• September 14, 2006

    Episode 57: HubbleWatch for September 2006

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    Hubble has found the dimmest stars in the galaxy. The faint red dwarfs, about as bright as a birthday cake candle viewed on the Moon from Earth, are located in the ancient globular star cluster NGC 6397. Globular star clusters are compact groups of hundreds of thousands of stars. Dark matter has long been a mystery to astronomers. Now Hubble has helped astronomers find conclusive proof of the existence of dark matter. Hubble and the Chandra X-Ray Observatory found that dark matter and normal matter were wrenched apart by a collision of two clusters of galaxies. The observations showed that most of the matter in the galaxy cluster IE 0657-556 is separate from the normal matter. Most of the matter in the cluster, in fact, is dark matter. The complex and intricate structure of an exploded star is on display in one of Hubble?s latest pictures, an image of supernova remanant Cassiopeia A. The remnant is young - only about 340 years old - and Hubble has viewed it repeatedly to look for changes in the filaments of gas cast off in the initial explosion.