The night sky tonight and on any clear night offers an ever-changing display of fascinating objects you can see, from stars and constellations to bright planets, the moon, and sometimes special events like meteor showers.
Observing the night sky can be done with no special equipment, although a sky map can be very useful, and a good telescope or binoculars will enhance some experiences and bring some otherwise invisible objects into view. You can also use astronomy accessories to make your observing easier, and use our Satellite Tracker page powered by N2YO.comto find out when and how to see the International Space Station and other satellites. We also have a helpful guide on how you can see and track a Starlink satellite train.
Read on to find out what's up in the night sky tonight (planets visible now, moon phases, observing highlights this month) plus other resources (skywatching terms, night sky observing tips and further reading)
Monthly skywatching information is provided to Space.com by Chris Vaughan of Starry Night Education, the leader in space science curriculum solutions. Follow Starry Night on Twitter @StarryNightEdu and Chris at @Astrogeoguy
Editor's note: If you have an amazing skywatching photo and would like to share them with Space.com’s readers, send your photo(s), comments, and your name and location to firstname.lastname@example.org.
Calendar of observing highlights
Friday, Sept. 1: The Andromeda Galaxy (all night)
September evenings feature the Andromeda Galaxy, which is already climbing the northeastern sky after dusk. This large spiral galaxy, also designated Messier 31 (or M31) and NGC 224, is the closest large galaxy to us — at a distance of "only" 2.5 million light years. It covers an area of the sky measuring 3 by 1 degrees (or six by two full moon diameters).
Under dark skies, the galaxy can be seen with unaided eyes as a faint smudge located 1.4 fist diameters to the left (or 14 degrees to the celestial northeast) of Alpheratz, the star that forms the left-hand (northwestern) corner of the square of Pegasus. The three highest (westernmost) stars of Cassiopeia, Caph, Shedar, and Navi (Gamma Cas), also conveniently form a triangle that points towards M31.
Binoculars (orange circle) will show the galaxy best. For telescopes, use low magnification and look for M31's two smaller companion galaxies, the foreground Messier 32 and more distant Messier 110 (inset)
Sunday, Sept. 3: Gibbous moon joins bright Jupiter (all night)
About half an hour after the bright gibbous moon rises in the east on Sunday night, Sept. 3, the brilliant planet Jupiter will rise to join it. The pair will cross the sky through the night and shine high in the southwestern sky before sunrise.
Hour by hour, the moon's easterly orbital motion (green line) will carry it closer to Jupiter, and the diurnal rotation of the sky will lift the planet higher than the moon. On Monday night, the moon will have hopped east to shine on Jupiter's left (or celestial northeast).
Monday, Sept. 4: Jupiter stands still (overnight)
On Monday, Sept. 4, the eastward prograde motion of the planet Jupiter across the stars of southeastern Aries will slow to a stop. After tonight, Jupiter will commence a westward retrograde loop that will last until early January (red path). The planet's bright, white dot will be shining in the lower part of the eastern sky in late evening.
Monday, Sept.4: Bright moon near Uranus (overnight)
In the eastern sky on Monday night, Sept. 4, the planet Uranus will be located just a few finger widths below the waning gibbous moon. That's cozy enough for them to share the view in binoculars (orange circle). Uranus' magnitude 5.7 speck can be seen in binoculars and is easily observed in backyard telescopes.
Watch for the bright little Pleiades Star Cluster positioned more than a palm's width to the moon's lower left and Jupiter a similar distance to Uranus' upper right. During the night, the moon's easterly orbital motion will carry it a bit closer to Uranus and shift it to the planet's upper left.
Tuesday, Sept. 5: Half-moon with the Pleiades (overnight)
Look in the lower part of the eastern sky late on Tuesday evening, Sept. 5, to see the remarkable Pleiades Star Cluster, also known as the Seven Sisters, Messier 45, and Subaru, positioned several finger-widths to the lower left (or 5 degrees to the celestial east) of the waning, half-illuminated moon.
