Radiant Points Research Articles

Electromagnetic resonance in nanosandwich photonic metamaterial

The magnetic plasmon (MP) modes in metal-dielectric-metal nanosandwich structures are investigated numerically using finite-difference time-domain method. We demonstrate the law of the quality factor in this kind of resonator.According to the MP modes in the nanosandwich structures, we design a series of resonators of this kind in order to investigate how to tune the resonante frequencies of MP modes through tuning the geometrical parameters and the dielectric layer refractive index of resonators, and the obtained result is well consonant with our analysis by the equivalent inductance capacitance circuit. We also investigate the electromagnetic energy confinement of the nanosandwich resonators, and analyse the Q factors of these structures from thermal and radiant points of view, which will guide one in designing new waveguides and lasers based on MP modes.

High-Precision Radiant Analysis of the 2001 Leonids Using Telescopic Optics

Abstract We employed a new line-detection method and tried to separate two radiant points corresponding to the dust trails of Comet 55P/Tempel–Tuttle’s perihelion passages in 1699 and 1866. This method integrates the pixel values of a CCD image along a line direction, which enables us to detect 30-times fainter meteors than when using the usual detection methods. It can also precisely determine the angle of the line direction. Two telescopic optics equipped with cooled CCD cameras were pointed to regions that make a right angle with the radiant points in order to precisely determine their positions. Radiant points of the 2001 Leonids derived by this method were found to be consistent with those predicted by McNaught and Asher.

Optical Imaging of the Radiant Points of Leonids during the 2001 Storm with the 105 cm Kiso Schmidt Telescope

Abstract We report on the results of CCD imaging of the radiant points of Leonids with the 105 cm Kiso Schmidt telescope during its storm in 2001. The center coordinates of the observed field were $\alpha(\mathrm{J}2000.0) = {10{}^{\mathrm {h}}17{}^{\mathrm {m}}02\rlap {.}{}^{\mathrm {s}}4}$ and $\delta(\mathrm{J}2000.0) = + {21{}^{\mathrm {\circ }}37{}^{\mathrm {\prime }}48\rlap {.}{}^{\mathrm {\prime \prime }}0}$, corresponding to the center position between the two radiant points originating from dust trails created by the 1699 and 1866 returns of the Comet 55P/Tempel–Tuttle (McNaught, Asher 2001; WGN, 29, 156). Six CCD images having a field of view of ${51\rlap {.}{}^{\mathrm {\prime }}2} \times {51\rlap {.}{}^{\mathrm {\prime }}2}$ were obtained successively from 16h 58 m to 18h 28 m on November 18 (UT) in order to cover the two expected peaks of activity of the distinct radiant points. A limiting surface brightness of $25.93 \,\mathrm{mag} \,\mathrm{arcsec}^{-2}$, i.e., the $1\,\sigma$ noise level of the sky background, was achieved in each image. As a result, we detected only one faint Leonid meteor which most likely originated from a dust trail created by the 1866 return. The integrated total magnitude of the meteor is $m_{V}=18.34\pm 0.34 \,\mathrm{mag}$ on the image. Assuming a duration time of 0.1–1 s, we estimate the magnitude at the maximum luminosity of this meteor to be $9.70\pm 1.59 \,\mathrm{mag}$. This corresponds to a photometric mass of $(2.65^{+13.5}_{-2.22})\times 10^{-10} \,\mathrm{kg}$, which makes this meteor one of the faintest and smallest Leonids detected so far.

Minor Meteor Showers of October Observed over Waltair during 1962?71

Systematic visual observations of meteors have been made over Waltair Qat. 17� 5� N.) in the month of October during 1962-71. From the data for 1835 meteors collected, after identification of 436 Orionid and 153 Taurid major shower meteors, 56 groups covering 439 meteors in the remainder have been observed to display common radiant points on the daily plotted meteor maps. These 56 groups are tentatively classed as minor meteor showers, after applying some tests of significance. The list is reduced to 20 groups by identifying common radiant coordinates within a divergence of � 10�. Of these 20 groups, 10 occur in at least two different years and on nearby dates and therefore are considered to be well-established minor meteor showers. It is found that a majority of the minor shower radiants lie close to the ecliptic.

Minor Meteor Showers of November, December, and January

Systematic visual observations of 7987 meteors were made during the montns November, December, and January in 1961-7. Major shower meteors were identified and the remaining data were analysed for evidence of minor meteor shower activity. By tracing the paths of 894 meteors which appeared to make up 70 groups, common radiant points were found suggesting the existence of minor meteor showers. Two further tests of significance supported this contention. Ten out of the 70 minor meteor showers were found to occur in at least two different years on approximately the same dates and therefore are considered to be established minor meteor showers. The majority of the minor shower radiants were found to lie close to the plane of the ecliptic.

