The Andromeda Galaxy as seen by the WISE Observatory

Andromeda at 12 and 22 microns
Andromeda Galaxy at 12 and 22 Microns
Image credit: NASA/JPL-Caltech/UCLA


NASA’s Wide-field Infrared Survey Explorer (WISE) is an observatory orbiting the Earth at an altitude of 325 miles designed to survey the entire sky in the 3 to 25 micron (μm) wavelength region of the electromagnetic spectrum. The Infrared region has longer wavelengths than visible light, which ranges from 0.39 to 0.75 μm.

This image of the Andromeda Galaxy showing the concentration of dust in the spiral arms, was taken by WISE. It shows light seen by the longest-wavelength infrared detectors on WISE (12-micron light has been color coded orange, and 22-micron light, red).

Newborn stars heat the dust, which radiates in the infrared. The spiral arms of the galaxy can be traced all the way to the center of the galaxy. Young stars also heat up the dust in the centers of Andromeda’s two smaller companion galaxies. These Messier objects are M32, just above and left, and M110 below and slightly to the left of the center of the galaxy in this image. See the next image in blue for a clearer view of their locations.

Andromeda, also called M31, is 2.5 million light-years away, and is the nearest large neighbor to our Milky Way galaxy.


This image from WISE was taken at 3.4 microns, the shortest wavelength that can be captured by the observatory. This wavelength is color coded in blue, and highlights Andromeda’s older stellar population.

Andromeda and the Milky Way are members of the Local Group, which includes the Triangulum Galaxy (M33) and about 30 other smaller galaxies. Although the largest galaxy in terms of star count and breadth, Andromeda may not be the most massive. Recent findings suggest that the Milky Way contains more dark matter and may be the most massive in the grouping.

A pronounced warp in the disk of the galaxy, the aftermath of a collision with another galaxy (most likely M32), can be clearly seen in the spiral arm to the upper left side of the galaxy. The hole in the spiral arms, surrounded by intense star formation is thought to have been caused by this collision.

In the combined image below, the ring shapes in Andromeda are more pronounced, and there is speculation that Andromeda is on the way to becoming a ring galaxy due to its collision.

Andromeda at 3.4 microns
Andromeda Galaxy at 3.4 Microns
Image credit: NASA/JPL-Caltech/UCLA
Combined Andromeda Image
Combined Andromeda Image
Image credit: NASA/JPL-Caltech/UCLA


This image combines views from all four of the WISE cameras. The 3.4 and 4.6 micron images are in blue, 12 microns in green and 22 microns in red.

This mosaic covers an area equivalent to more than 100 full moons, or five degrees across the sky. Blue highlights mature stars, while yellow and red show dust heated by newborn, massive stars.

Andromeda is located 2.5 million light-years from our sun, and is the closest large galaxy to our Milky Way galaxy. There is a strong likelihood that Andromeda and the Milky Way will collide in about 2.5 billion years. It is not clear yet whether the collision will result in a merger, or whether the two will simply disturb each other as they pass.

In its quest to map the whole sky, WISE will capture the entire Local Group.

One thought on “The Andromeda Galaxy as seen by the WISE Observatory

  1. Pingback: April 2010 « NSS Phoenix Space News

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