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Published in Observer's Handbook 1997, Royal Astronomical Society of Canada
Two solar and two lunar eclipses occur in 1997. The Sun and Moon each undergo one partial and one total eclipse. The eclipses occur as follows:
1997 March 9: Total Solar Eclipse
1997 March 24: Partial Lunar Eclipse
1997 September 2: Partial Solar Eclipse
1997 September 16: Total Lunar Eclipse
Predictions for eclipses are summarized in figures 1 through 4. World maps show the regions of visibility for each eclipse. The lunar eclipse diagrams also include the path of the Moon through Earth's shadows. Contact times for each principal phase are tabulated along with the magnitudes and geocentric coordinates of the Sun and Moon at greatest eclipse.
On Sunday, 1997 March 9, a total eclipse of the Sun will be visible from parts of eastern Asia. The path of the Moon's umbral shadow begins in eastern Kazakhstan, and travels through Mongolia and eastern Siberia where it swings northward to end at sunset in the Arctic Ocean. A partial eclipse will be seen within the much broader path of the Moon's penumbral shadow, which includes eastern Asia, the northern Pacific and the northwest corner of North America (Figure 1).
Due to the large value of gamma1 (=0.918) at this eclipse, the Moon's umbral shadow remains close to Earth's limb throughout the event. Thus, the Sun never climbs higher than 23° along the entire track. The path of the umbral shadow begins at sunrise in easternmost Kazakhstan at 00:41 UT. However, it requires an additional four minutes for the northern edge of the shadow to contact Earth. At 00:45 UT, the path is then 318 kilometres wide with the southeast edge of the umbra reaching deep into central Mongolia. An observer on the centre line will then witness a total eclipse lasting 2 minutes 11 seconds with the Sun 6° above the eastern horizon.
Mongolia's capital city Ulaanbaatar lies just south of the path and experiences a tantalizing partial eclipse of magnitude 0.996 at 00:48 UT. Only 0.2% of the Sun's photosphere will then be exposed and it may be possible to see the corona and the diamond ring effect if skies are clear. By 00:50 UT, the Sun's centre line altitude is 12° and the duration of totality is 2 minutes 24 seconds. The industrial city of Darchan lies within the path ~30 kilometres south of the centre line where it looses only one second from the maximum duration. North of the path, the Russian hydroelectric city of Irkutsk also witnesses a deep partial eclipse of magnitude 0.988 at 00:54 UT.
Traveling eastward, the shadow quickly crosses the Mongolian-Russian border as it passes south of Lake Baikal, the world's largest fresh water lake. At 00:55 UT, the path width is 361 kilometres, the centre line duration is 2 minutes 33 seconds and the Sun's altitude is 16°. Ulan-Ude lies just outside the northern limit and witnesses a partial phase of magnitude 0.998; only 0.1% of the Sun will then be visible. As the shadow's track curves northward, it engulfs the largest city in its path. Cita (pop. = 366,000) experiences mid eclipse at 01:00 UT and enjoys 2 minutes 15 seconds of totality. About 100 kilometres to the south, the centre line duration lasts 2 minutes 39 seconds at a solar elevation of 18°.
Although the umbra first touched Earth only nine minutes earlier, it has already traveled 2,000 kilometres. At 01:08 UT, Russia's city of Mogocha witnesses a 2 minute 32 second total eclipse with the Sun at 20°. The shadow's course takes it increasingly northward where its southern half briefly enters the northern provinces of China (01:10 UT). The instant of greatest eclipse2 occurs shortly thereafter at 01:23:44.8 UT. Totality then reaches its maximum duration of 2 minutes 50 seconds, the Sun's altitude is 23°, the path width is 356 kilometres and the umbra's velocity is 0.836 km/s. From this point on, the path rapidly turns north and crosses some of the most desolate regions of northern Siberia. Finally, the umbra reaches the coast of the East Siberian Sea at 01:52 UT. The umbral duration (2m33s), path width (314 km), and Sun's altitude (16°), are now decreasing while the shadow's ground velocity is increasing (1.3 km/s).
Continuing north across the East Siberian Sea and the Arctic Ocean, the Moon's umbra leaves Earth's surface near the North Pole at 2:06 UT. During the eighty minutes of central eclipse, the broad umbral shadow travels approximately 6800 kilometres, and encompasses 0.4% of Earth's surface.
