Our Milky Way is a dusty place. So dusty, in fact, that we cannot see the center of the galaxy in visible light. But when NASA's Spitzer Space Telescope set its infrared eyes on the galactic center, it captured this spectacular view. Taken with just one of Spitzer's cameras (at a wavelength of 8 microns), the image highlights the region's exceptionally bright and dusty clouds, lit up by young massive stars. Individual stars can also be seen as tiny dots scattered throughout the dust. The top mosaic shows a portion of the galactic center that stretches across a distance of 760 light-years. Thanks to Spitzer's excellent resolution, the dusty features within the galactic center are seen in unprecedented detail. Four examples are shown in the magnified insets at the bottom. The farthest left box shows a pair of star-forming regions resembling owl-like cosmic eyes. To the left of the "eyes," dark lanes of dust can be seen. This object is probably located in a spiral arm between Earth and the galactic center, in contrast to the following examples, which are all located at the galactic center. The next inset to the right includes the extremely luminous "Quintuplet" stars, a set of five massive stars believed to have buried themselves in cocoons of dust. Just below and to the right of the Quintuplet is the "Pistol" nebula, a bubble of ejected material from the central, massive Pistol star. The finger-like pillars to the left are part of a structure known as "Sickle." They are similar in size and shape to those in the famous picture of the Eagle Nebula taken by NASA's Hubble Space Telescope. Pillars like these are sculpted out of dense dust clouds by radiation and winds from hot stars. The pillars in the Sickle were likely to have been formed by a cluster of hot stars located to their right but not readily visible here. The third inset highlights a system of long, stringy structures that are seen for the first time near the base of a region known as the "Arched Filaments." These long filaments are about 10 light-years long and less than 1 light-year wide. The bright star-forming regions to the right are some of the brightest in the infrared sky. The final inset to the right shows the center of our galaxy, which is the brightest spot in the entire mosaic. The brightness is a result of dust being heated up by a compact cluster of hot stars. The bright spot also marks the location of a supermassive black hole, around which a rotating ring of gas and dust known as the circumnuclear disk can be seen. This image was taken with Spitzer's Infrared Array Camera (IRAC), using its 8-micron detector. It shows emissions from heated-up molecules in dust clouds called polycyclic aromatic hydrocarbons.
A Hidden, Massive Star Clust
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Title
A Hidden, Massive Star Cluster Awash with Red Supergiants
Description
The sky is a jewelry box full of sparkling stars in these infrared images. The crown jewels are 14 massive stars on the verge of exploding as supernovae. These hefty stars reside in one of the most massive star clusters in the Milky Way Galaxy. The bluish cluster is inside the white box in the large image, which shows the star-studded region around it. A close-up of the cluster can be seen in the inset photo. These large stars are a tip-off to the mass of the young cluster. Astronomers estimate that the cluster is at least 20,000 times as massive as the Sun. Each red supergiant is about 20 times the Sun's mass. The larger color-composite image was taken by the Spitzer Space Telescope for the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) Legacy project. The survey penetrates obscuring dust along the thick disk of our galaxy to reveal never-before-seen stars and star clusters. The false colors in the image correspond to infrared-light emission. The stars in the large color-composite image all appear blue because they emit most of their infrared light at shorter wavelengths. The inset image, a false-color composite, was captured by the Two Micron All Sky Survey (2MASS). Astronomers identified the cluster as a potential behemoth after spotting it in the 2MASS catalogue. They then used the Infrared Multi-object Spectrograph at the Kitt Peak National Observatory in Arizona to analyze the cluster's colors. From that analysis, they discovered the red supergiants. They confirmed the red supergiants' pedigree by studying the colors of other red supergiants in data taken by the Spitzer Space Telescope. The cluster lies 18,900 light-years away in the direction of the constellation Scutum. It is the first in a survey of 130 potentially massive star clusters in the Milky Way that astronomers will study over the next five years using a variety of telescopes, including the Spitzer and Hubble space telescopes. The Spitzer image was taken April 4, 2004, the 2MASS image on July 4, 1999. The science team that studied the star cluster consists of Don Figer, Space Telescope Science Institute/Rochester Institute of Techology, John MacKenty, Massimo Robberto, and Kester Smith, Space Telescope Science Institute, Francisco Najarro, Instituto de Estructura de la Materia in Madrid, Spain: Rolf Kudritzki, University of Hawaii in Honolulu, and Artemio Herrero, Universidad de La Laguna in Tenerife, Spain.
Artist's Impression of Massi
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Title
Artist's Impression of Massive Star Cluster
Description
This is an illustration of one of the most massive star clusters within our Milky Way Galaxy. The cluster is ablaze with the glow of 14 rare red supergiant stars. Interspersed among the supergiants are young blue stars. The cluster contains an estimated 20,000 stars and is 20 times more massive than typical clusters in our galaxy. The cluster is located in the direction of the Galaxy's center. Its visible light is obscured by interstellar dust, but infrared telescopes easily detect the cluster's glow. If it could be seen in visible light, it would resemble this illustration. In this perspective we are looking back across the Milky Way, in the direction of the Sun, 18,900 light-years away. The cluster is only 8 to 10 million years old, young enough for astronomers to see most of the red supergiants before they explode as supernovae. One supernova remnant is located in the cluster at far left. In the background at the 12:00 position is a distant region of stars called W 42.
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