沙罗周期和日食的一些英文资料
如果有兴趣，请翻译下面这篇有关日食与沙罗周期的文章吧，谢谢！Eclipses and the Saros
Fred Espenak
The periodicity and recurrence of eclipses is governed by the saros cycle, a period of approximately 6,585.3 days (18 years 11 days 8 hours). It was known to the Chaldeans as a period when lunar eclipses seem to repeat themselves, but the cycle is applicable to solar eclipses as well.
The saros arises from a natural harmony between three of the Moon's orbital periods:
Synodic Month (new moon to new moon) 29.53059 days = 29d 12h 44m
Draconic Month (node to node) 27.21222 days = 27d 05h 06m
Anomalistic Month (perigee to perigee) 27.55455 days = 27d 13h 19m
One saros is equal to 223 synodic months. However, 242 draconic months and 239 anomalistic months are also equal to this same period (to within a couple hours)!
Any two eclipses separated by one saros cycle share very similar geometries. They occur at the same node with the Moon at nearly the same distance from Earth and at the same time of year. Because the saros period is not equal to a whole number of days, its biggest drawback is that subsequent eclipses are visible from different parts of the globe. The extra 1/3 day displacement means that Earth must rotate an additional ~8 hours or ~120o with each cycle. For solar eclipses, this results in the shifting of each successive eclipse path by ~120o westward. Thus, a saros series returns to about the same geographic region every 3 saroses (54 years and 34 days).
A saros series doesn't last indefinitely because the three lunar months are not perfectly commensurate with one another. In particular, the Moon's node shifts eastward by about 0.5o with each cycle. A typical saros series for a solar eclipse begins when new Moon occurs ~18° east of a node. If the first eclipse occurs at the Moon's descending node, the Moon's umbral shadow will pass ~3500 km below Earth and a partial eclipse will be visible from the south polar region. On the following return, the umbra will pass ~300 km closer to Earth and a partial eclipse of slightly larger magnitude will result. After ten or eleven saros cycles (about 200 years), the first central eclipse will occur near the south pole of Earth. Over the course of the next 950 years, a central eclipse occurs every 18.031 years (= saros) but will be displaced northward by an average of ~300 km. Halfway through this period, eclipses of long duration will occur near the equator. The last central eclipse of the series occurs near the north pole. The next approximately ten eclipses will be partial with successively smaller magnitudes. Finally, the saros series will end a dozen or more centuries after it began at the opposite pole. Due to the ellipticity of the orbits of the Earth and Moon, the exact duration and number of eclipses in a complete saros is not constant. A series may last 1226 to 1550 years and is comprised of 69 to 87 eclipses, of which about 40 to 60 are central (i.e., total or annular).
Solar eclipses that take place near the Moon's ascending node have odd saros numbers. Each succeeding eclipse in a series shifts progressively southward with respect to the center of the Earth. On the other hand, solar eclipses occurring near the Moon's descending node have even saros numbers. Each succeeding eclipse in a series shifts progressively northward with respect to the center of the Earth. The numbering system used for the saros series was introduced by the Dutch Astronomer G. van den Bergh in his book Periodicity and Variation of Solar (and Lunar) Eclipses (Tjeenk Willink, Haarlem, Netherlands, 1955). He assigned the number 1 to a pair of solar and lunar eclipse series that were in progress during the second millennium BC.
Understanding the numbering sequence of the saros is complicated by the fact that it does not depend on when a series either begins or ends. Instead, the numbering is determined by the order in which each series peaks. In this context, the peak of a series occurs when the umbral shadow axis passes closest to the center of the Earth. Since the duration of each series varies up to several hundred years and the numbering is keyed to the order in which each series peaks, this explains why the first eclipse of a series which peaks later can actually preceed the first eclipse of a series that peaks earlier. From the solar eclipse catalogs, the column labeled Gamma is the parameter that gives the minimum distance (in Earth radii) of the shadow axis from the center of Earth during each eclipse. Gamma is positive or negative depending on whether the shadow axis passes north or south of Earth's center. Looking at any of the saros catalogs (e.g., Saros 145) one can see how the value of gamma changes with each eclipse in a series. When gamma reaches its minimum (absolute) value, the series is then at its peak. In the case of Saros 145, the peak occurs with the eclipse of 2342 Mar 08 (gamma=0.008).
Since there are two to five solar eclipses every year, there are approximately forty different saros series in progress at any one time. For instance, during the later half of the twentieth century, there are 41 individual series and 26 of them are producing central eclipses. As old series terminate, new ones are beginning and take their places.
