Sungrazing Comets: Snowballs in the Furnace

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By: Rowan Cocoan. Comets and Catastrophe Series. Special Reports. Covert News. This is one of the most interesting things I've ever read For generations astronomers have viewed comets as one of the most scientifically important phenomena in space. Comets are thought to be "Rosetta Stones" through which the early history of our solar system can be gleaned. We've been told for many decades that comets are loose aggregates of ice and dirt that originated billions of years ago in an ancient "Oort cloud".

A falsification of this model would signifiay an extraordinary jolt to the space sciences. Without any official acknowledgement from instutional science, the standard model of comets has been falsified, and repeatedly so. But a different view of comets has been far more successful at predicting comet discoveries. In this model, it is electricity that accounts for the comets behaviors that have so deeply puzzled mainstream astronomers.

As far back as the late 19th century, some astronomers and physicists speculated on the electrical nature of comets. In the early 20th century, the brilliant scientist Kristian Brikeland emulated cometary jets from a cathode in a vacuum tube. In recent years, Wallace Thornhill , the leading proponent of the alternative cosmology called the Electric Universe, has elaborated the electric comet hypothesis -- inculding many advance predictions that have proved accurate.

In Thornhill's view, comets acquire a negative charge during their time at the farther reaches of the solar system, and experience electrical stresses usually when moving toward the more positively charged region of the sun. The explosion would not eject the amount of water into the coma expected by astronomers. The surface would be dry. A sculpted comet surface with sharply defined craters, valleys, mesas, and ridges the precise opposite of what one expects of a " dirty snowball" : a rearrangement of the comet's jets due to charge distribution.

All of these predictions were confirmed , much to the astonishment of NASA and scientists around the world. The news service Wired. NASA declined. In comet science, it is not just a matter of a few anomalies or suprises occassionally upsetting the apple-cart. And as we will demonstrate as we continue, most of these facts on their own should be sufficient to falsify the standard model.

A perfect illustration of the crisis in comet science was recently provided by the extraordariny unanticipated "brightening" of Comet Holmes 17P. In less than 24 hours, the comet flared up from a magnitutde of 17 to a magnitude of 2. Holme's coma expanded from 28, km until it was an incredible 7,, km, making it "the largest object in the solar system.

The astronomers who talked publicly about Holmes mostly expressed bafflement. But a majority of major science publications barely discussed the comet at all. The most likely time to see a flare-up is during the passage of a sudden change in the solar wind. In fact, this may be what happend with Comet Holmes. Two days before the comet's flare-up, on October 22 at , there was a large spike in the density of the solar wind.

Table of contents

The relationship between the electric Sun and electric comet was graphically illustrated when a coronal mass ejection CME greeted Comet Neat, imaged right. The comet responded with a "kink" that propagated down the tail. While astronomers were quick to call this possible mutual interaction "coincidental" , it was not the first time such apparent exchanges between the Sun and the comets had been recorded. In , another CME was preceded immediately by the destruction of two Sun grazing comets.

The comet "suprises" stretch back over decades, and far outnumber any confirmations of the standard model. Certainly, no one who views comets as "dirty snowballs" ever imagined that they would be found to generate x-rays! In , Comet Hyakutake radiated x-rays as intense as those detected from stars. The x-rays flickered over a matter of hours like a failing fluorescent lamp. From the Electric Universe perspective, the analogy is apt: A comet is a light producing load in the circuit of an electrically powered Sun. X-rays were also detected from the Comet Linear as it experienced its strange, explosive demise.

As linear approached perihelion, it suddenly brightened more than 50 percent in 4 hours. In fact, there have been many unexplained "explosions" of comets, sometimes at great distances from the Sun. In , Comet West suddenly split into four fragments, although it never approached closer than 30 million kilometers from the Sun. And then there was the astonishing disintegration of Comet Schwassman-Wachmann 3. Some proposed that the comet disintegrated due to "thermal stress" - inconceivable even if one ignores the deep freeze of the vacuum through which the comet was moving, with its sunward face continually changing due to rotation.

Other explanations included "the outburst of trapped volatile gases. And as seems to be the case with most come jets, they remained intact across great distances - they did not disperse in the fashion of a gas in a vacuum. The Comet Hale-Bopp began discharging seven jets while it was still too far from the Sun for a "snowball" to "melt". Four years after Hale-Bopp left the inner solar system, it was still active.

