Each Monday I pick out the northern hemisphere’s celestial highlights (mid-northern latitudes) for the week ahead, but be sure to check my main feed for more in-depth articles on stargazing, astronomy, eclipses and more.
What To Watch For In The Night Sky This Week: September 27-October 3, 2021
Here comes a splendid week for stargazing. The final few days of September and the first few of October come just as fall gets going. With reasonably warm evenings comes a Last Quarter Moon midweek, which signals moonless skies dark enough to see the last stars of summer (see below) and a mighty sign that fall has arrived—the Andromeda Galaxy.
Although it’s been visible for a good few weeks if you know where to look, anyone with either inky-black night skies or (more likely) a small pair of binoculars should be able to make-out the famous galaxy (also called M31) high in the eastern sky after dark. The most distant object you can see with your naked eyes at around 2.5 million light-years, M31 is our sister galaxy and contains around a trillion stars.
Here’s how to find it—and everything else you need to know about stargazing and the night sky this week:
Wednesday, September 29, 2021: Last Quarter Moon
At 01:57 Universal Time today our satellite will reach its Last Quarter phase. For stargazers the coming of this Moon phase is great news because it begins to rise around midnight, and then later each night, thus leaving the early evening with dark skies—and clearing the way for 10 successive nights of moonless-ness.
Half of the Moon’s disk is lit during this phase, as seen from Earth, and because it rises late it will be possible to see it in the west in the mornings for the rest of this week.
Thursday, September 30, 2021: Moon in Gemini
In the early hours today due east you’ll find a 38%-lit waning crescent Moon a mere 3° from Pollux, one of the two bright “twins” stars in the constellation Gemini.
You’ll also see the winter constellation of Orion hanging in the southeast.
Friday, October 1, 2021: Moon and the Beehive Cluster
In the early hours of today you can see in the easy a 29%-lit waning crescent Moon just 3º from the Beehive Cluster (M44).
One of the closest open clusters to Earth and found in the constellation of Cancer, its 1,000 stars are a beautiful sight in binoculars.
Asterism of the week: ‘Summer Triangle’
Deneb and Vega, together with the bright star Altair in Aquila, “the Eagle,” down towards the horizon (halfway between Vega and Jupiter), form a shape called the “Summer Triangle.”
It’s one of the anchors of the summer night sky and, if you’re in a dark location, you’ll see the brightest part of the Milky Way (as seen from the northern hemisphere) streaming through it.
Just to the left of a line between Deneb and Altair is the tiny, sparkling kite-shaped constellation of Delphinus, “the Dolphin.” Just above Altair is Sagitta, “the Arrow,” another small constellation.
Constellation of the week: Delphinus, ‘the dolphin’
It’s a great week to find the beautiful constellation of Delphinus. It’s in the constellation of Aquarius, though it’s easier to find between Deneb and Altair the “Summer Triangle.”
Looking something akin to a diamond with a tail, Delphinus can be found about 10° above bright star Altair at the foot of the “Summer Triangle.”
Times and dates given apply to mid-northern latitudes. For the most accurate location-specific information consult online planetariums like Stellarium and The Sky Live. Check planet-rise/planet-set, sunrise/sunset and moonrise/moonset times for where you are.
Wishing you clear skies and wide eyes.