In the Eastern time zone, the cluster and the moon will share the field of view in binoculars (orange circle) — but hide the bright moon beyond the left edge of the field of view to see the cluster's stars more easily. The moon will be farther away from the Pleiades for skywatchers viewing the duo from more westerly longitudes
Wednesday, Sept. 6: Third Quarter Moon (at 22:21 GMT)
The moon will complete three-quarters of its orbit around Earth, measured from the previous new moon, on Wednesday, Sept. 6 at 6:21 p.m. EDT and 3:21 p.m. PDT or 22:21 GMT. At the third (or last) quarter phase the moon appears half-illuminated, on its western, sunward side.
It will rise around midnight local time, and then remain visible until it sets in the western daytime sky in early afternoon. Third-quarter moons are positioned ahead of the Earth in our trip around the sun. About 3½ hours later, Earth will occupy that same location in space. The week of dark, moonless evening skies that follow this phase are the best ones for observing fainter deep sky targets.
Thursday, Sept. 7: The Great Square of Pegasus (all night)
Pegasus, which climbs the Eastern sky during September evenings, contains one of the most recognizable asterisms in the sky, a giant square of four similarly bright stars called the Great Square.
The square's edges are about 1.6 fist diameters (or 16 degrees) in length, and it spans two fist-widths (about 20 degrees) measured corner to corner. The pattern might remind you of a baseball diamond when you see it because it's often tilted with one corner downwards.
For the Lakota people, the square represented the great shell of Keya, the Turtle. The Anishinaabe of the Great Lakes region views the square as the torso of Mooz, the Moose. Using unaided eyes only, from the suburbs, the Great Square appears empty. Look carefully for two dim stars offset to the upper right from the center of the square. They represent the moose's heart.
Friday, Sept. 8: The first known exoplanet (all night)
In the eastern sky on starry September evenings, look for a dim star shining a thumb's width just outside of the baseball diamond shape of Pegasus' Great Square, midway between the top and right corners. That yellow, sunlike star named Helvetios (or 51 Pegasi) is orbited by the first exoplanet ever discovered, in 1995.
The planet, which orbits that star every 4.23 days at a distance much closer to the star than Mercury does in our solar system, is categorized as a Hot Jupiter type. Originally nick-named Bellerophon, one of the original riders of Pegasus in Greek mythology, the planet is now officially named Dimidium, the Latin word for "half" — since the planet has half the mass of Jupiter.
Sunday, Sept. 10: Crescent moon joins Gemini's Twins (pre-dawn)
When the waning crescent moon rises over the northeastern rooftops during the wee hours of Sunday morning, September 10, it will make a pretty sight aligned below Gemini's brightest stars Pollux and Castor. The moon will be close enough to the lower star, warm-tinted Pollux, for them to share the field of view of binoculars. For observers viewing in westerly time zones, the moon will be a little farther from Pollux. Brilliant Venus will shine below the moon after it rises around 4 a.m.
Monday, Sept.11: Crescent moon buzzes the Beehive (pre-dawn)
Between about 3 a.m. local time and dawn on Monday morning, Sept.11, look in the eastern sky for the very slim crescent of the waning moon. The big open star cluster in Cancer known as the Beehive, Praesepe, and Messier 44 will be positioned several finger-widths to its lower right (or 3.5 degrees to the celestial south).
The moon and cluster will be close enough to share the field of binoculars (orange circle), but you'll see more of the "bees" if you tuck the moon just out of sight on the left and view them before the morning sky starts to brighten. You can use the bright planet Venus to find the cluster on the following mornings when the moon has moved on.
Wednesday, Sept.13: Watch Algol fade (from 11:23 p.m. EDT)
Algol, also designated Beta Persei, is among the most accessible variable stars for skywatchers. During a ten-hour period that repeats every 2 days, 20 hours, and 49 minutes, Algol's visual brightness dims and re-brightens by about a third. This happens when a fainter companion star with an orbit nearly edge-on to Earth crosses in front of its much brighter primary, reducing the total light output we perceive.
Algol normally shines at magnitude 2.1, similar to the nearby star Almach (aka Gamma Andromedae). But when fully dimmed, Algol's brightness of magnitude 3.4 is almost identical to Rho Persei (or Gorgonea Tertia or ρ Per), the star sitting just two finger widths to Algol's lower right (or 2.25 degrees to the celestial south). On Wednesday, Sept. 13 at 11:23 p.m. EDT (or 03:23 GMT on September 14), Algol will begin its drop in brightness. At that time it will be climbing the northeastern sky, approximately above and between the bright star Capella and Jupiter. Five hours later Algol will reach its minimum brightness while overhead in the eastern sky.