It displayed a coma, a fan-shaped dust tail, and an ion tail -- even though it was farther from the Sun than Jupiter, Saturn or even Uranus. On the question of what comets are made of and from where they came, the evidence simply does not support the notion s either of an ancient "Oort cloud", nor of comets as "dirty snowballs". They appear to be burnt rocks, physically little different from asteroids. Since this discovery, astronomers have sought desperately to adjust comet theory - but only in an 'acceptable' manner i.

Another "unsolved mystery" is presented by the main-belt comets -- according to mainstream theorists, these alleged "dirty snowballs" have existed in close proximity to the sun for BILLIONS of years!! But why have they not "melted"? The best guess of astronomers is that these comets are somehow protected by "dirt coatings". Such wild implausibilities would be unnecessary if astronomers were simply willing to allow the evidence to speak for itself. Indeed, in a court of law, the evidential case for the electric comet would easily defeat the wishful thinking of "dirty snowball" proponents.

But in this era of "science by press release", objective evidence is often overpowered by political maneuverings. While the Space Age has produced many stupendous feats, the cost of misdirection in the theoretical sciences has proved catastrophic - both financially and in terms of human knowledge and progress. Scientists continue to spend billions of taxpayer dollars chasing "black holes" and other chimeras - and the public remains unaware that another, better cosmology is being willfully ignored. The time has come for the truth to prevail over political self-interests and intellectual prejudice.

We're going to start with a very popular example. The Chicago Fires of I'm going to be quoting from the article off of Thunderbolts. Sunday evening, October 8, marked the beginning of one of the most devastating fires in U. The dry leaves and parched wood of Illinois in early autumn were the perfect kindling for a wildfire, and the fire spread with extraordinary rapidity, consuming homes and buildings, leaping from rooftop to rooftop with the speed of a locomotive. Between October 8 and 10, an estimated people perished. The fire destroyed the homes of up to one-third of the city's population, about 1, stores, 60 factories, and 28 public buildings.

Four square miles of the city burned to the ground. Contrary to popular folklore, the Chicago fire is not the worst in U. It was not even the worst to occur on October 8 that year. The same evening—in fact, at the same time, about —a fierce wildfire struck in Peshtigo, Wisconsin, over miles to the north of Chicago, destroying the town and a dozen other villages.

Estimates of those killed range upward from to in a single night. And there is more. On the same evening, across Lake Michigan, another fire also wreaked havoc. Though smaller fires had been burning for some time—not unusual under the reported conditions—the most intense outburst appears to have erupted simultaneously with the Chicago and Peshtigo fires.

The blaze is said to have then burned for over a month, consuming over 2,, acres and killing at least Wallace Thornhill breaks down the Electric Comet. The following information will be quoted off of [ link to www. The electric comet. On October 24th, periodic Comet Holmes 17P brightened by nearly a million times overnight. For no apparent reason, it erupted from a very dim magnitude 17 to about magnitude 2.

Formerly, the Sun was the largest object in the Solar System. Ediacara biota. Cambrian explosion. Earliest apes. See also: Human timeline , and Nature timeline. Universe events since the Big Bang Nature timeline. Matter-dominated era. Dark Ages. Earliest stars. Earliest galaxy. Omega Centauri. Andromeda Galaxy. Milky Way spirals. Alpha Centauri. Earliest mammals. See also: Human timeline , and Life timeline. Estimated size of a printed version of Wikipedia August To Drbogdan , for your excellent and quality contributions to Mars related content. Here is wishing you a great , and success in your editing.

Fotaun talk , 12 January UTC. For your tireless contributions and relevant details. Hadron talk , 11 September UTC. For your quick involvement in the development of the article Gravitational-wave observation which is noted on Wikipedia's main page In the news section! For exemplary contributions to articles related to space and space exploration. Fotaun talk , 18 July UTC. For outstanding contributions and editing on articles about space. Fotaun talk , 27 December UTC. For creating and developing KOI I, Ninney , hereby award Drbogdan this Template Barnstar, for his diligent work done on fine-tuning the template Comets.

Ninney talk , 1 December UTC. For your ongoinging and excellent contributions to the Wikipedia project! For contributions to various projects and related articles, especially articles related to spaceflight. This is for your great advice. Hopefully you remember me and this is my thanks. I found no other barnstar to reward your gesture of appreciation and this Special barnstar is for you.

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Path slopu talk , 10 July UTC. Great job on the article split of Mars Science Laboratory and the creation of Curiosity rover article. As a result, they both look really good just nine hours after the successful Mars landing! N2e talk , 6 August UTC. Top editor more. Created articles more. TV series [R] Genius U.

