2021, June 18 – 19: Moon in Virgo

Astronomy, Sky Watching
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June 18 – 19, 2021:  The waxing moon is moving through Virgo.  On June 18, it is near Porrima.  The next evening, the moon is above Spica.

Chart Caption – 2021, June 18 – June 19: The moon is with the stars of Virgo.

by Jeffrey L. Hunt

Step outside an hour after sunset during the next few evenings.  The waxing moon, past the First Quarter moon phase, is in the south-southwest.  It is moving eastward in Virgo.  Last night, the moon was in the constellation near the second brightest star in this pattern, Zavijava, and below the tail of Leo.

During the next two evenings, the moon moves farther eastward and the phase grows from 61% illuminated to 72%.

As the moon’s phase continues to grow, it brightly illuminates the ground.  Even before this gibbous phase, the moon was casting shadows at night.

The effect occurring with the bright moon is similar to what we see on the moon when it displays crescent phases.  On the moon we see a dimly-lit nightscape in the lunar night.  Reflected sunlight from Earth’s oceans, land, and clouds gently illuminates the moon’s night portion.

When the moon is crescent in our sky, an observer on the moon would see a gibbous moon. 

With the gibbous moon in the sky from Earth, from the moon, Earth’s phase is crescent.  Earth is gently illuminated by moonshine.

During the next few evenings, here’s what to see.

June 18:  The gibbous moon, 61% illuminated, is in the south-southwestern sky.  It is 1.1° to the upper right of the star Porrima. In his 1944 publication about star names and their meanings, George Davis wrote the star is “the name of the Roman nymph or goddess of prophecy and child-birth, and one of the companions, or one of the ancient attributes, of Carmenta, the leader of Camenae.

Chart Caption – 2021, June 18: Through a binocular the moon is to the upper right of Porrima.

June 19: The moon is over 5° above Spica – “the ear of corn.” The star is the 10th brightest star visible from mid-northern latitudes. The star’s blue tint indicates that it is hotter than the sun.  At 250 light years away, the star shines with an intensity of over 3,600 suns. Of those ten brightest stars visible from the midlands, Spica is intrinsically the third brightest after Betelgeuse and Rigel.

In their book, The Friendly Stars, Martha Evans Martin and Donald Howard Menzel wrote poetically about the distant suns.  They wrote, “During the short evenings in June, Spica lies toward the southwest, where in August it sets about ten o’clock, in September about 8 o’clock, and in October about the same time the sun goes down.  It can be seen between sunset and mid-night in some part of the sky from the middle of February to the early part of October” (p. 25).

Composed in 1907 and revised afterwards, the book needs another updating, but the stellar connection it inspires is worth the read. Martin’s original composition is in the public domain. From an internet search, a book’s revision (with Menzel) is available from some resellers and part of it is on Google books.

Spica passes behind the sun on October 17 and then begins a quick climb into the morning sky. By early November it is low in the east-southeast sky before sunrise.

Step outside during the next few evenings to catch the moon with the stars of Virgo.

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