PLATE 2.1 An optical picture of the star Beta Pictoris taken with a special instrument that blocks out light from the central star. Light from the star is scattered by a disk of solid particles, perhaps a remnant of the formation of planets. Courtesy of B. Smith, R. Terrile, and the Jet Propulsion Laboratory.



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THE DECADE OF DISCOVERY IN ASTRONOMY AND ASTROPHYSICS PLATE 2.1 An optical picture of the star Beta Pictoris taken with a special instrument that blocks out light from the central star. Light from the star is scattered by a disk of solid particles, perhaps a remnant of the formation of planets. Courtesy of B. Smith, R. Terrile, and the Jet Propulsion Laboratory.

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THE DECADE OF DISCOVERY IN ASTRONOMY AND ASTROPHYSICS PLATE 2.2 Voyager spacecraft images of Jupiter's moon Io revealed the presence of sulfurspewing volcanoes (left). Observations with an infrared camera on NASA's Infrared Telescope Facility (IRTF) on Mauna Kea made a diffraction-limited 3-µm image of the Loki, the brightest of these volcanoes (right). Courtesy of the Jet Propulsion Laboratory and the IRTF. PLATE 2.3 Radar images of the asteroid 1989 PB made at the Arecibo Observatory near the time of closest approach of 2.5 million miles. The dumbbell-shaped asteroid is about a mile across and rotates with a period of about 4 hours. Courtesy of S. Ostro, Jet Propulsion Laboratory.

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THE DECADE OF DISCOVERY IN ASTRONOMY AND ASTROPHYSICS PLATE 2.4 The entire sun vibrates at thousands of different frequencies that penetrate deeply into the solar core. Astronomers study these vibrations in a manner analogous to terrestrial seismology to learn about the sun's interior. The figure shows an artist's representation of one of the sun's vibrational modes. Courtesy of the National Solar Observatory.

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THE DECADE OF DISCOVERY IN ASTRONOMY AND ASTROPHYSICS PLATE 2.5 A roughly 40° region in the constellation Orion shows giant gas clouds and hundreds of recently formed stars. The bright regions in the lower right are the Orion Nebula (Messier 42) and the Orion B complex where hot, young stars are being formed. This IRAS image shows the warmest material emitting at 12 µm as blue, cool material emitting at 60 µm as green, and the coolest material emitting only at 100 µm as red. Courtesy of the Infrared Processing and Analysis Center, California Institute of Technology.

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THE DECADE OF DISCOVERY IN ASTRONOMY AND ASTROPHYSICS PLATE 2.6 A photograph made with the Wide-Field/Planetary camera on the Hubble Space Telescope shows a jet of material streaming away from a young star in the Orion Nebula, about 1,500 light-years away. Jets of this type are thought to be associated with the last stages of the accretion process by which stars are formed out of interstellar gas. The white bar at the top of the image represents 5 arcseconds. The smallest structures that can be resolved in this image are about one-tenth of an arcsecond, or roughly the size of our solar system. In this image red corresponds to radiation from ionized sulfur, green light to ionized hydrogen, and blue light to ionized oxygen. Courtesy of NASA.

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THE DECADE OF DISCOVERY IN ASTRONOMY AND ASTROPHYSICS PLATE 2.7 Two views of the NGC 2024 star-forming region in the Orion Nebula. A picture of a 300-arcsecond field taken with a visible-light camera (left), showing relatively few stars due to obscuration by dust, and one taken with an infrared camera (right), showing hundreds of newly forming stars. Courtesy of the National Optical Astronomy Observatories. PLATE 2.8 Images taken with the Hat Creek millimeter interferometer show close-up views at a number of different frequencies of a star forming in the Orion Nebula. The images are 60 arcseconds on a side. Radio emission from the SiO, SO2, HDO, and HC3N molecules probes physical conditions in different regions close to the forming star, indicated by a square. Image courtesy of the Berkeley-Illinois-Maryland Array.

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THE DECADE OF DISCOVERY IN ASTRONOMY AND ASTROPHYSICS PLATE 2.9 The Fly's Eye telescope at Dugway, Utah, measures light produced in the atmosphere by very high energy cosmic rays. Each of the mirrors is equipped with 14 phototubes that allow the reconstruction of the trajectory of the cosmic ray. Photograph courtesy of Technical Information Department, Lawrence Berkeley Laboratory, University of California.

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THE DECADE OF DISCOVERY IN ASTRONOMY AND ASTROPHYSICS PLATE 2.10 Radio and x-ray images of the supernova remnant Cassiopeia A. (a) The radio image shows emission from electrons that have been accelerated by the interaction of the supernova blast waves and local magnetic fields. (b) The x-ray image reveals about 20 solar masses of debris from a stellar explosion at temperatures of 50 million degrees celsius, which has been expanding for about 300 years at speeds of −5,000 km s−1. Radio image courtesy of the National Radio Astronomy Observatory/Associated Universities, Inc. X-ray image courtesy of S. Murray.

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THE DECADE OF DISCOVERY IN ASTRONOMY AND ASTROPHYSICS PLATE 2.11 Three views of the Milky Way. An optical image (top) shows mostly nearby stars. Clouds of gas and dust obscure the center of the galaxy, denoted by a (+). A near-infrared image (middle) from the COBE satellite penetrates the dust and shows the bulge of stars at the very center of the galaxy. A far-infrared image from IRAS (bottom) shows the cool, star-forming regions of the galaxy. Courtesy of the Palomar Observatory, Goddard Space Flight Center, and the Jet Propulsion Laboratory.

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THE DECADE OF DISCOVERY IN ASTRONOMY AND ASTROPHYSICS PLATE 2.12 Optical images of four infrared-luminous galaxies detected by IRAS show that many objects of this class are interacting or colliding galaxy pairs. Courtesy of D. Sanders and B.T. Soifer, California Institute of Technology.

