Is 2329 Orthos a dead comet?

Probably most meteor showers have a cometary origin. Investigation of Near-Earth asteroids' orbital evolution to determine whether they have related meteor showers is necessary to determine which asteroids evolved from comets. The results of calculations show that asteroid Orthos' orbit is an octuple Earth-crosser. Therefore, if Orthos has an old meteoroid stream it may produce eight meteor showers observable on the Earth. The existence of four Orthos' Northern meteor showers is confirmed by our search in the published catalogues of meteor radiants and orbits or in the archives of the IAU Meteor Data Center (Lund, Sweden).     

Meteor showers associated with 2003EH1

Using the Everhart radau19 numerical integration method, the orbital evolution of the near-Earth asteroid 2003EH1 is investigated. This asteroid belongs to the Amor group and is moving on a comet-like orbit. The integrations are performed over one cycle of variation of the perihelion argument ω. Over such a cycle, the orbit intersect that of the Earth at eight different values of ω. 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 2003EH1 confirm the supposition that this object is an extinct comet.     

Orthos' meteor showers

Probably the majority of meteor showers has a cometary origin. Investigation of Near-Earth asteroids' orbital evolution to determine whether they have related meteor showers are necessary to determine which asteroids evolved from comets. The results of calculations show that asteroid Orthos' orbit is an octuple Earth-crosser. Therefore, if Orthos has an old meteoroid stream it may produce eight meteor showers observable on the Earth. The existence of four Orthos' Northern meteor showers is confirmed by our search in the published catalogues of meteor radiants and orbits or in the archives of the IAU Meteor Data Center (Lund, Sweden).     

Is 2329 Orthos a dead comet?

Probably most meteor showers have a cometary origin. Investigation of Near-Earth asteroids' orbital evolution to determine whether they have related meteor showers is necessary to determine which asteroids evolved from comets. The results of calculations show that asteroid Orthos' orbit is an octuple Earth-crosser. Therefore, if Orthos has an old meteoroid stream it may produce eight meteor showers observable on the Earth. The existence of four Orthos' Northern meteor showers is confirmed by our search in the published catalogues of meteor radiants and orbits or in the archives of the IAU Meteor Data Center (Lund, Sweden).     

A Method for Determining the Coordinates of Meteor Shower Radiants from Meteor Radar Goniometric Data

We discuss a new method for measuring the coordinates of meteor shower radiants from meteor radar data. The method uses a high accuracy of radar goniometer measurements of one of the angular coordinates for meteor radiants and collective properties of incident meteor showers. It is based on a computer technology of searching for the coordinates of radiants using the intersections of meteor position lines on the celestial sphere and filtering nonrandom combinations of these intersections. The method allows the following: to detect meteor showers with a rate of more than 5 per day of observations and to separate meteor groups from different meteor showers with different radiants and velocities. The method makes it possible to increase the angular resolution from 10° × 10° achieved with a quasi-tomographic technique to 2° × 2°, with a prospect of a further increase in the accuracy through the individual reduction of separated meteor groups. We use the reduction of one-day-long observations during maximum activity of the Geminids meteor shower in 1993 to illustrate the potentialities of the method. We show an example of detecting a weak meteor shower that was active during December 1993.     

Physical Characteristics of Kazan Minor Showers as Determined by Correlations with the Arecibo UHF Radar

In the northern hemisphere, the month of February is characterized by a lack of major meteor shower activity yet a number of weak minor showers are present as seen by the Kazan radar. Using the Feller transformation to obtain the distribution of true meteor velocities from the distribution of radial velocities enables the angle of incidence to be obtained for the single beam AO (Arecibo Observatory) data. Thus the loci of AO radiants become beam-centered circles on the sky and one can, with simple search routines, find where these circles intersect on radiants determined by other means. Including geocentric velocity as an additional search criterion, we have examined a set of February radiants obtained at Kazan for coincidence in position and velocity. Although some may be chance associations, only those events with probabilities of association > 0.5 have been kept. Roughly 90 of the Kazan showers have been verified in this way with mass, radius and density histograms derived from the AO results. By comparing these histograms with those of the “background” in which the minor showers are found, a qualitative scale of dynamical minor shower age can be formulated. Most of the showers are found outside the usual “apex” sporadic source areas where it is easiest to detect discrete showers with less confusion from the background.     

