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How often are there 3 eclipses in a month?


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How often are there 3 eclipses in a month?

Seven people on green field with trees in background and solar eclipse above.

People watch a partial eclipse in Belfast, Northern Ireland, on March 20, 2015.

 

Source

 

In 2020, we’ll have three eclipses in one lunar month – the period of time between successive new moons or full moons – in June and July 2020. This time period during which eclipses are possible

 

is also called an eclipse season. We won’t have three eclipses in one eclipse season again until the year 2029.

 

    The year 2020:

 

    June 5, 2020: Penumbral lunar eclipse


    June 21, 2020: Annular solar eclipse

 

 

 

The last time we actually had three eclipses in the span of one lunar month (the time period between successive new moons or full moons) was in the year 2018. It started with the Friday the 13th

 

supermoon solar eclipse on July 13, 2018, and concluded with the solar eclipse of August 11, 2018:

 

    July 13, 2018: Partial solar eclipse


    July 27, 2018: Total lunar eclipse


    August 11, 2018: Partial solar eclipse

 

So how often do we get three eclipses in one month? Let the investigation begin …

 

Large yellow-orange circle with black curved bite out of one side.

Partial solar eclipse photo by Fred Espenak.

 

Three eclipses in one calendar month. Every calendar year has at

 

least four eclipses – two solar and two lunar. More rarely, we have

 

five, six or even seven eclipses in a single year. But four eclipses per

 

calendar year is the most common number. A solar eclipse always

 

comes within approximately two weeks of a lunar eclipse, and

 

usually in a single pair (one solar and one lunar). Then, generally,

 

another pair of eclipses (one solar and one lunar) comes some six months later.

According to NASA eclipse expert Fred Espenak, three eclipses fall

 

in the same calendar month only 12 times during the five-century

 

span from 1801-2300. Six times there are two solar eclipses and

 

one lunar eclipse in one calendar month. Six times there are two

 

penumbral lunar eclipses and a total (or annular) solar eclipse in

 

one calendar month.

 

The last time we had three eclipses in a calendar month was in July

 

2000, when two partial solar eclipses bracketed a total lunar

 

eclipse:

July 1, 2000: Partial solar eclipse


July 16, 2000: Total lunar eclipse


July 31, 2000: Partial solar eclipse

(We wish to state parenthetically that these three eclipses

 

happened exactly one Saros period – or exactly 223 lunar months –

 

before the eclipses of July 13, 27, and August 11, 2018.)

 

Previous to July 2000, the last time three eclipses took place in one

 

calendar month was in March 1904, when two penumbral lunar

 

eclipses bracketed an annular solar eclipse.

March 2, 1904: Penumbral lunar eclipse


March 17, 1904: Annular solar eclipse


March 31, 1904: Penumbral lunar eclipse

 

After July 2000, three eclipses will next occur within one calendar

 

month in December 2206:

December 01, 2206: Partial solar eclipse


December 16, 2206: Total lunar eclipse


December 30, 2206: Partial solar eclipse

Full moon, dark red in color.

 

Three eclipses in one lunar month. Some might argue that the

 

calendar month is an artificial constraint. It might be more

 

appropriate to use a lunar (or synodic) month, which is a natural

 

unit of time. A lunar month refers to the time period between

 

successive new moons, or successive full moons.

 

Although it is rare for three eclipses to happen in the same

 

calendar month, it’s not that uncommon for three eclipses to

 

occur in one lunar month. In fact, from the years 2000-2050, the

 

three-eclipses-in-one-month phenomenon takes place a total of

 

fourteen times. Six times, the lunar month features two solar

 

eclipses and one lunar eclipse (2000, 2011, 2018, 2029, 2036 and

 

2047). Eight times, the lunar month presents two lunar eclipses

 

and one solar eclipse (2002, 2009, 2013, 2020, 2027, 2031, 2038

 

and 2049).

 

Lunar month of 3 eclipses means 7 eclipses in one year’s time

 

Three eclipses last took place in one lunar month in the year

 

2018:

    July 13, 2018: Partial solar eclipse


    July 27, 2018: Total lunar eclipse


    August 11, 2018: Partial solar eclipse

 

Previous to 2018, three eclipses last took place in one lunar

 

month in 2013:

 

    April 25, 2013: Partial lunar eclipse


    May 10, 2013: Annular solar eclipse


    May 25, 2013: Penumbral lunar eclipse

 

After 2018, three eclipses in one lunar month will next occur in

 

2020:

    June 5, 2020: Penumbral lunar eclipse


    June 21, 2020: Annular solar eclipse


    July 05, 2020: Penumbral lunar eclipse

 

Sources:


Catalog of lunar eclipses 2001-2100

 

Catalog of solar eclipses 2001-2100

 

Bottom line: In one calendar month, three eclipses are rare. But

 

in one lunar month, three eclipses are more common. From

 

2000-2050, it happens 14 times.

 

Is it possible to have only two full moons in a single season?

Total lunar eclipse photo by Fred Espenak.

 

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