Title:[1100] Crab Nebula in Taurus Caption:Computer-reconstructed image of the Crab Nebula, NGC 1952, from exposures made through three separate filters (blue, visual and red) and recombined in the Image Reduction Analysis Facility (IRAF). The green light is from the green emission line of doubly ionized oxygen at 5007 angstroms. The blue light is the near-infrared continuum around 9500 angstroms. All three pictures were taken at the 0.9-meter telescope at Kitt Peak, with an RCA CCD, September 1984. Copyright: Credit:National Optical Astronomy Observatories

Title:[0597] Crab Nebula: radio image Caption:This radio image of the Crab Nebula at 20 cm was obtained at the VLA. The radio synchrotron emission is produced by relativistic electrons moving in a magnetic field. The electrons are accelerated by the pulsar at the center of the nebula. Much of this nonthermal radio emission is closely associated with the optical line-emitting filaments, the gas ejected from the outer parts of the supernova star. The enhanced radio emission from the filaments may be due to increased magnetic fields around each filament. The extent of the radio emission is approximately 5 x 7 arc minutes. The Crab pulsar (a neutron star with a 33-millisecond rotation period) was discovered in 1968 through radio observations. Copyright:(c) Smithsonian Astrophysical Observatory Credit:Provided by F Seward and Smithsonian Institution Astrophysical Observatory

Title:[1121] Veil Nebula in Cygnus Caption: Veil nebula, NGC 6979, in the constellation Cygnus. The large loop of gas was ejected about 30-40,000 years ago from a supernova, a star's final death throes. This Kitt Peak National Observatory 4-meter Mayall telescope photograph shows the north central portion of the nebula. It is also known as the Cygnus Loop. Copyright: Credit:National Optical Astronomy Observatories

Title:[1098] Expanding shell of a supernova Caption:This false-color computer-enhanced image shows the expanding shell of material expanding outward from a supernova - the cataclysmic death throes of a star with three solar masses or more. This particular remnant, known as SNR BB76, is from Tycho's Supernova. Copyright: Credit:National Optical Astronomy Observatories

Title:[0594] Cassiopeia A: radio image Caption:Cas A is the brightest nonsolar radio source in the sky. Its radio emission is synchrotron radiation produced by electrons moving in a magnetic field. This slide shows a fully processed radiograph obtained at the VLA of the total intensity of Cassiopeia A, at a wavelength of 6 cm. This image spans 6.1 x 6.1 arc minutes with 0.4-arc second resolution. Cassiopeia A is the remnant of the supernova event which was quite possibly that witnessed by Flamsteed in August 1680. At that time the outer layers of a massive star were ejected with high velocity, sweeping up a shell of the surrounding interstellar material. The fainter outer radio shell is believed to correspond to this swept-up gas. This shell has now decelerated sufficiently that the expanding material from deeper within the star is breaking through the shell from inside. The brighter inner shell is ejecta from the star and corresponds to the same regions in which fast-moving (6000 km/sec) optical knots have been found. The passage of this ejecta through the outer shell gives rise to conical extensions, which leave crater-like structures in their wake. Individual bright knots appear or fade on a time scale of a few years. The overall radio brightness of Cas A is declining by about 1 to 2 percent every year. Copyright:(c) Smithsonian Astrophysical Observatory Credit:Courtesy of NRAO/AUI

Title:[0595] Cassiopeia A: X-ray image Caption:Einstein x-ray images and spectra have demonstrated that much can be learned from x-ray observations of supernova remnants. This figure shows an x-ray image of the supernova remnant Cas A which exploded about 300 years ago. The x-ray emission is due to radiation from very hot gas (5 x 107 K).The bright clumpy shell of emission has a diameter of approximately 3 1/2 arc minutes. As also seen in the radio image, a second fainter shell surrounds the bright, inner shell. The outer shell may be due to emission from the shocked interstellar medium, while the inner shell is gas ejected by the supernova . About 15 solar masses of material are observed in the inner shell. Copyright:(c) Smithsonian Astrophysical Observatory Credit:Smithsonian Institution Astrophysical Observatory