To illustrate, the ten central solar eclipses of 1891, 1909, 1927, 1945, 1963, 1981, 1999, 2017, 2035 and 2053 are all members of Saros 145. The series began with a partial eclipse near the north pole in 1639. The first central eclipse of the series was an annular eclipse in 1891. It was followed by another annular in 1909. The next event was the first total eclipse in 1927. The total solar eclipse of 1999 August 11 is number 21 of 77 eclipses in Saros 145, and it is the 5th of 41 total eclipses in the series. Each of the subsequent total eclipses shifts southwards. The last total eclipse occurs in 2648 near the south pole. The last eclipse of the series takes place in 3009. Table of Saros 145 gives details for every eclipse in the series.
The saros cycle for lunar eclipses operates analogously with the solar eclipse saros. For lunar eclipses, the parameter gamma is the Moon's minimum distance measured with respect to the axis of Earth's shadow (units of Earth radii). Note however, that the saros numbering is opposite to that for solar eclipses. Lunar eclipses occurring near the Moon's ascending node have even saros numbers. Each succeeding eclipse in a series shifts progressively southward with respect to the axis of Earth's shadow. Correspondingly, lunar eclipses occurring near the Moon's descending node have odd saros numbers. Each succeeding eclipse in a series shifts progressively northward with respect to the axis of Earth's shadow.
Another significant eclipse cycle is the inex, a period of 358 synodic months (29 years minus about 20 days, or nearly 10,752 days). The inex is useful because it marks the time interval between consecutively numbered saros series. To see a diagram illustrating the relationship between the saros and inex cycles over a period of 26,000 years, visit the Saros-Inex Panorama page. 本帖最后由 q5968661 于 2009-6-25 18:16 编辑
如果上面的文章太长，请翻译这篇7月22日日全食所属的136号沙罗日食系列的文章，我可以帮你校对。
Saros Series 136
The periodicity and recurrence of solar (and lunar) eclipses is governed by the Saros cycle, a period of approximately 6,585.3 days (18 years 11 days 8 hours). When two eclipses are separated by a period of one Saros, they share a very similar geometry. The two eclipses occur at the same node with the Moon at nearly the same distance from Earth and at the same time of year. Thus, the Saros is useful for organizing eclipses into families or series. Each series typically lasts 12 to 13 centuries and contains 70 or more eclipses. Every saros series begins with a number of partial eclipses near one of Earth's polar regions. The series will then produce several dozen central eclipses before ending with a group of partial eclipses near the opposite pole.
Solar eclipses of Saros 136 all occur at the Moon’s descending node and the Moon moves northward with each eclipse. The series began with a partial eclipse in the southern hemisphere on 1360 Jun 14. The series will end with a partial eclipse in the northern hemisphere on 2622 Jul 30. The total duration of Saros series 136 is 1262.11 years. In summary:
First Eclipse =1360 Jun 14 05:56:04 TD
Last Eclipse =2622 Jul 30 12:18:09 TD
Duration of Saros 136=1262.11 Years
Saros 136 is composed of 71 solar eclipses as follows:
Solar Eclipses of Saros 136
Eclipse Type Symbol Number Percent
All Eclipses -71 100.0%
Partial P 15 21.1%
Annular A 6 8.5%
Total T 44 62.0%
Hybrid H 6 8.5%
Umbral eclipses (annular, total and hybrid) can be further classified as either: 1) Central (two limits), 2) Central (one limit) or 3) Non-Central (one limit). The statistical distribution of these classes in Saros series 136 appears in the following table. Umbral Eclipses of Saros 136
Classification Number Percent
All Umbral Eclipses56 100.0%
Central (two limits) 56 100.0%
Central (one limit) 0 0.0%
Non-Central (one limit) 0 0.0%
The following string illustrates the sequence of the 71 eclipses in Saros 136: 8P 6A 6H 44T 7P
The longest and shortest eclipses of Saros 136 as well as other eclipse extrema are listed below.
LongestTotalSolar Eclipse: 1955 Jun 20 Duration = 07m08s
ShortestTotalSolar Eclipse: 2496 May 13 Duration = 01m02s
Longest Annular Solar Eclipse: 1504 Sep 08 Duration = 00m32s
Shortest Annular Solar Eclipse: 1594 Nov 12 Duration = 00m04s
Longest HybridSolar Eclipse: 1703 Jan 17 Duration = 00m50s
Shortest HybridSolar Eclipse: 1612 Nov 22 Duration = 00m01s
Largest Partial Solar Eclipse: 1486 Aug 29 Magnitude = 0.9856
Smallest Partial Solar Eclipse: 1360 Jun 14 Magnitude = 0.0495
Local circumstances at greatest eclipse for every eclipse of Saros 136 are presented in the following catalog. The sequence number in the first column links to a global map showing regions of eclipse visibility. A detailed key and additional information about the catalog can be found at: Key to Catalog of Solar Eclipse Saros Series.
