Andromeda Galaxy Viewed in New Light Spectrum
A new image from the Herschel Space Observatory, a European Space Agency mission with NASA participation, shows very cold dust swirls in the Andromeda galaxy, the largest galaxy in our neighborhood with nearly one trillion stars. This view becomes only possible with the special ability of Herschel to detect light at the far end of the infrared spectrum, which means very long wavelengths of 250 to 500 micrometers, which is emitted by dust at temperatures of only a few tens of degrees above absolute zero - the same clouds are dark and opaque at shorter wavelengths, including the visible spectrum.
The galaxy core in this beautiful, colorful image is blue, because the color translation is inverted from the intuitive order, with the coldest clouds in the outskirts appearing in red. The colors have been enhanced to make them easier to see, and reflect the real variations in the data - light with a wavelength of 250 microns is rendered as blue, 350-micron is green, and 500-micron light is red.
The data, combines with those from other observatories, allowed astronomers to gain more knowledge about the galactic dust clouds, one of the main ingredients of galaxies. Apart from just temperature, there are other dust properties affecting the infrared color of the image. Clumping of dust grains, or growth of icy mantles on the grains towards the outskirts of the galaxy, appear to contribute to these subtle color variations.
These observations were made by Herschel's spectral and photometric imaging receiver (SPIRE) instrument. The data were processed as part of a project to improve methods for assembling mosaics from SPIRE observations.