The Labor Day holiday summons the beginning of summer’s swan song. Can you hear it? More so, can you feel it? It is a soft song. A familiar melody, beautiful and yet melancholy. The Milky Way, the celestial river of life, the “place of spirits”, the connection between Earth and sky, life and life beyond, now flows in a different path. Outside your window at night the Milky Way runs almost directly north to south, dividing the sky east and west. The constellation Cygnus, the swan, (appropriately and fittingly) majestically gliding overhead on this galactic river heading south, sings her song. What do we hear? A change of season is afoot.
Mark the night of September 17th on your calendar for a stargazing event you won’t want to miss, a full Moon that is a partial lunar eclipse. And while you're outside, take a moment to greet our closest galactic neighbor with your naked eye, and then soar to the new heights of the “Great Square” directly overhead, on the back of the winged horse Pegasus.
A season of harvest, fulfillment, and gratitude. Straddling the season of growth with the season of harvest, our September night sky is rich, full of delightful objects to view and events to observe. Get out and look up any pleasant night this month. You’ll find the night air is still comfortable but it has the mere hint of wispy chill occasionally passing through.
Saturn at Opposition: and Perigee: September 8th
Saturn at opposition is a special event. Simply, “opposition” refers to the moments when there is alignment between the Sun, the Earth, and any object in our solar system and the Earth is the middle. Wait, there’s more! Saturn is achieving perigee that evening. Perigee is when an object in our solar system achieves its closest point to Earth as it orbits the Sun. So what’s the big deal? With Saturn on the other side of the Sun (opposition), as well as its closest point to Earth for the year in its elliptical orbit (perigee), you can expect Saturn to be brilliantly illuminated and thus prime for viewing. If you’ve never seen Saturn’s rings – or long to see them again - this is the night to try and do so. When Saturn lies opposite to the Sun in the sky, it rises at around the time the Sun sets, and sets in the west around the time the Sun rises in the east the next day. So Saturn is visible all night.
Look for bright dull brownish-green Saturn in the constellation Aquarius. The key is to look for a pin prick of light that isn’t twinkling. While you will see Saturn with your naked-eye, even a small telescope or binocular at low power will reveal much more. Don't miss your chance to see the sixth planet in our solar system, the Roman God of agriculture, up-close and personal.
Partial Lunar Eclipse: September 17th
Much is afoot the night of September 17th with a partial lunar eclipse being the marquee event for us stargazers in the northern hemisphere. To review, an eclipse involves a straight line, and a line is made up of a set of points which is extended in opposite directions. In an eclipse, those set points are the Sun, the Earth, and the Moon. As the Earth passes between the Sun and the Moon, the Earth casts its shadow on the Moon. But, since the Moon’s orbit is tipped around 5 degrees off-plane, in relation to the Earth and Sun, that straight line usually isn’t entirely straight. Thus, a lunar eclipse is the result of the Moon crossing that plane of the Earth and Sun at the same time of a Full Moon. Hum, did you know that?
Sad to say, for this eclipse, emphasis is on the word “partial” as the majority of the time the Moon will slide through the Earth’s penumbra just grazing the umbra shadow. On the Danjon Scale of Lunar Eclipse Brightness, this partial lunar eclipse is an L=4 on the scale, suggesting the Moon will be quite bright displaying a copper-red or orange color.
At our location the eclipse gets underway shortly after the Moon rises over the eastern horizon around 6:42pm. At that time the Moon enters the Earth’s penumbra shadow. The eclipsed Moon’s journey that night is a slow arc across the southern horizon. The eclipse concludes around 10:48pm local time when the Moon leaves the Earth’s penumbra shadow. The moment of maximum eclipse is 8:45pm, with the Moon a lowly 19 degrees above the southern horizon.
Try to look at the full moon intermittently throughout the eclipse to notice the growing and changing red, copper, orange, and brown hued colors. Keen observers will recognize the subtle color difference in the shadow side of the Moon, and some will not. Finally, as the time of greatest eclipses approaches, notice the bright background stars near and right side of the Moon. Watch as they get eclipsed by the Moon only to reappear later on the other side. This is called an “occultation.”
