The shape of our gal­axy re­vealed

In­ge­nious re­search fi­nally re­veals the true shape of the Milky Way.

Cosmos - - Digest -

The Milky Way is warped and twisted, a col­lab­o­ra­tion be­tween Aus­tralian and Chi­nese as­tronomers has es­tab­lished.

The three-di­men­sional shape of the gal­axy in which Earth re­sides has been a mys­tery due to the in­her­ent dif­fi­cul­ties in try­ing to as­cer­tain what any ob­ject looks like when re­stricted to mak­ing only in­ter­nal mea­sure­ments.

Most as­sump­tions have pro­ceeded by means of anal­ogy. The gal­axy is spi­ral so, the logic runs, it’s prob­a­bly the same shape as other spi­ral galax­ies. The clos­est of these is An­dromeda, which is pretty much a pan­cake.

How­ever, we now know it isn’t spi­ral at all, thanks to re­search led by Richard de Grijs from Mac­quarie Univer­sity and Xiao­dian Chen from Chi­nese Academy of Sci­ences in Bei­jing.

To ac­cu­rately mea­sure the shape of the gal­axy the re­searchers plot­ted the po­si­tion of 1339 Cepheids – large pul­sat­ing stars each about 100,000 times brighter than the sun. Be­cause their bright­ness varies only very lit­tle, the stars func­tioned as ref­er­ence points for the gi­gan­tic map­ping ex­er­cise.

By com­par­ing the dis­tances be­tween the Milky Way Cepheids and those found in other galax­ies – the shapes of which can be eas­ily con­firmed through di­rect ob­ser­va­tion – Chen, de Grijs and col­leagues dis­cov­ered that our home sys­tem be­comes in­creas­ingly warped and twisted as dis­tance in­creases from its cen­tre.

The re­searchers say their ev­i­dence “sug­gests that the ori­gin of the warp is as­so­ci­ated with torques forced by the mas­sive in­ner disk”.

The re­search be­hind this find­ing was orig­i­nally pub­lished in the jour­nal Na­ture Astron­omy.

CREDIT: CHAO LIU / NA­TIONAL ASTRO­NOM­I­CAL OBSERVATORIES, CHI­NESE ACADEMY OF SCI­ENCES

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