Tuesday, 20 August, 2019

Scientists reveal true shape of Milky Way: It’s warped & twisted

The effect of 'torque' on the galaxy's outer reaches The effect of 'torque' on the galaxy's outer reaches Credit Telegraph
Sandy Nunez | 07 February, 2019, 15:55

Our Milky Way galaxy isn't a neat, flat disc of stars - it's actually being warped out of shape by its inner disc, scientists say.

In the centre, hundreds of billions of stars and dark matter hold the galaxy together. "However, we recently published a new catalog of well-behaved variable stars known as classical Cepheids, for which distances as accurate as 3 to 5% can be determined", added Dr. Chen Xiaodian from the National Astronomical Observatories of the Chinese Academy of Sciences.

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). But our human eyes are hopelessly inadequate for revealing the true nature of the Galaxy. However, the hydrogen gas appears to warp more than the stars do, specifically on one of the disk's sides.

The Milky Way turned out to be progressively twisted in its outer areas, which is most likely caused by the powerful rotating forces released by the galaxy's massive internal disk, according to the research.

"It is notoriously hard to determine distances from the Sun to parts of the Milky Way's outer gas disk without having a clear idea of what that disk actually looks like", said Chinese Academy of Sciences astronomer Dr. Xiaodian Chen, lead author of the study.

Combined with a Cepheid's observed brightness, its pulsation period can be used to obtain a highly reliable distance. The energetic stars pulsate, and by messing the timing of the stellar pulses and the changes in brightness, scientists can accurately measure their distance from Earth and the sun.

"We usually think of spiral galaxies as being quite flat, like Andromeda which you can easily see through a telescope", Richard de Grijs, a co-author of the paper from Macquarie, said in a statement. Just like a goldfish can't see its bowl from the outside, our position in the universe means we can't see our home galaxy, the Milky Way, as the rest of the universe sees it.

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This isn't completely abnormal, because astronomers have noticed the same pattern of progressively twisting spirals in about a dozen other galaxies.

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".

The Milky Way's shape is a disk ... with a twist.

Scientists have found similar warped shapes among the outer regions of other spiral 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.

The results were published online this week in the journal Nature Astronomy.