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Summer's on the Doorstep

by Geoff Chester, USNO Public Affairs | 14 June 2023

by Geoff Chester, USNO Public Affairs | 14 June 2023

Messier 57, the Ring Nebula in Lyra, imaged 2022 July 4 from North Beach, Maryland
with an Explore Scientific AR102 10.2-cm (4-inch) f/6.5 refractor and a ZWO ASI183MC CMOS color imager

The Moon begins the week greeting early risers as a slender waning crescent, then climbs back into evening twilight skies as the week ends.  New Moon occurs on the 18th at 12:37 am Eastern Daylight Time.  Look for the waxing crescent Moon between the bright stars Castor and Pollux and the dazzling planet Venus on the evening of the 20th.  

This is the week when we experience the earliest sunrises of the year in the Northern Hemisphere.  Even though the summer solstice won’t arrive until next week, the earliest sunrise and latest sunset don’t occur on that day.  Here in Washington Old Sol crests the horizon at 5:42 am EDT.  The farther north you are located, the earlier your sunrise will be, while above the Arctic Circle the Sun never sets.  The latest sunsets occur near June 28th, when sunset occurs at 8:38 pm EDT in Washington.  In between lies the solstice, when we experience our longest length of day.  These seemingly discrepant dates come about due to the way that we now measure time, using atomic frequency standards to mimic the “Mean Sun”, once used to correct sundials that recorded time of the “Apparent Sun.  You can find a detailed explanation of this phenomenon on our Astronomical Applications Department website.

The June campaign for the citizen science program Globe at Night continues this week, running through the evening of the 18th.  As we mentioned last week, the target constellations are Boötes, the Herdsman, and Hercules.  If you would like to get a better view of these star patterns as well as many of the interesting sights that they present to amateur astronomers in the Washington, DC area, consider coming out to Sky Meadows State Park near Paris, Virginia on the evening of the 17th.  This park, set on the eastern slope of the Blue Ridge Mountains, is the closest International Dark Sky Park to the nation’s capital.  Local amateurs will provide many telescopes, and will help you identify spring and summer constellations.  The Park has an entry fee, but the program itself is free.

Last week we looked in more detail at Boötes and Hercules.  This week we’ll stay up until early morning to welcome the signature stars of the summer sky.  The first thing that you will probably notice is that there are several bright stars climbing into the sky.  The most prominent of these are the stars that for the “Summer Triangle” asterism.  Vega, Altair, and Deneb are high in the eastern sky by local midnight.  Each star leads a separate constellation.  The brightest star, Vega, sits atop a small parallelogram that delineates Lyra, the Lyre of Orpheus.  Vega is the fifth-brightest star in the sky and gleams with an icy blue tint.  Altair, the southernmost apex of the Triangle, is the brightest star in Aquila, the Eagle, whose mythological task was to carry the thunderbolts of Zeus.  Deneb, the faintest of the Triangle’s stars, marks the tail of Cygnus, the Swan.  There are many myths associated with the Swan, ranging from one of Zeus’ many disguises when he visited the mortal world, to the transformed soul of Orpheus, the muse of poetry and song.  The name Deneb means “the tail”, and if you follow the line of stars that leads to the center of the Triangle you can trace out a reasonably swan-shaped stick figure.  In the middle of the Triangle you will see a third-magnitude star, Albireo, which is one of the finest double stars in the sky.  It is easily resolved in small telescopes, yielding bright gold and fainter blue components, which is why I like to call it the “Navy Double”! 

Each of these constellations hold a variety of interesting “deep sky” targets.  Lyra, the smallest constellation, holds two of the most popular objects on amateur observing lists.  The famous “Ring Nebula” may be found between the two stars that mark the southern short side of the parallelogram.  Just to the northeast of Vega, binoculars will show a pair of closely-spaced stars.  If you point a good 4-inch telescope at this pair, you will see that each component is itself a close binary pair.  Known as the “Double-double”, it is a good test for small-aperture instruments.

Venus is now beginning to lose ground on the advancing Sun.  She is also continuing her pursuit of ruddy Mars, but she won’t be able to catch the red planet before she starts her precipitous dive toward the horizon.  By the end of the month she will part ways with Mars and set at the end of evening twilight.

Mars spends the week keeping a few steps ahead of Venus as he moves from the constellation of Cancer, the Crab into Leo, the Lion.  Over the next few weeks he will draw a bead on the bright star Regulus, which he will pass close to in early July. 

Saturn now rises shortly before 1:00 am local time, holding court among the dim stars of Aquarius.  The ringed planet reaches the first stationary point in this year’s apparition on the 18th; he will begin retrograde motion back toward Capricornus after this time.

Jupiter rises at around 3:00 am and should be easy to spot in brightening morning twilight.  Look for him low in the southeastern sky at around 5:00 am. 


Commander, Naval Meteorology and Oceanography Command | 1100 Balch Blvd. | Stennis Space Center, Mississippi 39529

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