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THE DECADE OF DISCOVERY IN ASTRONOMY AND ASTROPHYSICS PLATE 2.13 An image of the elliptical galaxy 3C353 shows visible light (blue) and radio emission (red). Jets of energetic particles moving at close to the speed of light emanate from the center of the galaxy and create two bright lobes of radio emission stretching over 360,000 light-years. Courtesy of the National Radio Astronomy Observatory/Associated Universities, Inc. PLATE 2.14 X-rays from a “jet” in the active galax Centaurus A. X-rays are thought to come from a beam of very energetic particles emitted from the vicinity of a giant black hole in the nucleus of the galaxy. These particles, also detected at radio wavelengths, then stream out into intergalactic space. Image courtesy of E. Schreier.

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THE DECADE OF DISCOVERY IN ASTRONOMY AND ASTROPHYSICS PLATE 2.15 A supercomputer simulation of a jet of material such as might be ejected from the center of a galaxy (see Plate 2.13 and Plate 2.14). The top image shows the variation of total energy in the jet, the middle image the density of matter, and the bottom image the magnetic field strength. Courtesy of D. Payne and D. Meier of the Jet Propulsion Laboratory, K. Lind of the Naval Research Laboratory, R. Blandford of the California Institute of Technology, and T. Elvins of the San Diego Supercomputer Center.

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THE DECADE OF DISCOVERY IN ASTRONOMY AND ASTROPHYSICS PLATE 2.16 The observed three-dimensional distribution of galaxies (left) shows sheets, filaments, and voids over 100 million light-years in size, Reprinted by permission from M. Geller and J, Huchra. Copyright © 1990 by the Smithsonian Astrophysical Observatory, Theoretical models (right) attempt to show how galaxies arrange themselves in such complex structures. Courtesy of C. Park and J.R. Gott.

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THE DECADE OF DISCOVERY IN ASTRONOMY AND ASTROPHYSICS PLATE 3.1 The Mirror Laboratory of the University of Arizona's Steward Observatory has developed innovative techniques for the casting and polishing of mirrors for astronomical telescopes. The 3.5-m mirror blank is a prototype for the 8-m mirrors to be built in the Mirror Laboratory in the 1990s. Courtesy of R. Angel and the Steward Observatory.

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THE DECADE OF DISCOVERY IN ASTRONOMY AND ASTROPHYSICS PLATE 4.1 An artist's conception of the solar-system-sized ring of planetary debris around a star like Vega or Beta Pictoris. SIRTF would be able to study the mass, composition, and distribution of matter in such systems out to 1,000 light-years away. The typical size of a pixel in an image from SIRTF is indicated.

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THE DECADE OF DISCOVERY IN ASTRONOMY AND ASTROPHYSICS PLATE 4.2 A deep infrared survey looking for primeval galaxies. The image on the left was formed by superposing images taken in two visible wavelengths (0.55 and 0.9 µm in blue and green) and one infrared wavelength (2.2 µm in red). The image on the right was formed at three visible wavelengths (0.35, 0.55, and 0.9 µm). The images are 80 arcseconds on a side, and the infrared image required an exposure time of 22 hours to reach objects as faint as 21.4 magnitude at 2.2 µm. The reddest objects may be very distant spiral galaxies. Courtesy of L. Cowie, University of Hawaii.

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THE DECADE OF DISCOVERY IN ASTRONOMY AND ASTROPHYSICS PLATE 4.3 Optical aperture synthesis image of the binary star σ Her made with the Palomar 5-m telescope. The long exposure shows a typical astronomical image with 2-arcsecond “seeing.” The image on the left shows the reconstructed image of the two stars separated by 70 thousandths of an arcsecond. The image reconstruction required approximately 24 hours of processing on a supercomputer. Reprinted by permission from Nakajima et al. (1989) and the Astronomical Journal, published for the American Astronomical Society by the American Institute of Physics.

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THE DECADE OF DISCOVERY IN ASTRONOMY AND ASTROPHYSICS PLATE 5.1 What happens when two neutron stars collide head-on? Scientists programmed an NSF supercomputer with the known physics of neutron stars in an attempt to find out. The resultant smashup was spectacular. The streaks represent the trajectories of particles of stellar material. Courtesy of C. Evans, University of North Carolina, Chapel Hill, and C. Hoyer and R. Idaszak, National Center for Supercomputer Applications. PLATE 5.2 The effect of a black hole is obtained from a numerical solution of Einstein's equations that describe the behavior of the gravitational field. The shape of the diagram measures the curvature of space due to the presence of the black hole. The color scale represents the speed at which a clock would measure time (red is slow, blue fast). Courtesy of L. Smarr, D. Hobill, D. Bernstein, D. Cox, and R. Idaszak, National Center for Supercomputer Applications.

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THE DECADE OF DISCOVERY IN ASTRONOMY AND ASTROPHYSICS PLATE 8.1 This Hubble Space Telescope image of the planet Saturn was taken with the Wide-Field/Planetary Camera. The picture shows a storm system that grew from a small disturbance in the planet' s Southern Hemisphere to an equatorial belt surrounding nearly the entire planet. The study of weather systems on other planets helps scientists understand weather patterns on the earth. Courtesy of NASA.

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THE DECADE OF DISCOVERY IN ASTRONOMY AND ASTROPHYSICS PLATE 8.2 An image (obtained October 5, 1987) of the terrestrial ozone concentration shows a hole over Antarctica. Groundbased and orbiting instruments and analytical techniques similar to those developed for the study of interstellar clouds and planetary atmospheres are used to study this important environmental problem. Image courtesy of NASA's Goddard Space Flight Center.