[{"command":"openDialog","selector":"#drupal-modal","settings":null,"data":"\u003Cdiv id=\u0022republish_modal_form\u0022\u003E\u003Cform class=\u0022modal-form-example-modal-form ecl-form\u0022 data-drupal-selector=\u0022modal-form-example-modal-form\u0022 action=\u0022\/en\/article\/modal\/6164\u0022 method=\u0022post\u0022 id=\u0022modal-form-example-modal-form\u0022 accept-charset=\u0022UTF-8\u0022\u003E\u003Cp\u003EHorizon articles can be republished for free under the Creative Commons Attribution 4.0 International (CC BY 4.0) licence.\u003C\/p\u003E\n \u003Cp\u003EYou must give appropriate credit. We ask you to do this by:\u003Cbr \/\u003E\n 1) Using the original journalist\u0027s byline\u003Cbr \/\u003E\n 2) Linking back to our original story\u003Cbr \/\u003E\n 3) Using the following text in the footer: This article was originally published in \u003Ca href=\u0027#\u0027\u003EHorizon, the EU Research and Innovation magazine\u003C\/a\u003E\u003C\/p\u003E\n \u003Cp\u003ESee our full republication guidelines \u003Ca href=\u0027\/horizon-magazine\/republish-our-stories\u0027\u003Ehere\u003C\/a\u003E\u003C\/p\u003E\n \u003Cp\u003EHTML for this article, including the attribution and page view counter, is below:\u003C\/p\u003E\u003Cdiv class=\u0022js-form-item form-item js-form-type-textarea form-item-body-content js-form-item-body-content ecl-form-group ecl-form-group--text-area form-no-label ecl-u-mv-m\u0022\u003E\n \n\u003Cdiv\u003E\n \u003Ctextarea data-drupal-selector=\u0022edit-body-content\u0022 aria-describedby=\u0022edit-body-content--description\u0022 id=\u0022edit-body-content\u0022 name=\u0022body_content\u0022 rows=\u00225\u0022 cols=\u002260\u0022 class=\u0022form-textarea ecl-text-area\u0022\u003E\u003Ch2\u003EUncovering the Milky Way\u2019s traumatic past\u003C\/h2\u003E\u003Cp class=\u0022DefaultStyle\u0022\u003EOur galaxy is pretty average in the scheme of things. Like most other stars in the universe, the stars in the Milky Way are arranged in a wispy, spiral-shaped disc. Our sun is about half way out, on the rim of what is known as the Orion Arm.\u003C\/p\u003E\u003Cp class=\u0022DefaultStyle\u0022\u003EEven so, there are some peculiarities with the Milky Way. Simple theories of galaxy formation suggest that its disc of stars ought to be perfectly flat, not puffy as it appears through telescopes.\u003C\/p\u003E\u003Cp class=\u0022DefaultStyle\u0022\u003EThis has led astrophysicists like Professor Hans-Walter Rix from the Max Planck Institute for Astronomy in Heidelberg to wonder whether some initial turbulence in our corner of the universe prevented a neat formation \u2013\u0026nbsp;or whether a catastrophic collision with another galaxy really stirred things up.\u003C\/p\u003E\u003Cp class=\u0022DefaultStyle\u0022\u003EThanks to the EU-funded MWDISK project, Prof. Rix is attempting to find out. He and his students are creating a map that shows the proportions of chemical elements present in a sizeable portion of our galaxy\u2019s billions of stars.\u003C\/p\u003E\u003Cp class=\u0022DefaultStyle\u0022\u003EThose proportions will allow the scientists to determine the age of the stars, so that they can ultimately create something akin to a film strip that reveals the Milky Way\u2019s formation. \u2018We see beautiful structures in our galaxy but do we understand how they came about?\u2019 Prof. Rix said.\u0026nbsp;\u003C\/p\u003E\u003Cp class=\u0022DefaultStyle\u0022\u003E\u003Cstrong\u003EBackward equations\u003C\/strong\u003E\u003C\/p\u003E\u003Cp class=\u0022DefaultStyle\u0022\u003EIn theory, there is a more direct way of finding out about our galaxy\u2019s past than mapping chemical elements and ages. Through observations astronomers can already measure stellar masses and the direction in which stars are moving, so it ought to be possible to follow the equations of motion backwards, like watching a film in rewind.\u003C\/p\u003E\u003Cp class=\u0022DefaultStyle\u0022\u003EThe trouble is a process known technically as radial-migration. This is where a star essentially swaps its orbit with a nearby star, a bit like a runner passing the baton in a relay race. Observing a star now, it is impossible to tell from its motion whether it is on the same orbit it always had \u2013 or whether it stole the \u2018baton\u2019 from another star long ago.\u003C\/p\u003E\u003Cp class=\u0022DefaultStyle\u0022\u003EMeasuring chemical elements, on the other hand, gives an accurate picture of age because heavy elements can only be produced when certain stars reach the end of their lives and explode into supernovae. As time goes on, and more stars turn into supernovae, the proportion of heavy elements in the surroundings rises.