The Autumnal Equinox: September 22st
In the northern hemisphere, the autumnal equinox occurs on September 22rd, at 6:42am local time. The date of the autumnal equinox demarcates the end of the summer season and the beginning of the autumn season. On this day, the center of the Sun sits high over the equator and spends roughly equal amounts of time above and below the horizon at every location on the Earth. No matter where you are in the world, the sun rises due east, and sets due west. Stand anywhere on the equator at noon and look straight up, the sun is directly overhead. There are two equinox a year, one in autumn, and one in spring which are opposite of one another. More so, every planet in our solar system has an equinox when its tilt and orbit result in both hemispheres receiving equal amounts of light.
In Japan, Autumnal Equinox Day is a public holiday. It is a day when individuals take time to reconnect with their families and by tradition tend to the graves of ancestors, visit shrines, and meditate in temples.
The Andromeda Galaxy: The entire month of September
The arrival of autumn brings with it many of the night sky’s most spectacular constellations and grandest mythological stories. One of the easiest to find after sunset is the constellation Cassiopeia, the vain Queen, and mother of Andromeda. Look to the northeast horizon edge after 8:30pm locally for five bright stars all of similar brightness (magnitude) that together create an asterism, it is the shape of a somewhat flattened letter “W.” The brightest star of the “W 4” is called Schedar. It will be our pointer star to find the Andromeda Galaxy. Just to confuse things, there is a constellation named Andromeda, as well as a galaxy named Andromeda. The Andromeda Galaxy is a barred spiral galaxy like our Milky Way and is the nearest galaxy to us. It is our galactic neighbor galaxy. It has spectacular broad sweeping arms, one extending from each end of the bar. As it resides an intimate 2.5 million light-years from Earth, we can clearly see it with our unaided, naked-eye.
To find the Andromeda Galaxy, get to a dark location and first locate the constellation Cassiopeia and the five bright stars forming the “W.” Next, find Schedar, the brightest star of the five in the “W.” You’ll notice it is at the bottom of the most pronounced “V” in the “W” of Cassiopeia creating a pointer from which you draw an imaginary straight line from Schedar, back to the horizon. Extend your arm out and make a fist. Place the thumb of the closed fist on Schedar. Maintain the angle set by the pointer star, turn your wrist on the imaginary straight line down towards the horizon. When the line hits the horizon, at the other end of your fist, the pinky finger begins to look for a faint, slightly brighter patch of diffused light. Think of a light white finger print of chalk on a window pane about the size of a dime. That patch is the Andromeda Galaxy. Give your eyes time to adjust and as they do, the galaxy’s size will become more apparent. It will look like a large oval serving platter. It’d be appropriate to say “Whoa!” when you see it.
The Constellation Pegasus: The Great Square of a Winged Horse
While you’re in the neighborhood, take a step to the right of the Andromeda Galaxy and locate another asterism, the Great Square of Pegasus. It’s easy to find notwithstanding the stars in the square are a bit dimmer. The brightest star of the great square is Alpheratz. This star occupies the upper left corner of the square. To find it, start at the Andromeda Galaxy, and move one fist width towards the south maintaining the same latitude. Each side of the square is approximately two fist width in length. Yes, it does look like a half of a horse; there’s a head, a body (the Great Square), and front legs. The only problem is that Pegasus flies upside down through the night! You’ll need to be a little creative to visualize it, but it’s there and once you find it, you’ll never not see it again.
Each new season calls us forward, as well as asks us to be grateful for that which has passed. The summer celestial season has given much to us to see, enjoy, and contemplate. We feasted on the undeniable beauty and brilliance of Jupiter residing high in the sky. We “ooh and aah” at the unexpected sighting of a meteor streaking across the heavens. We stared dumbfounded at the brighter fuzzy patch of light at the southern end of the Milky Way after we learned we’re looking at the galactic center of our home. Throughout the season, we gazed up at the Summer Triangle of constellations, our constant companion through all of summer.
It is appropriate that we take a moment to pause and watch Cygnus lightly fly south through our river of stars. Equally fitting it is that we turn towards the new season of autumn. With anticipation and excitement let’s look up together towards a new season of stargazing full celestial joy and wonder just waiting to harvest.
Clear skies to you!
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