The Daytime Meteor Streams of 1948--I: Measurement of the Activity and Radiant Positions

The series of meteor streams incident on the sunlit side of the Earth between May and August, which were first studied in detail by the radio echo method during 1947, appear to be a recurrent phenomenon. Their radiant points lie in a narrow strip of the celestial sphere, situated somewhat to the north of the ecliptic, and extending from 330° to 120° in right ascension. They are unusually rich, giving hourly rates comparable with those of the Perseids and Geminids, and on many occasions two or three of these showers are active at the same time. In addition to confirming the 1947 observations during May and June, the work during 1948 led to the discovery of four further major showers in July and early August.

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The Leonid Meteor Shower.—Mr. W. F. Denning writes that “The nights of November 13 and 15 were alone suitable for observation at the period of the Leonid display this year, and very few meteors appeared. Mr. J. P. M. Prentice watched the heavens on the night of November 15 between 5.45 and 12.45 and recorded only 44 meteors during the seven hours, of which three were Leonids. At Bristol the sky was watched at a later hour, but only one Leonid was seen between 13h and 13h 45m, after which observations were discontinued. Mr. Prentice noticed several minor showers of which radiant points at 41°+29°, 42°+2i°, 53°+13°, and 55°+84° were the most actively pronounced.” The shower of Leonids was not expected to be abundant this year, as the parent comet (1866 I) will not return until 1933. It sometimes happens, however, that a moderately active display of Leonids occurs when the comet is far removed from perihelion, as in 1879 and 1888.

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September Meteors.—Though September is not a month in which any rich shower of meteors is periodically visible, a considerable number of meteors and many radiant points of moderate activity should be seen. Fireballs are also particularly abundant during the month, especially on September 13–15, and again on September 24–28. The principal systems of meteors at this time of the year radiate from Aries, Perseus, Auriga, and other constellations in that part of the heavens. At the middle of September there is usually a strong display of e Perseids from 61° + 36°; there is also a prominent shower from near a Cygni, at 314° + 48°, and swift, streaking meteors from the Lynx frequently manifest themselves. September is, in fact, usually a productive period for the meteoric student, and further watching may reveal a somewhat rich annual display that hitherto has not received the notice it merits.

Our Astronomical Column

LARGE METEORS ON MARCH 1 AND 2.—Mr. W. F. Denning, of Bristol, writes:—“On the evening of Tuesday, March i, two large meteors were observed, and on the following night three others were recorded. The most brilliant of them all appeared on March 2, at 10 p.m. It was seen at Bristol, at Dunton Green, Kent, at Holt, Norfolk, and at other places. It was a very fine object, and gave a flash which lit up the sky. Its radiant point was a few degrees east of δ Leonis, and the path of the meteor was over the English Channel approximately from Dieppe, France, towards the Isle of Wight, but reaching only about half that distance. Observations are still coming to i hand, and the real path will be calculated from them. It has been several times pointed out that the first few nights of March are specially distinguished by apparitions of bright meteors, although no periodic shower is known to occur on those dates. There appear, however, to be several fairly active displays in progress, and from the evidence obtained this year we may be enabled to determine their radiant points accurately.”

Our Astronomical Column

SEPTEMBER METEORS.-Mr. Denning writes that a fair number of meteors, including several brilliant fireballs, were observed in September. There was a well-defined shower, not far from the Pole, at 314° +79° at the middle of the month, and at the period from September 19-24 the chief radiant points were at 4° + 27°, 59° + 3S°, 271° + 22°, 2900 + S2°, 343° + 140, and 352° + 2°. A very brilliant meteor was observed on September 21 at 10h. 3m., from the radiant in Cygnus. As seen from Bristol it was brighter than Venus, and fell from a height of 67 to 28 miles. On September 23, at 7h. 42m., a fireball illuminated the sky as seen from Clevedon, and it had a long, slow, and nearly horizontal flight from a radiant at 3220 -230 in Capri-cornus. Its path was about 166 miles from over the English Channel to Welshpool, and it descended from 64 to 32 miles. Though it had a very extended path, only two observations of it were received, viz. from Clevedon (Somerset) and Fowey (Cornwall), but the sky was cloudy at many places.

The Daylight Fireball of July 5

VERY large meteors apparently exhibit a preference for the early evening hours. The fireball of March 28 last came at 7.48 p.m., and a great number of corroborative instances might be cited. The majority of these bodies travel with comparatively slow motion over extensive arcs, and are directed from radiant points in the o western region of the heavens.

