May 2018 Lunar Apogee Happens Sunday, May 6, During Eta Aquarids

Summary: May 2018 lunar apogee happens Sunday, May 6, during the Eta Aquarids, at the month's farthest Earth-moon center-to-center distance of 404,458 kilometers.

waning gibbous moon Sunday, May 6, at 00:00 UTC (Saturday, May 5, at 8 p.m. EDT), 35 minutes before May’s lunar apogee: Ernie Wright (USRA lead visualizer), John Keller (NASA GSFC scientist), Noah Petro (NASA GSFC scientist) and David Ladd (USRA producer), via NASA/Goddard Space Flight Center Scientific Visualization Studio

May 2018 lunar apogee happens Sunday, May 6, during the Eta Aquarid meteor shower, at the month's farthest Earth-moon center-to-center distance of 404,458 kilometers (251,318.55 miles), at 00:35 Coordinated Universal Time/Greenwich Mean Time (8:35 p.m. Eastern Daylight Time).

May 2018’s lunar apogee of 404,458 kilometers is 313 kilometers farther from Earth than April 2018’s apogee of 404,145 kilometers. April’s lunar apogee occurred Sunday, April 8, at 05:32 UTC/GMT (1:32 a.m. EDT).

April’s lunar apogee of 404,145 kilometers represents 2018’s minimum, or closest, apogee. The year’s maximum, or farthest, apogee happened Monday, Jan. 15, at 02:10 UTC/GMT (Sunday, Jan. 14, at 9:10 p.m. EST), at 406,461 kilometers.

May 2018’s lunar apogee of 404,458 kilometers is 858 kilometers closer to Earth than June 2018’s apogee of 405,316 kilometers. June logs lunar apogee Saturday, June 2, at 16:34 UTC/GMT (12:34 p.m. EDT).

The moon phase at May 2018’s lunar apogee is waning gibbous, with the lunar surface’s illumination at approximately 65 percent. Waning gibbous numbers sixth in the moon’s eight-phase cycle, as viewed by Earthlings. The waning gibbous phase follows the full phase’s complete surface illumination and transitions to the last quarter phase’s less-than-half surface illumination. A waning gibbous moon’s illumination appears as less than full but more than one-half of the lunar surface.

The year’s maximum, or farthest, apogee, in January, took place with a new moon, at the beginning of the eight-phase lunar cycle. April 2018’s lunar apogee happened during the moon’s last quarter phase. June 2018’s lunar apogee replicates May 2018’s waning gibbous phase.

May 2018’s apogeic waning gibbous moon shares the night sky with the Eta Aquarid meteor shower. The phase’s brightness, however, may interfere with viewing the meteor shower.

The Eta Aquarids annually shower the night sky from around April 19 to around May 28. Their peak viewing usually happens around May 5 or 6. The American Meteor Society places 2018’s peak night at Sunday, May 6, to Monday, May 7. The International Meteor Organization pegs Friday, May 4, to Saturday, May 5, as peak night. The Eta Aquarid shower exhibits a broad maximum, which means that good hourly rates are available for the week that centers on the peak night.

The Eta Aquarid meteor shower is one of two annual showers associated with Comet Halley. The Eta Aquarids occur as a spring shower in the Northern Hemisphere and as an autumn shower in the Southern Hemisphere. In mid- to late-October, the Orionids, the other Halley-induced meteor shower, appear as an autumn shower in the Northern Hemisphere and as a spring shower in the Southern Hemisphere.

The Eta Aquarids owe their name to their radiant, the apparent point of their origin in the sky. Their radiant lies near Eta Aquarii (η Aqr, η Aquarii) in Aquarius the Cup Bearer, or Water Carrier, constellation. Eta Aquarii also participates in Aquarius’s water jar asterism, or star pattern.

Aquarius’s current placement in the sky qualifies the Water Carrier as an equatorial constellation. Earth’s celestial equator, which abstractly projects outward from the terrestrial equator into outer space, passes through Aquarius and 14 other constellations. As an equatorial constellation, Aquarius reaches its upper culmination, or highest point from Earth’s perspective, in the tropics and subtropics.

