Rocket observation of interstellar molecular hydrogen
TL;DR: Interstellar molecular H Lyman resonance-absorption bands in far UV spectrum using rocket observation using satellite observation was used in this paper, where the authors proposed a method to estimate the distance to the star.
Abstract: Interstellar molecular H Lyman resonance-absorption bands in far UV spectrum using rocket observation
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TL;DR: In this article, the authors present the current knowledge and understanding of the interstellar medium of our galaxy and discuss the interaction of these interstellar constituents, both with each other and with stars, in the framework of the general galactic ecosystem.
Abstract: This article reviews the current knowledge and understanding of the interstellar medium of our galaxy. The author first presents each of the three basic constituents---ordinary matter, cosmic rays, and magnetic fields---of the interstellar medium, with emphasis on their physical and chemical properties as inferred from a broad range of observations. The interaction of these interstellar constituents, both with each other and with stars, is then discussed in the framework of the general galactic ecosystem.
986 citations
TL;DR: This work reports a class of impacts that yield an iron-poor Moon, as well as the current masses and angular momentum of the Earth–Moon system, and suggests that the Moon formed near the very end of Earth's accumulation.
Abstract: The Moon is generally believed to have formed from debris ejected by a large off-centre collision with the early Earth. The impact orientation and size are constrained by the angular momentum contained in both the Earth's spin and the Moon's orbit, a quantity that has been nearly conserved over the past 4.5 billion years. Simulations of potential moon-forming impacts now achieve resolutions sufficient to study the production of bound debris. However, identifying impacts capable of yielding the Earth-Moon system has proved difficult. Previous works found that forming the Moon with an appropriate impact angular momentum required the impact to occur when the Earth was only about half formed, a more restrictive and problematic model than that originally envisaged. Here we report a class of impacts that yield an iron-poor Moon, as well as the current masses and angular momentum of the Earth-Moon system. This class of impacts involves a smaller-and thus more likely-object than previously considered viable, and suggests that the Moon formed near the very end of Earth's accumulation.
919 citations
TL;DR: In this article, a new systematic classification method for the different types of diffuse clouds: diffuse atomic, diffuse molecular, translucent, and dense is proposed, which can be used as indicators of the physical and chemical conditions within these clouds.
Abstract: Diffuse interstellar clouds have long been thought to be relatively devoid of molecules, because of their low densities and high radiation fields. However, in the past ten years or so, a plethora of polyatomic molecules have been observed in diffuse clouds, via their rotational, vibrational, and electronic transitions. In this review, we propose a new systematic classification method for the different types of interstellar clouds: diffuse atomic, diffuse molecular, translucent, and dense. We review the observations of molecules (both diatomic and polyatomic) in diffuse clouds and discuss how molecules can be utilized as indicators of the physical and chemical conditions within these clouds. We review the progress made in the modeling of the chemistry in these clouds, and the (significant) challenges that remain in this endeavor. We also review the evidence for the existence of very large molecules in diffuse clouds, and discuss a few specific clouds of particular interest.
574 citations
Cites methods from "Rocket observation of interstellar ..."
...The first success, using rocket-based spectroscopy, was by Carruthers (1970), who detected strong H2 absorption in the line of sight toward ξ Persei....
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TL;DR: In this article, the authors enumerate the major surveys of CO emission along the Galactic plane and summarize the various approaches that leverage these data to determine the large-scale distribution of molecular gas: its radial and vertical distributions, its concentration into clouds, and its relationship to spiral structure.
Abstract: In the past twenty years, the reconnaissance of 12 CO and 13 CO emission in the Milky Way by single-dish millimeter-wave telescopes has expanded our view and understanding of interstellar molecular gas. We enumerate the major surveys of CO emission along the Galactic plane and summarize the various approaches that leverage these data to determine the large-scale distribution of molecular gas: its radial and vertical distributions, its concentration into clouds, and its relationship to spiral structure. The integrated properties of molecular clouds are compiled from catalogs derived from the CO surveys using uniform assumptions regarding the Galactic rotation curve, solar radius, and the CO-to-H2 conversion factor. We discuss the radial variations of cloud surface brightness, the distributions of cloud mass and size, and scaling relations between velocity dispersion, cloud size, and surface density that affirm that the larger clouds are gravitationally bound. Measures of density structure and gas kinematics within nearby, well-resolved clouds are examined and attributed to the effects of magnetohydrodynamic turbulence. We review the arguments for short, intermediate, and long molecular lifetimes based on the observational record. The review concludes with questions that shall require further observational attention.
459 citations
Cites background from "Rocket observation of interstellar ..."
...…somehow It’s cloud illusions I recall/I really don’t know clouds at all —Joni Mitchell The detections of interstellar molecular hydrogen (H2) in the UV (Carruthers 1970) and carbon monoxide (CO) at 2.6 mm (Wilson et al. 1970) spawned an exciting new era of research on the molecular interstellar…...
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TL;DR: In this article, the authors report the first ensemble results from the Far Ultraviolet Spectroscopic Explorer survey of molecular hydrogen in lines of sight with AV e1 mag, and find strong correlations between H2 and molecules such as CH, CN, and CO, in general agreement with predictions of chemical models.
Abstract: We report the first ensemble results from the Far Ultraviolet Spectroscopic Explorer survey of molecular hydrogen in lines of sight with AV e1 mag. We have developed techniques for fitting computed profiles to the low-J lines of H2, and thus determining column densities for J ¼ 0 and J ¼ 1, which contain e99% of the total H2. From these column densities and ancillary data we have derived the total H2 column densities, hydrogen molecular fractions, and kinetic temperatures for 23 lines of sight. This is the first significant sample of molecular hydrogen column densities of � 10 21 cm � 2 , measured through UV absorption bands. We have also compiled a set of extinction data for these lines of sight, which sample a wide range of environments. We have searched for correlations of our H2-related quantities with previously published column densities of other molecules and extinction parameters. We find strong correlations between H2 and molecules such as CH, CN, and CO, in general agreement with predictions of chemical models. We also find the expected correlations between hydrogen molecular fraction and various density indicators such as kinetic temperature, CN
379 citations