The first accurate 3D map of the Milky Way reveals its true shape
‘Warped and twisted’: The first accurate 3D map of our galaxy reveals the true shape of the Milky Way
- The galaxy was thought to be a flat spiral consisting of around 250 billion stars
- A new study has shown that in reality the Milky Way is warped and twisted
- It becomes increasingly twisted the further away stars are from the centre
- The warping is caused by the spinning galaxy’s packed inner disc of stars
Astronomers have uncovered the true twisted nature of our galaxy, the Milky Way.
Until now, the galaxy was generally thought to be a flat spiral consisting of an estimated 250 billion stars.
The sun and its planets, including the Earth, occupy an insignificant spot in one of the minor spiral arms.
But a new study has shown that in reality the Milky Way is warped.
It becomes increasingly twisted the further away stars are from the galactic centre.
The warping is thought to be caused by torque from the spinning galaxy’s densely packed inner disc of stars.
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Astronomers have uncovered the true twisted nature of our galaxy, the Milky Way. Until now, the galaxy was generally thought to be a flat spiral consisting of an estimated 250 billion stars. But a new study has shown that in reality the Milky Way is warped (artist’s impression)
Professor Richard de Grijs, one of the astronomers from Macquarie University in Sydney, Australia, said: ‘We usually think of spiral galaxies as being quite flat, like Andromeda, which you can easily see through a telescope.’
The scientists updated a 3D map of the Milky Way using 1,339 large pulsating stars, each up to 100,000 times brighter than the sun.
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The so-called Cepheid stars are used as ‘standard candles’ by astronomers to estimate galaxy-wide distances.
The Milky Way’s twists are rare but not unique, say the scientists, whose findings are published in the journal Nature Astronomy.
They have observed a dozen other galaxies which show similar progressively twisted spiral patterns in their outer regions.
Classical Cepheids are young stars that are some four to 20 times as massive as our Sun and up to 100,000 times as bright.
Such high stellar masses imply that they live fast and die young, burning through their nuclear fuel very quickly, sometimes in only a few million years.
They show day- to month-long pulsations, which are observed as changes in their brightness.
Combined with a Cepheid’s observed brightness, its pulsation period can be used to obtain a highly reliable distance.
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.
‘This offers new insights into the formation of our home galaxy.
‘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.’
The map sheds fresh light on the evolution of the galaxy – and also shows the warped disc also contains young stars.
The scientists updated a 3D map of the Milky Way using 1,339 large pulsating stars, each up to 100,000 times brighter than the sun. This graph represents those bright points in our galaxy
Co-author Dr Licai Deng, also of the Chinese Academy of Sciences, said: ‘This research provides a crucial updated map for studies of our galaxy’s stellar motions and the origins of the Milky Way’s disk.’
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 a great distance our galaxy would look like a thin disk of stars that orbit once every few hundred million years around its central region.
This is where hundreds of billions of stars can be found – together with a huge mass of dark matter.
This is the mysterious invisible material that provides the gravitational ‘glue’ that holds galaxies together.
The pull becomes weaker away from the inner regions. In the far outer disc hydrogen atoms making up most of the galaxy are no longer confined to a thin plane.
This gives the Milky Way its warped appearance – similar to an S-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.’
Dr Deng said: ‘This new morphology provides a crucial updated map for studies of our galaxy’s stellar motions and the origins of the Milky Way’s disk.’
The full findings of the study were published in the journal Nature Astronomy.
HOW OLD IS THE OLDEST STAR IN THE MILKY WAY?
Scientists in Spain have discovered one of the oldest stars in the Milky Way
A newly discovered star is thought to be one of the oldest in the Milky Way.
Scientists at the Instituto de Astrofísica de Canarias (IAC) in Spain believe that it might have formed about 300 million years after the ‘Big Bang’.
IAC researcher Jonay González Hernández said: ‘Theory predicts that these stars could form just after, and using material from, the first supernovae, whose progenitors were the first massive stars in the Galaxy.’
Researchers hope the star, known as J0815+4729, which is in line with the Lynx constellation, will help them learn more about the Big Bang, the popular theory about the galaxy’s evolution.
IAC director Rafael Rebolo said: ‘Detecting lithium gives us crucial information related to Big Bang nucleosynthesis. We are working on a spectrograph of high resolution and wide spectral range in order to be able to measure (among other things) the detailed chemical composition of stars with unique properties such as J0815+4729.’
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