An eclipse season is the period, roughly every six months, when

eclipse An eclipse is an astronomical event that occurs when an astronomical object or spacecraft is temporarily obscured, by passing into the shadow of another body or by having another body pass between it and the viewer. This alignment of three c ...

s occur. Eclipse seasons are the result of the axial parallelism of the Moon's tilted orbital plane ( tilted five degrees to the Earth's orbital plane), just as Earth's weather seasons are the result of the axial parallelism of Earth's tilted axis as it orbits around the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

. During the season, the "

lunar node A lunar node is either of the two orbital nodes of the Moon, that is, the two points at which the orbit of the Moon intersects the ecliptic. The ''ascending'' (or ''north'') node is where the Moon moves into the northern ecliptic hemisphere ...

s" – the line where the Moon's orbital plane intersects with the Earth's orbital plane – aligns with the Sun and Earth, such that a

solar eclipse A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby obscuring the view of the Sun from a small part of the Earth, totally or partially. Such an alignment occurs during an eclipse season, approximately every six mon ...

is formed during the

new moon In astronomy, the new moon is the first lunar phase, when the Moon and Sun have the same ecliptic longitude. At this phase, the lunar disk is not visible to the naked eye, except when it is silhouetted against the Sun during a solar ecl ...

phase and a

lunar eclipse A lunar eclipse occurs when the Moon moves into the Earth's shadow. Such alignment occurs during an eclipse season, approximately every six months, during the full moon phase, when the Moon's orbital plane is closest to the plane of the Ear ...

is formed during the

full moon The full moon is the lunar phase when the Moon appears fully illuminated from Earth's perspective. This occurs when Earth is located between the Sun and the Moon (when the ecliptic longitudes of the Sun and Moon differ by 180°). This mea ...

phase. Only two (or occasionally three) eclipse seasons occur during each year, and 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 Moon is at a low ecliptic latitude (less than around 1.5° north or south), hence the

, Moon, and

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's sur ...

become aligned straight enough (in syzygy) for an eclipse to occur. Eclipse seasons should occur 38 times within a saros period (6,585.3 days). 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 orbit In astrodynamics or celestial mechanics, an elliptic orbit or elliptical orbit is a Kepler orbit with an eccentricity of less than 1; this includes the special case of a circular orbit, with eccentricity equal to 0. In a stricter sense, i ...

s. If both orbits were

coplanar In geometry, a set of points in space are coplanar if there exists a geometric plane that contains them all. For example, three points are always coplanar, and if the points are distinct and non-collinear, the plane they determine is unique. How ...

(i.e. on the same plane) with each other, then two eclipses would happen every

lunar month In lunar calendars, a lunar month is the time between two successive syzygies of the same type: new moons or full moons. The precise definition varies, especially for the beginning of the month. Variations In Shona, Middle Eastern, and Eur ...

(29.53 days), assuming the Earth had a perfectly

circular orbit A circular orbit is an orbit with a fixed distance around the barycenter; that is, in the shape of a circle. Listed below is a circular orbit in astrodynamics or celestial mechanics under standard assumptions. Here the centripetal force is ...

centered around the Sun, and the Moon's orbit was also perfectly circular and centered around the Earth. A

would occur at every

, a

every

, and all solar eclipses would be the same type.

Details

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

to occur. During the season, whenever there is a full moon a

will occur and whenever there is a new moon a

will occur. If the Sun is close enough to a node, then a

total eclipse An eclipse is an astronomical event that occurs when an astronomical object or spacecraft is temporarily obscured, by passing into the shadow of another body or by having another body pass between it and the viewer. This alignment of three ce ...

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 A fortnight is a unit of time equal to 14 days (two weeks). The word derives from the Old English term , meaning "" (or "fourteen days," since the Anglo-Saxons counted by nights). Astronomy and tides In astronomy, a ''lunar fortnight'' is ha ...

) 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 In lunar calendars, a lunar month is the time between two successive syzygies of the same type: new moons or full moons. The precise definition varies, especially for the beginning of the month. Variations In Shona, Middle Eastern, and Euro ...

(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 A year or annus is the orbital period of a planetary body, for example, the Earth, moving in its orbit around the Sun. Due to the Earth's axial tilt, the course of a year sees the passing of the seasons, marked by change in weather, the hour ...

), the time it takes the Sun to travel from one node to the next along the

ecliptic The ecliptic or ecliptic plane is the orbital plane of the Earth around the Sun. From the perspective of an observer on Earth, the Sun's movement around the celestial sphere over the course of a year traces out a path along the ecliptic agains ...

. 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.Five Millennium Catalog of Lunar
an
Solar Eclipses: -1999 to +3000
Fred Espenak and Jean Meeus

Examples: Part 1 out of 4

Visual sequence of two particular eclipse seasons

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 cycle Eclipses may occur repeatedly, separated by certain intervals of time: these intervals are called eclipse cycles. The series of eclipses separated by a repeat of one of these intervals is called an eclipse series. Eclipse conditions Eclips ...

s''. (The two eclipse seasons above share similarities (

lunar Lunar most commonly means "of or relating to the Moon". Lunar may also refer to: Arts and entertainment * ''Lunar'' (series), a series of video games * "Lunar" (song), by David Guetta * "Lunar", a song by Priestess from the 2009 album ''Prior t ...

or solar centrality and

gamma Gamma (uppercase , lowercase ; ''gámma'') is the third letter of the Greek alphabet. In the system of Greek numerals it has a value of 3. In Ancient Greek, the letter gamma represented a voiced velar stop . In Modern Greek, this letter r ...

of each eclipse in the same column) because they are a half saros apart.)A Catalogue of Eclipse Cycles
Robert Harry van Gent

22-year chart of eclipses (1999–2020) demonstrating seasons

The penumbral lunar eclipse of November 29–30, 2020 was followed by the

solar eclipse of December 14, 2020 A total solar eclipse took place on Monday, December 14, 2020, when the Moon passed between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. Totality occurred in a narrow path across Earth's surfa ...

Examples: Part 2 out of 4

Visual sequence of two particular eclipse seasons

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 ''

s''. (The two eclipse seasons above share similarities (

or solar centrality and

of each eclipse in the same column) because they are a half saros apart.)

Examples: Part 3 out of 4

Visual sequence of two particular eclipse seasons

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 ''

s''. (The two eclipse seasons above share similarities (

or solar centrality and

of each eclipse in the same column) because they are a half saros apart.)

Examples: Part 4 out of 4

Visual sequence of two particular eclipse seasons

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 ''

s''. (The two eclipse seasons above share similarities (

or solar centrality and

of each eclipse in the same column) because they are a half saros apart.)

References

{{Reflist

External links

NASA Eclipse Web Site
UNL Astronomy

Season A season is a division of the year based on changes in weather, ecology, and the number of daylight hours in a given region. On Earth, seasons are the result of the axial parallelism of Earth's tilted orbit around the Sun. In temperate and ...

Moon Time in astronomy Units of time