What's Up in the Night Sky

July 2019 - Vol. 23, No. 7

This Month's Night Sky - NOTE: The next paragraph describes the sky as it appears at 10 pm EST (11 pm EDT) near mid- month. The sky also looks this way at 11 pm EST (midnight EDT) during the beginning of the month and at 9 pm EST (10 pm EDT) by month's end.

Bright blue-white Vega (Lyra) shines high overhead as it "leads" the Summer Triangle across the night sky. The "Triangle" is the summer’s most prominent asterism and is made up of three stars: Vega, the brightest, Deneb (Cygnus) and Altair (Aquila). In the SW, Arcturus (Bootes) is dropping towards the horizon as Spica (Virgo) vanishes from sight below. Also look for Antares (Scorpius) low in the SW. The stars of constellations Scorpius and Sagittarius, embedded in the "Milky Way" (part of one of the spiral “arms” of our galaxy), are at their best this month. Look for another famous asterism, "the teapot" (Sagittarius). The "Great Square of Pegasus" asterism, now appears on the E horizon just before the onset of morning twilight. These are the stars of autumn that will take over when the northern summer wanes!

MERCURY in the evening sky this month, may be difficult to see from the northern hemisphere as it heads for inferior conjunction on the 21st. VENUS disappears in morning twilight sky and will be too close to the Sun to be seen until September as it heads towards superior conjunction next month. MARS low in the evening sky, will be occulted by the Moon on the 4th (visible from Asia.) JUPITER falling behind as Earth speeds away, will still dominate the night sky. SATURN also prominent in the evening sky reaches opposition on the 9th. URANUS visible in the early morning twilight sky, in the constellation of Aries. NEPTUNE rising after twilight ends, continues retrograde motion through the stars of Aquarius.

Review how to determine Angular Measurement.

Calendar of Events

NOTE: For those observers not in the ET zone, convert the calendar times to your zone's time by subtracting one hour for CT, two for MT and three for PT. Don't forget to adjust for Daylight Savings Time when necessary by subtracting one hour from your planisphere's time. Dawn and dusk times must also be corrected. See your local newspaper, TV news, or cable TV's Weather Channel for sunrise and sunset times or check with the U.S. Naval observatory. Unfortunately some of these events may occur during daylight hours in your area.

DATE	EVENT
02	Total Solar Eclipse over the South Pacific Ocean. The total duration at the mid-ocean position of greatest eclipse is 4 min. 33 sec., the path makes landfall near La Serena, Chile where observers should enjoy 2 min. 17 sec. of totality and plunges into the Atlantic Ocean at sunset S. of Buenos Aires, Argentina where the Sun will be only 1 degree above the horizon.
04	Mars 0.1 deg S. of Moon, occultation from Asia, Arabian Peninsula, and E. Tip of Africa and Micronesia. Mercury 3 deg S. of Moon. Moon in Beehive cluster (M-44). Earth at aphelion, closest to the Sun in orbit.
05	Moon at perigee.
07	Mercury at aphelion. Mercury 4 deg. S. of Mars.
09	Saturn at opposition. (17 UT)
13	Jupiter 2.0 deg S. of Moon.
16	Saturn 0.2 deg N. of Moon, occultation from Easter Island, central S. America, Melanesia and S. Polynesia. Pluto 0.04 deg N. of Moon, occultation from E. Africa, Madagascar, N. and W. Australia, W. Micronesia and S. Indonesia. (Need a large scope for this event!!) Partial lunar eclipse over the South Pacific, only the later stages will be visible from S. America.
18	Mars at greatest heliocentric latitude N.
19	Ceres stationary.
21	Moon at apogee. Mercury in inferior conjunction.
25	Uranus 5 deg N. of Moon.
28	S. Delta Aquariid meteors peak, this shower produces up to 20 meteors at its peak. The shower is active from July 12 to August 23 so you may see them throughout the month and perhaps with some of the Perseids, so be sure to note the direction shooting stars are coming from to be sure. The Aquariids do not have the yellowish color of the Perseids.
31	Mercury stationary.

Lunar Almanac for July 2019

Phases of the Moon	Phase and Date(s)	Best viewed before local midnight
	New 02, 31	Deep Space Objects
	1st. Qtr 09	Planets & Moon
	Full 16	Moon
	Last Qtr 24	Deep Space & Planets

Topic of the month: Corona Borealis

The summer night sky brings a small constellation to the northern sky, Corona Borealis, the northern crown. It has no first magnitude stars, in fact most members of this constellation are third magnitude stars but its distinct curved pattern was noted by many cultures. The Greeks called it the Crown of Ariadne, the crown that Bacchus gave to his wife Ariadne and placed it in the heavens after she died. The Australian aborigines called it a boomerang, the Greeks saw it as a laurel wreath. This small constellation of stars can be seen in the summer nights between the constellations of Boötes and Hercules. The Welsh called it "Caer Arianrhod," the Castle of the Silver Circle that was the heavenly home of Lady Arianrod.

The Shawnee Indians also had a special myth about Corona Borealis, they called the constellation "The Celestial Sisters". In this legend twelve beautiful maidens came down from the sky in a silver basket to dance and sing. One night they were seen by a mighty hunter named "White Hawk", who tried to capture the youngest and most beautiful of the maidens, but they leaped back into the basket, and were instantly carried up into the sky. The next night White Hawk returned to the spot disguised as a field mouse. As the maidens danced, he resumed his form and succeeded in catching the youngest maiden and took her home as his bride. They lived together and soon they had a son. The maiden was still a member of the sky people and she became homesick. One day she made a silver basket, and singing a magic chant returned to the sky. She is thought to be the brightest star in the crown, second magnitude star Alphecca, also known as Gemma. White Hawk and his son were so sad after she left that the sky people took pity on them a brought them into the sky as well. White Hawk is thought to be represented by the the bright star, Arcturus, in the nearby constellation of Boötes.

finder chart for Corona Borealis

The stars of Corona Borealis are readily visible to the naked eye at a dark site on a moonless night, however two members of the modern constellation are not often seen, but have an interesting history. They are variable stars. The first is T Coronae Borealis, also called "The Blaze Star. Normally, a star of 10th magnitude, the Blaze Star has shot up to a brightness that rivalled Gemma. Astronomers noted two occurrences, it reached 2.0 magnitude on May 12, 1866 and 3.0 magnitude on February 9, 1946. T Coronae Borealis is an aging red giant star approximately 2,000 light years away. The second star is R Coronae Borealis, a yellow supergiant star, that has been seen to fade by several magnitudes at irregular intervals. It normally shines around 6 magnitude but at irregular intervals (months or years) it may fade down to magnitude 14. It gradually returns to its normal brightness in a few months. This has earned the star its nickname of "Reverse Nova" or the "Fade-Out star." The star is considered to be a carbon star and it is thought that carbon builds up in the star's atmosphere, causing it to fade in brightness. The carbon gas is blown away eventually by the stellar wind or some other mechanism. The approximate position of these variable stars are noted on the finder chart as "R" and "T."

--See You Under the Stars!
Astra for Astra's Almanac