More Than Stars: The Milky Way’s Dust Mapped In 3D For The First Time Ever



A complete dust map of the Milky Way, provided by Planck, showcases a lower-resolution, 2D map of what our galaxy’s dust distribution looks like.

It’s easy to look at the night sky and find that it’s full of stars.

The Milky way’s central region in visible light, with the location of the galactic center marked by E. Siegel. Billions of stars can be found there, and Pan-STARRS has collected data on more of them than ever before.

Moreover, the stars cluster together in a great plane spanning the sky, making up our galaxy: the Milky Way.

But the Milky Way is more than just stars, it’s also full of gas, plasma, and — most importantly — light-blocking dust.

The galaxies Maffei 1 and Maffei 2, in the plane of the Milky Way, can only be revealed by seeing through the Milky Way’s dust. Despite being some of the closest large galaxies of all, they were not discovered until the mid-20th century.

This dust indicates where clumped neutral atoms are, reddening the stars behind it, but not in front of it.

The dark regions show very dense dust clouds. The red stars tend to be reddened by dust, while the blue stars are in front of the dust clouds. These images are part of a survey of the southern galactic plane.

Where the dust is coolest and densest, future stars will someday form.

The dusty regions that visible-light telescopes cannot penetrate are revealed by the infrared views of ESO’s HAWK-I instrument, showcasing the sites of new and future star formation where the dust is densest.

Preferentially blocking bluer light, this dust distorts our view of any background objects.

Even the light from smallest, faintest, most distant galaxies ever identified must travel through the Milky Way’s dust. Without knowing how much reddening is due to dust, that data will be miscalibrated.

If you’re trying to measure distant nebulae, galaxies, supernovae or the effects of dark energy, it will throw off your results.

Pan-STARRS2 and PanSTARS1 telescopes atop Haleakalā on the island of Maui, Hawaii, whose data was instrumental for mapping the Milky Way’s dust.

Nearly complete sky maps from 2MASS and PAN-STARRS surveys come to the rescue.

With that multiwavelength data, Edward Schlafly and collaborators constructed the first 3D dust map of the Milky Way.

Future studies, especially of dark energy, will be much more accurate as a result.

Observatories like Hubble and SDSS will have better calibration information thanks to the 3D dust maps created from 2MASS and Pan-STARRS data, even for observations of distant galaxies and quasars.

Surprisingly, the size of dust grains hardly changes at all with where we look.

A small selection of the galaxy as seen by Pan-STARRS, where dust is very dense, but the grains themselves are little different than anywhere else. This survey provides the most comprehensive 3D data ever taken.

So why does dust clump together more densely in some places?

The planned APOGEE-2 survey area overlain on an image of the Milky Way. Each dot shows a position where APOGEE-2 will obtain stellar spectra.

That’s a mystery requiring additional studies to solve.