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Assume good faith Conflict of interest Disruptive editing Do not disrupt Wikipedia to illustrate a point Etiquette Gaming the system Please do not bite the newcomers Courtesy vanishing Responding to threats of harm. Data for comets are taken from the catalog [4] and the individual Circulars International Astronomical Union, issued in period after The data for TNO, mostly borrowed from the website [5], as well as the issues of the same circulars.

Considering this fact, and the ambiguities associated with how to accurately interpret the periodicity signatures seen in lightcurves of active comets , we have started an investigation to identify and characterize the periodicity signatures present in simulated lightcurves of active comets. We carried out aperture photometry of simulated cometary comae to generate model lightcurves and analyzed them with Fourier techniques to identify their periodicity signatures. These signatures were then compared with the input component periods of the respective NPA rotational states facilitating the identification of how these periodicity signatures are related to different component periods of the NPA rotation.

Ultimately, we also expect this study to shed light on why only a small fraction of periodic comets is in NPA rotational states, whereas theory indicates a large fraction of them should be in NPA states e. We explore the parameter space with respect to different rotational states, different orientations for the total rotational angular momentum vector, and different locations on the nucleus for the source region s. The initial results from our investigation will be presented at the meeting.

Long- period comet impact risk mitigation with Earth-based laser arrays. Unlike NEAs, LPCs follow nearly parabolic trajectories and approach from the distant outer solar system where they cannot be observed. An LPC on an Earth-impact trajectory is unlikely to be discovered more than a few years in advance of its arrival, even with significant advancements in sky survey detection capabilities, likely leaving insufficient time to develop and deliver an interception mission to deflect the comet.

Such a laser array can also be directed to target and heat a threatening comet , sublimating its ices and activating jets of dust and vapor which alter the comet 's trajectory in a manner similar to rocket propulsion. Simulations of directed energy comet deflection were previously developed from astrometric models of nongravitational orbital perturbations from solar heating, an analogous process that has been observed in numerous comets.

These simulations are used together with the distribution of known LPC trajectories to evaluate the effect of an operational Earth-based laser array on the LPC impact risk. We simultaneously fit the characteristics of eight meteor showers which have been proposed to be linked to the complex, using observations from a range of techniques - visual, video, TV and radar.

Hunting and Imaging Comets

The aim is to obtain a self-consistent scenario of past capture of a large comet into a short- period orbit, and its subsequent fragmentation history. Moreover, we also aim to constrain the dominant parent of these showers. A search for the micron silicate feature in periodic Comet Grigg-Skjellerup. No emission feature is obvious in the spectrum.

The observed spectrum can be fit equally well by a model of small hot absorbing grains or by a composite model with less than or equal to 30 percent 3sigma warm, 'dirty' silicate grains. The latter model is consistent with the silicate abundance in Comet Kohoutek, which did display an emission feature at 10 microns. Pursuing a historical meteor shower. The strong outburst of the Phoenicids was witnessed by people in a Japanese expedition ship, Soya, in After that, this meteor shower has never been observed at this activity level.

A newly discovered asteroid WY25 becomes a clue to the mystery of this meteor shower. We introduce our result on the investigation of this meteor shower on the basis of the dust trail theory. The effect of the solar motion on the flux of long- period comets. The long-term dynamics of Oort cloud comets are studied under the influence of both the radial and the vertical components of the Galactic tidal field.

Sporadic dynamical perturbation processes, such as passing stars, are ignored since we aim to study the influence of just the axisymmetric Galactic tidal field on the cometary motion and how it changes in time. We use a model of the Galaxy with a disc, bulge and dark halo, and a local disc density and disc scalelength constrained to fit the best available observational constraints. By integrating a few million of cometary orbits over 1 Gyr, we calculate the time variable flux of Oort cloud comets that enter the inner Solar system for the cases of a constant Galactic tidal field and a realistically varying tidal field, which is a function of the Sun's orbit.

The applied method calculates the evolution of the comets by using first-order averaged mean elements.

sungrazing comets snowballs in the furnace Manual

We find that the periodicity in the cometary flux is complicated and quasi- periodic. The amplitude of the variations in the flux is of the order of 30 per cent. The radial motion of the Sun is the chief cause of this behaviour, and should be taken into account when the Galactic influence on the Oort cloud comets is studied. The origin of the short period comets SPC periods less than years , the dynamical formation of their present reservoir s , the cause and rate of their transport to the inner planetary region where they can be detected, and the magnitude of selection effects in their discovery are important research questions directly coupled to the goals of understanding the origin and evolution of the Solar System.

