The center of our Milky Way Galaxy is located in the constellation of Sagittarius. In visible light the lion's share of stars are hidden behind thick clouds of dust. This obscuring dust becomes increasingly transparent at infrared wavelengths. This 2MASS image, covering a field roughly 10 x 8 degrees (about the area of your fist held out at arm's length) reveals multitudes of otherwise hidden stars, penetrating all the way to the central star cluster of the Galaxy.
This central core, seen in the upper left portion of the enlarged image, is about 25,000 light years away and is thought to harbor a supermassive black hole. The reddening of the stars here and along the Galactic Plane is due to scattering by the dust; it is the same process by which the sun appears to redden as it sets. The densest fields of dust still show up in this mosaic. Also evident are several nebulae to the lower right, including the Cat's Paw Nebula. The 2MASS analysis software has identified and measured the properties of almost 10 million stars in this spectacular field alone.
This panoramic view encompasses the entire sky as seen by Two Micron All-Sky Survey. The measured brightnesses of half a billion stars (points) have been combined into colors representing three distinct wavelengths of infrared light: blue at 1.2 microns, green at 1.6 microns microns, and red at 2.2 microns.
This image is centered on the core of our own Milky Way galaxy, toward the constellation of Sagittarius. The reddish stars seemingly hovering in the middle of the Milky Way's disc -- many of them never observed before -- trace the densest dust clouds in our galaxy. The two faint smudges seen in the lower right quadrant are our neighboring galaxies, the Small and Large Magellanic Clouds.
A GLIMPSE of the Milky Way
In visible light, the bulk of our Milky Way galaxy's stars are eclipsed behind thick clouds of galactic dust and gas. But to the infrared eyes of NASA's Spitzer Space Telescope, distant stars and dust clouds shine with unparalleled clarity and color.
In this panoramic image (center row) from the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) project, a plethora of stellar activity in the Milky Way's galactic plane, reaching to the far side of our galaxy, is exposed. This image spans 9 degrees of sky (approximately the width of a fist held out at arm's length).
The red clouds indicate the presence of large organic molecules (mixed with the dust), which have been illuminated by nearby star formation. The patches of black are dense obscuring dust clouds impenetrable by even Spitzer's super-sensitive infrared eyes. Bright arcs of white throughout the image are massive stellar incubators.
With over 160 megapixels, the full detail in this panorama cannot be appreciated without zooming in to various areas of interest (top and bottom rows). Bubbles, or holes, in the red clouds are formed by the powerful outflows from massive groups of forming stars. Wisps of green indicate the presence of hot hydrogen gas. Star clusters can also be seen as the groupings of blue, yellow, and green specks inside some of the red nebulae, or star-forming clouds. In contrast to the plentiful examples of stellar youth in this montage, Spitzer also sees an object called a planetary nebula (top row, middle). Such nebulae are the final gasp of dying stars like our sun, whose outer layers are blown into space, leaving a burnt -out core of a star, called a white dwarf, behind.
Although this panoramic image captures a large range of the galaxy, it represents only 7.5 percent of the primary GLIMPSE survey, which will image most of the star formation regions in our galaxy.