Meteor Showers Associated with the Taurid Complex Asteroids

Recent theoretical and observational work has shown that the asteroids belonging to the Taurid meteoroid complex have a cometary nature. If so, then they might possess related meteoroid streams producing meteor showers in the Earth atmosphere. We studied the orbital evolution of ten numbered Taurid complex asteroids by the Halphen-Goryachev method. It turned out that all of these asteroids are quadruple crossers relative to the Earth's orbit. Therefore their proposed meteoroid streams may in theory each produce four meteor showers. The theoretical orbital elements and geocentric radiants of these showers are determined and compared with the available observational data. The existence of the predicted forty meteor showers of the ten Taurid complex asteroids is confirmed by a search of the published catalogues of observed meteor shower radiants and orbits, and of the archives of the IAU Meteor Data Center (Lund). The existence of meteor showers associated with the Taurid Complex Asteroids confirms that, most likely, these asteroids are extinct comets. This revised version was published online in July 2006 with corrections to the Cover Date.     

The problem of linking minor meteor showers to their parent bodies: initial considerations

Efforts to link minor meteor showers to their parent bodies have been hampered both by the lack of high-accuracy orbits for weak showers and the incompleteness of our sample of potential parent bodies. The Canadian Meteor Orbital Radar (CMOR) has accumulated over one million meteor orbits. From this large data set, the existence of weak showers and the accuracy of the mean orbits of these showers can be improved. The ever-growing catalogue of near-Earth asteroids (NEAs) provides the complimentary data set for the linking procedure. By combining a detailed examination of the background of sporadic meteors near the orbit in question (which the radar data makes possible) and by computing the statistical significance of any shower association (which the improved NEA sample allows) any proposed shower–parent link can be tested much more thoroughly than in the past. Additional evidence for the links is provided by a single-station meteor radar at the CMOR site which can be used to dispel confusion between very weak showers and statistical fluctuations in the sporadic background. The use of these techniques and data sets in concert will allow us to confidently link some weak streams to their parent bodies on a statistical basis, while at the same time showing that previously identified minor showers have little or no activity and that some previously suggested linkages may simply be chance alignments.     

Associations of Meteor Microshowers or as the Kazan Radar “SEES” Radiants on Northern Celestial Hemisphere

The discrete quasitomographic method of the analysis of the interferometric data of meteor radar gives us the possibility of measuring coordinates and velocities of very weak meteor showers with a 2 × 2 square degree resolution on the celestial sphere. The minimal rate of the meteors in each microstream is five meteors per day. At such sensitivity, basic distinctions between irregularities of the sporadic background and meteor streams vanish. More than 1000 of the detected microshowers per month are associated with a combination of (a) the large known meteor showers, (b) the weaker known meteor showers and (c) till now unknown associations of microshowers. All microshowers regardless of association have the identical velocities, limited areas of radiation and near simultaneity of their acting dates. The results are compiled as maps of radiant distribution and average velocities of microstreams for different months. From these it is possible to see how the microshower activity for various discrete sites on the celestial sphere correlate with the behavior of the well-known meteor streams and thus to infer the orbital properties of the different microstream configurations.     

Observation and Research on Strong Meteor Showers and Their Catastrophic Space Weather Events

During the first international joint observation of the Leo strong meteor shower, multidisciplinary and multi-media synthetic observation of Leo and Draco strong meteor showers and their catastrophic space weather events were carried out. The comprehensive analysis of the observed and related data of the Leo, Perseus and Draco strong meteor showers obtained for near half a century (from 1957 to 2003) fully verifies that the non-sporadic periodic strong meteor shower may lead to catastrophic space weather events. Preliminary identification is made of the following: the mechanism of formation of strong meteor showers, the law of occurrence of the f_bE_s abnormal peak and serious safety hazards for astronavigation. Also discussed in this paper are the evolutionary process of cometary dust, the law of occurrence and loss of cosmic dust storm and the mechanism of maintaining cosmic dust in the mid-latitude E_s layer.     

