Our Milky Way galaxy is truly warped, at least around edges

Katie Ramirez
February 7, 2019

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. Using these pulses in brightness, scientists can detect the distance of these stars within 3 percent to 5 percent accuracy, study lead author Xiaodian Chen, a researcher at the National Astronomical Observatories, said in the statement. Data on these classical Cepheid stars were provided by the Wide-field Infrared Survey Explorer (WISE).

The paper, published in Nature Astronomy on February 4, details work by Australian and Chinese astronomers to examine the classical "Cepheids" - a collection of huge, young stars in the Milky Way that can be up to 100,000 times brighter than the sun. The distances of the stars were then used as markers to help map out the rest of the galaxy, even its distant outer regions.

Top: Three-dimensional distribution of the classical Cepheid variable stars in the Milky Way's warped disk (red and blue points) centered on the location of the Sun ( large orange symbol).

The new findings echo observations made over the last half century by scientists which indicated that gas clouds in the outer Milky Way were warped in shape.

Combining their new results with those other observations, the researchers concluded that the Milky Way's warped spiral pattern is most likely caused by "torques"-or rotational forcing-by the massive inner disk". Artist's impression above of the warped and twisted Milky Way disk. There, the hydrogen atoms making up most of the Milky Way's gas disk are no longer confined to a thin plane, instead they give the disk an S-like, or warped, appearance.

One of them is establishing distances from the sun to the Milky Way's outer disk when you don't know what the disk actually looks like yet.

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Combined with a Cepheid's observed brightness, its pulsation period can be used to obtain a highly reliable distance.

A team of astronomers from the Macquarie University in Australia and the Chinese Academy of Sciences have mapped out the Milky Way using 1,339 "standard stars".

A new map of the Milky Way Galaxy reveals its true shape.

"Perhaps more importantly, in the Milky Way's outer regions, we found the S-like stellar disc is warped in a progressively twisted spiral pattern".

"This research provides a crucial updated map for studies of our Galaxy's stellar motions and the origins of the Milky Way's disk", said co-author Dr. Licai Deng, also from the Chinese Academy of Sciences. A dozen other galaxies had previously been shown to display similar warping, the researchers reported today (Feb. 4) in the journal Nature Astronomy.

Co-author Professor Richard de Grijs, of Macquarie University in Sydney, said: "We usually think of spiral galaxies as being quite flat - like Andromeda (our neighbouring galaxy) which you can easily see through a telescope".

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