Download or read book Comets Their General Properties and Effects on Large Bodies written by John S. Jenckes and published by . This book was released on 1811 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Comets written by Julio A. Fernandez and published by Springer Science & Business Media. This book was released on 2005-11-13 with total page 386 pages. Available in PDF, EPUB and Kindle. Book excerpt: Comets are small bodies, but of great cosmic relevance. Given its pristine nature, they may preserve valuable and unique information on thechemical and physical processes that took place in theearly solar system, and that may be occurring in the formation of other planetary systems. They might have even played a very important role in the origin of life on Earth. Beyond that, since ancient times comets have inspired awe, superstition, and also curiosity anddebate. Their sudden apparitions challenged the long-held view of the immutability of the heavens, which triggered a long debate on whether comets had a heavenly or terrestrial nature. Therefore, comets have a prominent role in the history of scienti?cthought, that goes back to the most ancient civilizations. The last apparition of comet Halley in 1986 was a landmark since it arouse a great expectation in the scienti?c community and in the public at large. For the ?rst time, a ?otilla of spacecrafts visited a comet. Agreat number of popular and technical books were written on Halley, and comets in general, around the mid-eighties. The interest in comets never subsided after Halley’s passage which is re?ected in the large volume of printed material on these bodies. I have taken the challenge to write a new book on comets that summarizes most of the recent advances on thesubject, including my own workdeveloped during the last 25 years.
Download or read book Asteroid Impact Risk written by Josep M. Trigo-Rodríguez and published by Springer Nature. This book was released on 2022-03-08 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book describes the complexity of impact hazards associated with asteroids and comets. The challenge in this regard lies in the heterogeneous nature of these bodies that endanger our planet, which is why we are conducting new experiments to better understand their unique physicochemical properties. Several generations of astronomers have tracked and mapped the orbits of asteroids and comets over the past few centuries, and telescopic surveys have only begun to discover “new” interstellar objects. In addition, cutting-edge software allow our computers to combine the orbits of these elusive bodies to study how they evolve over time and seek to match asteroid complexes as fragments of asteroidal and cometary disruptions. Impact hazards represent one of the greatest threats to the survival of human beings in the medium term. Geological studies show that the stratigraphic record holds clear geological evidence of these rare but transcendental encounters in the history of life on our planet. The study and quantification of past catastrophes can give us clues to face future challenges in the form of potential impacts. Further, it would be illogical to assume that Earth’s interaction with space is limited to major impacts. Every night, Earth is struck by millions of particles, and dozens of meteor showers occur around the globe every year. The study of lake and ocean sediments reveals the magnitude of the continuous contribution of interplanetary matter reaching Earth: roughly 100,000 tons per year. Accordingly, the goal of this book is to underscore the need for society-wide awareness of the dangers associated with asteroid and comet impacts, on the basis of scientific evidence and with no intention of sparking alarmism. After all, we ourselves may only be the fruit of an opportunity given to mammals sixty-five million years ago to evolve after the conflagration that would be the downfall of the dinosaurs. If we have learned to read Earth’s geological history, we should consider ourselves a very fortunate species, and its teachings should equip us to face this problem. The also book emphasizes the role of space missions to gain insights on these bodies, particularly describing the relevance of the DART (NASA) and Hera (ESA) missions to deflect and study Dimorphos, respectively, the small satellite of the Didymos binary asteroid.
Download or read book Hazards Due to Comets and Asteroids written by Tom Gehrels and published by University of Arizona Press. This book was released on 2021-11-30 with total page 1317 pages. Available in PDF, EPUB and Kindle. Book excerpt: In 1993, the U.S. Department of Defense declassified information dealing with frequent explosions in the upper atmosphere caused by meteoric impact. It is estimated that impacts have occurred of a magnitude equivalent to the atomic bomb detonated at Hiroshima. Not all such space voyagers meet their end in the atmosphere, however; huge craters attest to the bombardment of earth over millions of years, and a major impact may have resulted in the extinction of dinosaurs. An impact in Siberia near the beginning of this century proves that such events are not confined to geologic time. Hazards Due to Comets and Asteroids marks a significant step in the attempt to come to grips with the threats posed by such phenomena. It brings together more than one hundred scientists from around the world, who draw on observational and theoretical research to focus on the technical problems related to all aspects of dealing with these hazards: searching for and identifying hazardous comets and asteroids; describing their statistics and characteristics; intercepting and altering the orbits of dangerous objects; and applying existent technologies—rocket boosters, rendezvous and soft-landing techniques, instrumentation—to such missions. The book considers defensive options for diverting or disrupting an approaching body, including solar sails, kinetic-energy impacts, nuclear explosives, robotic mass drivers, and various propulsion systems. A cataclysmic impact posing a threat to life on Earth is a possibility that tomorrow's technology is capable of averting. This book examines in depth the reality of the threat and proposes practical measures that can be initiated now should we ever need to deal with it.
