For September 2022, the moon is first quarter on September 3rd, just to the upper left of Antares in Scorpius. The Full Moon, the famed Harvest Moon, is on September 10th; it sits just to the right of brighter Jupiter, which comes to opposition on September 26th. The last quarter moon is on September 17th, and lies just above and to the left of red Mars, now getting brighter as the earth closes in on it. The autumnal equinox begins fall on September 22nd at 9:04 p.m. The thin waning crescent moon will lie just above bright Venus about 30 minutes before sunrise on September 24th, a last glimpse of both before they get lost in the sun’s glare. The new moon is on September 26th. The waxing crescent again passes Antares on September 30th, marking the synodic month, based on the moon’s position among the stars, as 27.3 days.
Mercury lies too close to the Sun for visibility from Earth this month, but will emerge into the dawn in October. But Venus says good bye; it passed Regulus in Leo in the dawn on September 4-6th, but will be behind the Sun by month’s end. But contrast the three superior planets are are well placed for telescopic observing. Mars rises about midnight, in the head of Taurus, and is striking now as gibbous in phase at 200X or more in good telescopes. It will be fully lit by opposition in December.
Jupiter reaches opposition on September 26thm and is striking with its four moons and racing stripes and Great Red Spot. Our planetary feature for the month is this fine shot of the huge moon Ganymede, just to the left of Jupiter on August 8th, casting its black shadow on the South Temperate belt of Jupiter. Look along the same belt toward the right limb, and you can also spot the round yellowish disk of Io, the innermost of the four Galilean moons. Their constant dance makes observing Jupiter a delight with even smaller scopes. Consider that within an hour, Io would revolve to the right, off the disk, before slower Ganymede even reached the left limb here. How quickly things change!
As noted last month, Saturn came to opposition in Capricornus, and is now well up in the SE sky. It rings are now tilted about ten degrees to our line of sight, and closing become edge on at its equinox in May 2025, almost invisible from earth for weeks.
To the northwest, we find the familiar Big Dipper getting lower each evening. Most know how to use the two pointers at the lower part of the bowl to find Polaris, our Pole Star, sitting about 30 degrees high all night in the northern sky.
From the Dipper’s handle, we "arc" SE to bright orange Arcturus, the brightest star of Spring, and still well up in the western twilight. Spike south to Spica, the hot blue star in Virgo. Note that Spica is now low in the SW, and by September’s end, will be lost in the Sun’s glare due to our annual revolution of the Sun making it appear to move one degree per day eastward.
To the south, Antares marks the heart of Scorpius. It appears reddish (its Greek name means rival of Ares or Mars to the Romans) because it is half as hot as our yellow Sun; it is bright because it is a bloated red supergiant, big enough to swallow up our solar system all the way out to Saturn’s orbit! Near the tail of the Scorpion are two fine open clusters, faintly visible to the naked eye, and spectacular in binoculars. The clusters lie to the upper left of the bright double star that marks the stinger in the Scorpion’s tail. The brighter, M-7, is also known as Ptolemy’s Cluster, since he included it in his star catalog about 200 AD.
East of the Scorpion’s tail is the teapot shape of Sagittarius, which marks the heart of our Milky Way galaxy. Looking like a cloud of steam coming out of the teapot’s spout is the fine Lagoon Nebula, M-8, easily visible with the naked eye.
The brightest star of the northern hemisphere, Vega dominates the NE sky. Binoculars reveal the small star just to the NE of Vega, epsilon Lyrae, as a nice double. Larger telescopes at 150X reveal each of this pair is another close double, hence its nickname, "The Double Double". This is fine sight under steady seeing conditions over 150X with scopes 4" or larger. Between the two bottom stars; the Ring Nebula, marked "M-57" on the Skymap, is a ring of gas and dust expelled by a dying red giant star while its core collapsed to a white dwarf. A similar fate is expected for our own sun in perhaps five billion more years.
To the northeast of Vega is Deneb, the brightest star of Cygnus the Swan. It was just NW of it that I discovered the brightest nova of my lifetime, Nova Cygni, on August 27, 1975. Here a shell of hydrogen around a white dwarf exploded suddenly, becoming a record (for a nova, at least) 20 million times brighter in a matter of hours. It went from not visible in any telescope to the sixth brightest star in the summer sky in less than a day, and I was looking at the right place and time to catch it still on the rise. But the total amount of expel gases was much less than in the Ring Nebula, and it faded below naked eye visibility in only two weeks. Fun while it lasted! Typically several nova outbursts are found every year in our Galaxy, and they do often recur, for neither star in the close binary system was destroyed, and the mass transfer can resume soon.
A much grander supernova explosion about 20,000 year ago created the famed Cygnus Loop, near the SE wing of the Swan, epsilon Cygni. It spans about three degrees across, or six times the full moon’s diameter, but needs a dark clear sky and a wide field 4" or larger telescope to see the faint loop. The supernova that created it was probably brighter than even Venus when our distant ancestors spotted it, about the time they first reached the New World. Did any of them portray it on a cave roof? It was probably visible for years to their naked eyes, for much more material was blown outward by the collapse of this massive star’s core, and today the Loop has swelled to over 100 light years across, and is estimated to lie about 2,400 light years distant.
At the other end of the "northern Cross" that makes up the body of Cygnus is Albireo, the finest and most colorful double star in the sky. Its orange and blue members (I call them the "Gator Stars") are well resolved at 20X by any small scope. To the south is Altair, the brightest star of Aquila the Eagle, the third member of the three bright stars that make the Summer Triangle so obvious in the NE these clear September evenings. Binoculars should be taken to the deep sky gazes to sweep the rich portion of the Galaxy now best placed overhead in this area.
To the east, the Square of Pegasus rises. The long axis of the square points to the SW to Saturn in the tail of Capricornus. The two easternmost stars in the square point south to even brighter Jupiter, rising due east in Pisces. Planet observing season has arrived.
