AstroCal – October 2021
October looks to be an excellent month for planetary viewing. Just to make sure our lunar companion does not get short shrift, we will start this AstroCal with a little about the Hunter’s Moon which will take place on October 20. According to the Farmers’ Almanac, the convention of naming seasonal Moons in North America can be attributed to Native Americans. The October Moon is so called because the falling leaves and shortening days meant it was time to begin storing meat for the long winter ahead. When the Europeans arrived, they adopted many of the same names and added a few of their own carried with them from the old country. The Full Harvest Moon was natural for September and October as the fields were reaped and crops were gathered. The sight of foxes and other critters roaming the newly cleared fields gleaning the fallen grain and stalking the small animals attracted by these leftovers reinforced the idea of the Hunter’s Moon.
The October Full Moon is also known as the Blood Moon or the Sanguine Moon in other parts.
The Waning Crescent Moon left over from September’s lunar cycle will be visible in the east during the last hours before sunrise. The New Moon begins the October cycle on October 6, followed by the First Quarter on Oct 12, and the Last Quarter on October 28. Sorry, but this year there will be no Full Moon to help track those witches, goblins, and ghosts this Halloween.
Mercury disappeared in the glare of the Sun in mid-September but will re-emerge in the morning sky after passing inferior conjunction on October 9. The Winged Messenger will brighten from a magnitude of +1.0 on October 17 to -0.7 on October 25. Prime viewing for Mercury 40 minutes before sunrise between the E and ESE as it reaches its greatest elongation (the farthest distance out we observe the planet from Earth) 18 degrees west of the Sun.
As for the Cornucopia of planets we can observe this month (sorry, had to slip in one more harvest reference), let’s start with the star of the evening planets, Venus. The planet will be low to the SW horizon at the beginning of the month, the -4.3 magnitude will make it hard to miss (the lower the number, the brighter the object appears. The Full Moon, for example, shines at about -12.5). Venus will be very close to the star Delta Scorpii from Oct 7 – 10 and the young Crescent Moon will join the fun on October 9 about 40 minutes after sunset. Venus will be moving about 1 degree per day (about the width of your little finger when held at arm’s length) across the background stars so you will be able to follow as it moves past the heart of Scorpius, the Scorpion. Venus will pass over the bright red star Antares, also known as Alpha Scorpii as it is the brightest star in the group, around October 17. The redness of Antares led people to call it The Rival of Mars when the two similarly hued bodies were close together. Antares comes from ‘rival of Ares’, ‘Ares’ being the Greek form of Mars, the Roman God of War. Unfortunately, Mars is still in the constellation of Virgo, the Virgin at this time and the two will not be seen together this year. Interestingly, Scorpius is known throughout Polynesia as The Fishhook, yet the Hawaiian name for it (Lehua-kona) means ‘southern lehua blossom’.
Saturn and Jupiter have been traveling in retrograde motion as the Earth’s orbit passes them. Both will pause in this motion (around October 10 and 17, respectively) and then resume their normal march against the background stars. An hour after sunset, look to the southeast to find Jupiter located 25 degrees above the horizon in Capricornus, the Sea Goat (make the Texas Longhorns ‘hook ‘em horns’ sign with your hands – 25 degrees spans pinky to thumb). Saturn is located near the SSE at a similar distance above the horizon. Jupiter’s -2.6 mag will make it easy to find and the four Galilean Moons can be seen with binoculars or a small telescope. Saturn’s magnitude will be +0.5 and with a small scope, the Rings may be visible as they are tilted 19 degrees from the edge-on view. The width of the rings spans about 39 seconds of arc compared to the 44 seconds for the face of Jupiter.
Compiled by Ken Raisanen of WOAS-FM – information provided by Abrams Planetarium Sky Calendar, Michigan State University. More information and subscription information can be found on their website at http://abramsplanetarium.org/skycalendar/ or on Twitter at http://twitter.com/AbramsSkyNotes. Yearly subscriptions cost $12 and can be started anytime.
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