What Is a Micromoon?

A Micromoon happens when there's a full Moon or a new Moon at the same time as the Moon's approach to its apogee – the point on its orbit farthest away from the Earth. It's also known as Micro Full Moon and Apogee Moon.

Illustration image — Micro Moon: A full or new moon at apogee

The Moon orbits the Earth in an elliptical path, which means one side of the path is closer to the Earth than the other.

The Farthest Point

The point closest to the Earth is called perigee, while the point farthest from the Earth is known as apogee. The average distance between these two points is 382,500 km or 237,700 miles.

When a full or new Moon is at apogee it's called a Micromoon, Minimoon or Apogee Moon. A full or new Moon at perigee is called a Supermoon

May Look Smaller

A Micromoon looks approximately 14% smaller than a Supermoon. Because it is further away, the illuminated area appears 30% smaller, so it might look a little less bright. In reality however, there is no difference in the actual size of the Moon whether it is a supermoon, a Micromoon or an ordinary full Moon.

Defining a Micromoon

There are no universal rules as to how far away the Moon must be to qualify as a Micromoon. timeanddate.com uses the following definition:

If a full moon is further away than 400,000 kilometers at apogee, it is listed as a Micromoon.
If a full moon is closer than 360,000 kilometers at perigee, it’s called a Super Full Moon.

Effects on Earth

The Moon’s gravitational pull affects tides on earth. When the Moon is closer to the Earth – perigee – the gravitational pull leads to high tides and a larger variation between high and low tides. On the other hand, when the Moon is at apogee, the lower gravitational pull leads to low tides and a smaller variation between high and low tides. This tidal effect is the same regardless of which phase the Moon is in.

Old folklore accounts suggest that full Moons and Micromoons affect human mental health and bring on natural disasters, like earth quakes, but no scientific evidence supports any such correlation.

Topics: Astronomy, Moon