What's Up in the Night Sky

August 2023 - Vol. 27, No. 8

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). Scorpius and the bright star Antares occupy the southern sky. Look for another famous asterism, "the teapot" (Sagittarius). 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.

MERCURY presents the best apparition for the southern hemisphere this year. VENUS disappears from the northern sunset sky, moving toward inferior conjunction on the 13th. Afterwards, Venus returns to the morning sky. MARS at +1.8 magnitude will be difficult to see as the end of the 2022-2023 opposition draws to a close. JUPITER rises around midnight as the month opens and appears in the evening sky. SATURN in Aquarius, will be at opposition on the 27th. URANUS rises around midnight, reaching its first stationary point on August 27th. NEPTUNE rises in the evening sky.

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
01	August's full moon is often called the "Sturgeon Moon" because it is the time of year that when this fish was easiest to catch in the Great Lakes and other lakes in North America. It is the first of two full moons in August.
02	Moon at perigee, expect large tides.
03	Saturn 2.0 deg. N. of Moon.
04	Neptune 1.5 deg. N. of Moon.
07	Venus at aphelion.
08	Jupiter 3 deg. S. of Moon.
09	Uranus 3.0 deg. S. of Moon. Moon 1.4 deg. S. of the Pleiades (M-45).
10	Mercury at aphelion Mercury at greatest elongation E (27 deg.)
13	Perseid meteor shower This shower is caused by dust ejected from Comet 109/Swift-Tuttle as it crossed Earth's orbit for thousands of years. The atmosphere encounters these particles at about 37 miles/second causing the streaks of light we enjoy every August. This year's shower should be very good as the Moon is 3 days away from new and will rise well after midnight about 8 percent illuminated. The peak of the shower is at 8 UT so the night of August 12-13 may be the best night to plan for observing the meteors. Venus at inferior conjunction. Pollux, Alpha Geminorum 1.7 deg. N of the Moon.
16	Moon at apogee.
18	The asteroid Pallas is 1.1 deg. S. of the Moon, occultation from extreme N. Canada, N. Greenland, Svalbard, central Russia, Mongolia, and most of China. Mars 2 deg. S. of Moon.
23	Mercury stationary.
25	Antares, Alpha Scorpii, 1.1 deg. S of the Moon, occultation from southern half of Canada, most of U.S.A., northern Mexico.
27	Saturn at opposition.
29	Uranus stationary.
30	The second full moon in August is considered to be blue moon. On this day the Moon is also at perigee and will be the largest full moon in 2023. The moon will not actually be blue, but it should seem a bit larger. Venus at greatest heliocentric lat. S. Saturn 2 deg. N. of Moon
31	Mercury at greatest heliocentric lat. S.

Lunar Almanac for August 2023

Phases of the Moon	Phase and Date(s)	Best viewed before local midnight
	New 16	Deep Space Objects
	1st. Qtr 24	Planets & Moon
	Full 01, 30	Moon
	Last Qtr 08	Deep Space & Planets

Topic of the month: Ophiuchus, the Serpent Bearer

The Summer sky merits a good long look into Ophiuchus, the constellation of the serpent bearer. It is called this because it splits the constellation of Serpens into two parts. Owing to its lack of bright stars, (none over 2nd magnitude) and its unpronounceable name (O-fee-u-kus), this constellation may remain obscure to casual observers.

Ophiuchus is generally identified with Aesculapius, a mythological doctor. The staff of Aesculapius wrapped with serpents is a well-known medical symbol. A good deal of this constellation is on the ecliptic (more than Scorpius), and its field is resplendent with globular clusters, because it lies near the center of our galaxy.

Two fine globular clusters, visible in the same wide angle field, M-10 and M-12 are beautiful specimens. M-12 is closer, larger and looser than M-10. The other Messier globulars in Ophiuchus include M-14, M-19, M-62 and M-107, but these are not as spectacular as the first two.

Ophiuchus also contains some beautiful star clusters, notably NGC 6633 which contains about 65 stars of 7th magnitude, and IC 4665, a loose cluster of 7th magnitude stars that is quite nice in binoculars or a wide angle telescopic eyepiece.

Venus on May 8, 2023 — Ophiuchus the Serpent Bearer

Nor is Ophiuchus without double stars. Tau Ophiuchi is a close pair of stars, mag 5.3 and 6.0, that require at least 75 mm of aperture to separate. 36 Oph contains two orange dwarf stars shining at 5.3 magnitude. 70 Oph is more well known, once suspected of harboring planets. It is a color contrasting double with orange and yellow components that need 100 mm of aperture, high power and good seeing to separate. William Herschel proved that the two stars were orbiting a common center, providing proof that Newton's law of gravitation worked outside of the solar system

Ophiuchus also contains more than a few planetary nebulae, the best of these is probably NGC 6572, 10th magnitude. Perhaps the most celebrated of all objects in this fascinating constellation is Barnard's Star, the star with the highest proper motion of all known stars. Barnard's star does have at least one planet, it is a red dwarf and at 9.5 magnitude it can't be seen without a telescope.

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

The IAU Ophiuchus chart is courtesy of the International Astronomical Union and Sky & Telescope magazine (Roger Sinnott and Rick Fienberg) This file is licensed under the Creative Commons Attribution 3.0 Unported license. It has been modified for use on Astra's Stargate. The file is available at Wikimedia Commons with full license details.