An worldwide team of astronomers have discovered that the Milky Way's disc of stars becomes increasingly "warped" and twisted the further away the stars are from the galaxy's center.
A new study by the National Astronomical Observatories of Chinese Academy of Sciences (NAOC) might explain the Milky Way's spiral appearance - it's warped.
Professor de Grijs and colleagues built their map using data for 1,339 classical Cepheid stars from NASA's Wide-field Infrared Survey Explorer (WISE). Such stars are hot and massive - five to twenty times the mass of our sun and up to 100,000 times as bright. The resulting map reveals a tipped, uneven disk of material different from our standard picture.
3D distribution of the classical Cepheid variable stars in the Milky Way's warped disc (red and blue points) centred on the location of the Sun (shown as a large orange symbol).
Without accurate measures of the distance between the sun and stars in the Milky Way's outer regions, it's hard to determine the precise shape of the galaxy and its gas disk.
It confirms that the warped spiral pattern is caused by torque from the spinning of the Milky Way's massive inner disk of stars.
The Milky Way really is warped - like a bent old vinyl record, according to new research. In the far outer disc hydrogen atoms making up most of the galaxy are no longer confined to a thin plane. They also pulsate radially for days to months at a time - and this period of pulsation can be combined with the Cepheid's brightness to reliably establish its distance from the sun.
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The map sheds fresh light on the evolution of the galaxy - and also shows the warped disc also contains young stars.
"It is notoriously hard to determine distances from the Sun to parts of the Milky Way's outer gas disc without having a clear idea of what that disc actually looks like", says Xiaodian Chen, lead author, from the Chinese Academy of Sciences in Beijing.
The Milky Way galaxy's new shape has a twist - exaggerated here for effect. Their paper is published online today in Nature Astronomy. These stars providing high distance accuracy were used as primary distance indicators to develop an intuitive and accurate three-dimensional picture of the galaxy.
"We usually think of spiral galaxies as being quite flat, like Andromeda, which you can easily see through a telescope", Macquarie University's Richard de Grijs, who took part in the study, said in a statement from Sydney.
The same twisted spiral patterns have been seen before in more than a dozen other galaxies.
"This new finding may help us to know the shape of the Milky Way, and provide a key clue to understanding how galaxies such as the Milky Way form and evolve", said Deng Licai, co-author of the study.