Super moon

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On the left an average full moon, on the right near the earth

Supermoon ( English super moon ) is an expression coined in 1979 by astrologer Richard Nolle for a full moon or new moon , which is located in or near the closest point ( perigee ) of its orbit around the earth. The case that is predominantly perceived by the public is the slightly larger and brighter full moon closest to the earth, which should be made clear to distinguish it from the super new moon with super full moon .

Nolle coined the term in connection with his thesis that when the moon is close to the earth - at full moon and at new moon - the probability of volcanic eruptions and earthquakes is greater than at greater distances from the earth. Even if the small difference in size (see Fig.) Is not recognizable when observing with the naked eye due to the lack of direct comparison with an average full moon, a super full moon is still a popular report in the daily media because of its apparent size and brightness, which at least refers to the "delightful and captivating image of a full moon in the sky ”draws attention.

The actual size difference is quite small, but the super full moon is often observed when the moon rises . Like all objects that are close to the horizon , it then appears larger than when it is far from the horizon . The same phenomenon is also evident at sunrise or sunset.

General

Fuzzy criterion

The minimum distance to earth ( Moon at or near (within 90% of) its closest approach to Earth in a given orbit ) formulated by Nolle is not particularly small at around 367,600 km. This results in at least four “super moons” per year, with rather inconspicuous media reports.

With a much narrower limit of, for example, 356,500 km - drawn arbitrarily like that of Nolle - there were only three “super full moons” in the 20th century and only four in the 21st century.

With a similar criterion, the following headline was possible: "You're lucky: soon the largest super moon since 1948 will shine in the sky". This affected the full moon in November 2016 (with about 356,520 km little more than 356,500 km), almost as close to the earth as the full moon in January 1948 (about 356,460 km), 68 years earlier.

Extreme values

Distribution of the terrestrial distances of the perigees (left) and the apogea (right) between −3000 and +3000 a:
The perigees show maxima at 357,000 km - the current short-term average - and at 369,000 km.

The quantities that determine the appearance of the full moon are:

  • the apparent diameter; it changes inversely proportional to the distance between the moon and the earth, which in turn is variable due to the elliptical orbit; Variation in the apparent diameter about ± 7%, based on the mean value
  • the apparent brightness ; its fluctuation follows the square of the diameter fluctuation: about ± 15%, based on the mean value.

The orbital ellipse of the moon around the earth is disturbed by both the sun and the planets . Because the influence of the planets is irregular, the above-mentioned Largest values ​​of the lunar orbit, however, rarely one. If only the regular influence of the sun is taken into account, the fluctuation values ​​are reduced to theoretically ± 6.5% in diameter or ± 13.4% in brightness, which would then be reached by every 14th full moon in a row (see below: relative frequency).

For a full moon with negative extreme values ​​- greatest distance from the earth, i.e. H. Passage of the apogee - there is no special name such as “sub full moon”.

No relation to science

The term super moon is not used in science in general and in scientific astronomy in particular. This is because there is no need for such a use, for example, with representations of the apparent moon diameter, the moon brightness or the tidal forces that depend on the moon phases . The changes that can be observed during a full moon or a new moon can be adequately reproduced scientifically without using a term such as “super moon”. What certain - apparently arbitrarily determined - distance range should be used as a basis would also remain unclear.

All other influences of a "super" full moon that concern astrology are referred to by science in the area of esotericism . This applies in particular to Nolle's thesis of the influence of the super moon on volcanic eruptions and earthquakes.

Relative frequency

Supermoons are full moons (filled dots) at a minimum distance from the earth.

With a super full moon , the moon reaches (approximately) the perigee at full moon, the point of its orbit closest to the earth. In the subsequent lunar orbit , these two conditions of the event are no longer given at the same time in one night. An anomalous month (average duration: 27.5546 days ) passes between two passages of the same orbit point (here: perigee), but a synodic month (average duration: 29.5306 days) between two identical moon phases (here: full moon ).

A similar super full moon only occurs again when whole multiples of these two periods are equal to one another. This is the case after around 14 synodic or around 15 anomalous months at the earliest, as can be seen from a rough calculation with the average values:

However, the actual date of the fourteenth subsequent full moon cannot be calculated with these average values, since the duration of individual lunations fluctuates considerably due to the orbital disturbances .

In this 14th cycle of full moons near perigee, u. a. also contain those few super full moons, where a near limit of 356,500 km is undershot.

See also

Web links

Commons : Super Full Moon  - Collection of images, videos and audio files
Commons : worldwide images and media from the 2016 supermoon  - collection of images, videos and audio files

References and comments

  1. ^ A b c Richard Nolle: Supermoon - What It Is, What It Means
  2. ↑ a b Discover Magazine: Kryptonite for the supermoon , “But I'll add that the Moon will actually be a bit closer than usual, and while you might not notice the size or brightness difference by eye, the full Moon is always a lovely and compelling sight in the sky. So I urge everyone to go out and take a look. "
  3. ↑ a b c AstroPixels ( Fred Espenak ): Full Moon at Perigee (Super Moon): 2001 to 2100
  4. ↑ a b c Earth Sky: Closest supermoon since 1948!
  5. ↑ AstroPixels (Fred Espenak): Ultimate Full Moon Perigees (Super Moons): 2001 to 2100
  6. ↑ watson.ch - Knowledge - Astronomy
  7. ^ Vienna Working Group for Astronomy: Supervollmond on November 14th? Not really great ...
  8. ↑ There are also specific forgeries ( telephoto lens photos, photomontages, etc.) in which the super moon is shown abnormally large; see Matt Novak: 86 Viral Images From 2014 That Were Totally Fake . On gizmodo.com.au, January 2, 2015, images 20, 43, 44, 61
  9. ↑ AstroPixels (Fred Espenak): Ultimate Full Moon Perigees (Super Moons): 2001 to 2100. astropixels.com ; see. the full moons marked with an m.