Television meteor radiant mapping

We have carried out double-station TV meteor observations between 1990 and 1994. The orbits of 326 meteors have been determined from doubly observed meteors, and radiant distributions are studied. The mean magnitude of the observed meteors was as faint as +4.7, since I.I. (Image Intensifier) and Video cameras were used. Radiants were widely distributed over the celestial sphere. The velocity distribution showed some similarity with the distribution predicted by the theoretical radiant distribution from comets rather than that from asteroids. In all 13 showers including both major and minor meteor showers were detected from radiant distributions of the observed meteors; from the orbital elements and meteor velocities as well as from the radiant directions.     

Annual and Diurnal Variation of Meteor Rates by the Forward-Scatter Radio Observation

Forward-scatter radio meteor observations have been made at Japan since 1996 using inexpensive and low-end equipment. The activity of some major meteor showers and the seasonal variability of sporadic meteors in 2006 are presented.     

Benefits of an impact mission to 3200 Phaethon: nature of the extinct comet and artificial meteor shower

The asteroid 3200 Phaethon is suggested as a candidate for direct impact research. The object is considered to be an extinct comet and the parent of the Geminid meteor shower. One could say that this provides a possible argument for a space mission. Based on such a mission, this paper proposes to investigate the nature of the extinct comet and the additional interesting possibility of artificially generated meteor showers.
Dust trail theory can calculate the distribution of a bundle of trails and be used to show in which years artificial meteors would be expected. Results indicate that meteor showers will be seen on Earth about 200 yr after the event, on 2022 April 12.     

Meteor outbursts from long-period comet dust trails

Long-period comets have narrow one-revolution old dust trails that can cause meteor outbursts when encountered by Earth. To facilitate observing campaigns that will characterize and perhaps help find Earth-threatening, long-period comets from their trace of meteoric debris, we use past accounts of outbursts from 14 different showers to calculate the future dust trail positions near Earth’s orbit. We also examine known near-Earth, long-period comets and identify five potential new showers, which can be utilized to learn more about these objects. We demonstrate that it is the one-revolution trail that is responsible for meteor outbursts. A method that calculates in what year these showers are likely to return and at what hour is presented. The calculations improve on earlier approximate methods that used the Sun’s reflex motion to gauge the trail motion relative to Earth’s orbit.     

Meteor shower detection with density‐based clustering

We present a new method to detect meteor showers using the density‐based spatial clustering of applications with noise algorithm (DBSCAN; Ester et al. 1996 ). The DBSCAN algorithm is a modern cluster detection algorithm that is well suited to the problem of extracting meteor showers from all‐sky camera data because of its ability to efficiently extract clusters of different shapes and sizes from large data sets. We apply this shower detection algorithm on a data set that contains 25,885 meteor trajectories and orbits obtained from the NASA All‐Sky Fireball Network and the Southern Ontario Meteor Network (SOMN). Using a distance metric based on solar longitude, geocentric velocity, and Sun‐centered ecliptic radiant, we find 25 strong cluster detections and six weak detections in the data, all of which are good matches to known showers. We include measurement errors in our analysis to quantify the reliability of cluster occurrence and the probability that each meteor belongs to a given cluster. We validate our method through false‐positive/negative analysis and with a comparison to an established shower detection algorithm.     

Orbital structure of the meteor complex according to radar observations in Kazan. 1. Apparent distributions of aphelia

The results of an analysis of the orbital structure of the meteor complex accessible for radar observations at northern midlatitudes are reported. Experimentally, the study is based on the long-term monitoring of the influx of meteor matter into the Earth’s atmosphere performed with the meteor radar of Kazan State University starting from 1986. The study uses a discrete quasi-tomographic method to measure the radiants and velocities of meteor showers based on goniometric data of the meteor radar and diffraction measurements of meteor velocities. The discretization of the detection environment—in particular, in terms of velocity—is shown to result in no substantial loss of measurement accuracy. The error of the measured velocity of the shower does not exceed 1.5 km/s for a standard deviation of a single velocity measurement equal to 3 km/s. Microshower representation is used with microshowers either representing the correlated part of the sporadic complex or being partial streams of major and minor showers, or fragments of the dust environment of minor bodies passing by Earth or falling onto it. The data of measurements made over the entire annual cycle are used to construct combined maps of the distribution of the observed 2263 microshowers (a total of 22 604 orbits) by their inclination, aphelion distance, and longitudes of the ascending nodes of their orbits. The observing conditions are shown to have a significant effect on the parameters of the distribution of aphelion distances for different months, and the corresponding distributions for prograde and retrograde orbits are shown to differ fundamentally. A specific feature of such distribution maps is that they allow uniform representation of both meteor showers and irregularities of the sporadic complex.     