Thursday, Sept.14: Morning zodiacal light for mid-northern observers (pre-dawn)
During autumn at mid-northern latitudes every year, the ecliptic extends nearly vertically upward from the eastern horizon before dawn. That geometry favors the appearance of the faint Zodiacal light in the eastern sky for about half an hour before dawn on moonless mornings.
Zodiacal light is sunlight scattered by interplanetary particles that are concentrated in the plane of the solar system — the same material that produces meteor showers. It is more readily seen in areas free of urban light pollution. Between now and the full moon on Sept. 29, look for a broad wedge of faint light extending upwards from the eastern horizon and centered on the ecliptic (the green line). It will be strongest in the lower third of the sky below the very bright planet Venus, which may suppress the phenomenon. Don't confuse the zodiacal light with the Milky Way, which is positioned nearby in the southeastern sky.
Friday, Sept.15: New Moon (at 9:40 p.m. EDT)
On Friday, Sept.15 at 9:40 p.m. EDT, which converts to Thursday at 01:40 GMT or 6:40 p.m. PDT, the moon will officially reach its new moon phase.
At that time our natural satellite will be located in Leo, 2 degrees north of the sun. While new, the moon is traveling between Earth and the sun. Since sunlight can only illuminate the far side of the moon, and the moon is in the same region of the sky as the sun, it becomes completely hidden from view from anywhere on Earth for about a day. After the new moon phase, Earth's celestial night light will return to shine as a young crescent in the western evening sky.
Saturday, Sept.16: Crescent moon meets Mars (after sunset)
After sunset on Saturday evening, Sept. 16, the slim crescent of the young moon will pose very close to the very faint, reddish dot of Mars. For mid-northern latitude observers, the pair will set about 45 minutes after the sun.
As the sky starts to darken look for them less than a palm's width above the western horizon and descending, making their meet-up a challenge to see. Observers in the southern USA and tropical latitudes will see them more easily. In most places, Mars will be positioned less than a finger's width below (or 0.6 degrees to the celestial west) of the moon's lit crescent, close enough to share the view in binoculars (orange circle) or a backyard telescope. The moon will pass in front of (or occult) Mars in the daytime for most of North America (except western Mexico), the Caribbean, and Central America. Skywatchers in northern South America will see that event in a darker sky.
Tuesday, Sept.19: Venus at greatest illuminated extent (pre-dawn)
For several hours before sunrise on Tuesday, Sept. 19, Venus will shine in the eastern sky at its greatest illuminated extent for the current morning apparition. In a telescope, the planet will show a 27%-illuminated waxing crescent phase and an apparent disk size of 38 arc seconds. Even with a less than fully illuminated disk (inset), Venus' nearness to Earth of only 0.442 Astronomical Units (41.05 million miles or 66.06 million km) will boost its brightness to a brilliant magnitude -4.76. Skywatchers outside before dawn can see the bright stars of winter sparkling to Venus' right. Mercury will rise below Venus around 5:15 a.m. local time.
Tuesday, Sept. 19: Neptune at opposition (all night)
On Tuesday, Sept. 19, Neptune will reach opposition. At that time the distant planet will be closest to Earth for this year — a distance of 2.68 billion miles, 4.32 billion km, 4 light-hours, or 28.9 Astronomical Units.
At opposition, blue Neptune will shine with a slightly enhanced magnitude of 7.8. Since it will be opposite the sun in the sky, Neptune will be visible all night long in backyard telescopes. Good binoculars (orange circle) can show it, too, if your sky is very dark. Your best views will come after 9 p.m. local time, when the blue planet has risen higher.
Around opposition, Neptune's apparent disk size will peak at 2.4 arc-seconds and its large moon Triton will be the most visible (inset). Throughout September, Neptune will be located below the circle of stars that forms Pisces' western fish, and about 2.4 fist diameters to the lower left (or 24 degrees to the celestial east-northeast) of Saturn.
Wednesday, Sept. 20: Moon in the Scorpion's Claws (evening)
In the southwestern sky after dusk on Wednesday, Sept. 20, the nearly half-illuminated moon will shine in western Scorpius near the up-down row of small white stars that form the scorpion's claws. From top to bottom, they are Jabbah or Nu Scorpii, Graffias or Acrab, Dschubba, Pi Scorpii, and Rho Scorpii.
