Science 101: What exactly is a Supermoon?

Jace Amodo
PUBLISHED December 4, 2017 04:57 pm | UPDATED January 31, 2018 10:38 am
Illustration by Mark Renacido/Inside Manila

(Inside Manila) A supermoon happens when a full moon coincides with perigee—the point in the orbit of the moon at which it is closest to Earth. It is the opposite of micromoon which happens when a full or a new moon occurs close to the moon’s apogee—the point in the moon’s orbit farthest to Earth.

Supermoons, technically termed “perigee-syzygy of the Earth-Moon-Sun system,” can vary by time zone. According to, a Super Full Moon will be observed on December 3 until 4:46 p.m. on December 4. You wouldn’t wanna miss that as it is the last supermoon of the year 2017.

Today, we list some things you might not know about this sky event.

Bigger than usual                   

Well, obviously. Since a supermoon is closer to Earth, it appears approximately 14% bigger than a micromoon.

In addition, the illuminated area looks 30% brighter, which means a brighter moon and a brighter world.

Universal Rules

Universal rules as to how close the Moon must be to the Earth to qualify as a supermoon are still quite unclear, but uses the following definitions:

Supermoon: A Full Moon or New Moon that occurs when the center of the Moon is less than 360,000 kilometers from the center of Earth.

Micromoon: A Full or New Moon that takes place when the center of the Moon is farther than 405,000 kilometers from the center of Earth.

Effect on Tides

We all know that moon phases are connected to the tide. The combined effect of the Sun and Moon on Earth’s oceans pull the ocean’s water in the same direction.

During a New Moon or a Full Moon, the tide is generally at its greatest. A Super Full Moon or Super New Moon hence intensifies it more, causing tidal differences of about inches at most.

Micromoons lead to around five cm or two inches larger variation than regular spring tides, called perigean spring tides. The tidal range is smallest during the 2 Quarter Moons, known as neap tides.

Natural Disaster Trigger

The theory is that the Moon’s association with both oceanic and crustal tides may lead to an amplified risk of geological hazards such as earthquakes and volcanic eruptions. However, supermoon occurrences are hardly linked to natural disasters, as proven by myriad studies by scientists.

NASA said it best: Lunar tides happen every day so the Moon being at its closest and at Full Moon should barely affect our planet’s internal energy balance.



Meet the stars and the moon through Manila Street Astronomers’ FREE telescope viewings

When was the last time you saw the stars? Or actually took a minute or two to appreciate (and have the occasional existential crisis by) the night skies? Probably when you were at the beach, the mountains or the province.