Astronomy EssentialsHuman World

When is the next supermoon?

Supermoon as a large full moon, slightly smaller full moon, split moon with one side large and the other small.
Here’s a comparison between the December 3, 2017, full moon at perigee or supermoon (closest to Earth for the month) and the year’s farthest full moon in June 2017 at apogee (farthest from Earth for the month) by Muzamir Mazlan at Telok Kemang Observatory, Port Dickson, Malaysia. More photos of the December 2017 supermoon.

A supermoon is a new or full moon that closely coincides with perigee, the moon’s closest point to Earth in its monthly orbit.

The moon is full, or opposite Earth from the sun, once each month. It’s new, or more or less between the Earth and sun, once each month. And, every month, in its elliptical orbit around Earth, the moon comes closest to Earth, or to perigee. The moon naturally swings farthest away once each month, too; that point is called apogee. Each year, on a few occasions, the new or full moon coincides closely with perigee; that’s when we have a supermoon.

The original definition of supermoon was coined by astrologer Richard Nolle in 1979. It stated that a full moon or new moon is called a supermoon when it comes within 90% of its closest approach to Earth.

For 2022, EarthSky is adopting supermoon dates determined by astronomer Fred Espenak. His method takes into account changes in the moon’s orbit during each lunar cycle.

Supermoons for 2022

Here are the supermoons, both full and new moons, for 2022.

2022 full moon supermoons:
These values — date and moon’s distance — are from Fred Espenak’s full supermoon table.

May 16 362,127 km (225,015 miles)
June 14 357,658 km (222,238 miles)
July 13 357,418 km (222,089 miles)
August 12 361,409 km (224,569 miles)

Of these four supermoons, the one on July 13 is the closest supermoon for 2022; On that day, the full moon aligns with the lunar perigee – the moon’s closest point to Earth in its monthly orbit – that falls on the same day.

Of course, the closest and therefore the biggest full moon of the year will cause larger-than-usual perigean spring tides, which people living near the coast will surely experience.

2022 new moon supermoons:
Fred Espenak does not have a table for new moon supermoons. But we can figure that out from other tables on his website. Details about that are provided in the section below, but meanwhile, here are the new supermoon dates and the moon’s distance from Earth on those dates.

January 2 358,044 (222,478 miles)
February 1 364,505 (226,493 miles)
December 23 360,013 (223,702 miles)

How do you figure out when supermoons happen?

Astronomers like Fred Espenak use detailed calculations of the Sun-Earth-Moon orbital systems to predict the distances, velocities, and orientations of these bodies in the future.

But we can hitch a ride on the wealth of data he has already generated to see when supermoons will happen. Keep reading this section if you’re curious to know how we determined the dates for the 2022 new supermoons.

A supermoon is defined as a full moon or new moon that comes within 90% of its closest approach to Earth. That “within 90% of its closest approach” is called, in this context, the limiting distance.

A diagram to compare distances between apogee and perigee, to visualize “90% of closest approach.”

The moon’s orbit is elliptical, so the moon has a closest distance to Earth — perigee — and a farthest distance — apogee — during each orbit. However, each successive orbit is slightly different. That’s because the sun’s gravitational influence tweaks each orbit so perigee and apogee distances are slightly different from one lunar cycle to another. The mean perigee is 363,396 km (225,804 miles) and the mean apogee is 405,504 km (251,968 miles).

So, let’s get started ….

Step 1: What’s the limiting distance for the mean apogee and perigee? We’re going to use that value to narrow down some supermoons candidates.

Mean limiting distance =
mean apogee – 0.9 * (mean apogee – mean perigee) =
405504 – 0.9 * (405504 – 363396) =
367606.8 km

Step 2: Identify new supermoon candidates using Espenak’s lunar geocentric ephemeris table for 2022. New moons are flagged in the last column of that table as “NEW.” For each new moon, check its distance (fourth column) to see if it is less than the mean limiting distance from step 1.

There are three candidates.
Candidate 1: Jan 2 new moon at 18:35 UTC, distance 358,044 km
Candidate 2: Feb 1 new moon at 5:47 UTC, distance 364,505 km
Candidate 3: Dec 23 new moon att 10:18 UTC, distance 360,013 km

Step 3. Now, we need to determine the limiting distances for the orbits during those three new moons, using Espenak’s lunar apogee-perigee table. For each candidate, use the new moon’s date to find its orbit’s perigee and apogee, then use those values to determine that orbit’s limiting distance.
limiting distance = apogee – 0.9 * (apogee – perigee)

Values below are in kilometers.
Candidate 1: perigee 358,037; apogee 405,806; Limiting distance = 362,814
Candidate 2: perigee 362,250; apogee 404,897; Limiting distance = 366,515
Candidate 3: perigee 358,270; apogee 405,869; Limiting distance = 363,030

Step 4: Compare the distance of each new moon with its orbit’s limiting distance. If the new moon distance is less than the limiting distance, it qualifies as a supermoon. Here, all three new moons qualify as supermoons.

January 2: The new moon is at a distance of 358,044 km (222,478 miles) — that’s less than its orbit’s limiting distance of 362,814 km (225,442 miles).

February 1: The new moon is at a distance of 364,505 km (226,493 miles) — that’s less than its orbit’s limiting distance of 366,515 km (227,742 miles).

