3D Dust Mapping Reveals that Orion Forms Part of a Large Ring of Dust

E. F. Schlafly, G. Green, D. P. Finkbeiner, H.-W. Rix, et al.

The Project

Orion Ring

The PS1 survey provides 5 band photometry on millions of stars in our Galaxy. This photometry allows the distance and reddening to every star to be estimated individually. This data set has the potential to dramatically advance our knowledge of the 3D structure of the Galaxy's dust. We have so far used it to find the distances to major molecular clouds, and to map the total dust column within 4.5 kpc.

The Orion Dust Ring

Schematic of Orion Ring

The most sensitive current maps of the Galaxy measure the total column of dust in each direction. This can make it challenging to understand the structure of dust clouds in the Galactic plane, where these maps see the superposition of many different dust clouds along the line of sight. Our 3D technique allows us to separate out the dust at different distances, removing this problem.

When applied to the Orion Molecular Complex, our technique immediately revealed a large (100 pc, 14 degree) ring of dust, that includes the main Orion A and B star-forming clouds. This suggests that these clouds formed as an ancient bubble in the interstellar medium, powered by a previous generation of stars. The Orion Molecular Complex is among the best studied star-forming regions in the sky. This new hint about the history of the Orion Molecular Complex may shed light on some of the mysteries of Orion; for instance, why Orion is so much more effective at forming stars than the similar mass California Molecular Cloud.

The first Figure at right shows the Orion dust ring in green (300-640 pc), as compared to more nearby dust in red and more distant dust in blue. The larger green ring at left in the newly discovered Orion dust ring; the smaller at right is the λ Orionis molecular ring. The second figure shows just the dust at Orion's distance, plus a number of possible bubble sources in the region. It also shows three prominent rings in the area---the Orion dust ring, the λ Orionis molecular ring, and Barnard's Loop.

The Paper

Edward Schlafly, ‮ed.aipm ta ylfalhcs
Gregory Green, ‮ude.dravrah.afc ta neergg