The P/Halley Stream: Meteor Showers on Earth, Venus and Mars

We have simulated the formation and evolution of comet 1P/Halley’s meteoroid stream by ejecting particles from the nucleus 5000 years ago and propagating them forward to the present. Our aim is to determine the existence and characteristics of associated meteor showers at Mars and Venus and compare them with 1P/Halley’s two known showers at the Earth. We find that one shower should be present at Venus and two at Mars. The number of meteors in those atmospheres would, in general, be less than that at the Earth. The descending node branch of the Halley stream at Mars exhibits a clumpy structure. We identified at least one of these clumps as particles trapped in the 7:1 mean motion resonance with Jupiter, potentially capable of producing meteor ourbursts of ZHR∼1000 roughly once per century.     

The IAU Meteor Shower Nomenclature Rules

The International Astronomical Union at its 2006 General Assembly in Prague has adopted a set of rules for meteor shower nomenclature, a working list with designated names (with IAU numbers and three-letter codes), and established a Task Group for Meteor Shower Nomenclature in Commission 22 (Meteors and Interplanetary Dust) to help define which meteor showers exist from well defined groups of meteoroids from a single parent body.     

Search for Past Signs of October Ursae Majorids

A new meteroid stream—October Ursa Majorids—was announced by Japanese observers on Oct. 14–16, 2006 (Uehara et al. 2006). Its weak manifestation was detected among coincidental major meteor showers (N/S Taurids, Orionids), as its meteors radiated from a higher placed radiant on the northern sky. We have tried to find out previous displays of the stream throughout available meteor orbits databases, and among ancient celestial phenomena records. Although we got no obvious identification, there are some indications that it could be a meteor shower of cometary origin with weak/irregular activity, mostly overlayed by regular coincidental meteor showers. With a procedure based on D-criterion (Southworth and Hawkins 1963) we found a few records in IAU MDC database of meteor photographic orbits which fulfill common similarity limits, for October Ursae Majorids. However, their real association cannot be established, yet. With respect to the mean orbit of this stream, we suggest for its parent body a long-period comet.     

A meteoroid stream survey using the Canadian Meteor Orbit Radar: II: Identification of minor showers using a 3D wavelet transform

A 7 year survey using the Canadian Meteor Orbit Radar (CMOR), a specular backscattering orbital radar, has produced three million individually measured meteoroid orbits for particles with mean mass near 10⁻⁷ kg. We apply a 3D wavelet transform to our measured velocity vectors, partitioning them into 1° solar longitude bins while stacking all 7 years of data into a single “virtual” year to search for showers which show annual activity and last for at least 3 days. Our automated stream search algorithm has identified 117 meteor showers. We have recovered 42 of the 45 previously described streams from our first reconnaissance survey (Brown, P., Weryk, R.J., Wong, D.K., Jones, J. [2008]. Icarus 195, 317-339). Removing possible duplicate showers from the automated results leaves 109 total streams. These include 42 identified in survey I and at least 62 newly identified streams. Our large data sample and the enhanced sensitivity of the 3D wavelet search compared to our earlier survey have allowed us to extend the period of activity for several major showers. This includes detection of the Geminid shower from early November to late December and the Quadrantids from early November to mid-January. Among our newly identified streams are the Theta Serpentids which appears to be derived from 2008 KP and the Canum Venaticids which have a similar orbit to C/1975 X1 (Sato). We also find evidence that nearly 60% of all our streams are part of seven major stream complexes, linked via secular invariants.