What's Up in the Night Sky

October 2023 - Vol. 27, No. 10

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.

Although the Summer Triangle is still visible in the W, the "Great Square of Pegasus" is now prominent high in the S. Far below, lonely Fomalhaut [FOE-ma-lot] of Piscis Austrinus still glitters near the S horizon. Between Pegasus and the N pole star, Polaris (Ursa Minor), find the familiar "W" shaped asterism of Cassiopeia. If you are fortunate to be viewing from a dark site, you will also see the constellations, Perseus and Auriga, with its bright star, Capella, embedded in a starry band stretching across the night sky from East to West. You are looking at the Milky Way, one of the spiral arms of our galaxy. In the East the constellations, Gemini, with its bright twin stars, Castor and Pollux, and Orion, with its distinctive hour glass asterism, rise above the eastern horizon. Now the Big Dipper (Ursa Major) dips low in the North.

MERCURY hovers low on the horizon before reaching superior conjunction on the 20th. VENUS in the morning sky this month, reaches greatest elongation on the 23rd. MARS too close to the Sun to be seen. Brilliant JUPITER shines at -2.9, dominating the night sky before next month's opposition. SATURN in Aquarius shines at .6 magnitude by month's end. URANUS is visible in a telescope most of the night. NEPTUNE visible in Pisces most of the night.

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	Jupiter 3 deg. S. of Moon. Uranus 3.0 deg. S. of Moon.
03	Moon 1.2 deg. S. of the Pleiades (M-45).
07	Pollux, Alpha Geminorum 1.4 deg. N of the Moon.
10	Moon at apogee. Venus 2 deg. S of Regulus. Venus 6 deg. S of Moon.
12	The Zodiacal Light or "false dawn" is visible in the E about 2 hours before sunrise. This pyramidal glow is caused by meteoroids, dust particles spawned by passing comets, etc., that have settled into the ecliptic plane (path followed by the Sun, Moon and planets), reflecting the Sun’s light before it rises here. This phenomenon will be visible until about October 26th as long as the Moon does not interfere.
14	Annular solar eclipse crossing the United States and Mexico and South America, truly the great American eclipse. Even though it is an annular eclipse, 99.6% of the sun's disk will be covered, making a fabulous Ring of Fire for those watching with proper solar protection. To see the Sun eclipsed in the center by the Moon, you must be located on the centerline. For more information go to the 2023 Annular Eclipse page of Astra's Eclipse Guide.
15	Mars 1.0 deg. N. of Moon but this conjunction won't be visible.
18	Antares, Alpha Scorpii, 0.8 deg. S of the Moon, occultation from Azores, E. Canary islands, most of Europe, most of N. Africa, and most of Middle East.
20	Mercury at superior conjunction.
22	Orionids meteor shower peak. This shower produces up to 20 meteors per hour. Meteors in this shower are generated by Halley's comet. The orbit of this periodic comet leaves a trail of dust particles on its way to the Sun. This trail of particles remains in this area of space until they encounter the Earth's orbit. This produces the annual shower.
23	Venus greatest elogation W. (46 deg.).
24	Saturn 3.0 deg. N. of Moon.
26	Moon at perigee. Neptune 1.5 deg. N. of Moon.
28	October's full moon is often called the "Hunter's Moon" because it is the time of year that meat is prepared for winter storage. (Every three years the Hunter's Moon is the Harvest Moon that occurred in September in 2023.) Partial lunar Eclipse visible from Europe, Africa and Asia.
29	Jupiter 3 deg. S. of Moon.
30	Uranus 3.0 deg. S. of Moon. Moon 1.1 deg. S. of the Pleiades (M-45).

Lunar Almanac for October 2023

Phases of the Moon	Phase and Date(s)	Best viewed before local midnight
	New 14	Deep Space Objects
	1st. Qtr 21	Planets & Moon
	Full 28	Moon
	Last Qtr 06	Deep Space & Planets

Topic of the month: The Charioteer, Auriga

Awash in the winter Milky Way, rising behind Perseus is the constellation of the charioteer, Auriga. The constellation of Auriga is completely over the horizon in the mid-fall when evening comes to the northern latitudes. For some unclear reason, the charioteer is depicted with goats under his arm perhaps from the time that the constellation was associated with the Good Shepard. Auriga features Capella, whose name means little she goat, the northernmost first magnitude star as seen from planet Earth. At 45 light years distant, this star was discovered to be a double by spectroscope just before the turn of the 20th century. Later observations revealed that Capella was actually a multiple star system with at least 4 components.

The constellation Auriga is usually identified as a pentagon, but the star in the southern tip is El Nath, the Beta star of the constellation Taurus and not "officially" recognized as part of Auriga. Near Capella, three stars form an elongated triangle. Eta and Zeta are known as "the kids," part of the triangle formed with Epsilon Aurigae. Eta Auriga (Almaaz, or "he-goat") is one of the most interesting stars in the night sky. It is an eclipsing binary star, containing two stars that revolve around a common center, every 9,883 days or 27 years. For two years, the eclipsing binary system dims from 3.0 to 3.8 magnitude as an unseen companion star hides the view of the primary for Earthbound viewers. The last time this happened was in 2009-2011 and the star was studied intensely by variable star observers. Still, a conclusive model has not been constructed that explains the complete system dynamics.The best theories will be tested again in 2036.

Other stars in the constellation have well-known proper names as well. Beta Auriga is known as Menkalinan, itself an eclipsing binary, shines around mag 1.92 to 2.01 about 10 deg. East of Capella. Perhaps best remembered in Auriga, are the fine star clusters M36, M37, and M38. M36 is the smallest, consisting of 60 stars. M37 is the largest containing about 150 stars and is about 20' in diameter. M38 contains perhaps 100 stars and also has a smaller and fainter cluster of stars nearby, NGC 1907.

A number of galactic clusters lie in this region of the Milky Way, including NGC 1664 containing 40, 10th magnitude stars. NGC 2281 consists of 30 stars arranged in a crescent shape. Auriga offers a wealth of star clusters as well as variables and doubles to intrigue amateurs. This constellation never disappears in the Sun from the northern hemisphere and can be seen at some time every night of the year.

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