To address these questions in an intensive way, an interdisciplinary, five month long Workshop from Jan. The goal of this Workshop was to advance the state of understanding about the origins, dynamical evolution, and present location of short period comets and their reservoir s. On the dependence on inclination of capture probability of short- period comets. Calculation is made of probability of capture whereby a nearly parabolic comet with perihelion near the Jovian orbit comes to have a perihelion distance less than 2. The probability is found to depend strongly on the inclination, in accordance with earlier results of Everhart and of Stagg and Bailey.

It is large for orbits close to the ecliptic but decreases drastically for large inclinations. The overall probability of capture from randomly distributed orbits is 0. Asteroids, Comets , Meteors Dust environment and dynamical history of a sample of short- period comets. Pozuelos, F. Aims: In this work, we present an extended study of the dust environment of a sample of short- period comets and their dynamical history. With this aim, we characterize the dust tails when the comets are active, and we make a statistical study to determine their dynamical evolution.

To model these observations, we use our Monte Carlo dust tail code. From this analysis, we derive the dust parameters, which best describe the dust environment: dust loss rates, ejection velocities, and size distribution of particles. Results: From the Monte Carlo dust tail code, we derived three categories according to the amount of dust emitted: weakly active P, P, and Rinner , moderately active 30P, P, and P , and highly active 22P, 78P, and P. The study points to a certain correlation between comet activity and time spent in the Jupiter family region, although this trend is not always fulfilled.

The largest particle sizes are not tightly constrained, so that the total dust mass derived should be regarded as a lower limit. Tidal disruption of Periodic Comet Shoemaker-Levy 9 and a constraint on its mean density. The apparent tidal disruption of Periodic Comet Shoemaker-Levy 9 e during a close encounter within approximately 1. Depending on the theoretical model used, these upper bounds range from rho sub c less than 0. The quoted uncertainties stem from an assumed uncertainty in the perijove radius.

However, the uncertainty introduced by the different theoretical models is the major source of error; this uncertainty could be eliminated by future SPH simulations specialized to cometary disruptions, including the effects of initially prolate, spinning comets. If the SPH-based upper bound turns out to be most appropriate, it would be consistent with the predisruption body being a comet with a relatively low density and porous structure, as has been asserted previously based on observations of cometary outgassing.

Meteoroid Streams from Sunskirter Comet Breakup. Meteoroid streams are known with q about 0. The Sun has a profound effect on comets that pass at 0. Sunlight is efficiently scattered by small m sized fragments, making those fragments visible even when far from Earth. These comet groups are associated with meteor showers on Earth, in particular the Daytime Arietids and Delta Aquariids.

The proximity of the Sun speeds up the disintegration process, providing us a unique window on this important decay mechanism of Jupiter family comets and creating meteoroid streams. These are not the only sunskirting comets , however. In this presentation, we will present CAMS observations of the complete low-q meteoroid population at Earth and review their association with known parent bodies. We have conducted simulations of the perturbation of the Oort cloud in order to estimate the significance of known encounters in generating long- period comets.

We collected the data of stellar encounters from three sources: Bailer-Jones, , Cat. Following BJ15, we use the term 'object' to refer to each encountering star in our catalogue. A specific star may appear more than once but with different data, thus leading to a different object. A Million Comet Pieces. The flame-like objects are the comet 's fragments and their tails, while the dusty comet trail is the line bridging the fragments.

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Since then, the comet has continued to disintegrate into dozens of fragments, at least 36 of which can be seen here. Astronomers believe the icy comet cracked due the thermal stress from the sun. The Spitzer image provides the best look yet at the trail of debris left in the comet 's wake after its breakup. The observatory's infrared eyes were able to see the dusty comet bits and pieces, which are warmed by sunlight and glow at infrared wavelengths. This comet debris ranges in size from pebbles to large boulders. When Earth passes near this rocky trail every year, the comet rubble burns up in our atmosphere, lighting up the sky in meteor showers.

In , Earth is expected to cross close to the comet 's trail, producing a noticeable meteor shower. Astronomers are studying the Spitzer image for clues to the comet 's composition and how it fell apart. This image was taken from May 4 to May 6 by Spitzer's multi-band imaging photometer, using its micron wavelength channel. Cometary showers and unseen solar companions. The possibility that an invisible solar companion passing through the Oort cloud every 28 Myr precipitates a sufficiently high rate of cometary collisions with the earth to account for periodic mass species extinctions recorded in the fossil record is discussed.

