It’s hard to follow up a month like August: every year the August night sky wows with the Perseids shower and a host of other astronomical events. But this year September does its best: the September night sky is full of interesting astronomical events.
This month you’ll be treated to a series of planet-gazing opportunities, a few other celestial objects, and of course the September equinox. Whether you’re new to stargazing or just seeking some of the other interesting astronomical sights (Neptune! 4P/Faye! 2 Pallas!), there’s plenty to see in the night sky in September.
Additionally, September signals a season change. This means your chances to see the aurora begin to shift hemispheres; it’s the perfect time to plan your trip to see the northern lights for those in the northern hemisphere.
Before jumping into the list, I want to provide some recommendations for telescopes and binoculars; some of the events this month will require having one if you want to see them. I have guides based on price, whether you want to buy a solid telescope under $300 or splurge on a one of the best telescopes under $1000 instead. If you’d rather use astronomical binoculars, I have a guide to binoculars under $100 and under $1000.
Ready to learn more about what you can see in the September night sky this year? Read on for 10 of the most interesting astronomical events in the night sky in September 2021.
This post was originally published in August 2018, and was updated most recently in August 2021.
Featured image credit: Lukas Schlagenhauf via Flickr
September 1: Peak of the Aurigid Meteor Shower
Auriga is one of my favorite winter constellations: its big bright stars are easy to spot in the sky. And while it’s not winter yet, Auriga is beginning to rise in the sky. With it comes its own meteor shower.
The Aurigid meteor shower is definitely a minor shower; its maximum rate (ZHR) is only about six meteors per hour. That said, if you’re out stargazing on September 1st, you might spot a few of them! The moon will be just 26% illuminated and shouldn’t pose any interference to starting September with shooting stars.
September 3: Mercury at its Evening Peak
Due to its proximity to the sun Mercury never appears particularly high in the night sky. Those mornings and evenings when it does are worth marking on your calendar to try and spot the small planet.
On September 3rd, Mercury will reach its highest point in the evening sky, just 11° above the horizon after the sun has set. You’ll need a clear view of the western horizon. This means no mountains, trees, or other obstructions, if you’re trying to spot Mercury as the night comes on.
September 9: Peak of the ε-Perseid Meteor Shower
September is not known for its meteor showers. Even those do that occur have a hard time comparing to the show the Perseids put on in August. Still, any chance to spot them is worth trying if the skies are clear!
On September 9th, you can try to spot ε-Perseids meteors. Despite their name, these meteors are likely not caused by the same comet (109P/Swift-Tuttle) as the August Perseids; instead, they simply appear to radiate from the same point in the night sky – which is how meteor showers get their names.
At their maximum, you can look for roughly 5 ε-Perseids per hour, coming from the general area of the constellation Perseus high in the southwest sky. Like we said – not as spectacular as Perseids, but still interesting!
September 9: Close Approach of the Moon & Venus
As we move past the new moon on September 6th-7th, head out for a cool close approach between the Moon and Venus. On the night of 9th, bright Venus will appear within 4°04′ of the waxing crescent Moon. It’ll be hard to miss the pair, and a great opportunity to try your hand at astrophotography!
September 10: Comet 4P/Faye at Perihelion
Love to rise early for a good astronomical challenge? This ones’ for you!
Throughout early September, Comet 4P/Face is approaching perihelion – its closest point to the sun – which it will reach on September 10th. On that day, it will be just 1.62 AU from the sun; to view it, you’ll need a large telescope and to head out between roughly 2am and 5am local time to try and find the comet as it streaks through the constellation Taurus.
September 11: Asteroid 2 Pallas at Opposition
In 2021, I’ve become way more interested in asteroids and objects in the asteroid belt; I find it fascinating that there’s all this extra mass in the solar system, composed of different substances and moving around and behaving very differently than the planets. That’s why I’ve taken every opportunity I can to get out and try to spot asteroids when they reach opposition and are ideally lit by the sun for viewing.
On September 11th, asteroid 2 Pallas will be ideally placed for such an opportunity. Best of all, it’s very close to Neptune in the night sky, which is also approaching opposition on the 14th. Any time between the 11th and 14th is a great chance to pull out your telescope and try to spot these two objects in the constellation Aquarius
September 14: Neptune at Opposition
Unlike Uranus which can be spotted under the most pristine dark sky conditions, ice giant Neptune can never be seen without some sort of magnification. So the fact that Neptune will be at opposition on September 14th and well-lit by the sun makes it a great time to try and spot the distant planet.
Neptune will be high in the southern sky, in the constellation Aquarius. The moon will be just 61% illuminated this night and shouldn’t pose an obstacle to seeing this distant solar system object.
September 16: Close Approach of the Moon & Saturn
Saturn and Jupiter continue stepping further apart in the night sky after their Great Conjunction last year; now they each make a close approach with the Moon more than a day apart – a good indication about their relative distance from one another in our view of the nigt sky.
On the night of September 16th, you can see Saturn near the Moon, roughly 3°45′ apart. The Moon is a waxing gibbous on this night and pretty brightly illuminated at 87% – so you may have some light pollution from the moon when trying to spot Saturn’s rings or any of its own moons (if you have a telescope powerful enough for that!).
September 17: Close Approach of the Moon & Jupiter
The next night, Jupiter gets its turn. On September 17th at almost midnight, Jupiter and the Moon will appear at their closest, just 3°57′ apart. Saturn will be in the same general area of the sky, if you want to try and observe it too.
All three night sky objects will be in the constellation Capricornus and a bright 11-day-old Moon might affect your ability to spot Jupiter and its Galilean moons.
September 22: September Equinox
On September 22nd this year, the seasons officially changed. The September Equinox – called the “autumnal equinox” in the northern hemisphere and the “vernal equinox” in the southern hemisphere – signals the point where earth experiences roughly equal lengths of day and night.
While there is no night sky event to view for the equinox, it’s a cool time to consider our planet’s place in the solar system and how we orbit around the sun.
Learn more about the September Equinox and how it is marked in different parts of the world.
Do you have questions or comments about these September night sky events? Let us know in the comments.