A year ago, the Pan-STARRS 1 (PS1) telescope completed a five-band optical and near-infrared survey of three quarters of the sky. The nearly one billion stars with high-quality multiband PS1 photometry provide a powerful dataset for constraining the three-dimensional distribution of dust in our Galaxy. Dust extinguishes and reddens astronomical sources, particularly those buried deep in the plane of the Milky Way, and itself traces the structure of the interstellar medium. Understanding the distribution of interstellar dust is therefore important for correcting observations in many subfields of astronomy, and in understanding the structure of our Galaxy.

Using PS1 and 2MASS stellar photometry for 800 million stars, we have inferred dust reddening as a function of distance along 2.4 million sightlines, covering the sky north of a declination of -30 degrees. Our method is fully probabilistic, yielding the uncertainty both in the reddening distribution along each line of sight, as well as distances, reddenings and types for the individual stars. Our map has a typical angular resolution of ~7' and distance bins with 25% width, and reveals a wealth of detailed structure on a wide range of scales, from filaments to large cloud complexes.

We expect three-dimensional reddening maps, such as the one presented here, to find a wide range of uses, among them correcting for reddening and extinction for objects embedded in the plane of the Galaxy, studies of Galactic structure, calibration of future emission-based dust maps and determining distances to objects of known reddening. Stellar parallaxes and photometry from Gaia in the near future, and much deeper photometry from LSST in the not-so-near future, can be leveraged to provide an even better view of the three-dimensional structure of the ISM.