A Monte Carlo simulation shows that any hypothesized 'death star' with a 28 Myr orbit would experience an average 10 percent change in period per orbit.


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Production of an fold increase in cometary impacts would be associated with a 0. However, if the death star orbit has a 0. A survey of large terrestrial impact craters indicates that craters with diameters over 10 km originated in periodic showers. The extinctions in any case occur at 26 Myr periods and cannot be correlated with the 33 Myr period of recrossing the galactic plane, or with any other known phenomena.

A shower look-up table to trace the dynamics of meteoroid streams and their sources. Meteor showers are caused by meteoroid streams from comets and some primitive asteroids. They trace the comet population and its dynamical evolution, warn of dangerous long- period comets that can pass close to Earth's orbit, outline volumes of space with a higher satellite impact probability, and define how meteoroids evolve in the interplanetary medium.

Ongoing meteoroid orbit surveys have mapped these showers in recent years, but the surveys are now running up against a more and more complicated scene. The picture is even more complicated with the discovery that radar-detected streams are often different, or differently distributed, than video-detected streams. Complicating matters even more, some meteor showers are active over many months, during which their radiant position gradually changes, which makes the use of mean orbits as a proxy for a meteoroid stream's identity meaningless.

The dispersion of the stream in space and time is important to that identity and contains much information about its origin and dynamical evolution. To make sense of the meteor shower zoo, a Shower Look-Up Table was created that captures this dispersion. Visualization tools have been built that depict the streams in a planetarium setting. Examples will be presented that sample the range of meteoroid streams that this look-up table describes. Possibilities for further dynamical studies will be discussed.

We summarize the results of observations made between 10 Jun. Meteor showers associated with EH1. This asteroid belongs to the Amor group and is moving on a comet -like orbit. The orbital parameters are different at each of these intersections and so a meteoroid stream surrounding such an orbit can produce eight different meteor showers , one at each crossing.

The geocentric radiants and velocities of the eight theoretical meteor showers associated with these crossing points are determined. Using published data, observed meteor showers are identified with each of the theoretically predicted showers. The character of the orbit and the existence of observed meteor showers associated with EH1 confirm the supposition that this object is an extinct comet.

Background Material for Science Teachers. This document has been provided to better inform students of the work that will be done by scientists and others involved in the study of this event. This document offers some background material on Jupiter, comets , what has and possibly will happen, and how scientists….

The age and the probable parent body of the daytime arietid meteor shower. The daytime Arietid meteor shower is active from mid-May to late June and is amongst the strongest of the annual meteor showers , comparable in activity and duration to the Perseids and the Geminids. Due to the daytime nature of the shower , the Arietids have mostly been constrained by radar studies.

The Arietids exhibit a long-debated discrepancy in the semi-major axis and the eccentricity of meteoroid orbits as measured by radar and optical surveys. Radar studies yield systematically lower values for the semi-major axis and eccentricity, where the origin of these discrepancies remain unclear.

Icarus 86, ApJS , In this work, we present detailed numerical modelling of the daytime Arietid meteoroid stream, with the goal to identifying the parent body and constraining the age of the stream. Comet rendezvous mission study. Four periodic comets with perihelia between and Encke, d'Arrest, Kipff, and Halley are used as candidates for the comet rendezvous mission study. All these comet apparitions are especially favorable for rendezvous missions, because of early earth-based comet recovery, good opportunities to view their activity from earth, and reasonable launch vehicle and trajectory requirements for nominal payloads.

Sekanina jpl. Kracht t-online. We present the history of investigation of the dynamical properties of pairs and groups of genetically related long- period comets other than the Kreutz sungrazing system. Members of a comet pair or group move in nearly identical orbits, and their origin as fragments of a common parent comet is unquestionable.

The only variable is the time of perihelion passage, which differs considerably from member to member owing primarily to an orbital-momentum increment acquired during breakup. Meter-per-second separation velocities account for gaps of years or tens of years, thanks to the orbital periods of many millennia. We exploit orbital similarity to examine whether the enigmatic and as-yet-unidentified object discovered from the Lick Observatory near the Sun at sunset on August 7 happened to be a member of such a pair and to track down the long- period comet to which it might be genetically related.