This eclipse is a member of Saros 120, the same series which produced the widely observed eclipse of 1979 February 26. Saros 120 is in its old age and will produce only two more total eclipses after 1997, each at increasingly northern latitudes. Dedicated eclipse observers will be drawn to this low Sun event for the possibility of seeing a naked eye comet during totality (Comet Hale-Bopp) as well as the reasonable weather prospects it offers. Only two previous comets have been naked eye spectacles during total eclipses (1882 and 1948), but Hale-Bopp must live up to its most optimistic predictions in order to make it number three.
Mean cloud cover data suggest a 60% probability of clear skies in Mongolia with temperatures in the range of -10° C to -15° C. As one travels northeast along the path, visibility statistics increase while the mercury plunges. Eastern Siberia experiences some of the coldest temperatures on Earth, surpassed only by interior Antarctica! Although the probability of clear skies exceeds 80% here, the mean low temperature drops to -40° C with records below -60° C. Such temperatures make equipment operation all but impossible. Furthermore, transportation to this portion of the path is long, difficult and expensive. Perhaps the best trade off between cloud cover statistics and temperature is in Mongolia north of the capital city Ulaanbaatar. The city of Darchan lies just south of the centre line where the Sun stands 13° above the horizon during the 2 minute 24 second total phase. Darchan also offers logistical merit since it is readily accessible from Ulaanbaatar some 180 kilometres to the south. In any event, this will be a cold weather eclipse offering a serious challenge to keep equipment, film, batteries and fingers from freezing up before and during the crucial seconds of totality.
Local circumstances for cities throughout Asia are given in Table 1. All times are given in Universal Time. Sun's altitude and azimuth, the eclipse magnitude and obscuration are all given at the instant of maximum eclipse. A detailed report on this eclipse is available from NASA as Reference Publication 1369 (see: NASA Solar Eclipse Bulletins).
2 The instant of greatest eclipse occurs when the distance between the Moon's shadow axis and Earth's geocenter reaches a minimum. Although greatest eclipse differs slightly from the instants of greatest magnitude and greatest duration (for total eclipses), the differences are usually negligible.
The year's first lunar eclipse occurs in western Virgo three days after the Moon's apogee (Figure 2). The event is a relatively large partial eclipse, with the Moon's southern limb dipping deeply into Earth's umbral shadow. While first penumbral contact occurs at 01:40 UT, most observers will have difficulty detecting the eclipse much before 02:30 UT. The partial eclipse commences with first umbral contact at 02:57 UT. The partial phases last nearly three and a half hours before ending with last umbral contact at 06:21 UT. Although it can not actually be observed, the eclipse technically ends when the Moon leaves the penumbral shadow at 07:38 UT.
At the instant of greatest eclipse (04:39 UT), the Moon will stand at the zenith for observers near the Equator in South America. At this time, the umbral magnitude peaks at 0.92710 as the Moon's southern limb passes within 12 arc-minutes of the shadow's axis. In comparison, the Moon's northern limb lies a mere 2 arc-minutes outside the northern edge of the umbra. If the umbra is as bright as it was during last April's eclipse, observers should have no trouble tracing the deeply eclipsed southern limb of the Moon with the aid of binoculars or a small telescope. During the eclipse, Mars shines brightly (mv = -1.2) at opposition and is located ten degrees northwest of the Moon near the Virgo/Leo border.
This event is well placed for most of the Western Hemisphere. Only observers in the western most portions of North America will miss the beginning of the eclipse which occurs before moonrise from the region. In contrast, most of Europe and Africa will witness moonset before the eclipse ends.
Table 2 lists predicted umbral immersion and emersion times for twenty well-defined lunar craters. The timing of craters is useful in determining the atmospheric enlargement of Earth's shadow (see: Crater Timings During Lunar Eclipses). This eclipse will be particularly useful in determining the umbra's enlargement due to the depth of the eclipse and the off-axis geometry of the Moon's path through the shadow.
The second solar eclipse of 1997 is a partial eclipse visible primarily from Australia, New Zealand and portions of Antarctica (Figure 3). First and last penumbral contacts occur at 21:44 UT (Sep 1) and 02:23 UT (Sep 2), respectively. Greatest eclipse takes place at 00:04 UT (Sep 2) when the magnitude reaches 0.898.
