New Image Shows Andromeda's Colorful Rings
A new image from the Herschel Space Observatory shows ring-like swirls of dust filling the Andromeda galaxy, which is the largest spiral galaxy closest to the Milky Way.
The glow appearing around the image of Andromeda is from the longest and the coolest wavelength of light, at the end of the infrared spectrum. These light wavelengths span from 250 to 500 microns.
Herschel Space Observatory, a European Space Agency mission with important NASA participation, has the ability to detect light as far as at end of the infrared spectrum. This allows astronomers to view the cold cloud of dust filling the Andromeda galaxy at temperatures of only a few tens of degrees above absolute zero. Hershel also gives a view of spokes of dust between the concentric rings.
If the same cloud of dust is viewed at shorter wavelengths, it would appear dark and opaque. In order to make visibility easier, the colors on the image have been enhanced - the warmer clouds of dust take on a bluish tinge, while the coldest clouds (brightest in the longest wavelengths) are colored in red. Light with a wavelength of 250 microns is in blue, 350 microns is in green and 500-micron light is red.
These observations combined with data from other observatories reveal that there are other factors, apart from temperature, affecting the infrared color of the image. Clumping of dust grains, or growth of icy mantles on the grains toward the outskirts of the galaxy also contribute to the slight variations in the color.
The Andromeda galaxy is located two million light-years away from the Milky Way. They are the two most massive and dominant galaxies within the local group of galaxies that include the Triangulum Galaxy and about 30 other smaller galaxies, according to EarthSky.