IRAS Composite All-Sky Survey
IRAS Composite All-Sky Survey
| Group Name | mwIRASc |
| Reference | IRAS Sky Survey Atlas Explanatory Supplement (Wheelock, S. L., et al. 1994) |
| Prepared by | Carter Emmart (AMNH/Hayden) |
| Labels | No |
| Files | mw-iras.speck |
| Dependencies | iras.sgi |
| Wavelength | Composite of 12, 60, 100 microns |
| Frequency | Composite of 25,000, 5,000, 3,000 GHz |
IRAS (Infrared Astronomy Satellite) was one of the most successful astronomical missions, increasing the number of known cataloged objects by 70%. The orbiting telescope observed in the mid- and far infrared at 12, 25, 60, and 100 microns. This all-sky survey is a composite of the 12, 60, and 100 micron observations. [More information on IRAS can be found in “Far Infrared Survey.”
Because heat is infrared radiation, it was necessary to cool the telescope to temperatures below 10 Kelvin (-440o F). This cooling was achieved with liquid helium; however, the coolant ran out a little early, causing the detector to become saturated by the telescope's own heat. These “missed orbits” are seen in this all-sky image as two slits of missing data. Astronomers have since filled in these regions with other data, but we leave the empty regions in this composite survey to preserve the original IRAS data.
Image Features
The most obvious feature in the IRAS all-sky is the missing data from those lost orbits (discussed above). Another, more subtle artifact is present as two purple bands running perpendicular to the swaths of missing data. If you turn on the ecliptic coordinates, you will notice that these purple bands are along the ecliptic, which marks the plane of our solar system. These bands result from the subtraction of the zodiacal light. The plane of the solar system is filled with particulate matter, dust grains that absorb sunlight and radiate in the infrared. In order to see the infrared light from the Galaxy, astronomers subtracted the light from within our solar system, producing these two bands.
Toward Galactic center in Sagittarius, the infrared light is tightly constrained to the Galactic plane. In the opposite side of the sky near Orion, the infrared light seems to break up, becoming more clumpy. Here we are looking away from the center of the Galaxy.
Some objects glow in this part of the sky, though. The Orion Nebula and the Rosette Nebula, two nearby star-forming regions, are bright. The Andromeda Galaxy is visible but faint, and the Rho Ophiuchi cloud is visible above Scorpius.
© 2002-2005 American Museum of Natural History
Last Modified: 2007-12-19 by Brian Abbott