By Dr. S.A. Mohan Krishna, Amateur Astronomer

Tonight (Mar.21), Indians will be privileged to witness the spectacular, biggest, resplendent, and brightest full Moon as it will pass by Earth at a distance of 3,58,246 kms. This is known as lunar perigee and a normal lunar perigee averaging a distance of 357,492 kms happens once every orbital period. This event can be referred to as “Supermoon.” The term “Supermoon” was coined by astrologer Richard Nolle. He generally describes Supermoon as perigee-syzygy — 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 March, full Moon ushers in the third in a series of three full Moon Supermoons occurring on Jan.21, Feb.19 and Mar.21, 2019. In contrast, the year’s farthest full Moon on Sept.14, 2019, will reside at a distance of 4,06,248 km or 2,52,431 miles. The full Moons of January, February and March 2019 are regarded as Supermoons because of their relative nearness to Earth. The year’s closest full Moon on Feb.19, 2019, swings a whopping 49,402 km (30,697 miles) closer to Earth than does the year’s farthest full Moon (or micro-moon) on Sept.14, 2019. Hence, the diameter of the February full Moon is about 14 percent greater than that of the September full Moon. But the disk size and brightness of this February Supermoon exceed those of the September micro-moon by about 30 percent.

The Supermoons that occurred in 1955, 1974, 1992, 2005, 2011, 2016 and 2018 were amazing. 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.

The Earth has stored a tremendous amount of internal energy within its thin outer shell or crust, and the small differences in the tidal forces exerted by the Moon (and Sun) are not enough to fundamentally overcome the much larger forces within the planet due to convection and other aspects.

‘Supermoon’ is a situation when the Moon is slightly closer to Earth in its orbit than on average, and this effect is most noticeable when it occurs at the same time as a full Moon. So, the Moon may seem bigger although the difference in its distance from Earth is only a few percent at such times. It is called a Supermoon because this is a very noticeable alignment that at first glance would seem to have an effect. The ‘Super’ in Supermoon is really just the appearance of being closer, but unless we measure the Earth-Moon distance by laser range-finders, the LRO [Lunar Reconnaissance Orbiter] spacecraft in low lunar orbit and to watch the Earth-Moon distance over years, there is really no difference. The Supermoon really attests to the wonderful new wealth of data NASA’s LRO Mission has returned for the Moon.

Astronomers have estimated that the Supermoon will be around 14 percent brighter and 30 percent bigger than the average full Moon. Full Moons from the way we see it, vary in size because of the oval orbit of the Moon. It is an ellipse with one side (perigee) about 50,000 km closer to Earth than the other (apogee). Experts say the short distance difference isn’t enough to cause any earthquakes or tidal effects. Although, the Earth’s tides are expected to be particularly high and low when the Moon comes closest to our planet which is known as perigean tides. That’s when the moon exerts about 42 percent more tidal force than it will during its next cycle two weeks later.

To view this 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. But if we need to witness the similar type of Supermoon with almost the same distance, we may have to wait till 2026.

So, tonight (Mar.21) do not miss to witness this exciting astronomical spectacle and spread the grandeur and essence of Astronomy.