Although the Eta Aquarid display is a global phenomenon, the meteor shower particularly favors the Southern Hemisphere. EarthSky Tonight’s lead writer, Bruce McClure, explains that the Southern Hemisphere’s later sunrises in May encourage Eta Aquarid visibility. In May, the Southern Hemisphere is experiencing autumn, whereas the Northern Hemisphere is undergoing spring’s earlier sunrises.

Later sunrises equate to later darkness for meteor visibility. Also, the Eta Aquarid radiant point climbs higher in the Southern Hemisphere’s later predawn skies than in the Northern Hemisphere’s mid-latitudes.

The takeaway for the May 2018 lunar apogee, happening Sunday, May 6, at 404,458 kilometers, is that the moon reaches its closest center-to-center distance from Earth during its waning gibbous phase, on a peak date for the annual Eta Aquarid meteor shower.

Eta Aquarid radiant in Aquarius’s water jar at 4 a.m. local time:
(left) oriented for Northern Hemisphere observers, as seen from Huntsville, Alabama;
(right) oriented for Southern Hemisphere observers, as seen from Brazil;
Marshall Space Flight Center, "First Observations of the 2013 Eta Aquarids," Watch the Skies, May 7, 2013: Watch the Skies, via NASA Blogs

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

waning gibbous moon Sunday, May 6, at 00:00 UTC (Saturday, May 5, at 8 p.m. EDT), 35 minutes before May’s lunar apogee: Ernie Wright (USRA lead visualizer), John Keller (NASA GSFC scientist), Noah Petro (NASA GSFC scientist) and David Ladd (USRA producer), via NASA/Goddard Space Flight Center Scientific Visualization Studio @ https://svs.gsfc.nasa.gov/4604

Eta Aquarid radiant in Aquarius’s water jar at 4 a.m. local time: (left) oriented for Northern Hemisphere observers, as seen from Huntsville, Alabama; (right) oriented for Southern Hemisphere observers, as seen from Brazil;
Marshall Space Flight Center, "First Observations of the 2013 Eta Aquarids," Watch the Skies, May 7, 2013: Watch the Skies, via NASA Blogs @ https://blogs.nasa.gov/Watch_the_Skies/tag/halleys-comet/

For further information:

Blaauw, Rhiannon. “First Observations of the 2013 Eta Aquarids.” NASA Blogs > Watch the Skies. May 7, 2013.
Available @ https://blogs.nasa.gov/Watch_the_Skies/tag/halleys-comet/

Espenak, Fred. “Moon at Perigee and Apogee: 2001 to 2100 Greenwich Mean Time.” Astro Pixels > Ephemeris > Moon.
Available @ http://www.astropixels.com/ephemeris/moon/moonperap2001.html

Espenak, Fred. “Phases of the Moon: 2001 to 2100 Universal Time.” Astro Pixels > Ephemeris > Moon.
Available @ http://www.astropixels.com/ephemeris/phasescat/phases2001.html

Kronk, Gary W. “Observing the Eta Aquarids.” Meteor Showers Online.
Available @ http://meteorshowersonline.com/eta_aquarids.html

Marriner, Derdriu. “Eta Aquarids: Spring Meteor Showers Gifted to Earth From Comet Halley.” Earth and Space News. Tuesday, May 5, 2015.
Available @ https://earth-and-space-news.blogspot.com/2015/05/eta-aquarids-spring-meteor-showers.html

McClure, Bruce. “Why More Eta Aquariid Meteors in Southern Hemisphere?” EarthSky > Space. May 3, 2017.
Available @ http://earthsky.org/space/why-more-eta-aquarid-meteors-in-southern-hemisphere

“Moon Phases May 2018.” Calendar-12.com > Moon Calendar > 2018.
Available @ https://www.calendar-12.com/moon_calendar/2018/may