The Sky This Week
U.S. Naval Observatory's Weekly Blog

The Flower Moon in eclipse.

by Geoff Chester, USNO Public Affairs
10 May 2022

The total lunar eclipse of 2019 January 21, imaged from Alexandria, Virginia
with an 80mm (3-inch) f/6 Antares Sentinel refractor, iOptron Cube Pro mount, and a Canon EOS Rebel SL2 DSLR

The Moon brightens the evening sky this week as she dives toward the southern reaches of the ecliptic.  Full Moon occurs on the 16th at 12:14 am Eastern Daylight Time.  May’s Full Moon is popularly called the Flower Moon due to the abundance of wildflowers in bloom during the month.  It is also known as the Grass Moon, Milk Moon, and Egg Moon.  Luna passes very close to the second-magnitude star Porrima in the constellation of Virgo on the evening of the 12th.  Use binoculars to look for the star.  On the following evening the Moon passes four degrees north of Virgo’s brightest star, Spica.  On the evening of the 16th look for Luna just to the north of the ruddy star Antares in the constellation Scorpius.

In addition to being a Full Moon, the Flower Moon will also be eclipsed by the Earth’s shadow in the first total lunar eclipse visible in the U.S. since 2019.  Most residents of the “lower 48”states will see the eclipse in its entirety except for residents of the Pacific coast, where the Moon will rise after the umbral phase begins.  Here in the eastern time zone the penumbral phase will begin at 9:30 pm on the evening of the 15th, but you probably won’t notice much of a change in Luna’s appearance until around fifteen to twenty minutes before the umbral phase begins at 10:27 pm.  The Moon becomes fully immersed in Earth’s shadow at 11:28 pm, with mid-eclipse occurring at 12:11 am on the 16th.  Luna exits totality at 12:54 am, then exits the umbra an hour later.  The Moon exits the penumbra at 2:52 am, bringing the eclipse to a close.  As with all total lunar eclipses, the Moon will take on a deep red tint during the umbral portion of the event.  Just how dark it will be is anybody’s guess.  Luna will pass through the southern portion of Earth’s shadow, and stratospheric aerosols from the January 15 explosive eruption of the Hunga volcano in Tonga may cause the shadow to be anomalously dark.  Enjoy this eclipse, as we won’t get a good view of another one until March 14, 2025.

The eclipse will occur just to the west of the rising stars of Scorpius, one of summer’s signature constellations.  As the Moon dims the surrounding sky you should have a good view of the constellation as it skirts the southern horizon.  The brightest star in Scorpius is Antares, a red-supergiant star analogous to Betelgeuse in Orion.  These stars are massive luminaries that have exhausted the supply of hydrogen in their cores and are fusing hydrogen into helium in an expanding shell around their cores.  This “shell-burning” phase results in the stars’ girth expanding to gigantic size.  If Antares occupied the Sun’s place in our solar system all of the planets out to Mars would be located inside it!  

Betelgeuse and Antares won’t last too much longer on the cosmic scale.  They will eventually become supernovae shining with the brilliance of a first-quarter Moon in our future skies.  Not only are they stars with a common evolutionary fate, they are also related in mythology.  Orion, the boastful Hunter, claimed that he could slay any animal on the Earth, angering Gaia, goddess of the Earth.  To spite Orion Gaia dispatched a scorpion to teach the brash demi-god a lesson.  The scorpion duly dispatched Orion with its venomous sting, and Zeus placed both combatants in the sky, but on opposite sides so that their paths would never cross again.
 
Apart from fleet Mercury’s quick appearance in the evening twilight sky over the past couple of weeks, the evening sky is once again bereft of planets.  All of the action still remains in the early morning sky, where you will find, from west to east, Saturn, Mars, Jupiter, and Venus.  Saturn is the first to rise, cresting the horizon at around 2:30 am local time.  Mars comes up an hour later, followed by the bright glimmers of Jupiter and Venus, brightest of them all.  The best time to see them is between 5:00 am and sunrise, low in the southeast.  Watch Mars close the gap with Jupiter this week.  The red planet will scoot south of Old Jove over Memorial day weekend.
 
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