Located in the vicinity of the second-magnitude star Gamma Cygni, the Cygnus X star-forming region was discovered as a diffuse radio source by surveys in the 1950s. Now, a study using data from NASA's Fermi Gamma-ray Space Telescope finds that the tumult of star birth and death in Cygnus X has managed to corral fast-moving particles called cosmic rays.
Cosmic rays are subatomic particles — mainly protons — that move through space at nearly the speed of light. In their journey across the galaxy, the particles are deflected by magnetic fields, which scramble their paths and make it impossible to backtrack the particles to their sources. Yet when cosmic rays collide with interstellar gas, they produce gamma rays — the most energetic and penetrating form of light — that travel to us straight from the source.
The Cygnus X star factory is located about 4,500 light-years away and is believed to contain enough raw material to make two million stars like our sun. Within it are many young star clusters and several sprawling groups of related O- and B-type stars, called OB associations. One, called Cygnus OB2, contains 65 O stars — the most massive, luminous and hottest type — and nearly 500 B stars. These massive stars possess intense outflows that clear out cavities in the region's gas clouds. A tangled web of shockwaves associated with this process impedes the movement of cosmic rays throughout the region. Cosmic rays striking gas nuclei or photons from starlight produce the gamma rays Fermi detects.
Tour the Cygnus X star factory. This video opens with wide optical and infrared images of the constellation Cygnus, then zooms into the Cygnus X region using radio, infrared and gamma-ray images. Fermi LAT shows that gamma rays fill cavities in the star-forming clouds. The emission occurs when fast-moving cosmic rays strike hot gas and starlight.
This image combines observations at radio wavelengths (74 and 21 cm, colored rose and green, respectively) with data from the Infrared Astronomical Satellite (60 and 25 microns, shaded turquoise and blue, respectively). The expanding shell of the Gamma Cygni supernova remnant, about 80 light-years across, stands out clearly in the radio data as a ruffled brown disk (upper right). White knots reveal the presence of newly formed stars embedded in dense gas. Diffuse ionized gas blown into delicate filaments and arcs by the outflows of massive stars appear green. Hot dust, which fills the entire region, shows up as blue.
Credit: Composed by Jayanne English (CGPS/Univ. of Manitoba) with support by A. R. Taylor (CGPS/U. of Calgary)
Cygnus X hosts many young stellar groupings, including the OB2 and OB9 associations and the cluster NGC 6910. The combined outflows and ultraviolet radiation from the region's numerous massive stars have heated and pushed gas away from the clusters, producing cavities of hot, lower-density gas. In this 8-micron infrared image, ridges of denser gas mark the boundaries of the cavities. Bright spots within these ridges show where stars are forming today. Labeled.
Cygnus X hosts many young stellar groupings, including the OB2 and OB9 associations and the cluster NGC 6910. The combined outflows and ultraviolet radiation from the region's numerous massive stars have heated and pushed gas away from the clusters, producing cavities of hot, lower-density gas. In this 8-micron infrared image, ridges of denser gas mark the boundaries of the cavities. Bright spots within these ridges show where stars are forming today. Unlabeled.
Gamma-ray emission detected by Fermi LAT fills bubbles of hot gas created by the most massive stars in Cygnus X. The turbulence and shock waves produced by these stars make it more difficult for high-energy cosmic rays to traverse the region. When the particles strike gas nuclei or photons of starlight, gamma rays result.
Credit: NASA/DOE/Fermi LAT Collaboration/I. A. Grenier and L. Tibaldo
GCMD keywords can be found on the Internet with the following citation:
Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version 220.127.116.11.0