The gap of CAMS confirmation of previously reported meteor showers. Jenniskens, P. If confirmed, each shower would provide a record of past comet or asteroid activity. They manifest as meteoroids arriving at Earth from a similar direction and orbit, after removing the daily radiant drift due to Earth's motion around the Sun.

This adds to 31 previously confirmed showers from CAMS data. For each shower , finding charts are presented based on , meteors observed up to March of , calculated by re-projecting the drift-corrected Sun-centered ecliptic coordinates into more familiar equatorial coordinates.

Showers that are not detected, but should have, and duplicate showers that project to the same Sun-centered ecliptic coordinates, are recommended for removal from the Working List. Tidal disruption and the appearance of periodic comet Shoemaker-Levy 9. Since there is no evidence for the comet 's out-gassing, the model does not assume activity.

The discruption of the parent comet was due primarily to tidal stesses during its extremely close approach to Juptier in July The original nucleus is found to have been most probably approximately 5 km in radius or, equivalently, approximately 10 exp 17 g in mass. The dynamical separation of the debris occurred apparently approximately 2. Physical breakp was accompanied by ubiquitous low-velocity collisions among the particulates, resulting in a rearrangement of the initial rotaional velocities into a rapidly 'thermalized' distribution, characterized by a long tail of relatively high velocities for the debris that populates the dust trails far from the nuclear train.

Compelling evidence is presented for secondary fragmentation events, indicative of the comet 's continuing disintegration. Secondary fragmentation may be caused by rotational bursting of the massive fragments that had been cracked but unbroken during the tidal disruption. Impact conditions and possible interactions of the comet 's debris with the jovian system during the encounter in July are described. The Stardust spacecraft returned cometary samples that contain crystalline material, but the origin of the material is not yet well understood.

Chondrules are submillimeter particles that dominate chondrites and are believed to have formed in the inner solar nebula. The comet particles show oxygen isotope compositions similar to chondrules in carbonaceous chondrites that compose the middle-to-outer asteroid belt. The presence of the chondrulelike objects in the comet suggests that chondrules have been transported out to the cold outer solar nebula and spread widely over the early solar system. Meteor Shower Forecasting for Spacecraft Operations.

Although sporadic meteoroids generally pose a much greater hazard to spacecraft than shower meteoroids, meteor showers can significantly increase the risk of damage over short time periods. Because showers are brief, it is sometimes possible to mitigate the risk operationally, which requires accurate predictions of shower activity. NASA's Meteoroid Environment Office MEO generates an annual meteor shower forecast that describes the variations in the near-Earth meteoroid flux produced by meteor showers , and presents the shower flux both in absolute terms and relative to the sporadic flux.

The shower forecast incorporates model predictions of annual variations in shower activity and quotes fluxes to several limiting particle kinetic energies. In this work, we describe our forecasting methods and present recent improvements to the temporal profiles based on flux measurements from the Canadian Meteor Orbit Radar CMOR. The impact of the fragmented comet Shoemaker-Levy 9 SL9 into Jupiter this July promises to change our understanding of the outer solar system. More than twenty mountain-sized conglomerates of ice and rock will hit the atmosphere at approx.

Because the fragments will strike the far side of Jupiter, data acquisition, analysis and interpretation will be quite sensitive to the actual size and energy of the fragments. We therefore examine an event which took place two summers ago, unnoticed and unobserved: the disruption of SL9 into a "string of pearls' as it passed within the Roche limit at perijove.

Next, noting that the tidal stress was too weak to have even fragmented an uncompressed mass of freshly fallen snow, we run models for a strengthless comet held together only by self-gravity. We explore the initial size, density, and rotation. We conclude that a 4 km diameter comet smaller if a prograde rotator of density approx. Gravitational reaccumulation is evidently the answer, and there is no need to invoke the presence of 21 "cometesimals" as the subscale of the comet. To explain how a comet can be weaker than uncompacted snow, we show that the ring-plane crossing prior to perijove could have caused total damage.

Finally, we compute the tidal stress on impactors as they approach Jupiter this July. Objects of various density are moderately distorted but not disrupted by the time they strike the planet. Aims: This paper is a continuation of the first paper in this series, where we presented an extended study of the dust environment of a sample of short- period comets and their dynamical history.