For an animation showing how the eclipse path changes with each member of the series, see Saros 136 Animation.
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Catalog of Solar Eclipse Saros 136
TD of
Seq. Rel. Calendar Greatest LunaEcl. Ecl. SunSunPath Central
Num. Num. Date Eclipse ΔT Num.TypeGamma Mag. Lat. Long. AltAzm Width Dur.
s ° ° ° ° km
01-35 1360 Jun 1405:56:04 359-7910 Pb-1.52270.049565.8S78.2E 0 13
02-34 1378 Jun 2512:45:16 330-7687 P -1.43920.197664.8S34.3W 0 23
03-33 1396 Jul 0519:37:40 302-7464 P -1.35680.344963.9S 147.2W 0 32
04-32 1414 Jul 1702:35:03 276-7241 P -1.27700.488163.1S98.9E 0 42
05-31 1432 Jul 2709:39:02 251-7018 P -1.20110.625062.4S16.4W 0 51
06-30 1450 Aug 0716:48:49 226-6795 P -1.12860.756061.8S 132.9W 0 60
07-29 1468 Aug 1800:08:08 208-6572 P -1.06270.875361.3S 108.3E 0 68
08-28 1486 Aug 2907:34:56 191-6349 P -1.00180.985661.0S12.2W 0 77
09-27 1504 Sep 0815:12:15 174-6126 A -0.94860.992455.3S 102.6W18 58 8300m32s
10-26 1522 Sep 1922:57:33 159-5903 A -0.90110.994653.9S 146.0E25 55 4200m23s
11-25 1540 Sep 3006:54:11 145-5680 A -0.86200.996054.6S29.1E30 54 2700m17s
12-24 1558 Oct 1114:58:55 133-5457 A -0.82890.997156.5S90.3W34 53 1800m12s
13-23 1576 Oct 2123:13:06 122-5234 A -0.80310.998159.2S 147.9E36 51 1100m08s
14-22 1594 Nov 1207:34:49 111-5011 A -0.78290.999162.4S25.1E38 48 500m04s
15-21 1612 Nov 2216:04:35 98-4788 H -0.76911.000265.7S98.4W39 43 100m01s
16-20 1630 Dec 0400:38:59 81-4565 H -0.75851.001768.7S 139.6E40 36 900m07s
17-19 1648 Dec 1409:17:55 48-4342 H -0.75101.003570.9S19.6E41 25 1800m14s
18-18 1666 Dec 2517:59:16 29-4119 H -0.74521.005871.6S98.3W42 11 3000m24s
19-17 1685 Jan 0502:42:50 11-3896 H -0.74091.008670.7S 143.1E42357 4400m35s
20-16 1703 Jan 1711:24:25 8-3673 H2-0.73451.012067.9S22.2E42347 6100m50s
21-15 1721 Jan 2720:05:11 10-3450 T -0.72691.015864.0S 102.4W43340 7901m07s
22-14 1739 Feb 0804:41:13 11-3227 T -0.71491.020359.2S 131.0E44336 9901m27s
23-13 1757 Feb 1813:14:12 14-3004 T -0.69991.025153.8S 2.9E4533511901m51s
24-12 1775 Mar 0121:39:20 17-2781 T -0.67831.030447.9S 124.8W4733513902m20s
25-11 1793 Mar 1206:00:07 16-2558 T -0.65241.035941.7S 107.8E4933615802m51s
26-10 1811 Mar 2414:12:13 12-2335 T -0.61901.041635.2S18.0W5233817603m27s
27-09 1829 Apr 0322:18:36 8-2112 T -0.58031.047428.5S 142.6W5434119204m05s
28-08 1847 Apr 1506:16:13 7-1889 T -0.53391.053021.6S95.0E5834320604m44s
29-07 1865 Apr 2514:08:34 6-1666 T -0.48261.058414.8S25.8W6134621905m23s
30-06 1883 May 0621:53:49 -6-1443 T -0.42501.0634 8.1S 144.6W6534922905m58s
31-05 1901 May 1805:33:48 -1-1220 T -0.36261.0680 1.7S98.4E6935323806m29s
32-04 1919 May 2913:08:55 21 -997 T -0.29551.0719 4.4N16.7W7335624406m51s
33-03 1937 Jun 0820:41:02 24 -774 T -0.22531.0751 9.9N 130.5W77 025007m04s
34-02 1955 Jun 2004:10:42 31 -551 T -0.15281.077614.8N 117.0E81 525407m08s
35-01 1973 Jun 3011:38:41 44 -328 T -0.07851.079218.8N 5.6E86 925607m04s
36 00 1991 Jul 1119:07:01 58 -105 Tm-0.00411.080022.0N 105.2W90 3025806m53s
37 01 2009 Jul 2202:36:25 66 118 T 0.06981.079924.2N 144.1E8619825806m39s
38 02 2027 Aug 0210:07:50 75 341 T 0.14211.079025.5N33.2E8220225806m23s
39 03 2045 Aug 1217:42:39 88 564 T 0.21161.077425.9N78.5W7820625606m06s
40 04 2063 Aug 2401:22:11 122 787 T 0.27711.075025.6N 168.4E7420925205m49s
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Catalog of Solar Eclipse Saros 136
TD of
Seq. Rel. Calendar Greatest LunaEcl. Ecl. SunSunPath Central
Num. Num. Date Eclipse ΔT Num.TypeGamma Mag. Lat. Long. AltAzm Width Dur.
