

The study also explains that the advantage of using cepheids is so the scientists could determine direct distances to them with a very high accuracy, better than 5 percent, while in the case of other traces, the distances are not measured directly, but rely on assumptions.

“We had to monitor much greater area of the sky and in much more challenging directions for our telescope. It took six years, but it was worth it,” says Skowron.