Skip to content
Starts With A Bang

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

If you thought our galaxy was just the luminous matter within it, think again.

“Things need not have happened to be true. Tales and adventures are the shadow truths that will endure when mere facts are dust and ashes and forgotten.” –Neil Gaiman

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. Image credit: Jaime Fernández of

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. Image credit: WISE mission; NASA/JPL-Caltech/UCLA.

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. Image credit: Legacy Survey/NOAO, AURA, NSF.

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. Image credit: ESO/H. Drass et al.

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. Image credit: NASA, ESA, R. Bouwens and G. Illingworth (UC, Santa Cruz).

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. Image credit: Pan-STARRS collaboration.

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

This compressed view of the entire sky visible from Hawai’i by the Pan-STARRS1 Observatory is the result of half a million exposures, each about 45 seconds in length. Image credit: Danny Farrow, Pan-STARRS1 Science Consortium and Max Planck Institute for Extraterrestrial Physics.

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. Image credit: ESA, NASA, K. Sharon (Tel Aviv University) and E. Ofek (Caltech).

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. Image credit: Danny Farrow, Pan-STARRS1 Science Consortium and Max Planck Institute for Extraterrestial Physics.

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. Image credit: APOGEE-2 / SDSS-III.

That’s a mystery requiring additional studies to solve.

Mostly Mute Monday tells an astronomical story in pictures, visuals and no more than 200 words total.

This post first appeared at Forbes, and is brought to you ad-free by our Patreon supporters. Comment on our forum, & buy our first book: Beyond The Galaxy!


Up Next