Title:[0274] Clouds of stars and dust in Sagittarius Caption:Around the center of our Galaxy are found huge numbers of stars that are faint and often billions of years old, as ancient as the Galaxy itself. These stars are seen with the unaided eye as the star clouds of the southern Milky Way, especially rich in Sagittarius. Our line of sight is strongly affected by dust, which reveals itself by both dimming the starlight passing through it and by selectively removing the blue component, changing the color to a deeper yellow. Appropriately, near the center of the picture, is a region known as Baade's Window after the astronomer who selected this part of the Milky Way for special study. Copyright:(c) 1987 Royal Observatory Edinburgh Credit:D. F. Malin

Title:[0926] The infrared sky Caption:All-sky image with plane of Milky Way Galaxy Copyright: Credit:National Optical Astronomy Observatories

Title:[0553] The visible sky Caption:If we could view our galaxy from the outside, it would appear like the Andromeda galaxy (M31), a central bulge surrounded by extensive spiral arms. However, since the Sun lies in the plane of the galaxy, our view is through the galactic disc that we see as the luminous band of faint stars and nebulae called the Milky Way. This visible light map of the Milky Way was hand-drawn by Martin and Tatjiana Keskula under the direction of Knut Lundmark. The display is in galactic coordinates with the galactic center at the midpoint of the graph. The bright stars and nebulae delineate the plane of our galaxy which is horizontal in this representation. Absorption by cold matter is apparent in the dark regions of the galactic plane. This is particularly apparent toward the galactic center. Although there are many more stars in the direction of the center, there also are dense clouds whose dust particles obscure the light from the stars behind them. The Large and Small Magellanic Clouds (LMC and SMC), companion galaxies to the Milky Way, are visible in the lower right. The Andromeda galaxy is on the left, below the galactic plane. Copyright:(c) Smithsonian Astrophysical Observatory Credit:Courtesy of Lund Observatory, Sweden

Title:[0555] All-sky survey: neutral hydrogen Caption:This slide shows the distribution of neutral hydrogen (HI) gas in the galaxy measured through 21-cm radio observations. The relative amounts (column densities) of neutral hydrogen are shown in false colors with black and dark blue regions having the smallest, and red and white regions the largest amounts. As this slide shows, the neutral hydrogen is strongly concentrated in the galactic plane. At high galactic latitudes the gas shows a filamentary structure. These filaments arise from low-velocity gas (nearby - less than 200 pc from the Sun) and follow the local magnetic field. These low-velocity filaments may arise through stellar winds from massive stars that create bubbles in the interstellar medium. Copyright:(c) Smithsonian Astrophysical Observatory Credit:Smithsonian Institution Astrophysical Observatory

Title:[0554] All-sky survey: radio map Caption:The 408 MHz (73-cm wavelength) all-sky survey is shown in false color in galactic coordinates. The radio intensities are displayed in a linear color scale going from deep blue (lowest intensities) to red (highest intensities). The angular resolution of the map is ~2 degrees. A number of well-known sources are seen along the galactic plane including the Cas A and Crab supernova remnant. The local arm complexes (Cygnus-X and Vela-X) stand out clearly surrounded by diffuse radio emission. The diffuse radio emission from the Milky Way is predominantly due to synchrotron radiation from cosmic-ray electrons interacting with magnetic fields in our galaxy. A large number of "spurs" can be seen above the galactic plane. The most prominent of these is the North Polar spur which may be the remnant of a nearby (500 light years distant), ancient (~300,000 years ago) supernova. In addition, numerous bright extragalactic objects can be recognized, e. g., Centaurus A, Virgo A, LMC and SMC. Our sister galaxy, M31, is seen as a light blue spot south of Cassiopeia A. Copyright:(c) Smithsonian Astrophysical Observatory Credit:Courtesy of CGT Haslam, CJ Salter, WE Wilson, and H Stoffel, Max Planck Institute fur Radioastronomie, Bonn

Title:[0830] The center of the Galaxy in the infrared Caption:Central Milky Way, w/Galactic Center-IRAS Copyright: Credit:National Optical Astronomy Observatories

Title:[0829] The center of the Galaxy in visible light Caption:Central Milky Way, w/Galactic Center-Palomar Copyright: Credit:National Optical Astronomy Observatories

Title:[1093] Fish-eye lens view of the Milky Way Caption:Fish-eye lens view shows the arch of the Milky Way over Cerro Tololo Inter-American Observatory in Chile. Copyright: Credit:National Optical Astronomy Observatories

Title:[0627] Galactic center: infrared image Caption:At the far-infrared wavelengths available to IRAS, most of the radiation from the direction of the galactic center is due to interstellar dust and gas. All the optical and ultraviolet luminosity emitted by the galactic center region is absorbed by the interstellar dust grains and reradiated in the far-infrared. Thus, the infrared maps can be used to determine both the column density of the absorbing dust and the distribution of sources that heat the dust. The field of view in this slide is approximately 15 degrees x 15 degrees. At shorter, near-infrared wavelengths (~2 microns), the radiation is primarily stellar. Copyright:(c) Smithsonian Astrophysical Observatory Credit:Courtesy of JPL/IPAC

Title:[1072] Infrared image of the central region of the Milky Way Caption:An infrared image of the central 150 light years of our Galaxy at a wavelength of 2.2 microns. The plane of the Milky Way extends from upper left to lower right. The bright central region is the nucleus of the Galaxy, a region which some astronomers believe harbors a black hole. In optical images, the center of the Galaxy is completely obscured by dust. Kitt Peak National Observatory 1.3-meter telescope photograph by Dr Ian Gatley and Dr Dick Joyce, 1989. Copyright: Credit:National Optical Astronomy Observatories/Dr. Ian Gatley and Dr. Dick Joyce

