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Lunar Perigee and Apogee

The Moon's orbit around Earth is elliptical. The point of the orbit closest to Earth is called perigee, while the point farthest from Earth is known as apogee.

Illustration indicating the difference between a Supermoon and a Micromoon's distance from Earth.

The difference between apogee and perigee.

The difference in Moon's Distance–from its center–to the center of Earth, at perigee and apogee.

timeanddate.com

Elliptical Orbit

The Moon's orbit around Earth is elliptical, with one side closer to Earth than the other.

As a result, the distance between the Moon and Earth varies throughout the month and the year. On average, the distance is about 382,900 kilometers (238,000 miles) from the Moon's center to the center of Earth.

The point on the Moon's orbit closest to Earth is called the perigee and the point farthest away is the apogee.

Supermoons & Micromoons

Illustrative comparison of a Supermoon and Micromoon.
A Supermoon versus a Micromoon.
A Full Moon looks bigger and brighter when it occurs around perigee and smaller and dimmer at apogee.

The Moon's phase and the date of its approach to its perigee or apogee are not synced. When a Full Moon or New Moon occurs close to the Moon's perigee, it is known as a Supermoon. On the other hand, when a Full Moon or New Moon occurs close to the Moon's apogee, it is known as a Micromoon.

The Moon passes through the 2 extreme points–or apsides–perigee and apogee about once a month. The time it takes for the Moon to travel from perigee to perigee, is called the anomalistic month, and takes around 27.55455 days.

This is not to be confused with the synodic month, which lasts a little longer, and is the time it takes the Moon to orbit once around Earth, from New Moon through all the Moon phases to the next New Moon.

Close to Earth

The Supermoon on November 14, 2016, was the closest a Full Moon has been to Earth since January 26, 1948. The next time a Full Moon is even closer to Earth will be on November 25, 2034 (dates based on UTC time).

Moonrise is the best time to view the Moon, weather permitting, of course. At this time, illusion mixes with reality to make a low-hanging Moon that looks unnaturally large when compared to foreground objects.

Lunar Libration

In addition to its counterclockwise orbit around Earth, the Moon rotates around its axis at a constant speed. Like all celestial objects with elliptical orbits, the Moon's speed varies on its path around the Earth. It speeds up when it is at its perigee and slows down when it is at the apogee. This means that at its perigee, the Moon's orbital speed is faster than its rotational speed.

When the Moon rocks slightly from north to south and wobbles a little from east to west, it is called lunar libration. This motion makes it possible, over time, to see up to 58% of the Moon’s surface from Earth, but only 50% at a time.

Tidal Effects

The Full Moon lighting up the ocean.
Moon's gravitational pull causes tides.
Moon's gravitational pull causes tides.
©bigstockphoto.com/duallogic

The tides on Earth are mostly generated by the Moon’s gravitational pull, in combination with the Sun. The tidal range, which is the difference between high and low tide, is greatest at Full and New Moon because the Sun and Moon are aligned on the same or opposite sides of Earth, and the oceans are affected by the combined gravitational pull of both the Sun and the Moon.

During Supermoons, the gravitational pull leads to even larger variation between high and low tides. It causes higher spring tides, known as perigean spring tides. This has nothing to do with the season spring, but rather it is a synonym for jump or leap.

The tidal range is smallest during the 2 Quarter Moons (Half Moons). These tides are known as neaps or neap tides, from Anglo-Saxon, meaning without the power.

Natural Disaster Trigger?

Although the Sun and the Moon’s alignment cause a small increase in tectonic activity, the effects of the Supermoon on Earth are minor. Many scientists have conducted studies and haven’t found anything significant that can link the Super Moon to natural disasters.

According to NASA, the combination of the Moon being at its closest and at Full Moon, should not affect the internal energy balance of the Earth since there are lunar tides every day.

Topics: Astronomy, Moon

Next Apogee

Jan 21, 2017 at 7:13 pm

Distance: 404,914 km / 251,602 mi

Next Perigee

Feb 6, 2017 at 9:02 am

Distance: 368,816 km / 229,172 mi

Apogees and Perigees in 2017

Times for Apogee/Perigee can vary by time zone. Dates are based on the local time in Washington DC. Change location

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The Moon

  1. What Is a Supermoon?
  2. The Moon Phases
  3. What Is a Micro Moon?
  4. Is a Blue Moon blue?
  5. The Moon's Orbit
  6. What Is a Black Moon?
  7. What Are Moonbows?
  8. Full Moon Names
  9. Taking pictures of the Moon

Moon index

Moon Distance

The Moon Phases

  1. The Lunar Month
  2. New Moon
  3. Waxing Crescent Moon
  4. First Quarter Moon
  5. Waxing Gibbous Moon
  6. Full Moon
  7. Waning Gibbous Moon
  8. Third Quarter Moon
  9. Waning Crescent Moon

Moon Phases

Moon Phases In Your City

Moonrise & Moonset Times

Eclipse Lookup

Weather Look-Up

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