A backyard telescope at high magnification will reveal that Nu Scorpii, Graffias, and Dschubba are close-together double stars. On Thursday evening, observers in the region extending south from Japan will be able to see the moon pass in front of (or occult) Antares.
Friday, Sept. 22: Mercury at greatest western elongation (pre-dawn)
On Friday, Sept. 22, the planet Mercury will reach a maximum angle of 18 degrees from the sun, and peak visibility, for its current morning apparition. Look for the innermost planet shining brightly while it climbs the eastern pre-dawn sky between about 5:15 and 6:15 a.m. in your local time zone. In a telescope (inset) Mercury will exhibit a 48%-illuminated, waxing phase. Mercury's position above the nearly upright morning ecliptic (green line) will make this an excellent apparition for Northern Hemisphere observers, but a very poor one for those located south of the Equator, where the ecliptic will be tipped over.
Friday, Sept. 22 - First Quarter Moon (at 3:32 p.m. EDT)
When the moon completes the first quarter of its journey around Earth on Friday, September 22 at 3:32 p.m. EDT or 12:32 p.m. PDT and 19:32 GMT, its 90-degree angle away from the sun will cause us to see the moon half-illuminated — on its eastern side. At first quarter, the moon always rises around mid-day and sets around midnight, so it is also visible in the afternoon daytime sky, too. The evenings surrounding first quarter are the best ones for seeing the lunar terrain when it is dramatically lit by low-angled sunlight, especially along the terminator, the pole-to-pole boundary that separates the lit and dark hemispheres.
Saturday, Sept. 23: September equinox (at 2:50 a.m. EDT)
On Saturday, September 23 at 2:50 a.m. EDT or 06:50 GMT, the sun's apparent motion along the ecliptic (green line) will carry it across the celestial equator traveling southward, marking the autumnal equinox in the Northern Hemisphere and the beginning of autumn there. On the equinoxes in March and September, day and night are of equal length and the sun rises due east and sets due west (yellow arc).
Monday, Sept. 25: Major Mare Imbrium (evening)
On Monday, Sept. 25, the lunar terminator will fall beyond the western rim of Mare Imbrium, the Sea of Rains, allowing it to be fully illuminated. That dark, circular feature dominates the northwestern quadrant of the moon's Earth-facing hemisphere.
The mare is the moon's largest impact basin, measuring more than 715 miles (1,145 km) in diameter. It was formed during the late heavy bombardment period approximately 3.94 billion years ago. Telescope views of Mare Imbrium at this phase will reveal ejecta blankets around its major craters (Aristillus and Archimedes), several nearly-submerged ghost craters (Cassini and Wallace), and numerous subtle wrinkle ridges (Heim, Stille).
Tuesday, Sept. 26:Bright moon shines with Saturn (all night)
At sunset on Tuesday, Sept. 26, look low in the southeastern sky to see the bright, waxing gibbous moon rising. As the sky darkens more, the bright, creamy-yellow dot of Saturn will appear shining several finger widths to the moon's upper left (or 4 degrees to its celestial north). The pair will be cozy enough to share the view in binoculars (orange circle) as they cross the sky all night long.
Friday, Sept. 29: Full Harvest Supermoon (at 09:57 GMT)
The moon will officially reach its full phase on Friday, Sept. 29 at 5:57 a.m. EDT or 2:57 a.m. PDT and 09:57 GMT, so it will appear to be full on both Thursday and Friday evening in the Americas. The September full moon, traditionally known as the "Corn Moon" and "Barley Moon", always shines in or near the stars of Aquarius and Pisces.
The indigenous Anishinaabe people of the Great Lakes region call this moon Waatebagaa-giizis or Waabaagbagaa-giizis, the Leaves Turning or Leaves Falling Moon. Full moons always rise around sunset and set around sunrise. Because this is the closest full moon to the autumnal equinox in 2023, it is also the Harvest Moon. On the evenings around its full phase, the moon normally rises about 50 minutes later than the previous night. But the shallow slope of the evening ecliptic (and the moon's orbit) around the equinox causes Harvest Moons to rise at almost the same time each night — only delayed by as little as 10 minutes, depending on your latitude. This phenomenon traditionally allowed farmers to work into the evening under bright moonlight — hence the name. This full moon will also be the last of the supermoon series for 2023.
