First 3D map of Milky Way reveals warped galaxy

  • First 3D map of Milky Way reveals warped galaxy

First 3D map of Milky Way reveals warped galaxy

The Milky Way's disk of stars is "warped" and twisted, according to scientists who have built the first accurate 3D map of Earth's home galaxy.

There are several hundred billion stars in our Milky Way Galaxy. "This offers new insights into the formation of our home galaxy", Richard de Grijs, senior study co-author and professor at Macquarie University's Department of Physics and Astronomy, said in a statement.

Astronomers looked at data from the WISE survey of infrared stars and noted that it contained a large sample of Cepheids.

They show day- to month-long pulsations, which are observed as changes in their brightness.

Because they are so bright, Cepheids can be clearly seen millions of light years away and can be easily distinguished from other bright stars in their vicinity, making them indispensable tools in any astronomers' kit.

Researchers from the Macquarie University in Australia and the Chinese Academy of Sciences have found for the first time that our solar system is anything but stable and flat. Artist's impression above of the warped and twisted Milky Way disk. Since a Cepheid's period tells astronomers how bright the star truly is, measuring how bright it appears lets astronomers draw an accurate distance map.

A dozen other galaxies with similar progressively twisted spiral patterns in their outer regions have been observed - so the Milky Way's shape is rare but not unique.

From afar, the Milky Way appears like a thin rotating disk of stars, orbiting the centre every few hundred million years.

This is the mysterious invisible material that provides the gravitational "glue" that holds galaxies together.

However, the pull of gravity becomes weaker far away from the Milky Way's inner regions. Since hydrogen atoms in the far outer disk are no longer confined to a thin plane, they get warped.

Prof de Grijs said: 'Somewhat to our surprise, we found in 3D our collection of 1,339 Cepheid stars and the Milky Way's gas disc follow each other closely.

The research team showed, with the help of the Cepheids, how the Milky Way isn't a flat cosmic disk shaped like a lipless frisbee or a pancake, but instead it's markedly warped into an S-like shape.

Co-author Dr Liu Chao, also of the Chinese Academy of Sciences, said: "Combining our results with those other observations, we concluded the Milky Way's warped spiral pattern is most likely caused by 'torques" - or rotational forcing - by the massive inner disk'.

This finding allowed for an updated map of the galaxy's "stellar motions", says Dr. Deng Licai, senior researcher at NAOC. Their paper is published online today in Nature Astronomy. Looking at 1,339 Cepheid stars from that catalog, the scientists discovered that their positions reveal a warping at the outer edges of the galaxy. And with the amount of stars in the Milky Way increasing thanks to observations by spacecraft such as the European Space Agency's Gaia, there's always room to improve the model even more.

IAC director Rafael Rebolo said: 'Detecting lithium gives us crucial information related to Big Bang nucleosynthesis.