An­dromeda’s last meal

Sky at Night Magazine - - BULLETIN -

Astronomer­s have just dis­cov­ered what our neigh­bour­ing galaxy An­dromeda last had for lunch. An­dromeda has been snack­ing on dwarf gal­ax­ies for bil­lions of years, and re­cent ob­ser­va­tions have now tracked down the stel­lar left­overs of its pre­vi­ous meals.

“By trac­ing the faint re­mains of these smaller gal­ax­ies with em­bed­ded star clus­ters, we’ve been able to recre­ate the way An­dromeda drew them in and ul­ti­mately en­veloped them at dif­fer­ent times,” says Dou­gal Mackey from the Aus­tralian Na­tional Univer­sity, who co-led the study.

These traces show that An­dromeda was re­cently feed­ing from its plane of satel­lite gal­ax­ies (see yel­low or­bit in the im­ages, right). This sur­prised astronomer­s, as these gal­ax­ies are at right an­gles to those it fed on over 10 bil­lion years ago (see pink or­bit in the im­ages, right). How­ever, these dwarf gal­ax­ies are only an ap­pe­tiser. The main course is due to ar­rive in a few bil­lion years, when An­dromeda and our own Milky Way col­lide and de­vour each other to be­come one gi­ant galaxy.

Galac­tic menu: An­dromeda shreds in­com­ing gal­ax­ies

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