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Radiant Points of Meteors Visible in July and August

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Radiant Points of Meteors Visible in July and August ASTRONOMISCHE NACHRICHTEN. NZ 3874. Band 162. 10. Radiant points of meteors visible in July and August. By W. P. Dennizg. The most important and interesting, and certainly the of the three and very many others exist. The firmament best known meteoric epoch of the year, is that which in- is indeed exceedingly rich in meteoric showers not only at cludes the great Perseid stream and its numerous contem- the August epoch but at all times though certainly not in porary showers, distributed over the months of July and the same degree for the first six months of the year supply August. Perhaps the Leonid shower of November sometimes scarcely more than one half the number of meteors furnished excites more attention than the Perseids from the magni- by the second half. ficence of its displays but, to the meteoric observer, the A prominent feature of the majority of feeble displays summer shower is ordinarily more reliable and attractive or minor showers is that they are apparently visible for a than the autumnal one which comes when cloud or fog is long time from the same fixed radiants. A really large pro- often prevalent in English skies. Every year the Perseids portion of these tenuous streams will not always yield a are plentiful and their luminous incursions may be observed single meteor during a 5 -hours watch of the sky by one during an interval ranging over about 5 weeks for early observer and there are many systems more feeble still for members of the stream fall at the middle of July and the they seem only capable of discharging three or four meteors shower is not exhausted until the end of the third week in during a number of lengthy observations on several successive August. But it is difficult to assign definite limits to its period nights which may amount in the aggregate to 40 or 50 hours. of visibility for it apparently blends with showers of Cassio- Like the Perseids a great number of other showers peids at its oncoming and with showers of Camelopardids appear to form continuous orbits and to recur annually near the date of its extinction. The maximum is now reached though with decided variation in their visible strength from on the morning of Aug. IZ or 13. year to year. In 1876, 1877 and 1878 I obtained plentiful During the past 30 years I have obtained a con- evidence of the principal systems in simultaneous action with siderable number of observations in the two months July the Perseids and the same identical showers are obvious at and August and with a view to redetermine and compare the present time. They are not all determinable every year the radiant positions 1 have examined the materials and owing probably to the variable conditions under which they grouped them into three periods viz July 6-16, July 20 to are manifested. Some notable fluctuations are occasionally Aug. 16 and Aug. 19-25. Many of the radiants derived for remarked in the case of the Perseids for in certain years, these periods exhibit a significant resemblance and appear at a time of night when the radiant is high, the horary rate to be common to them all. I have arranged them in the of apparition may reach 150 or zoo whereas at other times following table side by side so that the correspondences it may be as low as zo or 30. Often enough daylight must may be seen at a glance. The centres here given show veil the shower just at the most important hours and at slight differences with what are obviously the same radiants other returns moonlight nearly overcomes it. A cloudy included in several of my previously published lists (Astr. or hazy atmosphere is also sometimes responsible for its Nachr. 3513, Radiants of minor showers visible at the chief partial obliteration. In view of the facts referred to it is meteoric epochs, and Astr. Nachr. 3531, Catalogue of 177 cleqr that perfectly fair and safe comparisons of the strength long enduring and stationary radiants) but the present sum- of this meteoric display at various returns must be very mary is based upon a new reduction and is therefore in a difficult depending as it does on several varying conditions great measure independent of former results. For the period materially affecting its visibility. July 20 - Aug. 16 the number of meteors given for the in- The time of revolution of the Perseid swarm is un- dividual showers is in nearly all cases much less than the known though there is indefinite evidence that it lies be- total actually observed. But to have gone carefully over tween 104 and 123 years. Careful observations of the every recorded path and allotted each one to its radiant meteors were only commenced in the last century so the would have involved a very large amount of time without accumulated results extend over far too short an interval to an equivalent advantage so it is thought that from the afford a good clue to