Title:[1073] Near-infrared image of the nucleus of the Milky Way Caption:A near-infrared image of the Galactic nucleus, which is located about 32,600 light years from the Earth. The color in this picture was produced by taking images using two filters at wavelengths of 1.65 microns (blue) and 2.2 microns (red) and combining them, similar to the method used by color television. The dark red patch to the right of the bright nucleus is part of a ring of dust and gas that surrounds the nucleus at a radius of about 6 light years. Kitt Peak National Observatory 2.1-meter telescope photo by Ian Gatley, 1989. Copyright: Credit:National Optical Astronomy Observatories/Dr. Ian Gatley

Title:[0275] NGC 6522, gamma Sagittarii and Baade's Window Caption:The German-American astronomer Walter Baade selected a region of the crowded star fields in Sagittarius where he believed the Galactic dust obscuration was both uniform and minimal. He used this line of sight to establish the distance to the galactic center, using variable stars as his yardstick. The distribution of these stars along this chance line of sight seems to peak at a distance of about 32,600 light years, which can be taken as the distance to the unseen Galactic center. This part of the sky, around the globular cluster NGC 6522, is now known as Baade's window; the brightest star in the photograph is gamma Sagittarii, a deep yellow naked eye star of about third magnitude. It is in the foreground at a distance of about 100 light years. Copyright:(c) 1987 ROE/Anglo-Australian Telescope Board, photograph by David Malin Credit:D. F. Malin

Title:[0626] Optical view toward Galactic center Caption:Our solar system lies about 10 kpc (32,600 light years) from the center of our galaxy. The optical view toward the galactic center indicates the structure of the galaxy. Prominent in the image is the Milky Way's reddish nuclear bulge and dust lanes marking the mid plane. This field covers a region of approximately 30 degrees x 50 degrees. The light and dark clouds are elongated in a disk-like system with a concentration in the direction of the galactic center. The center itself is heavily obscured by intervening dust and gas, which make it essentially unobservable at optical wavelengths. From the galactic center, only one of each 10 12 optical photons emitted can reach the distance of the Sun. Copyright:(c) Smithsonian Astrophysical Observatory Credit:Courtesy of National Optical Astronomy Observatories

Title:[0052] The Milky Way south of Messier 17 Caption:The French astronomer Charles Messier (1730-1817) listed over 100 objects he saw as nebulous to avoid confusing them with comets, which were his main interest. Three of Messier's objects appear in this picture. A little below the bright red emission nebula M17 is M18, a group of stars which is only conspicuous because, like M17, it is set in a relatively dark region of the Milky Way. The rich cloud of stars more or less in the middle of the photograph was listed by Messier as number 24 in his catalogue and it contains the open cluster NGC 6603, while towards the bottom of this field is a small group of nebulosities that Messier either did not see or which he considered to be too faint to interfere with his comet seeking. These are the two blue reflection nebulae NGC 6589-90 and the emission nebulae IC 1283-4. Copyright:(c) 1987 Royal Observatory Edinburgh Credit:D. F. Malin

Title:[1086] Towards the center of the Milky Way Caption:A wide-angle view towards the center of our Milky Way galaxy, taken by Dr. David Talent at Cerro Tololo in Chile. The teapot shape of the stars in the constellation Sagittarius can be seen but the central region of the galaxy is obscured from sight by intervening gas and dust clouds and by myriad stars between Earth and the galactic core. Copyright: Credit:National Optical Astronomy Observatories

Title:[0236] Wide-angle view towards the galactic center Caption:The center of our Galaxy is totally hidden at visible wavelengths by the band of dust which divides the Milky Way along much of its span. The dust can be seen in this wide-angle picture, which covers over 50 degrees of the southern Milky Way. It was made with a conventional camera pointing towards the constellation of Sagittarius. Against this dark lane can be seen many bright red emission nebulae. The brightest, near the center of the picture, is Messier 8, the Lagoon Nebula. At least 16 other prominent objects catalogued by Messier can be found on the photograph. Copyright:(c) 1980 Anglo-Australian Telescope Board, photograph by David Malin Credit:D. F. Malin

Title:[0628] Sagittarius A: radio image Caption:These radio continuum observations of the bright source Sagittarius A (Sgr A), plus the continuum arc in the direction of the galactic center, were obtained at a wavelength of 20 cm with the VLA. This observation covers a region 25 x 25 arc minutes. The most interesting result from these observations is the recognition of a system of narrow filamentary structures, which make up the continuum arc, having lengths of ~30 pc and typical widths of ~1pc (20 arc seconds). These radio filaments are perpendicular to the galactic plane, parallel to each other, regular, unbroken, and homogeneous in their appearance. These features are without a doubt associated with the magnetic field structure in the center of the galaxy. In fact, the radio emission mechanism from this region is synchrotron radiation from fast electrons moving in a magnetic field. Copyright:(c) Smithsonian Astrophysical Observatory Credit:Courtesy of NRAO/AUI.

Title:[3072] All-sky images of the infrared sky from the DIRBE experiment on the COBE satellite Caption:Two all-sky images constructed from data gathered in 1990 by the Diffuse Infrared Background Experiment (DIRBE) onboard the COBE satellite. Both show the strong emission from the Milky Way. The top panel combines data at the far infrared wavelengths of 25, 60 and 100 microns, shown in blue, green and red respectively. The radiation comes from cold dust between the stars. The faint blue background emission is from interplanetary dust in the solar system. The lower panel combines data at the near infrared wavelengths, 1.2, 2.2 and 3.4 microns, shown in blue, green and red. Stars are the dominant source in this image. Copyright: Credit:NASA