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The Sky This Week
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A Honey Moon, Apsides, and Mars Flies Through the Beehive
by Geoff Chester, USNO Public Affairs
22 June 2021
Amber Moon rising, imaged 2020 December 29 at Ocean City, Maryland
with a Canon EOS Rebel SL2 DSLR and 300mm lens
The Moon brightens the evening sky this week, wending her way through the southern reaches of the ecliptic as she waxes to Full Moon, which occurs on the 24th at 2:40 pm Eastern Daylight Time. June’s Full Moon is popularly known as the Strawberry Moon since this is the peak season for harvesting these sweet treats. Other names are the Green Corn Moon, Hatching Moon, Hot Moon, and Honey Moon. The latter name is not only associated with the month as the most popular one for weddings, it is also a good descriptor of the light amber hue that the Moon takes on as she courses through these southern declinations. Her light not only has more of Earth’s atmosphere to penetrate, that summer air is often hazy, further tinting the Moon’s glow. Luna begins the week just north of the red-tinted star Antares, the heart of Scorpius, the Scorpion. You will find her near the rising planets Saturn and Jupiter on the 26th, 27th, and 28th. Last Quarter occurs on July 1st at 5:11 pm EDT.
The year’s latest sunset for temperate northern latitudes occurs on June 28th, closing out the phenomena associated with the summer solstice. Here in Washington Old Sol slips below the western horizon at 8:38 pm EDT that evening, then begins to slowly set earlier on successive nights. Despite these latest evening sunsets, the total length of daylight is gradually decreasing, a trend that will continue for the next six months. For those of us who relish the dark night sky, this is also the time when we have to wait the longest to ply our trade. Evening astronomical twilight doesn’t end until 10:37 pm, which is almost past my bedtime!
Another annual phenomenon occurs on July 5th at 6:27 pm EDT. At that time the Earth will reach aphelion, its greatest distance from the Sun. At that moment we will be 152,100,514 kilometers (94,510,878 miles) from the “Day Star”. The interval between successive perihelions defines the “anomalistic year”, which is about 25 minutes longer than the “tropical year”, which the interval between successive vernal equinoxes. This causes the dates of these “apsides” to gradually slip later through the years. In the year 1800 Aphelion occurred on June 30th.
Late June evenings offer a transition from the springtime constellations to the rising stars of summer. By the end of evening twilight the bright springtime star Arcturus has passed the meridian and starts to heel to the west. The Big Dipper is prominent in the northwest, but it, too is diving westward as the night passes. Looking eastward, the rising stars of the Summer Triangle asterism are making their way toward the meridian. The brightest of these stars, and the highest of the trio, is Vega, lead star of the diminutive constellation of Lyra, the Harp, and fifth-brightest star in the sky. It is one of our nearest bright stellar neighbors, shining at a distance of 25 light-years. Another near neighbor is Altair, the southernmost star in the Triangle. It is the brightest star in Aquila, the Eagle, and it lies just under 17 light-years away. The final star in the asterism is Deneb, brightest star in Cygnus, the Swan. Although it appears on par with its two companions, it is not a nearby jaunt away. It is located at a staggering 2500 light-years distance! To appear as bright as it does in our sky it must shine with nearly 200,000 times the luminosity of our Sun.
Venus should now be easy to find in the west during fading evening twilight. She begins the last week of June near the stars Castor and Pollux, and draws a bead on the slower-moving planet Mars.
Mars opens the week nestled among the stars of the galactic star cluster known as the Praesepe or “The Beehive”. This cluster should be easy to spot in binoculars and is probably the most distinguishing feature of the star-poor constellation of Cancer, the Crab. Mars lies smack in the middle of the cluster on the evening of the 23rd. Once the red planet leaves Cancer he’s looking over his shoulder at the rapidly-approaching Venus.
Saturn and Jupiter are now rising before midnight and continue to make inroads into the evening sky. They are still best seen by night-owls and early risers, but by the end of July they will be well-placed for late evening observation. The pair entertain the Moon on the last few nights of June.
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