Institution
Jet Propulsion Laboratory
Facility•La Cañada Flintridge, California, United States•
About: Jet Propulsion Laboratory is a facility organization based out in La Cañada Flintridge, California, United States. It is known for research contribution in the topics: Mars Exploration Program & Telescope. The organization has 8801 authors who have published 14333 publications receiving 548163 citations. The organization is also known as: JPL & NASA JPL.
Topics: Mars Exploration Program, Telescope, Galaxy, Coronagraph, Planet
Papers published on a yearly basis
Papers
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TL;DR: In this paper, the authors studied the CO emission from protoplanetary nebulae (PPNe) and identified a slowly expanding shell (represented in the spectra by a central core) and a fast outflow (corresponding to the line wings).
Abstract: We have studied the CO emission from protoplanetary nebulae (PPNe). Our sample is composed of 37 objects and includes, we think, all well identied PPNe detected in CO, together with the two yellow hypergiants emitting in CO and one young PN. We present a summary of the existing CO data, including accurate new observations of the 12 CO and 13 CO J = 1{0 and J = 2{1 lines in 16 objects. We identify in the nebulae a slowly expanding shell (represented in the spectra by a central core) and a fast outflow (corresponding to the line wings), that in the well studied PPNe is known to be bipolar. Excluding poor data, we end up with a sample of 32 sources (including the 16 observed by us); fast flows are detected in 28 of these nebulae, being absent in only 4. We present a method to estimate from these data the mass, \scalar" momentum and kinetic energy of the dierent components of the molecular outflows. We argue that the uncertainties of our method can hardly lead to signicant overestimates of these parameters, although underestimates may be present in not well studied objects. The total nebular mass is often as high as 1 M, and the mass-loss rate, that (presumably during the last stages of the AGB phase) originated the nebula, had typical values 10 4 M yr 1 . The momentum corresponding to this mass ejection process in most studied nebulae is accurately coincident with the maximum momentum that radiation pressure, acting through absorption by dust grains, is able to supply (under expected conditions). We estimate that this high-eciency process lasts about 1000{10 000 yr, after which the star has ejected a good fraction of its mass and the AGB phase ends. On the other hand, the fast molecular outflows, that have probably been accelerated by shock interaction with axial post-AGB jets, carry a signicant fraction of the nebular mass, with a very high momentum (in most cases between 10 37 and 10 40 gc m s 1 ) and very high kinetic energy (usually between 10 44 and 10 47 erg). In general, yellow hypergiants and post-AGB objects with low initial mass show nebular masses and momenta that are, respectively, higher and lower than these values. We compare the momenta of the fast outflows with those that can be supplied by radiation pressure, taking into account the expected short acceleration times and some eects that can increase the momentum transfer. We nd that in about 80% of PPNe, the fast molecular flows have too high momenta to be powered by radiation pressure. In some cases the momentum of the outflow is1000 larger than that carried by radiation pressure; such high factors are dicult to explain even under exceptional conditions. Wind interaction is the basic phenomenon in the PN shaping from the former AGB envelopes; we conclude that this interaction systematically takes place along a dominant direction and that this process is not powered by radiation pressure. Due to the lack of theoretical studies, the possible momentum source remains a matter of speculation.
291 citations
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TL;DR: In this article, a simple model of local heat transport on Mars demonstrates that transient melting of ice may occur in depressions and gullies nearly anywhere on the planet where thin ice is illuminated by normal-incidence insolation.
291 citations
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TL;DR: In this paper, radar speckle patterns tied to the rotation of the planet Mercury were used to establish that the planet occupies a Cassini state with obliquity of 2.11 ± 0.1 arc minutes.
Abstract: Observations of radar speckle patterns tied to the rotation of Mercury establish that the planet occupies a Cassini state with obliquity of 2.11 ± 0.1 arc minutes. The measurements show that the planet exhibits librations in longitude that are forced at the 88-day orbital period, as predicted by theory. The large amplitude of the oscillations, 35.8 ± 2 arc seconds, together with the Mariner 10 determination of the gravitational harmonic coefficient C22, indicates that the mantle of Mercury is decoupled from a core that is at least partially molten.
291 citations
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TL;DR: In this article, a new class of apodizing functions suitable for Fourier spectrometry (and similar applications) is introduced, and three specific functions are discussed in detail, and the resulting instrumental line shapes are compared to numerous others proposed for the same purpose.
Abstract: A new class of apodizing functions suitable for Fourier spectrometry (and similar applications) is introduced. From this class, three specific functions are discussed in detail, and the resulting instrumental line shapes are compared to numerous others proposed for the same purpose.
291 citations
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01 Oct 2014TL;DR: Immersion provides benefits beyond the traditional “desktop” visualization tools: it leads to a demonstrably better perception of a datascape geometry, more intuitive data understanding, and a better retention of the perceived relationships in the data.
Abstract: Effective data visualization is a key part of the discovery process in the era of “big data”. It is the bridge between the quantitative content of the data and human intuition, and thus an essential component of the scientific path from data into knowledge and understanding. Visualization is also essential in the data mining process, directing the choice of the applicable algorithms, and in helping to identify and remove bad data from the analysis. However, a high complexity or a high dimensionality of modern data sets represents a critical obstacle. How do we visualize interesting structures and patterns that may exist in hyper-dimensional data spaces? A better understanding of how we can perceive and interact with multidimensional information poses some deep questions in the field of cognition technology and human-computer interaction. To this effect, we are exploring the use of immersive virtual reality platforms for scientific data visualization, both as software and inexpensive commodity hardware. These potentially powerful and innovative tools for multi-dimensional data visualization can also provide an easy and natural path to a collaborative data visualization and exploration, where scientists can interact with their data and their colleagues in the same visual space. Immersion provides benefits beyond the traditional “desktop” visualization tools: it leads to a demonstrably better perception of a datascape geometry, more intuitive data understanding, and a better retention of the perceived relationships in the data.
290 citations
Authors
Showing all 9033 results
Name | H-index | Papers | Citations |
---|---|---|---|
B. P. Crill | 148 | 486 | 111895 |
George Helou | 144 | 662 | 96338 |
H. K. Eriksen | 141 | 474 | 104208 |
Charles R. Lawrence | 141 | 528 | 104948 |
W. C. Jones | 140 | 395 | 97629 |
Gianluca Morgante | 138 | 478 | 98223 |
Jean-Paul Kneib | 138 | 805 | 89287 |
Kevin M. Huffenberger | 138 | 402 | 93452 |
Robert H. Brown | 136 | 1174 | 79247 |
Federico Capasso | 134 | 1189 | 76957 |
Krzysztof M. Gorski | 132 | 380 | 105912 |
Olivier Doré | 130 | 427 | 104737 |
Mark E. Thompson | 128 | 527 | 77399 |
Clive Dickinson | 123 | 501 | 80701 |
Daniel Stern | 121 | 788 | 69283 |