Visible planets in September
For mid-northern latitude planet-watchers, Mercury will begin September hidden while it passes the sun at inferior conjunction on Sept. 6. Late in the second week of September, the speedy planet will climb far out of the eastern pre-dawn twilight to commence its finest morning appearance of the year for northerners — but a poor showing for mid-southern latitude observers. On Sept. 22 Mercury will reach its maximum angle of just 18 degrees from the sun. That's less than is typical because the planet will be at perihelion for this elongation. Its brightness will be boosted to about magnitude -0.35, but it will not rise far enough ahead of the sun to shine in a very dark sky.
Viewed in a telescope this month, Mercury will wax from a crescent phase to gibbous on a disk that steadily diminishes in apparent diameter. As September winds down, Mercury will descend sunward and fade in brightness. On Sept. 13, the very slim crescent of the old moon will be located a generous palm's width (or 7.7 degrees) to Mercury's upper left.
The brilliant planet Venus will dominate the eastern pre-dawn sky during September and beyond. At the beginning of the month, Venus' magnitude -4.6 "morning star" will rise around 4:30 a.m. local time. In a telescope it will show a slim, waxing crescent phase, and a generous apparent disk diameter of 49.64 arc-seconds. With each passing day, Venus will grow in illuminated phase and shrink in size. Its brightness will increase to a peak of -4.8 at its greatest illuminated extent on the Sept. 19. Venus will spend most of September traveling first retrograde and then prograde through southeastern Cancer, including a close pass just 1 degree to the lower right of the open star cluster Messier 67 on the nights surrounding September 8. The planet will cross into Leo on Sept. 25.
At the end of September, Venus will be rising around 3:15 a.m. local time, shining at magnitude -4.7, and exhibiting a 36%-illuminated, 32 arc-seconds wide crescent in backyard telescopes. The waning crescent moon will pose far to Venus' left (or celestial northeast) on Sept. 12.
Mars will spend September among the stars of Virgo, approaching its maximum distance from Earth on the far side of the sun. As the month begins the planet will be located just above the western horizon after sunset, but the twilight and thicker blanket of intervening air will make the magnitude 1.75 planet very difficult to see. Mars will sink lower each night, eventually disappearing altogether - first for mid-latitude observers, and then for everyone else.
After sunset in the Eastern Time zone on September 16 the young crescent moon will be positioned several moon diameters to Mars' left (celestial east). A few hours earlier, the moon will pass in front of (or occult) Mars — an event visible through telescopes in daytime for most of North America (except western Mexico), the Caribbean, and Central America. Skywatchers in northern South America will see that event in a darker sky. The moon will take 8 seconds to fully cover Mars' little disk.
The easterly motion of Jupiter through the stars of southern Aries will slow to stop on September 4 in preparation for its four-month-long retrograde loop and the planet's best observing window for this year. As September begins the very bright, magnitude -2.6 planet will rise at around 10 p.m. local time. Jupiter will make it halfway across the sky by dawn, when it will catch your eye high in the southern sky. At month's end Jupiter will rise at about 8 p.m., culminate due south at 3 a.m., and then set in the morning daylight.
Over the month, Jupiter will brighten a little and grow in apparent size from 44 to 48 arc-seconds. Binoculars will reveal Jupiter's four large Galilean moons flanking the planet. A backyard telescope will show its equatorial bands. A better quality instrument will reveal the Great Red Spot every 2nd or 3rd night, Jupiter's Galilean satellites frequently eclipsing and occulting one another, and the passages of the round, black shadows they cast upon on the planet. In evening on Sept. 28, Io's shadow will cross along with the Great Red Spot. The waning gibbous moon will hop past Jupiter on Sept. 3-4.
Creamy-yellow Saturn will be available for viewing all night long during September because it will be rising in the east shortly before the sun sets in the west. The ringed planet will be travelling retrograde westward through central Aquarius - with faint Neptune positioned 24 degrees to its lower left (or celestial ENE). Unfortunately for mid-northern latitude observers, the low night-time ecliptic will prevent Saturn from climbing from very high up in the southern sky.