Title:[1067] Crab Nebula Caption:This true-color picture was taken using Ektachrome film at the prime focus of the Kitt Peak 4-m telescope in 1973. In this relatively short exposure, the pulsar is clearly visible (just below the center). The red filaments are tendrils of excited gas, emitting strong H-alpha radiation, still bearing mute testimony to the violence of the supernova explosion that created both the nebula and the pulsar. One of the more spectacular historical supernovae, it was recorded by Chinese astronomers in the year 1054 AD. Labeled the Crab from original perceptions of its shape, which no longer seem compelling, it is actually in the constellation Taurus. Copyright: Credit:National Optical Astronomy Observatories/W. Schoening/N. Sharp

Title:[1095] Crab Nebula in Taurus Caption:Crab Nebula, M1, NGC 1952, Taurus X-1, Taurus A, 3C 144, in the constellation Taurus. This well-known nebula, which was viewed on Earth in the year 1054 AD, is a supernova remnant. It is located about 6300 light years away and is approximately six light years in diameter and still spreading outward. This composite of images, taken with the Kitt Peak 4-meter Mayall telescope, shows hydrogen (red) and sulfur (blue) emission; different colors signify different ionization conditions and chemical compositions in various portions of the nebula. Copyright: Credit:National Optical Astronomy Observatories

Title:[0535] Part of the Vela supernova remnant Caption:A supernova event marks the catastrophic end-point in the life of a massive star. The self-destruction of the star releases a huge amount of energy as radiation of all kinds, but a substantial fraction of the force of the explosion creates an expanding shell of matter that travels through the space between the stars. As the blast wave encounters the relatively stationary interstellar medium it creates a very narrow, luminous shock front that appears as a faint nebula. Because the interface is very convoluted the nebulosity appears to be highly structured and the various colors define different energy levels within the interaction. Though the star responsible for the Vela supernova remnant exploded 12,000 years ago, it is still affecting its environment. Copyright:(c) 1992 Anglo-Australian Telescope Board, photograph by David Malin Credit:D.F. Malin

Title:[0259] Part of the Vela supernova remnant Caption:About 120 centuries ago an inconspicuous star in the constellation of Vela brightened by about 100 million times to rival the Moon as the brightest object in the night sky. This photograph shows a portion of the north-western quadrant of an expanding nebulous shell, which now surrounds the site of the explosion. Near the center of the nebula is the Vela pulsar, a rapidly-spinning neutron star only a few kilometers in diameter, the remnant of the star that exploded. This tiny object spins about 11 times a second and is among the faintest stars ever studied at optical wavelengths, a far cry from its brief glory as one of the brightest stars ever seen. Copyright:(c) 1979 Royal Observatory Edinburgh Credit:D. F. Malin

Title:[1038] Puppis A Caption:This color image was created from three images of Puppis A taken at the Cerro Tololo Inter-American Observatory (CTIO) 4-meter telescope. The three separate images were obtained through filters that isolate the emission lines of different elements. In this case, the images were combined at the Harvard-Smithsonian Center for Astrophysics using the Wolbach Image Processing Center. The stars were removed from the image using IRAF. The color image shows the light from nitrogen as red, oxygen as blue, and sulfur as green. The fact that distinct, unmixed debris is visible is a strong clue that these elements, cooked in the nuclear oven of a massive star, are the fresh result of a recent explosion. This small swirl of emission is a possible second explosion inside the large, old, Puppis A supernova remnant. Copyright: Credit:National Optical Astronomy Observatories

Title:[0600] Puppis A: X-ray Image Caption:This 1 degree x 1 degree soft (0.2- 4 ke V) x-ray map of the supernova remnant Puppies A was made from observations with the high resolution imager (HRI) on the Einstein Observatory. The approximately 50' angular diameter of Puppies A corresponds to a linear size of 30 pc or equivalently 100 light years (at the assumed distance of 2 kpc). Since there are no historical records of Puppies A, its age is calculated based on its observed properties and is estimated to be 5,000-10,000 years. Copyright:(c) Smithsonian Astrophysical Observatory Credit:Smithsonian Institution Astrophysical Observatory