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High-sensitivity x-ray measurements with the recently launched Einstein Observatory are having a major impact on wide areas of astronomical research. The x-ray luminosity of young O, B, and A stars and late K and M stars is found to be several orders of magnitude greater than predicted by current theories of coronal heating. Detailed x-ray images and spectra of supernova remnants are providing new information on the temperature, composition, and distribution of material ejected in supernova explosions as well as of the material comprising the interstellar medium. Observations of galaxies are yielding insights on the formation and evolution of stellar systems and galaxies over a wide range of variables. X-ray time variations are being used to probe the underlying energy source in quasars and active galactic nuclei. The distribution of mass in clusters of galaxies is being traced through detailed x-ray images, and the data are being used to classify clusters and trace their formation and evolution. Substantial progress is being made in several areas of cosmological research, particularly in the study of the diffuse x-ray background.  相似文献   

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通过检索和统计河南科技大学发表在2008年—2012年间被EI收录的文献,并借助于Refine Results进行定量分析,提出个人意见和看法,对科研工作者在论文投稿和学校制定发展规划具有一定的参考价值。  相似文献   

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The most accurate infrared photometric observations (8 to 14 microns) to date of the average limb darkening of Jupiter have been combined with the most refined deduction of jovian model atmospheres in which flux constancy has been closely maintained in the upper regime of radiative equilibrium and a much more accurate approximation of the 10-and 16-micron vibration-rotation bands of ammonia has been incorporated. The theoretically predicted emergent specific intensity has been multiplied by the spectral response function and folded (mathematically convolved-intersmeared) with the spatial response function of the atmosphere-telescope-photometer combination. The resulting comparison indicates that Jupiter is radiating from three to four times as much power as the planet is receiving from the sun.  相似文献   

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Eugster O 《Science (New York, N.Y.)》1989,245(4923):1197-1202
In large asteroidal or cometary impacts on the moon, lunar surface material can be ejected with escape velocities. A few of these rocks were captured by Earth and were recently collected on the Antarctic ice. The records of noble gas isotopes and of cosmic ray-produced radionuclides in five of these meteorites reveal that they originated from at least two different impact craters on the moon. The chemical composition indicates that the impact sites were probably far from the Apollo and Luna landing sites. The duration of the moon-Earth transfer for three meteorites, which belong to the same fall event on Earth, lasted 5 to 11 million years, in contrast to a duration of less than 300,000 years for the two other meteorites. From the activities of cosmic ray-produced radionuclides, the date of fall onto the Antarctic ice sheet is calculated as 70,000 to 170,000 years ago.  相似文献   

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