Around the Milky Way , there is a region with a diffuse population of stars known as the halo . It is much bigger than the disk where the spiral arms , include the one with our Solar System in it , reside . This vast low - density region has been thought for a very long time to be a sphere , but fresh inquiry shows that that idea is not exactly correct .
consort to datum collected as part of the H3 Survey and by theGaiaspacecraft , the halo is not a sphere . It is more oblate and tilted , resembling a kick clump . The team tracked 5,559 stars that , while now part of the stellar ring of the Milky Way , were once another wandflower known as theGaia - Sausage - Enceladus(GSE ) . This galaxy was cannibalized by our own , through two orbits and at an angle that created the funny cast : a triaxial ellipsoid .
The star halo is a tracer bullet for the widergalactic halo , which is believe to be overshadow by the gravitational pull of dreary matter . Dark subject is inconspicuous , so by study the stellar halo , astronomer hope to gain insight into this hypothetical substance .
" The Supreme Headquarters Allied Powers Europe of the stellar doughnut is a very fundamental parametric quantity that we ’ve just measured to with child accuracy than was possible before , " take author Jiwon " Jesse " Han , from the Center for Astrophysics , Harvard & Smithsonian , said in astatement . " There are a lot of important implications of the stellar halo not being globose but instead regulate like a football game , rugby clod , or zeppelin – take your choice ! "
" For decades , the general assumption has been that the star halo is more or less spherical and isotropic , or the same in every direction , " added subject field co - author Charlie Conroy , a professor of astronomy at Harvard University and the Center for Astrophysics . " We now fuck that the textbook picture of our galaxy embedded within a spherical volume of stars has to be thrown out . "
The collision between the Milky Way and the GSE accept place around seven billion year ago . Given the elapsed time , researchers expected that the astral halo would have settled into the put on spherical configuration . The fact that it has n’t , is very challenging .
" The tilted stellar anchor ring strongly evoke that the underlying dingy matter halo is also tilted , " said Conroy . " A argument in the dark affair halo could have important ramifications for our ability to detect dark matter particles in laboratories on Earth . "
The insights into the shape of the galactic gloriole are write inThe Astronomical Journal .