Download or read book The Comets written by John Russell Hind and published by . This book was released on 1852 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A History of Physical Theories of Comets From Aristotle to Whipple written by Tofigh Heidarzadeh and published by Springer Science & Business Media. This book was released on 2008-05-23 with total page 283 pages. Available in PDF, EPUB and Kindle. Book excerpt: Although the development of ideas about the motion and trajectory of comets has been investigated piecemeal, we lack a comprehensive and detailed survey of ph- ical theories of comets. The available works either illustrate relatively short periods in the history of physical cometology or portray a landscape view without adequate details. The present study is an attempt to review – with more details – the major physical theories of comets in the past two millennia, from Aristotle to Whipple. My research, however, did not begin with antiquity. The basic question from which this project originated was a simple inquiry about the cosmic identity of comets at the dawn of the astronomical revolution: how did natural philosophers and astronomers define the nature and place of a new category of celestial objects – comets – after Brahe’s estimation of cometary distances? It was from this turning point in the history of cometary theories that I expanded my studies in both the pre-modern and modern eras. A study starting merely from Brahe and ending with Newton, without covering classical and medieval thought about comets, would be incomplete and leave the fascinating achievements of post-Newtonian cometology unexplored.
Download or read book Comets written by Julio A. Fernandez and published by Springer. This book was released on 2005-07-19 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Comets are small bodies, but of great cosmic relevance. Given its pristine nature, they may preserve valuable and unique information on thechemical and physical processes that took place in theearly solar system, and that may be occurring in the formation of other planetary systems. They might have even played a very important role in the origin of life on Earth. Beyond that, since ancient times comets have inspired awe, superstition, and also curiosity anddebate. Their sudden apparitions challenged the long-held view of the immutability of the heavens, which triggered a long debate on whether comets had a heavenly or terrestrial nature. Therefore, comets have a prominent role in the history of scienti?cthought, that goes back to the most ancient civilizations. The last apparition of comet Halley in 1986 was a landmark since it arouse a great expectation in the scienti?c community and in the public at large. For the ?rst time, a ?otilla of spacecrafts visited a comet. Agreat number of popular and technical books were written on Halley, and comets in general, around the mid-eighties. The interest in comets never subsided after Halley’s passage which is re?ected in the large volume of printed material on these bodies. I have taken the challenge to write a new book on comets that summarizes most of the recent advances on thesubject, including my own workdeveloped during the last 25 years.
Download or read book Comets II written by Michel C. Festou and published by University of Arizona Press. This book was released on 2004-11-01 with total page 780 pages. Available in PDF, EPUB and Kindle. Book excerpt: The study of comets is a field that has seen tremendous advances in recent years, far surpassing the knowledge reflected in the original Comets volume published as part of the Space Science Series in 1982. This new volume, with more than seventy contributing authors, represents the first complete overview of comet science in more than a decade and contains the most extensive collection of knowledge yet assembled in the field. Comets II situates comet science in the global context of astrophysics for the first time by beginning with a series of chapters that describe the connection between stars and planets. It continues with a presentation of the formation and evolution of planetary systems, enabling the reader to clearly see the key role played in our own solar system by the icy planetesimals that were the seeds of the giant planets and transneptunian objects. The book presents the key results obtained during the 1990s, in particular those collected during the apparition of the exceptional comets C/Hyakutake and C/Hale-Bopp in 1996-1997. The latest results obtained from the in situ exploration of comets P/Borrelly and P/Wild 2 are also discussed in detail. Each topic of is designed to be accessible to students or young researchers looking for basic, yet detailed, complete and accurate, information on comet science. With its emphasis on the origin of theories and the future of research, Comets II will enable scientists to make connections across disciplinary boundaries and will set the stage for discovery and new understanding in the coming years.