The dust environment of comets dust loss rate, ejection velocities, and size distribution of the particles was derived from our Monte Carlo dust tail code. To determine their dynamical history we used the numerical integrator Mercury 6. Biofilms in shower hoses. Shower hoses offer an excellent bacterial growth environment in close proximity to a critical end-user exposure route within building drinking water plumbing. However, the health risks associated with and processes underlying the development of biofilms in shower hoses are poorly studied.

In a global survey, biofilms from 78 shower hoses from 11 countries were characterized in terms of cell concentration 4. In countries using disinfectant, biofilms had on average lower cell concentrations and diversity. In a controlled study, 15 identical shower hoses were installed for the same time period in the same country, and both stagnant and flowing water samples were collected. Ecological theory of dispersal and selection helped to explain microbiome composition and diversity of different sample types.

Shower hose age was related to metal accumulation but not biofilm cell concentration, while frequency of use appeared to influence biofilm cell concentration. This study shows that shower hose biofilms are clearly a critical element of building drinking water plumbing, and a potential target for building drinking water plumbing monitoring. All rights reserved. Additionally, we obtained an optical spectrum and multi-band images to examine the influence of gas emission.

The increments of polarization obtained from the gas correction show that the polarimetric properties of the dust in this low-polarization comet are not different from those in high-polarization comets.


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  • In this process, the cometocentric distance dependence of polarization has disappeared. Our study confirms that the dichotomy of cometary polarization does not result from the difference of dust properties, but from depolarizing gas contamination. This conclusion can provide a strong support for similarity in origin of comets. We are conducting an observational program designed to determine the overall distributions of size, shape, rotation period , and surface characteristics of cometary nuclei.

    On the age and parent body of the daytime Arietids meteor shower. The daytime Arietid meteor shower is active from mid-May to late June and is among the strongest of the annual meteor showers , comparable in activity and duration to the Perseids and the Geminids. Our simulations suggest that the age and observed characteristics of the daytime Arietids are consistent with cometary activity from 96P, over the past years. The sunskirting comets that presumably formed in a major comet breakup between - AD Chodas and Sekanina, , alone, cannot explain the observed shower characteristics of the Arietids.

    Thus, the Marsden sunskirters cannot be the dominant parent, though our simulations suggest that they contribute to the core of the stream.

    Rosetta Data Challenges "Dirty Snowball" Comet Theory - Video

    ScienceCast Summer Meteor Shower. If you're camping out and can't sleep, maybe your slumber is being interrupted by the flash of meteors. The summer Perseid meteor shower is getting underway as Earth enters the debris stream from comet Swift-Tuttle. These circumstances allowed us to study its coma morphology in search of possible jets, whose appearance and motion as a function of time would yield the rotation period and, with appropriate modeling, the pole orientation of the nucleus and source location s.

    Imaging was obtained on a total of 45 nights between February 16 and July 2, using Lowell Observatory's 4. All narrowband CN images exhibit either one or two gas jets, and on most nights both jets appear as partial spirals with a clockwise rotation. Only a slow evolution of the jet morphology took place from mid-March to early June, presumably due to viewing geometry changes coupled with seasonal changes. Our coverage in late March was sufficient to rule out aliases of the rotation period , and further revealed a rapidly increasing period from about 24 hr to about 27 hr at the end of the month Knight et al.

    This rate of increase is roughly consistent with the solution of Images from April 15 to May 4 yield an accelerating change in periods , passing 48 hr approximately on April This is the fastest rate of change ever measured for a comet nucleus. These and other results, including those from Monte Carlo jet modeling just begun by us, will be presented. Aims: Cometary ions are constantly produced in the coma, and once produced they are accelerated and eventually escape the coma. We describe and interpret the dynamics of the cometary ion flow, of an intermediate active comet , very close to the nucleus and in the terminator plane.

    Methods: We analysed in situ ion and magnetic field measurements, and characterise the velocity distribution functions mostly using plasma moments. We propose a statistical approach over a period of one month. Results: On average, two populations were observed, separated in phase space. The motion of the first is governed by its interaction with the solar wind farther upstream, while the second one is accelerated in the inner coma and displays characteristics compatible with an ambipolar electric field.

    Both populations display a consistent anti-sunward velocity component. A consistent anti-sunward component is observed for all cometary ions. An asymmetry is found in the average cometary ion density in a solar wind electric field reference frame, with higher density in the negative south electric field hemisphere. There is no corresponding signature in the average magnetic field strength.

    Of these 9 comets 6 were long- period comets and 3 were possibly dynamically new. Water production rates were calculated from each of the images using our standard time-resolved model that accounts for the whole water photodissociation chain, exothermic velocities and collisional escape of H atoms.