December 23: The new moon is at a distance of 360,013 km (223,702 miles)– that’s less than its orbit’s limiting distance of 363,030 km (225,576.384 miles).

Supermoon hype?

Some astronomers complain about the name supermoon. They like to call supermoons hype. But supermoons aren’t hype. They’re special. Many people now know and use the word supermoon. We notice even some diehards are starting to use it now. Such is the power of folklore.

Before we called them supermoons, we in astronomy called these moons perigean full moons, or perigean new moons. Perigee just means near Earth.

No doubt about it. Supermoon is a catchier term than perigean new moon or perigean full moon. That’s probably why the term supermoon has entered the popular culture. For example, Supermoon is the title track of Sophie Hunger’s 2015 album. It’s a nice song! Check it out.

The hype aspect of supermoons probably stems from an erroneous impression people had when the word supermoon came into popular usage … maybe a few decades ago? Some people mistakenly believed a full supermoon would look much, much bigger to the eye. It doesn’t. Full supermoons don’t look bigger to the eye than ordinary full moons, although experienced observers say they can detect a difference.

But supermoons do look brighter than ordinary full moons! The angular diameter of a supermoon is about 7% greater than that of the average-size full moon and 14% greater than the angular diameter of a micro-moon (year’s farthest and smallest full moon). Yet, a supermoon exceeds the area (disk size) and brightness of an average-size full moon by some 15%, and the micro-moon by some 30%. For a visual reference, the size difference between a supermoon and micro-moon is proportionally similar to that of a U.S. quarter versus a U.S. nickel.

So go outside on the night of a full supermoon, and – if you’re a regular observer of the moon – you’ll surely notice the supermoon is exceptionally bright!

Tides during supermoons

Earth’s oceans feel the extra pull of supermoons. All full moons (and new moons) combine with the sun to create larger-than-usual tides, called spring tides. But closer-than-average full moons (or closer-than-average new moons) – that is, supermoons – elevate the tides even more. These extra-high spring tides are wide-ranging. High tides climb up especially high, and, on the same day, low tides plunge especially low. Experts call these perigean spring tides, in honor of the moon’s nearness. If you live along an ocean coastline, watch for them! They typically follow the supermoon by a day or two.

Do extra-high supermoon tides cause flooding? Maybe yes, and maybe no. Flooding typically occurs when a strong weather system accompanies an especially high spring tide.

Diagram showing sun and moon lined up with ocean stretched toward moon.
Around each new moon (left) and full moon (right) – when the sun, Earth, and moon are located more or less on a line in space – the range between high and low tides is greatest. These are called spring tides. A supermoon – new or full moon at its closest to Earth – accentuates these tides. Image via physicalgeography.net.
Two diagrams: Perigee on sun side of earth (new) and perigee opposite the sun (full).
About 3 or 4 times a year, or more often, a new or full moon coincides with the moon’s closest point to Earth, or perigee. There’s usually only a small difference – typically a couple of inches (or centimeters) – between these “perigean spring tides” and normal tidal ranges. But, at these times, if a storm strikes along a coastline, flooding can occur. Image via NOAA.

How often do we have supermoons?

Often! But it also depends on your definition of supermoon.

Here’s a list of each year’s closest full supermoon perigees from 2010 to 2022 (from Espenak’s full supermoon table):

January 30, 2010 (356,607 km or 221,585 miles)

March 19, 2011 (356,580 km or 221,569 miles)

May 6, 2012 (356,954 km or 221,801 miles)

June 23, 2013 (356,991 km or 221,824 miles)

August 10, 2014 (356,898 km or 221,766 miles)

September 28, 2015 (356,878 km or 221,754 miles)

November 14, 2016 (356,523 km or 221,533 miles)

December 3, 2017 (357,987 km or 222,443 miles)

January 2, 2018 (356,604 km or 221,583 miles)

February 19, 2019 (356,846 km or 221,734 miles)

April 8, 2020 (357,035 km or 221,851 miles)

May 26, 2021 (357,462 km or 222,117 miles)

July 13, 2022 (357,418 km or 222,089 miles)

The recurring cycle of supermoons

The full moon supermoon series of 2022 will recur after 14 lunar months (14 returns to full moon). That’s because 14 returns to full moon almost exactly equal 15 returns to perigee, a period of about one year, one month, and 18 days.

The mean lunar month (full moon to full moon, or new moon to new moon) = 29.53059 days, whereas the mean anomalistic month (perigee to perigee, or apogee to apogee) = 27.55455 days. Hence:

14 lunar months (14 returns to full moon) x 29.53059 days = 413.428 days
15 anomalistic months (15 returns to lunar perigee) x 27.55455 days = 413.318 days

Given that supermoons recur in cycles of 413 days (about one year, one month and 18 days), we can can expect the full moon supermoons to come about one month and 18 days later next year, in 2023.

Silhouette of woman holding full moon in her hand.
View at EarthSky Community Photos. | Ana Paola Cavazos in Monterrey, México, captured this photo of the moon on April 26, 2021. She wrote: “The bright supermoon from yesterday shining on Monterrey’s night sky.” Thank you, Ana!

Bottom line: For 2022, the full moons of May, June, July and August are supermoons. New moon supermoons of 2022 will be the new moons of January, February, and December. The supermoon of July 13, 2022, is the closest and brightest full supermoon of the year.

Posted 
January 1, 2022
 in 
Astronomy Essentials

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