Radiant points of meteors visible in July and August

Radiant points of meteors visible in July and August

Scientific Serial

Bulletin de l'Académie de Sciences de St. Pétersbourg, 5th series, vol. xii.—On the compound (so-called stationary) radiants of shooting stars, by Th. Bredikhine (in French). The supposed existence of stationary radiant points (or radiant points of long duration) is an obstacle against all more or less admissible theories of shooting stars. Taking advantage of the 918 meteoric orbits calculated by J. Kleiber in 1891, and of subsequent data, the author concludes that each stationary (or long duration) radiant consists of several individual radiants, even when these radiants do not much differ from each other in their dates; this means that each stationary radiant is a compound radiant which originates from several individual radiants, each of which has its own position in space and its own origin, and all of which are intersected by the orbit of earth. Thus, in the well-known radiant of β Persei he finds “thirteen or fourteen different orbits, i.e. as many different streams ” (p. 102). The author examines next the theories of Profs. H. H. Turner and A. S. Herschel, and concludes that “the deductions of Prof. Turner are only admissible under the impossible supposition that the earth moves with a uniform speed along a straight line. But if the theory itself is inconsistent, its secondary complications, such as the spinning of the meteoritic stream, the resisting medium, &c, have no more signification” (p. 115). Applying his explanation next to the polar stationary radiants of Mr. Denning, the author shows that in the radiant (Draconis (No. 36 of catalogue A), one may recognise “twelve different individual streams (twelve comets) apparently composing one single stationary radiant.” The author's final conclusion is:—“A stationary radiant does not originate from a single individual stream or from one single comet; it must be named a compound radiant, because it is produced by several comets or independent streams. The phenomenon is so simple that all complicated and artificial theories are useless and superfluous.... Thanks to the numerous and careful observations of Mr. Denning, the phenomenon has lost its supposed individuality and has become decomposable and explicable.”—On photographic observations of the satellite of Neptune at Pulkova, by S. Kostinsky (Russian; with a plate).—Report on zoological researches at Sebastopol in 1899, by A. Kovalevsky: hypodermal fertilisation with the leeches; on Batracobdella latastii; on Hedyle Tyrtowii (n.sp.); on Pseudovermis paradoxus, Periasl.—On faint lines in stellar spectragrams, by A. Belopolsky.—On a MS. in Coptish language attributed to Dionysius Areopagita, by Oscar Lemm.

Radiant points derived from doubly observed meteors

Astronomische NachrichtenVolume 155, Issue 23 p. 365-368 Article Radiant points derived from doubly observed meteors W. F. Denning, W. F. Denning Bishopston, BristolSearch for more papers by this author W. F. Denning, W. F. Denning Bishopston, BristolSearch for more papers by this author First published: 1901 https://doi.org/10.1002/asna.19011552306AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume155, Issue231901Pages 365-368 RelatedInformation

Stationary radiant points of meteors

Astronomische NachrichtenVolume 152, Issue 13 p. 197-200 Miscellaneous Stationary radiant points of meteors W. F. Denning, W. F. Denning Bishopston, BristolSearch for more papers by this author W. F. Denning, W. F. Denning Bishopston, BristolSearch for more papers by this author First published: 1900 https://doi.org/10.1002/asna.19001521303AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume152, Issue131900Pages 197-200 RelatedInformation

Radiant points of the minor showers visible during the chief meteoric epochs of the year

Astronomische NachrichtenVolume 147, Issue 9 p. 155-158 Article Radiant points of the minor showers visible during the chief meteoric epochs of the year W. F. Denning, W. F. Denning BristolSearch for more papers by this author W. F. Denning, W. F. Denning BristolSearch for more papers by this author First published: 1898 https://doi.org/10.1002/asna.18981470907AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume147, Issue91898Pages 155-158 RelatedInformation

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AN INSTRUMENT FOR PHOTOGRAPHING METEORS.—Up to the present time meteoric astronomy has had little, if any, instrumental equipment to further its development, the nature of the phenomena rendering simple naked eye observations the only available means of research. It is true that even now we know of a very considerable number of radiant points, and what is more, we have been able to note the daily movements of some of these in the heavens; but this knowledge has only been gained by the great patience and perseverance of astronomers, the most notable being Mr. W. F. Denning. With a thorough knowledge of the constellations, a good globe or star-map, and an accurate eye, he has been able to plot down track after track of these travellers through space, deducing from their paths the points in the heavens from which they are coming.

The August Meteors

BETWEEN August 4 and 20, 174 shooting stars were recorded here in 161/2 hours of observation. These included about 37 Perseids, chiefly seen on August 5, 8, and 13, but the shower was not well observed owing to cloudy weather. The following are the chief radiant points determined from the paths registered:—

July Meteors

BETWEEN July 8 and 14, 111 shooting stars were recorded herein 113/4 hours of observation. The paths of these, reproduced upon an 18-inch celestial globe, enabled me to fix the radiant points of 12 showers with considerable distinctness:—

Pens' Comet and Meteors.—The Quadrantids

I SEE in Greg's list of possible cometary radiant points there is one given for Pons' Comet, the date December 6, radiant point R.A. 200°, N.D. 68°.5. The radius-vector of the comet at its descending node is 0.77, so that the likelihood of a shower of meteors seems very small; but it might be worth while to look out for one on the 6th of next month.