the cycle of recurring maxima. It is number of meteors apportioned to the various positions their to be hoped that observers in future years will continue relative strength may be pretty well estimated. to gather observational facts relating to this strong shower About 85 radiants were satisfactorily (though some and to the host of minor systems visible at the same season feebly) observed during the middle period (July 20 - Aug. 16) of the year. These secondary streams though extremely 10 feeble individually are yet very plentiful in number, varied plays like the swift flashing Perseids they can teach as much in their aspect and character and widely distributed in their concerning the arrangement and general features of the positions and if they cannot yield rich and attractive dis- radiants which so numerously abound in the heavens. Period 6-16 Period July zo-Aug. 16 ! Period Aug. 19-25 Name of shower July 473 shooting stars 7200 shooting stars 888 shooting stars in -~ shoot- General Catalogue Radiant point shoot- I899 1899 Radiant point ~ ing IAspect 1 ing (A.Dect a 8 stars a 8 stars ~- ___- __---__ - 6 1 z Andromedids 6"+35" 1 ISEX6 1 RK 3 y Pegasids 7 +II '31 RK 6 +II 26 S 7 a Cassiopeids 8 +53 8 RK - -- 10 p Andromedids 9 +39 44 RK 8 +40 5 R 11 6 Piscids - --' J4+7 7 RKI - -- 20 +5r\ 57 +59\ 3I RK 40 Perseids 7 +451 ') 1 to16 +49( I' 1 RK to52 +58( RK to68 +60j 8 z Cassiopeids - - - 11 +47 26 - -- 13 /? Andromedids - - - 17 +31 22 RK 18 +3I j RK 5 R 15 d Cassiopeids 22 +59 6 RK I 1 20 +58 5 R - Cassiopeids - - - - -- - - - 16 /3 Arietids 22 +22 1 7 RK I 23 +21 RK 2 I y Andromedids 23 +42 12 RK 25 +42 23 RK - - 18 z Andromedids - -- 23 +36 5 RK 1: - 22 Cassiopeids (50) 27 +71 9 R 1 26 +72 24 26 +71 9 R RK I - - - 2 9 L Triangulids 30 +30 7 RK I 28 +28 25 j3 Triangulids 30 +36 12 RK 30 8 Perseids - _- 27 a Arietids + - _- 33 Arietids (39) + -- 40 +28 8 RK 41 +27 13 RK 37 E Arietids + - - 42 +ZI 12 RK 42 +41 5 RK 39 17 Perseids - - - I 43 +58 8 RK 42 +58 8 RK 35- B Perseids - - - I 42 +39 6 RK 43 +39 9 RK 42 Arietids (56) - - - 47 +25 '9 RK + - - 43 a-/?Perseids 48 5 Perseids 50 +31 5 KK 45 y Camelopardids - -- 54 +71 10 RK 49 e Taurids + 57 + 9 5 RK 56 y Perseids 61 +50 26 RK 55 Camelopardids (Piazzi 1II 208) 60 +59 9 RK -- 58 E Perseids + 62 +37 20 RK 53 E Taurids -- 63 Camelopardids (8) 71 +so 16 RK 62 a Camelopardids 70 +66 14 R 65 a Aurigids 67 L Aurigids 68 (3 Camelopardids + 77 +57 'I RK 82 Camelopardids (43) - -- 96 +72 5 s + - - 84 Lyncids (Groombr. I 2 7 2) + - - I04 +52 8 j + - - Camelopardids (Piazzi I 3 2) -- - - - 9 2 a VII - 104 +I9 5 R 99 o Ursids - -- 122 +62 5 R. - ' 103 Ursids (22) 116 a Ursids - --150 +62 5 - -- 123 B Ursids I/ 160 +59 5 -- ~ *) The sign + placed in a blank space means that some meteors from the radiant were observed but not in sufficient numben to indicate the radiant. - *) About 2800 meteors. 3874 Period July 6 16 Period July 20 - Aug. 16 Period Aug. 19-25 Name of shower - 473 shooting stars 7200 shooting stars 888 shooting stars in ___.- ~ General Catalogue hoot Radiant point Radiant point Radiant point I899 ing ispect a.3 a6 ;tars a6 _____._____- ~ ______ __~ ~_________~. ~ ___.__ x Draconids - 189" +73" I2 S - - 5 Ursids + 201 +57 6 S 8 Bootids + 212 +53 6 S + @ Ursae minorids 218O +73O 215 4-76 5 S - 7 Draconids 239 +60 - - - - z Herculids 243 +47 + - - 242" +49" y Ursae minorids + 245 4-71 12 S - a Scorpiids 252 -21 + - - - JE Herculids 255 +31 + - - - - y Draconids 254 +47 - - - w Draconids I - 260 +69 I1 S 263 +69 5 Draconids 265 +63 263 +62 20 S 264 -1-62 y Draconids 269 +47 271 +48 32 S 266 +47 Herculids (9 7) 271 +22 + - - - Ophiuchids (B.A.C. 62 13 274 +I1 - - - - Q) Draconids I1 273 +67 277 +70 '5 S 277 +68 R Aquilids 283 -13 283 -12 I0 S 283 -14 Lyrids (13) - 285 +44 5 S - y Lyrids 289 +31 - - - - o Draconids 290 +60 291 +60 44 S 291 +60 B Cygnids + 292 +52 72 R 289 +53 d Cygnids 292 +40 - - - - fl Cygnids + 290 +24 9 S - 6 Draconids + 291 +70 20 R 292 +70 7 Aquilids 296 o 297 + I 29 S - r] Sagittids 301 +23 302 +23 18 S 302 +23 y Cygnids - - - - 301 +41 a Capricornids 303 -12 304 -12 3' S L E Draconids - 307 +67 5 S 309 +66 1c Cepheids 3'0 +I7 315 +78 24 S 312 +78 a Cepheids 315 +60 311 +62 24 S 310 +61 y Delphinids 312 +13 312 +12 30 S 311 +12 /3 Aquarids 311 -12 318 -11 '5 S - a Cygnids 3'5 +48 31.5 +48 38 S 3'5 +47 5 Cygnids + 3x9 +31 '5 S 3'9 +30 E Pegasids 321 +lo + - - 320 +II - Vulpeculids (33) 322 +22 321 +23 '7 S E Capricornids + 324 -21 8 S 323 -24 8 Pegasids - 323 + 4 23 S 326 + 2 Lacertids (4) 335 +49 333 +48 53 S 327 +48 - 3t Pegasids 330 +36 332 +37 16 S r] Pegasids 333 +28 333 +27 37 S 333 +28 5 Cepheids 333 +57 334 +58 18 S 334 +58 @ Cepheids 333 +I2 333 +71 50 R 335 +7' 332 +I0 5 Pegasids + 52 33' + 7 333 +I8 8 - - - 3 5 Aquarids - 336 + I y Cepheids - - - - 337 f82 a Piscis Australids - 338 -25 13 S + - 6 Aquarids 339 -11 137 S 339 -10 o Andrornedids 340 -+4' - - - - a Pegasids + 343 +I2 10 R 343 +I3 3874 15'2 Period July 6 - 16 Period July 20 - Aug.
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