    For most of these comets there were enough observations over a broad enough range of heliocentric distances to calculate power-law fits to the variation of production rate with heliocentric distances for pre- and post-perihelion portions of the orbits. A possible interpretation suggests that a large fraction of the comet 's mass was lost during the apparition. Fluffy comets. The density of typical comet nuclei is estimated on the basis of published empirical and theoretical density data on meteors.

    The nuclei are assumed to consist of aggregated interstellar dust silicate cores with complex organic refractory mantles as proposed by Greenberg and and Van de Bult et al. The theoretical density 0. A birdsnest structure comprising elongated crystals and about 60 percent empty space is proposed; its albedo is estimated as about 0. The mean density of reconstituted cometary matter is found to be in the range 0.

    The IUE was used to study comets including the first dynamically new comet to approach closer than 3 AU. Differences between old and new comets are studied. Results relevant to the nature of cometary nuclei are discussed. Identification of species in the spectra; relative abundances; variability of comets ; and comet mass are considered. Are periodic bombardments real? Consideration is given to the hypothesis that showers of comets or asteroids strike the earth every 26 m yrs, causing climatic castastrophes and mass extinctions Raup and Sepkoski, Possible explanations for the alleged periodicity are discussed, including the possibility that the sun has a small faint companion star and perturbations of the Oort cloud as the solar system passes through the Galactic plane.

    Also, the possible causes of the extinction at the K-T boundary are examined. The implications of these theories are noted and evidence suggesting that impacts do not have periodicity is presented. Missing in Action? The Quaternary period represents the interval of oscillating climatic extremes glacial and interglacial periods beginning about 2.

    Modeling suggests that an average of between and perhaps as many as 5 globally catastrophic ca. A slightly larger number of substantive but somewhat less than globally catastrophic impacts in the 10,, Mt range would also be predicted to have occurred during the Quaternary. However, databases of validated impact structures on Earth, contain only two examples of Quaternary period impacts in the 10,, Mt range Zhamanshin, Bosumtwi , dating to around a million years ago, while no examples of Quaternary period globally catastrophic impact structures have been yet identified.

    In addition, all of the 27 validated Quaternary period impact structures are terrestrial--no Quaternary period oceanic impacts have been yet validated. Two likely globally catastrophic probable oceanic impacts events, Eltanin ca. These and the 8-km diameter Bolivian Iturralde candidate impact structure ca. This suggests that one or more Quaternary period globally catastrophic impacts and. Forbidden Mass Ranges for Shower Meteoroids. Burns et al. The central potential that these particles experience is effectively reduced by a factor of 1- beta , which in turn lowers the escape velocity.

    We use our expression to compute the critical value and corresponding mass for cometary ejecta leading, trailing, and following the parent comet 's nucleus for 10 major meteor showers. Finally, we numerically solve for critical beta values in the case of non-geometric optics. These values determine the mass regimes within which meteoroids are ejected from the Solar System and therefore cannot contribute to meteor showers. The evolution of the Quarantid meteoroid shower.

    The Everhart method is used to trace the orbital evolution of 36 model Quadrantid meteoroids over a yr period. It is found that the Quadrantid shower is responsible for eight related showers. A volatility index for comets. The variations in total brightness of a comet when it is most active, near perihelion, are presently used as the bases of a volatility index VI for short- period SP and long- period LP comets.

    Volatility does not correlate with period among the LP comets , and thereby shows no 'aging' effect; similarly, the VI measurements are the same for SP and for LP comets and exhibit no correlation with 1 absolute magnitude near perihelion, 2 orbital inclination, or 3 activity index measuring the intrinsic brightness change from great solar distances to the maximum near perihelion. Active comets are shown to be basically alike irrespective of their orbits or 'ages'. Comet Halley - The orbital motion. The orbital motion of Comet Halley is investigated over the interval from A.

    Using the observations from through , least-squares differential orbit corrections were successfully computed using the existing model for the nongravitational forces. The nongravitational-force model was found to be consistent with the outgassing-rocket effect of a water-ice cometary nucleus and, prior to the return, these forces are time-independent for nearly a millennium. For the return, viewing conditions are outlined for the comet and the related Orionid and Eta Aquarid meteor showers. DRBE comet trails. All these comets have known associations with meteor showers. This re-examination also reveals 1 additional comet and 13 additional asteroids that had not previously been recognized in the DIRBE data.