\u003C\/p\u003E\u003Cp class=\u0022DefaultStyle\u0022\u003EBy examining a star\u2019s spectrum \u2013 that is, the colours of light it emits \u2013 astronomers can work out what proportion of heavy elements it was made up from, and therefore how old it is.\u0026nbsp;\u003Cblockquote class=\u0022tw-text-center tw-text-blue tw-font-bold tw-text-2xl lg:tw-w-1\/2 tw-border-2 tw-border-blue tw-p-12 tw-my-8 lg:tw-m-12 lg:tw--ml-16 tw-float-left\u0022\u003E\n \u003Cspan class=\u0022tw-text-5xl tw-rotate-180\u0022\u003E\u201c\u003C\/span\u003E\n \u003Cp class=\u0022tw-font-serif tw-italic\u0022\u003E\u2018We see beautiful structures, but do we understand how they came about?\u2019\u003C\/p\u003E\n \u003Cfooter\u003E\n \u003Ccite class=\u0022tw-not-italic tw-font-normal tw-text-sm tw-text-black\u0022\u003EProf. Hans-Walter Rix, Director, Max Planck Institute for Astronomy, Heidelberg, Germany\u003C\/cite\u003E\n \u003C\/footer\u003E\n\u003C\/blockquote\u003E\n\u003C\/p\u003E\u003Cp class=\u0022DefaultStyle\u0022\u003E\u003Cstrong\u003EStar origins\u003C\/strong\u003E\u003C\/p\u003E\u003Cp class=\u0022DefaultStyle\u0022\u003EAccording to Prof. Rix, these chemical abundances are a bit like a \u2018genetic fingerprint\u2019, and they also give astro-detectives like him a way of figuring out where the different stars came from. For example, a star with few heavy elements might well have been born early on, when there was relatively pristine gas and few previous generations of stars.\u003C\/p\u003E\u003Cp class=\u0022DefaultStyle\u0022\u003EIt is hoped that by putting all this information together, a clearer picture will emerge of how exactly the Milky Way was formed, including the traumas it suffered along the way.\u003C\/p\u003E\u003Cp class=\u0022DefaultStyle\u0022\u003EOne theory is that the Milky Way\u2019s trauma was fairly mild, just some general turbulence in the early universe. This would mean our galaxy evolved a bit like the city of Paris \u2013 growing out from the centre, with suburbs being added concentrically around one another.\u003C\/p\u003E\u003Cp class=\u0022DefaultStyle\u0022\u003EOn the other hand, some believe the \u2018puffiness\u2019 of the Milky Way is the remnant of an ancient collision or merger with another galaxy. This would mean our galaxy evolved more like Berlin, which is the amalgamation of various other historic cities and suburbs.\u003C\/p\u003E\u003Cp class=\u0022DefaultStyle\u0022\u003EProf. Rix hopes he will have sorted through enough information on the chemical abundances to produce a map of Milky Way stars, sorted by age, by the end of next year. \u2018That would be qualitatively new, and be the most direct measurement of describing how the Milky Way built up over time,\u2019 he said. \u2018Whether we find surprises in there or not, I don\u2019t know.\u2019\u0026nbsp;\u003Cdiv class=\u0022moreinfoblock\u0022\u003E\n \u003Ch3\u003EDark matter\u003C\/h3\u003E\n \u003Cp class=\u0022DefaultStyle\u0022\u003EProf. Rix\u2019s previous work has already borne fruit on a related question: the amount of dark matter in our cosmic neighbourhood. Dark matter is an invisible substance believed to make up four-fifths of the matter in the universe, yet no-one knows what exactly it is made of.\u003C\/p\u003E\u003Cp class=\u0022DefaultStyle\u0022\u003EDark matter doesn\u2019t emit or absorb light or other electromagnetic radiation, making direct detection extremely difficult. However its existence is inferred from its gravitational effect on other bodies in the universe.\u003C\/p\u003E\u003Cp class=\u0022DefaultStyle\u0022\u003EIn 2013, Prof. Rix and colleagues managed to put strong limits on the amount of dark matter in our region of the Milky Way. It was less than had been predicted by computer simulations, which might explain \u2013 at least in part \u2013 why experimental physicists have had so much trouble in directly detecting it.\u003C\/p\u003E\n\u003C\/div\u003E\n\u003C\/p\u003E\u003C\/textarea\u003E\n\u003C\/div\u003E\n\n \u003Cdiv id=\u0022edit-body-content--description\u0022 class=\u0022ecl-help-block description\u0022\u003E\n Please copy the above code and embed it onto your website to republish.\n \u003C\/div\u003E\n \u003C\/div\u003E\n\u003Cinput autocomplete=\u0022off\u0022 data-drupal-selector=\u0022form-wle6hegw-hcgtf3e9kpkush0twcox0emi8fpippj7de\u0022 type=\u0022hidden\u0022 name=\u0022form_build_id\u0022 value=\u0022form-WLe6Hegw_hCGtf3E9kPKUsh0twCox0EMi8FpIppJ7DE\u0022 \/\u003E\n\u003Cinput data-drupal-selector=\u0022edit-modal-form-example-modal-form\u0022 type=\u0022hidden\u0022 name=\u0022form_id\u0022 value=\u0022modal_form_example_modal_form\u0022 \/\u003E\n\u003C\/form\u003E\n\u003C\/div\u003E","dialogOptions":{"width":"800","modal":true,"title":"Republish this content"}}]