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WMAP

WMAP Worldwide Telescope Microwave Sky Images

This page provides access to a number of WMAP images that have been formatted to be compatible with the Microsoft Research Worldwide Telescope 3D imaging tool. Prior to using these files, you will need to download and install Worldwide Telescope as a separate application on your computer. These images are provided here as a courtesy to our users; they do not constitute an endorsement of any product or service.

You should:

  • Download the file wmap5year.wtml We recommend right-clicking on this link and selecting (for example) "Save Target As" (for Internet Explorer) or "Save Link As" (for Firefox). Be sure to retain the '.wtml' extension of the file!
  • Ideally, the file should be moved to the following location:
    Windows XP: My Documents>WWT Collections
    Windows Vista: Documents>WWT Collections
    Please note that this folder will not exist until the Worldwide Telescope has been run at least once.
  • If the wtml file is located anywhere else, it can be manually accessed within WWT through the menu command
    Explore−>Open−>Collection or by double clicking the file.

This file and the underlying WWT-formatted image files have been provided through the courtesy of Microsoft Research.

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 4.6% atoms, 23% dark matter, and 72% dark energy.

The WMAP images will be available under "Collections>My Collections" when the Explore menu is selected; simply double-click on the desired image. The following maps are available (please note that these thumbnails link link to wmap5year.wtml):

WMAP 5-Year CMB Map

WMAP ILC Map

The first image shows the CMB fluctuations from the 5-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 5-Year Frequency Band Maps (Linear Color Scale)

WMAP K Band Map
K Band -- 23 GHz
WMAP Ka Band Map
Ka Band -- 33 GHz
WMAP Q Band Map
Q Band -- 41 GHz
WMAP V Band Map
V Band -- 61 GHz
WMAP W Band Map
W Band -- 94 GHz

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 (shown above), we can suppress the signal from the Milky Way.

WMAP 5-Year Frequency Band Maps (Nonlinear Color Scale)

WMAP K Band Map
K Band -- 23 GHz
WMAP Ka Band Map
Ka Band -- 33 GHz
WMAP Q Band Map
Q Band -- 41 GHz
WMAP V Band Map
V Band -- 61 GHz
WMAP W Band Map
W Band -- 94 GHz

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 5-Year Polarization Maps by Frequency Band

WMAP K Band Map
K Band -- 23 GHz
WMAP Ka Band Map
Ka Band -- 33 GHz
WMAP Q Band Map
Q Band -- 41 GHz>
WMAP V Band Map
V Band -- 61 GHz>
WMAP W Band Map
W Band -- 94 GHz>

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 white lines indicate the direction of polarization. (The segment lengths are logarithmically proportional to the strength of the polarization, and they are not drawn where the polarization is weak enough that it cannot be distinguished from instrument noise.)

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.

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