By Dr. S.A. Mohan Krishna, Observational Astronomer
On May 7, Indians will have an opportunity to witness the spectacular, resplendent, and last Supermoon of this year. This is known as lunar perigee and a normal lunar perigee averaging a distance of 362,479 kilometers happens once every orbital period. This event can be referred as “Supermoon.” The term “Supermoon” was coined by the astrologer Richard Nolle. He generally describes Supermoon as perigee-syzygy; that is a new or Full Moon (syzygy) which occurs with the Moon at or near (within 90%) its closest approach to Earth (perigee) in a given orbit. In short, Earth, Moon and Sun are all in a line, with Moon in its nearest approach to Earth.
This February, Full Moon ushered in the second in a series of four Full Moon Supermoon occurring on Feb.9 (362,479 km), Mar.9 (357,404 km), Apr.8 (357,035 km) and the final one will happen on May 7 (361,181 km) and three New Moon Supermoon on Sept.17, Oct.16 and Nov.15. All of these full moons are less than 363,000 km (225,000 miles) distant as measured from the centers of the Earth and Moon. In contrast, the previous year’s farthest full moon on Sept.14, 2019 resided at a distance of 406,248 km or 252,431 miles. The Full Moons of February, March, April and May of 2020 are regarded as Supermoons because of their relative nearness to Earth.
It is a scientific fact that when the Moon is at perigee there is more gravitational pull, creating higher tides or significant variations in high and low tides. In addition, the tidal effect of the Sun’s gravitational field increases the Moon’s orbital eccentricity when the orbit’s major axis is aligned with the Sun-Earth vector. The average tidal bulge closely follows the Moon in its orbit, and the Earth rotates under this tidal bulge in just over a day. However, the rotation drags the position of the tidal bulge ahead of the position directly under the Moon. Generally tidal forces contribute to ocean currents, which moderate global temperatures by transporting heat energy toward the poles. It has been suggested that in addition to other factors, harmonic beat variations in tidal forcing may contribute to climate changes.
From extreme coastal tides to severe storms to powerful earthquakes and volcanic eruptions, the entire natural world surges and spasms under the sway of the Supermoon alignment — within three days either way of the exact syzygy, as a general rule. The geocosmic risk raised by Supermoon alignments will pass with little notice in our immediate vicinity. A Supermoon is planetary in scale, being a special alignment of Earth, Sun and Moon. It’s likewise planetary in scope, in the sense that there’s no place on Earth not subject to the tidal force of the perigee-syzygy. The effects on Earth from a Supermoon are minor, and according to the most detailed studies by terrestrial seismologists and volcanologists, the combination of the Moon being at its closest to Earth in its orbit, and being in its ‘Full Moon’ configuration (relative to the Earth and Sun), should not affect the internal energy balance of the Earth since there are lunar tides every day.
To view this weekend’s Supermoon to best effect, look for it just after it rises or before it sets, when it is close to the horizon. There, you can catch a view of the moon behind buildings or trees, an effect which produces an optical illusion, making the moon seem even larger than it really is. We are even privileged to see this spectacle on May 7 of 2020 (Buddha Poornima). But if we need to witness the similar type of Supermoon with almost the same distance, we may have to wait till 2026. So, today, everyone be curious to witness this exiting astronomical spectacle and spread the grandeur and essence of Astronomy.