Credit: NASA/JPL-Caltech/A. Marston (ESTEC/ESA) & A. Noriega-Crespo (SSC/Caltech)

Star Formation in the DR21 Region

Hidden behind a shroud of dust in the constellation Cygnus is an exceptionally bright source of radio emission called DR21. Visible light images reveal no trace of what is happening in this region because of heavy dust obscuration. In fact, visible light is attenuated in DR21 by a factor of more than 10,000,000,000,000,000,000,000,000,000, 000,000,000,000 (ten thousand trillion heptillion).

New images from NASA's Spitzer Space Telescope allow us to peek behind the cosmic veil and pinpoint one of the most massive natal stars yet seen in our Milky Way galaxy. The never-before-seen star is 100,000 times as bright as the Sun. Also revealed for the first time is a powerful outflow of hot gas emanating from this star and bursting through a giant molecular cloud.

The upper image is a large-scale mosaic assembled from individual photographs obtained with the InfraRed Array Camera (IRAC) aboard Spitzer. The image covers an area about two times that of a full moon. The mosaic is a composite of images obtained at mid-infrared wavelengths of 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange) and 8 microns (red). The brightest infrared cloud near the top center corresponds to DR21, which presumably contains a cluster of newly forming stars at a distance of 10,000 light-years.

Protruding out from DR21 toward the bottom left of the image is a gaseous outflow (green), containing both carbon monoxide and molecular hydrogen. Data from the Spitzer spectrograph, which breaks light into its constituent individual wavelengths, indicate the presence of hot steam formed as the outflow heats the surrounding molecular gas. Outflows are physical signatures of processes that create supersonic beams, or jets, of gas. They are usually accompanied by discs of material around the new star, which likely contain the materials from which future planetary systems are formed. Additional newborn stars, depicted in green, can be seen surrounding the DR21 region.

The red filaments stretching across this image denote the presence of polycyclic aromatic hydrocarbons. These organic molecules, comprised of carbon and hydrogen, are excited by surrounding interstellar radiation and become luminescent at wavelengths near 8.0 microns. The complex pattern of filaments is caused by an intricate combination of radiation pressure, gravity and magnetic fields. The result is a tapestry in which winds, outflows and turbulence move and shape the interstellar medium.

To the lower left of the mosaic is a large bubble of gas and dust, which may represent the remnants of a past generation of stars.

The lower panel shows a 24-micron image mosaic, obtained with the Multiband Imaging Photometer aboard Spitzer (MIPS). This image maps the cooler infrared emission from interstellar dust found throughout the interstellar medium. The DR21 complex is clearly seen near the center of the strip, which covers about twice the area of the IRAC image.

Perhaps the most fascinating feature in this image is a long and shadowy linear filament extending towards the 10 o'clock position of DR21. This jet of cold and dense gas, nearly 50 light-years in extent, appears in silhouette against a warmer background. This filament is too long and massive to be a stellar jet and may have formed from a pre-existing molecular cloud core sculpted by DR21's strong winds. Regardless of its true nature, this jet and the numerous other arcs and wisps of cool dust signify the interstellar turbulence normally unseen by the human eye.

About the Object	Object Name: DR21 Object Type: Star formation region in dark cloud Position (J2000): RA: 20h39m00.9s Dec: 42d19m57s Distance: 2000 parsecs (6200 light years) Constellation: Cygnus (The Swan)
About the Data	Image Credit: NASA/JPL-Caltech/A. Marston (ESTEC/ESA) & A. Noriega-Crespo (SSC/Caltech) Instrument: IRAC, MIPS Wavelength:    IRAC: 3.6 (blue), 4.5 (green), 5.8 (orange), 8.0 (red) microns    MIPS: 24 microns Exposure Date:    IRAC: October 11, 2003 & November 22, 2003    MIPS: November 18, 2003 Exposure Time:    IRAC: 5 seconds per position    MIPS: 84 sec (total) Image Scale:    IRAC: 61 x 37 arcmin    MIPS: 104 x 32.6 arcmin (rectangular dimensions) Orientation:    IRAC: North is 88 deg CW from up    MIPS: North is 88 deg CW from up (22 deg CW from up for separate download) Release Date: April 13, 2004
Observers	IRAC Tony Marston, Principal Investigator (ESA/ESTEC) Lori Allen (Smithsonian Astrophysical Observatory) Ted Bergin (U. Michigan) Sean Carey (Spitzer Science Center) Gary Melnick (Smithsonian Astrophysical Observatory) Alberto Noriega-Crespo (Spitzer Science Center) Judy Pipher (University of Rochester) Bill Reach (Spitzer Science Center) Jeonghee Rho (Spitzer Science Center) Howard Smith (Smithsonian Astrophysical Observatory) Dan Watson (University of Rochester) MIPS Alberto Noriega-Crespo, Principal Investigator (Spitzer Science Center) Eiichi Egami (Steward Observatory, University of Arizona) William B. Latter (Spitzer Science Center) James Muzerolle (Steward Observatory, University of Arizona) Deborah Padgett (Spitzer Science Center) Luisa Rebull (Spitzer Science Center) Jeonghee Rho (Spitzer Science Center) George Rieke (Steward Observatory, University of Arizona) Karl Stapelfeldt (Jet Propulsion Laboratory)

Individual Images

	IRAC view of DR21. Screen-Resolution (450x239): JPEG High-Resolution (3652x1936): JPEG | Mac TIFF | PC TIFF Credit: NASA/JPL-Caltech/A. Marston (ESTEC/ESA)
	MIPS view of DR21. Note that the orientation of the image has been changed to allow for a rectangular image, and no longer matches the IRAC image. Screen-Resolution (450x140): JPEG High-Resolution (2499x779): JPEG | Mac TIFF | PC TIFF Credit: Credit: NASA/JPL-Caltech/A. Noriega-Crespo (SSC/Caltech)

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