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An eclipse season is one of only two periods during each year when eclipses can occur, due to the variation in the orbital inclination of the Moon. Each season lasts about 35 days and repeats just short of six months later, thus two full eclipse seasons always occur each year. Either two or three eclipses happen each eclipse season. During the eclipse season, the inclination of the Moon's orbit is low, hence the Sun, Moon, and Earth become aligned straight enough (in syzygy) for an eclipse to occur.

The type of each solar eclipse (whether total or annular, as seen from the sublunar point) depends on the apparent sizes of the Sun and Moon, which are functions of the distances of Earth from the Sun and of the Moon from Earth, respectively, as seen from Earth's surface. These distances vary because both the Earth and the Moon have elliptic orbits.

If the Earth had a perfectly circular orbit centered around the Sun, and the Moon's orbit was also perfectly circular and centered around the Earth, and both orbits were coplanar (on the same plane) with each other, then two eclipses would happen every lunar month (29.53 days). A lunar eclipse would occur at every full moon, a solar eclipse every new moon, and all solar eclipses would be the same type.

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An eclipse season is the only time when the Sun (from the perspective of the Earth) is close enough to one of the Moon's nodes to allow an eclipse to occur. During the season, whenever there is a full moon a lunar eclipse will occur and whenever there is a new moon a solar eclipse will occur. If the Sun is close enough to a node, then a total eclipse will occur. Each season lasts from 31 to 37 days, and seasons recur about every 6 months. At least two (one solar and one lunar, in any order), and at most three eclipses (solar, lunar, then solar again, or vice versa), will occur during every eclipse season. This is because it is about 15 days (a fortnight) between full moon and new moon and vice versa. If there is an eclipse at the very beginning of the season, then there is enough time (30 days) for two more eclipses.

In other words, because the eclipse season (34 days long on average) is longer than the synodic month (one lunation, or the time for the Moon to return to a particular phase and about 29.5 days), the Moon will be new or full at least two, and up to three, times during the season. Eclipse seasons occur slightly shy of six months apart (successively occurring every 173.31 days - half of an eclipse year), the time it takes the Sun to travel from one node to the next along the ecliptic. If the last eclipse of an eclipse season occurs at the very beginning of a calendar year, it is possible for a total of seven eclipses to occur since there is still time before the end of the calendar year for two full eclipse seasons, each having up to three eclipses.[1][2][3]

Examples: Part 1 out of 3Edit

Visual sequence of two particular eclipse seasonsEdit

In each sequence below, each eclipse is separated by a fortnight. The first and last eclipse in each sequence is separated by one synodic month. See also Eclipse cycles.

Eclipse season of May/June 2002
May 26th
Descending Node (Full Moon)
June 10th
Ascending Node (New Moon)
June 24th
Descending Node (Full Moon)
     
Penumbral lunar eclipse
Lunar saros 111
Annular solar eclipse
Solar saros 137
Penumbral lunar eclipse
Lunar saros 149
Eclipse season of June/July 2011
June 1st
Descending Node (New Moon)
June 15th
Ascending Node (Full Moon)
July 1st
Descending Node (New Moon)
     
Partial solar eclipse
Solar saros 118
Total lunar eclipse
Lunar saros 130
Partial solar eclipse
Solar saros 156

(The two eclipse seasons above share similarities (lunar or solar centrality and gamma of each eclipse in the same column) because they are a half saros apart.)[4]

