The Milky Way

These all-sky maps portray the entire Milky Way Galaxy by taking images of the entire celestial sphere, and then unwrapping and stretching them to fit onto a two-dimensional surface. The Galactic Center is at the center of each image, with the plane of the Galaxy stretching from left to right in a manner similar to the equator on Earth.

Gamma-Ray >100MeV (CGRO, NASA)

Gamma-Ray (N. Gehrels GSFC, EGRET, NASA)

X-Ray 2-10keV (HEAO-1, NASA)

X-Ray 0.25, 0.75, 1.5 keV (S. Digel et. al. GSFC, ROSAT, NASA)

Ultraviolet (J. Bonnell, NASA)

Visible (Axel Mellinger)

Infrared (DIRBE Team, COBE, NASA)

Radio 1420MHz (J. Dickey UMn. NRAO SkyView)

Radio 408MHz (C. Haslam et al., MPIfR, SkyView)

Each image is dominated by the emission from the disk and central bulge of the Milky Way, where most of the contents of our galaxy are contained.

In the first gamma-ray image (top-left), we see the entire sky at energies above 100 million electron volts. Gamma-rays have more than a million times the energy of visible light! This picture shows us areas where high-energy cosmic rays collide with hydrogen in interstellar clouds. The next gamma-ray image highlights the most intense gamma-ray sources. Some of these bright areas have been identified as black holes, neutron stars and quasars. Most of these however, remain a mystery and have not yet been identified.

X-rays are about 1,000 times more energetic than visible light. The first x-ray image (top-right) shows the brightest x-ray emitters in the Milky Way. These high-energy x-rays are produced in high-temperature environments. They are identified as white dwarfs, black holes, neutron stars, pulsars, supernova remnants, active galaxies, flare stars, and high energy binary star systems. The next X-ray image is a map of three bands centered at 0.25 keV (red), 0.75 keV (green), and 1.5 keV (blue). These bands maps hot gas and show large, looping structures. The gas and dust clouds in the plane of the Milky Way block x-rays and cause this area to appear dark.

The ultraviolet image shows sources studied by a satellite launched in 1978. These include stars, quasars, external galaxies, supernovae and nebulae. Visible light provides us with a view of the overall distribution of stars. The dark patches along the galactic plane are regions of dense gas and dust which block visible light. In the infrared we see glowing dust which is heated by starlight as well as regions of intense star formation (brightest areas). The S-shaped blue sash are the zodiacal dust bands which are small pieces of rock and dust orbiting between the Sun and Jupiter. Notice how the galactic plane no longer shows dark patches in the infrared. This is because infrared light can penetrate gas and dust clouds causing this region to glow in the infrared.

The higher energy radio image maps the distribution of the hydrogen gas which fills our galaxy. No stars are seen in this image. All we see are vast, diffuse clouds of hydrogen - the most abundant element in the Universe. The next radio view of the sky shows areas where synchrotron radiation, and hence electrons and magnetic fields, are dominant. This image also shows the location of pulsars and supernova remnants.

To see images of the plane of our Milky Way galaxy at many wavelengths see the Multiwavelength Milky Way.

Let's look even farther, at objects outside of our Galaxy!

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