Viewed in a telescope during September Saturn will show an apparent disk diameter of 18.9 arc-seconds, and its rings will subtend 43.9 arc-seconds. Saturn's rings will be tilting more edge-on to Earth every year until the spring of 2025. The bright, waxing gibbous moon will be positioned four degrees below (or celestial west of) Saturn on Sept. 26.
Blue-green Uranus will be following far brighter Jupiter across the sky this year. The Pleiades Cluster will be positioned a similar distance to its lower left (or celestial northeast). As September begins, the magnitude 5.71 planet, which is visible in binoculars and backyard telescopes in a dark sky, will be rising at about 10:30 a.m. local time.
At the end of the month, it will be clearing the eastern treetops two hours earlier. Uranus' westerly retrograde motion through eastern Aries will accelerate during the month. Its small, 3.7 arc-seconds-wide disk will best be seen in a telescope during the wee hours of the morning when the planet will be relatively high in the southeastern sky. On Sept. 5, the waning gibbous moon will shine about 2 degrees above (or celestial north of) Uranus.
During September, the distant, magnitude 7.8 planet Neptune will cross the night sky all night long, following much brighter Saturn, which will be shining about 24 degrees to Neptune's upper left (celestial west). Both planets will be moving retrograde westward.
On Sept. 19, Neptune will reach opposition — closest to Earth for this year at a distance of 2.68 billion miles, 4.32 billion km, 4 light-hours, or 28.9 Astronomical Units. Around opposition, Neptune's apparent disk size will peak at 2.4 arc-seconds and its large moon Triton will be the most visible. Throughout September, Neptune will be located 7 degrees below the circle of stars that forms Pisces' western fish, and about 24 degrees to the lower left (or celestial east-northeast) of Saturn.
Gibbous: Used to describe a planet or moon that is more than 50% illuminated.
Asterism: A noteworthy or striking pattern of stars within a larger constellation.
Degrees (measuring the sky): The sky is 360 degrees all the way around, which means roughly 180 degrees from horizon to horizon. It's easy to measure distances between objects: Your fist on an outstretched arm covers about 10 degrees of sky, while a finger covers about one degree.
Visual Magnitude: This is the astronomer's scale for measuring the brightness of objects in the sky. The dimmest object visible in the night sky under perfectly dark conditions is about magnitude 6.5. Brighter stars are magnitude 2 or 1. The brightest objects get negative numbers. Venus can be as bright as magnitude minus 4.9. The full moon is minus 12.7 and the sun is minus 26.8.
Terminator: The boundary on the moon between sunlight and shadow.
Zenith: The point in the sky directly overhead.
Night sky observing tips
Adjust to the dark: If you wish to observe fainter objects, such as meteors, dim stars, nebulas, and galaxies, give your eyes at least 15 minutes to adjust to the darkness. Avoid looking at your phone's bright screen by keeping it tucked away. If you must use it, set the brightness to minimum — or cover it with clingy red film.
Light Pollution: Even from a big city, one can see the moon, a handful of bright stars, and the brightest planets - if they are above the horizon. But to fully enjoy the heavens — especially a meteor shower, the fainter constellations, or to see the amazing swath across the sky that is the disk of our home galaxy, the Milky Way — rural areas are best for night sky viewing. If you're stuck in a city or suburban area, use a tree or dark building to block ambient light (or moonlight) and help reveal fainter sky objects. If you're in the suburbs, simply turning off outdoor lights can help.
Prepare for skywatching: If you plan to be outside for more than a few minutes, and it's not a warm summer evening, dress more warmly than you think is necessary. An hour of winter observing can chill you to the bone. For meteor showers, a blanket or lounge chair will prove to be much more comfortable than standing, or sitting in a chair and craning your neck to see overhead.
Daytime skywatching: On the days surrounding first quarter, the moon is visible in the afternoon daytime sky. At last quarter, the moon rises before sunrise and lingers into the morning daytime sky. When Venus is at a significant angle away from the sun it can often be spotted during the day as a brilliant point of light - but you'll need to consult an astronomy app to know when and where to look for it. When large sunspots develop on the sun, they can be seen without a telescope — as long as you use proper solar filters, such as eclipse glasses. Permanent eye damage can occur if you look at the sun for any length of time without protective eyewear.