Download or read book Studies of Comets and Active Asteroids From Dynamics to Physical Properties written by Wentao Xu and published by . This book was released on 2019 with total page 185 pages. Available in PDF, EPUB and Kindle. Book excerpt: In order to have a better understanding of the early history of the solar system, it is scientifically important to study comets and active asteroids, which are believed to be leftovers from the formation epoch. This work presents our studies of two of the least understood families of cometary objects -- active asteroids and near-Sun comets, in terms of their non-gravitational effects and physical properties. We also present a summary of our two short-term surveys specifically for Kreutz-group comets, and an examination of a widely adopted cometary nucleus-extraction technique. We first systematically investigate the non-gravitational effects of the known active asteroids. Two of the members (313P/Gibbs \& 324P/La Sagra) exhibit statistically significant non-gravitational effects, while for the remaining members we are only able to place upper limits. The result is broadly consistent with the fact that the mass loss of active asteroids is generally less than that of typical comets. Thus, previous dynamical studies of active asteroids without consideration of the non-gravitational effects are still valid, and the majority were likely formed in situ in the main belt rather than from other cometary sources. For near-Sun comets, we conducted ground-based surveys from the Canada-France-Hawaii telescope (CFHT) and the VLT Survey Telescope (VST) in 2012 and 2014, respectively, without detection of any dwarf Kreutz-group comets. Our non-detection of two bright members which were later discovered by the {\it Solar and Heliospheric Observatory} ({\it SOHO}) but within our CFHT search region suggests that dwarf Kreutz comets brighten much more rapidly than previously thought, or they undergo outburst at larger heliocentric distances. We also present an unprecedentedly detailed study of near-Sun comet C/2015 D1 ({\it SOHO}), which was the first sunskirting comet observed from the ground over the past half century. This comet disintegrated around perihelion due to excessive thermal stress within its nucleus, or to rotational instability. The enormous mass loss ($\dot{M}_\mathrm{N} \sim 10^5$ kg s$^{-1}$) caused a strong non-gravitational effect. Together with photometric measurements, the nucleus mass and radius are inferred ($M_\mathrm{N} \sim 10^8$-10$^9$ kg, $R_\mathrm{N} \sim 50$-150 m), and we probe the emission of dust grains and dust-size distribution based on the morphology, as well as its composition using {\it SOHO} multiband observations. Finally, we examine the nucleus-extraction technique, an important tool for revealing cometary nucleus sizes, based on which statistics of the nucleus-size distribution are established. By testing the method on our synthetic comet images, we identify an obvious systematic bias stemming from neglect of the distortion of the coma brightness profile after convolution with point-spread functions (PSF). Thus, we conclude that published nucleus-size determinations using this technique are likely invalid. Our main suggestion is to better apply the technique on high spatial resolution images of weakly active comets when the nucleus signal occupies $\gtrsim$10\% of the total around the central region.
Download or read book Comets and the New Comet of 1874 With a Complete Popular Account of All that is Known of These Wonderful Bodies written by Comets and published by . This book was released on 1874 with total page 64 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Geological Implications of Impacts of Large Asteroids and Comets on the Earth written by Leon Theodore Silver and published by Geological Society of America. This book was released on 1983-02-01 with total page 549 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Comets written by Laurel L. Wilkening and published by University of Arizona Press. This book was released on 1982-04 with total page 784 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over forty authorities present sections on the nucleus, dust, coma, and tails of comets, along with sections on their origin, and relationships to other solar system bodies. . . . An excellent book.ÑSpace News "The volume is highly recommended to all interested in comets and the Solar System."ÑJournal of the British Astronomical Association "A good representation of the studies that are currently being done on comets, and it is an extremely good source of information on a wide variety of topics."ÑInternational Comet Quarterly "Extremely well-written and informative. . . . A must for library collections."ÑThe Observatory
Download or read book Mitigation of Hazardous Comets and Asteroids written by M. J. S. Belton and published by Cambridge University Press. This book was released on 2004-09-06 with total page 448 pages. Available in PDF, EPUB and Kindle. Book excerpt: It is known that large asteroids and comets can collide with the Earth with severe consequences. Although the chances of a collision in a person's lifetime are small, collisions are a random process and could occur at any time. This book collects the latest thoughts and ideas of scientists concerned with mitigating the threat of hazardous asteroids and comets. It reviews current knowledge of the population of potential colliders, including their numbers, locations, orbits, and how warning times might be improved. The structural properties and composition of their interiors and surfaces are reviewed, and their orbital response to the application of pulses of energy is discussed. Difficulties of operating in space near, or on the surface of, very low mass objects are examined. The book concludes with a discussion of the problems faced in communicating the nature of the impact hazard to the public.
Download or read book Evolutionary and Physical Properties of Meteoroids written by Curtis L. Hemenway and published by . This book was released on 1973 with total page 388 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Physics and Chemistry of Comets written by Walter F. Huebner and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 389 pages. Available in PDF, EPUB and Kindle. Book excerpt: As this excellent book demonstrates, the study of comets has now reached the fas cinating stage where we understand comets in general simple tenns while, at the same time, we are uncertain about practically all the details of cometary nature, structure, processes, and origin. In every aspect, even including dynamics, a choice among several or many competing theories is made impossible simply by the lack of detailed knowledge. The space missions, snapshot studies of two comets, partic ularly the one that immortalizes the name of Sir Edmund Halley, have produced a huge mass of valuable new infonnation and a number of surprises. Nonetheless, we face the tantalizing realization that we have obtained only a fleeting glance at two of perhaps a hundred billion (lOll) or more comets with possibly differing natures, origins, and physical histories. To my personal satisfaction, comets seem to have discrete nuclei made up of dirty snowballs, as I concluded four decades ago, but perhaps they are more like frozen rubbish piles.
Download or read book Comet and Asteroid Impact Hazards on a Populated Earth written by John S. Lewis and published by Academic Press. This book was released on 2000 with total page 224 pages. Available in PDF, EPUB and Kindle. Book excerpt: Disk contains: HAZARDS version 5.5, designed to predict asteroid or comet impacts with the Earth.
Download or read book Complete Works written by Thomas Dick and published by . This book was released on 1855 with total page 762 pages. Available in PDF, EPUB and Kindle. Book excerpt:
