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WMAP

WMAP Google Earth Microwave Sky Images
Seven Year Maps

This page provides access to a number of WMAP images that have been formatted to be compatible with the Google Earth 3D imaging tool. Prior to using these files, you will need to download and install Google Earth as a separate application on your computer. You may configure your browser to launch Google Earth when a .kmz file is encountered; clicking on the images below will then automatically load them into the application. These images are provided as a courtesy to our users; they do not constitute an endorsement of any product or service.

The Cosmic Microwave Background (CMB) radiation is the remnant heat from the Big Bang. This radiation pervades the universe and, if we could see in microwaves, it would appear as a nearly uniform glow across the entire sky. However, when we measure this radiation very carefully we can discern extremely faint variations in the brightness from point to point across the sky, called "anisotropy". These variations encode a great deal of information about the properties of our universe, such as its age and content. The "Wilkinson Microwave Anisotropy Probe" (WMAP) mission has measured these variations and found that the universe is 13.7 billion years old, and it consists of 5% atoms, 23% dark matter, and 72% dark energy.

Click on the images below to retrieve the Google Sky files. The files wmap_google_images_v4.tar.gz (103.5 MB) and wmap_google_images_v4.zip (103.5 MB) contain all these files for those that would like to have a local copy for improved browser performance; when using these images, select the File->Open command in the Google Earth application and simply navigate to these files.

WMAP Seven Year CMB Map

WMAP ILC Map
(6362 kB)

The first image shows the CMB fluctuations from the Seven Year WMAP survey. The average brightness corresponds to a temperature of 2.725 Kelvins (degrees above absolute zero; equivalent to -270 C or -455 F). The colors represent temperature variations, as in a weather map: red regions are warmer and blue regions are colder than average by 0.0002 degrees. This map was formed from the five frequency bands shown below in such a way as to suppress the signal from our own Milky Way Galaxy.

WMAP Seven Year Frequency Band Maps (Linear Color Scale)

WMAP K Band Map
K Band -- 23 GHz
4724 kB
WMAP Ka Band Map
Ka Band -- 33 GHz
7147 kB
WMAP Q Band Map
Q Band -- 41 GHz
8000 kB
WMAP V Band Map
V Band -- 61 GHz
8978 kB
WMAP W Band Map
W Band -- 94 GHz
9080 kB

In addition to the CMB, our own Milky Way Galaxy is a source of microwave radiation. Fortunately, the two sources have a different frequency spectrum (or "color"), so they can be separated using multifrequency observations. WMAP uses 5 frequency bands to discern CMB emission from Galactic emission: 23, 33, 41, 61, and 94 GHz. These five images show the microwave brightness measured in each frequency band. The signal is measured in units of Kelvins, and the color scale goes from blue at -0.0002 Kelvins below average (-200 microKelvins) to red at 0.0002 Kelvins above average (+200 microKelvins). The red band running through the center of the image is the emission from our Milky Way, which is much brighter than the CMB signal. By combining these five images in a particular way (as shown in the Internal Linear Combination Map), we can suppress the signal from the Milky Way.

WMAP Seven Year Frequency Band Maps (Nonlinear Color Scale)

WMAP K Band Map
K Band -- 23 GHz
5698 kB
WMAP Ka Band Map
Ka Band -- 33 GHz
6747 kB
WMAP Q Band Map
Q Band -- 41 GHz
7216 kB
WMAP V Band Map
V Band -- 61 GHz
7983 kB
WMAP W Band Map
W Band -- 94 GHz
8249 kB

These are the same five images as above, except the color scale is distorted to show both the faint variations in the CMB and the much brighter variations in the Milky Way signal.

WMAP Seven Year Polarization Maps by Frequency Band

WMAP K Band Map
K Band -- 23 GHz
5067 kB
WMAP Ka Band Map
Ka Band -- 33 GHz
5161 kB
WMAP Q Band Map
Q Band -- 41 GHz
4565 kB
WMAP V Band Map
V Band -- 61 GHz
4675 kB
WMAP W Band Map
W Band -- 94 GHz
6272 kB

In addition to measuring brightness variations, the WMAP mission is also capable of measuring a more specialized property of the microwaves called polarization. CMB polarization can provide information about when the first stars turned on and whether there were gravity waves in the very early universe.

These images show the polarized portion of the microwave signal at two of the five frequency bands: 23 and 33 GHz. The color represents the strength of the polarization: blue is no polarization while red is relatively strong; the color scale ranges between 0 to 50 μK for K band and between 0 to 35 μK for the other bands.

The signal seen in the polarization maps arises almost entirely from our own Milky Way Galaxy. Specifically it is mostly due to "synchrotron radiation" that is produced by high energy electrons spiraling around magnetic field lines in our Galaxy. As with the brightness variations, the polarized signal can be largely suppressed by combining multifrequency data. Once this is done, the CMB polarization left behind tells us that the first stars in the universe first formed when the universe was about 400 million years old. As of yet, the polarization provides no evidence for gravity waves in the early universe.

Projection Conventions

Google Earth places the observer at the center of a sphere looking out at the sky.

The images projected here are in celestial coordinates (right ascension (RA) and declination (Dec)), with the center representing zero degrees RA and Dec. The entire top of the image corresponds to 90 degrees Dec and the entire bottom corresponds to -90 degrees Dec. This orientation was chosen to allow Google Earth to correctly position star and constellation overlays on top of the image.

Also available:

A service of the HEASARC and of the Astrophysics Science Division at NASA/GSFC
Goddard Space Flight Center, National Aeronautics and Space Administration
HEASARC Director: Dr. Alan P. Smale
LAMBDA Director: Dr. Eric R. Switzer
NASA Official: Dr. Eric R. Switzer
Web Curator: Mr. Michael R. Greason