s ° ° ° ° km
41 05 2081 Sep 0309:07:31 161 1010 T 0.33781.072024.6N53.6E7021124705m33s
42 06 2099 Sep 1416:57:53 202 1233 T 0.39421.068423.4N62.8W6721124105m18s
43 07 2117 Sep 2600:55:42 245 1456 T 0.44421.064521.9N 178.4E6421123305m03s
44 08 2135 Oct 0709:00:03 291 1679 T 0.48841.060320.3N57.6E6121022404m50s
45 09 2153 Oct 1717:12:18 336 1902 T 0.52591.056018.8N65.7W5820821404m36s
46 10 2171 Oct 2901:31:03 375 2125 T 0.55771.051617.6N 169.1E5620620304m23s
47 11 2189 Nov 0809:57:28 417 2348 T 0.58301.047416.5N41.6E5420219204m10s
48 12 2207 Nov 2018:30:26 461 2571 T 0.60271.043415.8N87.8W5319818003m56s
49 13 2225 Dec 0103:08:36 506 2794 T 0.61781.039815.4N 141.4E5219416903m43s
50 14 2243 Dec 1211:52:14 554 3017 T 0.62841.036515.5N 9.0E5119015703m30s
51 15 2261 Dec 2220:38:50 604 3240 T 0.63601.033716.1N 124.2W5018514703m17s
52 16 2280 Jan 0305:28:11 656 3463 T 0.64141.031417.2N 101.9E5018013803m04s
53 17 2298 Jan 1314:16:27 710 3686 T 0.64741.029619.0N31.9W5017613102m52s
54 18 2316 Jan 2523:05:17 766 3909 T 0.65261.028221.4N 166.0W4917212602m42s
55 19 2334 Feb 0507:50:29 824 4132 T 0.66031.027224.6N60.8E4916812202m33s
56 20 2352 Feb 1616:32:06 884 4355 T 0.67091.026628.5N71.8W4816412102m24s
57 21 2370 Feb 2701:07:02 946 4578 T 0.68651.026233.2N 157.0E4616112102m17s
58 22 2388 Mar 0909:36:21 1011 4801 T 0.70641.026038.5N27.0E4515812402m10s
59 23 2406 Mar 2017:57:23 1077 5024 T 0.73271.025844.5N 101.3W4315512802m03s
60 24 2424 Mar 3102:10:10 1146 5247 T 0.76521.025451.3N 131.9E4015213301m55s
61 25 2442 Apr 1110:14:04 1216 5470 T 0.80461.024858.7N 6.2E3614814201m45s
62 26 2460 Apr 2118:09:49 1289 5693 T 0.85031.023666.8N 119.8W3114215401m34s
63 27 2478 May 0301:55:59 1363 5916 T 0.90341.021875.7N 107.7E2512817601m20s
64 28 2496 May 1309:34:25 1440 6139 T 0.96221.018581.0N70.4W15 6524301m02s
65 29 2514 May 2517:04:32 1519 6362 P 1.02720.950768.5N 123.2E 0 13
66 30 2532 Jun 0500:28:58 1600 6585 P 1.09620.822467.5N 1.3E 0 2
67 31 2550 Jun 1607:45:35 1683 6808 P 1.17080.684066.4N 118.1W 0352
68 32 2568 Jun 2614:58:55 1768 7031 P 1.24720.542665.5N 123.7E 0342
69 33 2586 Jul 0722:07:07 1855 7254 P 1.32700.395764.5N 7.2E 0332
70 34 2604 Jul 1905:14:31 1944 7477 P 1.40620.250963.7N 108.8W 0323
71 35 2622 Jul 3012:18:09 2035 7700 Pe 1.48720.103963.0N 136.4E 0314
原文链接http://eclipse.gsfc.nasa.gov/SEsaros/SEsaros136.html
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