Eleven-year chart of eclipses (2005-2015) demonstrating seasonsEdit

Date Type (phase) Time of season Saros series next eclipse will occur...
April 8, 2005 solar (new) beginning Solar Saros 129 (51 of 80) next full moon
April 24, 2005 lunar (full) end Lunar Saros 141 (23 of 72) next eclipse season
... no eclipses for about 5 and a half months...
October 3, 2005 solar (new) beginning Solar Saros 134 (43 of 71) next full moon
October 17, 2005 lunar (full) end Lunar Saros 146 (10 of 72) next eclipse season
... no eclipses for about 5 months...
March 14, 2006 lunar (full) beginning Lunar Saros 113 (63 of 71) next new moon
March 29, 2006 solar (new) end Solar Saros 139 (29 of 71) next eclipse season
... no eclipses for about 5 and a half months...
September 7, 2006 lunar (full) beginning Lunar Saros 118 (51 of 73) next new moon
September 22, 2006 solar (new) end Solar Saros 144 (16 of 70) next eclipse season
... no eclipses for about 5 and a half months...
March 3, 2007 lunar (full) beginning Lunar Saros 123 (52 of 72) next new moon
March 19, 2007 solar (new) end Solar Saros 149 (20 of 71) next eclipse season
... no eclipses for about 5 and a half months...
August 28, 2007 lunar (full) beginning Lunar Saros 128 (40 of 71) next new moon
September 11, 2007 solar (new) end Solar Saros 154 (6 of 71) next eclipse season
... no eclipses for about 5 months...
February 7, 2008 solar (new) beginning Solar Saros 121 (60 of 71) next full moon
February 21, 2008 lunar (full) end Lunar Saros 133 (26 of 71) next eclipse season
... no eclipses for about 5 and a half months...
August 1, 2008 solar (new) beginning Solar Saros 126 (47 of 72) next full moon
August 16, 2008 lunar (full) end Lunar Saros 138 (28 of 82) next eclipse season
... no eclipses for about 5 and a half months...
January 26, 2009 solar (new) beginning Solar Saros 131 (50 of 70) next full moon
February 9, 2009 lunar (full) end Lunar Saros 143 (17 of 72) next eclipse season
... no eclipses for about 5 months...
July 7, 2009 lunar (full) beginning Lunar Saros 110 (71 of 72) next new moon
July 22, 2009 solar (new) middle Solar Saros 136 (37 of 71) next full moon
August 6, 2009 lunar (full) end Lunar Saros 148 (3 of 70) next eclipse season
... no eclipses for about 5 months...
December 31, 2009 lunar (full) beginning Lunar Saros 115 (57 of 72) next new moon
January 15, 2010 solar (new) end Solar Saros 141 (23 of 70) next eclipse season
... no eclipses for about 5 and a half months...
June 26, 2010 lunar (full) beginning Lunar Saros 120 (57 of 83) next new moon
July 11, 2010 solar (new) end Solar Saros 146 (27 of 76) next eclipse season
... no eclipses for about 5 and a half months...
December 21, 2010 lunar (full) beginning Lunar Saros 125 (48 of 72) next new moon
January 4, 2011 solar (new) end Solar Saros 151 (14 of 72) next eclipse season
... no eclipses for about 5 months...
June 1, 2011 solar (new) beginning Solar Saros 118 (68 of 72) next full moon
June 15, 2011 lunar (full) middle Lunar Saros 130 (34 of 71) next new moon
July 1, 2011 solar (new) end Solar Saros 156 (1 of 69) next eclipse season
... no eclipses for about 5 months...
November 25, 2011 solar (new) beginning Solar Saros 123 (53 of 70) next full moon
December 10, 2011 lunar (full) end Lunar Saros 135 (23 of 71) next eclipse season
... no eclipses for about 5 and a half months...
May 20, 2012 solar (new) beginning Solar Saros 128 (58 of 73) next full moon
June 4, 2012 lunar (full) end Lunar Saros 140 (24 of 77) next eclipse season
... no eclipses for about 5 and a half months...
November 13, 2012 solar (new) beginning Solar Saros 133 (45 of 72) next full moon
November 28, 2012 lunar (full) end Lunar Saros 145 (11 of 71) next eclipse season
... no eclipses for about 5 months...
April 25, 2013 lunar (full) beginning Lunar Saros 112 (65 of 72) next new moon
May 10, 2013 solar (new) middle Solar Saros 138 (31 of 70) next full moon
May 25, 2013 lunar (full) end Lunar Saros 150 (1 of 71) next eclipse season
... no eclipses for about 5 months...
October 18, 2013 lunar (full) beginning Lunar Saros 117 (52 of 71) next new moon
November 3, 2013 solar (new) end Solar Saros 143 (23 of 72) next eclipse season
... no eclipses for about 5 and a half months...
April 15, 2014 lunar (full) beginning Lunar Saros 122 (56 of 74) next new moon
April 29, 2014 solar (new) end Solar Saros 148 (21 of 75) next eclipse season
... no eclipses for about 5 and a half months...
October 8, 2014 lunar (full) beginning Lunar Saros 127 (42 of 72) next new moon
October 23, 2014 solar (new) end Solar Saros 153 (9 of 70) next eclipse season (spring of 2015)
... no eclipses for about 5 months...
March 20, 2015 solar (new) beginning Solar Saros 120 (61 of 71) next full moon
April 4, 2015 lunar (full) end Lunar Saros 132 (30 of 71) next eclipse season
... no eclipses for about 5 and a half months...
September 13, 2015 solar (new) beginning Solar Saros 125 (54 of 73) next full moon
September 28, 2015 lunar (full) end Lunar Saros 137 (26 of 78) next eclipse season

The partial lunar eclipse of August 7-8, 2017 was followed by the solar eclipse of August 21, 2017.

Examples: Part 2 out of 3Edit

Visual sequence of two particular eclipse seasonsEdit

In each sequence below, each eclipse is separated by a fortnight. The first and last eclipse in each sequence is separated by one synodic month. See also Eclipse cycles.

Eclipse season of July/August 2009
July 7th
Ascending Node (Full Moon)
July 22nd
Descending Node (New Moon)
August 6th
Ascending Node (Full Moon)
     
Penumbral lunar eclipse
Lunar saros 110
Total solar eclipse
Solar saros 136
Penumbral lunar eclipse
Lunar saros 148
Eclipse season of July/August 2018
July 13th
Ascending Node (New Moon)
July 27th
Descending Node (Full Moon)
August 11th
Ascending Node (New Moon)
     
Partial solar eclipse
Solar saros 117
Total lunar eclipse
Lunar saros 129
Partial solar eclipse
Solar saros 155

(The two eclipse seasons above share similarities (lunar or solar centrality and gamma of each eclipse in the same column) because they are a half saros apart.)[5]

Examples: Part 3 out of 3Edit

See alsoEdit

ReferencesEdit

  1. ^ Littmann, Mark; Fred Espenak; Ken Willcox (2008). Totality: Eclipses of the Sun. Oxford University Press. pp. 18–19. ISBN 0-19-953209-5.
  2. ^ Periodicity of Lunar and Solar Eclipses, Fred Espenak
  3. ^ Five Millennium Catalog of Lunar and Solar Eclipses: -1999 to +3000, Fred Espenak and Jean Meeus
  4. ^ A Catalogue of Eclipse Cycles, Robert Harry van Gent
  5. ^ A Catalogue of Eclipse Cycles, Robert Harry van Gent

External linksEdit