Local circumstances for cities throughout Australia and New Zealand are given in Table 3. All times are listed in Universal Time. Sun's altitude and azimuth, the eclipse magnitude and obscuration are all given at the instant of maximum eclipse. If the eclipse is in progress at sunrise or sunset, this information is indicated by 'Ð r' or 'Ð s', respectively. The appearance of the eclipse at maximum phase for a number of locations is depicted in
What Will The Eclipse Look Like?
This is the fifty-third eclipse of Saros series 125. The series produced its last central eclipse in 1979 and is winding down with a series of partial eclipses of progressively decreasing magnitude. The series ends with a partial eclipse in 2358.
1997 September 16: Total Lunar Eclipse
The last eclipse of the year is a total lunar eclipse. Unfortunately, it is not visible from the Western Hemisphere (Figure 4). This time, Eastern Hemisphere observers are favored by the event which occurs in southern Pisces. The penumbral phase begins at 16:11 UT, but sharp eyed observers won't notice anything until over half the Moon lies within the tenuous outer shadow. The partial eclipse commences as the Moon enters the dark umbra at 17:08 UT. The one hour total phase begins at 18:15 UT and ends at 19:18 UT. Afterwards, the partial phases resume and continue until 20:25 UT. The eclipse ends as the Moon finally exits the penumbra at 21:22 UT.
At greatest eclipse (18:47 UT), the umbral magnitude reaches a value of 1.200 with the Moon in the zenith from the Indian Ocean. The Moon's northern limb then passes within 6 arc-minutes of the umbra's centre while the southern limb lies 7 arc-minutes inside the shadow's edge. A large variation in shadow brightness can be expected and observers are encouraged to estimate the Danjon value at different times during totality (see: Danjon Scale of Lunar Eclipse Brightness). Note that it may also be necessary to assign different Danjon values to different portions of the Moon (i.e. - north vs. south).
Observers in the western most Europe will miss the beginning of totality which occurs before moonrise. However, most of Asia and East Africa will see the entire event. Two bright planets are well placed during the eclipse. Saturn (mv =+0.5) is 25° northeast of the Moon while Jupiter (mv =-2.5) lies 40° southwest of it.
Table 4 lists predicted umbral immersion and emersion times for twenty well-defined lunar craters. The timing of craters is useful in determining the atmospheric enlargement of Earth's shadow (see: Crater Timings During Lunar Eclipses).
1997 March 9: Total Solar Eclipse
1 Minimum distance of the Moon's shadow axis from Earth's center in units of equatorial Earth radii.
1997 September 2: Partial Solar Eclipse
Key to Solar Eclipse Maps
Key to Lunar Eclipse Maps
Danjon Scale of Lunar Eclipse Brightness
h = 15 (GST + UT - ra ) + l
a = ArcSin [ Sin d Sin f + Cos d Cos h Cos f ]
A = ArcTan [ - (Cos d Sin h) / (Sin d Cos f - Cos d Cos h Sin f) ]
where:
h = Hour Angle of Sun or Moon
a = Altitude
A = Azimuth
GST = Greenwich Sidereal Time at 0:00 UT
UT = Universal Time
ra = Right Ascension of Sun or Moon
d = Declination of Sun or Moon
l = Observer's Longitude (East +, West -)
f = Observer's Latitude (North +, South -)
During the eclipses of 1996, the values for GST and the geocentric Right Ascension and Declination of the Sun or the Moon (at greatest eclipse) are as follows:
Date GST ra d
Mar 09 11.115 23.296 -4.542
Mar 24 12.113 12.228 -1.001
Sep 02 22.745 10.742 7.981
Sep 16 23.717 23.636 -2.778
1998 February 26: Total Solar Eclipse
1998 March 13: Penumbral Lunar Eclipse
1998 August 8: Penumbral Lunar Eclipse
1998 August 22: Annular Solar Eclipse
1998 September 16: Penumbral Lunar Eclipse A full report Eclipses During 1998 will be published next year in the Observer's Handbook 1998. Details for the 1997 March 9 total solar eclipse have been published by NASA (see: NASA Solar Eclipse Bulletins).
The author wishes to thank Goddard's Laboratory for Extraterrestrial Physics for several minutes of computer time. All calculations, diagrams, tables and opinions presented in this paper are those of the author and he assumes full responsibility for their accuracy.
Webmaster: Fred Espenak Planteary Systems Laboratory - Code 693 Email: fred.espenak@nasa.gov NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA |
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