Sunrise and sunset
• Sun rises at 6:30 a.m. and sets at 7:32 p.m. on the 1st
• Sun rises at 6:57 a.m. and sets at 6:45 p.m. on the 30th
Moon’s phases
• Full “Corn Moon” on the 9th
• New Moon on the 21st
Naked-eye planets
Eight months after its most recent close approach to Earth back in January, Mars is now located on the far side of the sun, over 200 million miles away, and has faded considerably.
As September opens, Mars lies within Virgo, an orange spark to the west, the right, of Virgo’s brightest star, Spica. Mars continues its eastward glide through Virgo this month, eventually passing just above bluish-white Spica on the 13th, providing a lovely, color-contrasting duo.
During September, Mars sets around 9 p.m. on the 1st, which is 1½ hours after sunset, and just before 8 p.m., or only about one hour before sunset, on the 30th.
Cream-colored Saturn beams from within the faint constellation of Pisces, which is low in the east at nightfall.
Saturn reaches opposition with the sun on the night of Sept. 20, when it is closest to Earth and at peakbrightness, outshining autumn’s first-magnitude jewel Fomalhaut, which lies to its lower right in late evening.
Saturn is visible all night this month, rising at sundown, standing due south around 1 a.m., and setting at sunrise.
A small telescope or high-power binoculars will reveal Saturn’s amazing ring system, now beginning to open up after having been oriented edge-on for much of 2025.
Also visible is Saturn’s largest moon, Titan, and, as a bonus, the faint, bluish-green world Neptune just over 2 degrees to Saturn’s east, to the left.
Jupiter is well-placed for viewing in the wee hours of the morning this September. Jupiter resembles a majestic golden star within the constellation Gemini, which is up in the east-northeast during the hours before daybreak.
On Sept. 1, Jupiter peeks above the horizon shortly after 2 a.m. and steadily earlier during the month to around 12:30 a.m. on the 30th.
Jupiter far outshines the nearby stars, including Gemini’s Pollux and Castor. Jupiter will be up in the east, well above the even more brilliant Venus.
Venus gleams like a yellow jewel in the pre-dawn sky. Venus rises in the east-northeast shortly before 4 a.m., or 2½ hours before the sun, in early September, and around 5 a.m., or just two hours before sunrise, at month’s end.
On the morning of the 19th, Venus, the star Regulus, and the thin, waning crescent Moon will form a tight trio low in the eastern sky, best visible about an hour before sunrise.
As September opens, Mercury, paired with Leo’s brightest star Regulus, is rising just one hour before sunrise, but within a week it vanishes into the dawn glow.
Mercury passes behind the sun — superior conjunction — on the 13th, then swings into the evening sky.
Earth reaches the autumnal equinox on Sept. 22 at 2:19 p.m. Summer ends and autumn begins in thenorthern hemisphere.
Stars and constellations
September is one of the most appealing months for night sky viewing, and for good reason: temperatures are often comfortably cool and the sky frequently clear.
And best of all, the star groups of summer, and even a few stragglers from spring, are still well placed for viewing during the early evening hours, while those of autumn are waiting in the wings for a late evening appearance.
By 9 p.m., yellowish-orange Artcurus in the constellation Boötes, the Herdsman, is low, but still visible, in the west.
Somewhat above Boötes is Corona Borealis, the Northern Crown. The Big Dipper, a part of the constellation Ursa Major, is low on the northwestern horizon.
The parade of summer constellations includes Scorpius, whose brightest star, orangish Antares, lies quite low in the southwest.
Just east of Scorpius is Sagittarius, which contains the famous asterism known as the “teapot.”
The constellation Sagittarius harbors the nucleus, or core, of our own Milky Way galaxy, which may be seen, away from urban light pollution, as a hazy band stretching across the sky.
Corona Australis, the Southern Crown, lies just below Sagittarius and is the southern counterpart to Corona Borealis.
Following Sagittarius to the east is the faint constellation Capricornus, the Sea Goat. Scorpius, Sagittarius and Capricornus are all zodiac constellations, which means that the sun lies within their boundaries at some point during the course of the year.
Specifically, the sun passes through Scorpius, Sagittarius and Capricornus between about Nov. 23 through 28, Dec. 18 through Jan. 18, and Jan. 19 through Feb. 15, respectively.
The “missing” zodiac constellation is Ophiuchus, through which the sun passes from Nov. 29 through Dec. 17.
Of course, the overwhelming glare of the daytime sun prevents the constellations from being seen at these times.
Hovering nearly overhead during the early evening hours is the Summer Triangle of Vega in Lyra, Deneb inCygnus and Altair in Aquila.
In the same general vicinity, four relatively faint, diminutive and lesser-known constellations can also be spotted on late summer evenings if the sky is dark and clear enough: Equuleus (Little Horse), Delphinus (Dolphin), Sagitta (Arrow) and Vulpecula (Fox).
Sagitta and Vulpecula actually lie within the Summer Triangle, while Equuleus and Delphinus lie just outside it, to the upper left of Altair.
Finally, Vulpecula consists of only scattered, faint stars and lies between Cygnus and Delphinus.
Vulpecula is, unlike the other three, a modern constellation, created in 1690 by Johannes Hevelius. It was originally known as Vulpecula et Anser, the Fox and Goose, but today only the Fox exists.
As the stars of summer gradually fade into the evening twilight, the first stars of autumn are rising in the eastern sky.
Making its appearance in the southeast after about 10 p.m. is the whitish star Fomalhaut, which lies in theconstellation of Pisces Austrinus, the Southern Fish.
Rising due east at about this time is the Great Square of Pegasus, four stars in the form of a rectangle, though not quite square, lying on its edge.
Low in the northeast is the famous “W” shape of the constellation Cassiopeia, the mythical Queen of ancient Ethiopia. The “W” opens up toward Polaris, the North Star.
In the region just above Cassiopeia is the faint but significant constellation Cepheus, the King of Ethiopia and Cassiopeia’s husband.
Cepheus is one of the oldest constellations in the heavens, and one that was known to ancient Middle Eastern civilizations. The shape of Cepheus has been likened to that of a simple house as drawn by a child, with a triangle sitting atop a box.
Test your smarts
Astronomy question of the month: What is the most massive star known, and is there an upper limit to howmassive a single star can be? (Answer next month)
Answer to last month’s question (What are Saturn’s rings made of?): Saturn’s rings are composed of small particles of rock and ice, the latter of which explains why the rings are so bright: the icy surfaces reflect significant amounts of sunlight. Theoretical models provide several possible explanations of how Saturn’s rings formed: tidal disruption of a moon that got too close to Saturn, the collision between two moons, or the accretion of leftover material when Saturn formed.
The fine print
• Astronomical information is obtained from The Astronomical Almanac (2021-2025) by Richard J. Bartlett, and from Astronomical Calendar 2025 by Guy Ottewell, available online at www.universalworkshop.com/astronomical-calendar-2025.
• For more information on the night sky, visit the Widener Observatory Stargazing website at www.widener.edu/stargazing.
• A set of free sky maps can be obtained at www.skymaps.com.
Augensen is the director of the Widener University Observatory and emeritus professor of physics and astronomy at Widener University.
