New all-sky map shows the trail left by the Large Magellanic Cloud

Astronomers recently released the above map of the Milky Way’s furthest reaches — the galactic halo. The band across the middle is the Milky Way itself. The two blobs to the lower left of the centre are the Magellanic Clouds.

There are two Magellanic Clouds — Large (LMC) and Small (SMC) — which are each dwarf galaxies orbiting the Milky Way. They’ve previously passed through the disk of the Milky Way, dragging a “wake” of stars out of the disk. This wake is visible in the new map, as you can see in the annotated version:

The annotated version of the new all-sky map of the outer Milky Way, showing the Large Magellanic Cloud and the trail of stars it has left behind. Image credit: NASA/ESA/JPL-Caltech/Conroy et. al. 2021

It’s worth mentioning that the new map isn’t a photograph. It really is a map in the sense that it’s a drawing made from precise measurements of the locations of the stars. It was produced using data from Gaia and NEOWISE. By measuring the distribution of stars in the Milky Way’s halo we can learn about the Galaxy’s dark matter, since we can see the effects of the dark matter’s gravity on the halo.

Featured image credit: NASA/ESA/JPL-Caltech/Conroy et. al. 2021

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