Jupiter and Saturn along the Perseid meteor shower made August an exciting event for those who love sky gazing. While the two gas giants made their closest approach to the Earth last month and continue to dominate the night sky, the Perseid meteor shower put up a great show of ‘shooting stars.’ However, as we head towards the Fall, the night sky is in transit. The summer constellations are making way for the winter constellations. Let’s have a look at some of the exciting astronomical events in September 2021.

Astronomical events in September 2021

September 1: Aurigid meteor shower

The month will begin with the Aurigid meteor shower. It’s an annual meteor shower active from 28 August – 5 September and will peak on 1 September this year. The shower’s radiant (the point from where all the meteors appear to originate) lies in Auriga, hence the name Aurigids. It’s a minor meteor shower that will produce up to 6 meteors per hour under dark skies. The best time to see the ‘shooting stars’ is after midnight, preferably in the early hours of 1 September.

September 2: Mercury at highest point in the evening sky

September 2021 Astronomical Events
Looking west at dusk on September 2 (Image: Stellarium Web)

The tiniest planet of the solar system will reach its highest point in the evening sky in its Aug-Sept 2021 evening apparition. The planet will shine at a magnitude of 0.1 in Virgo in the west at dusk. However, because of its proximity to the Sun,  this apparition will not be one of the most prominent and tricky to observe.

September 7: New Moon

The Moon will pass too close to the Sun and remain hidden in its glare for a couple of days. It’s a chance to see faint star clusters, nebulae, and galaxies.

September 9: ε-Perseid meteor shower

ε-Perseids will peak on the night of September 2021. The shower is active between September 5 – September 21. It can produce up to 5 meteors per hour. The radiant of the shower lies in the constellation of Perseus. The closest star to the radiant is epsilon persei, hence the name.

Neptune's Closest Approach, Meteor Showers, And Other Exciting Events In September 2021 1
Image showing the radiant of the meteor shower (Created using Stellarium App)

The shower will peak close to the New Moon, and so moonlight will present minimal interference.

September 11: Moon at perigee

The Moon will reach its closest point in its elliptical orbit around the Earth, appearing slightly bigger than normal.

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September 14: Neptune at opposition

In celestial mechanics, a planetary opposition occurs when the Earth lies between the Sun and the planet, with Earth being on the same side of the planet, as shown below.

Neptune's Closest Approach, Meteor Showers, And Other Exciting Events In September 2021 2
The concept of opposition

Thus on September 14, Sun, Earth, and Neptune will almost align, with Earth in the middle. This optimal positioning occurs when Neptune is almost directly opposite the Sun in the sky. Since the Sun reaches its greatest distance below the horizon at midnight, the point opposite to it is the highest in the sky at the same time. At around the same time that Neptune passes opposition, it also makes its closest approach to the Earth – termed its perigee – making it appear at its brightest and largest.

However, Neptune’s orbit lies far out in the solar system, at 30 AU, and hence the angular size doesn’t vary much over the course of conjunction and opposition. So despite being the closest to Earth around this time of the year, Neptune won’t be visible to naked eyes.

September 17-18: Moon, Jupiter, Saturn conjunction

Neptune's Closest Approach, Meteor Showers, And Other Exciting Events In September 2021 3
Looking southeast around midnight on September 17 (Image: Stellarium Web)

The Moon will pass close to Jupiter and Saturn on September 17 and 18. The three celestial bodies will be in Capricornus and will become visible in the west soon after sunset.

September 21: Full Moon

The Moon will reach its full phase on September 21 and lie opposite to the Sun in the sky. It will rise around sunset, reach its highest point in the sky around midnight, and set in the west at dawn.

September 23: Autumn Equinox

Neptune's Closest Approach, Meteor Showers, And Other Exciting Events In September 2021 4
The concept of equinox and solstice (Image: TimeAndDate)

September 23 will mark the second time when the Sun will shine directly over the equator. The Autumn equinox is the beginning of fall in the Northern Hemisphere and Spring in the Southern. On this day, every part of the world experiences 12 hours of day and night each. From this day, the nights will start getting longer than the days in the North and shorter in the South.

September 27: Moon at apogee

The Moon will reach its farthest point in its elliptical orbit around the Earth, appearing slightly smaller than normal.

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September 2021 Planet Round-Up

Mercury

September 2021 is not the best month to see the tiniest planet of the solar system. Although Mercury will reach its highest point in the evening sky on September 2, its proximity to the Sun will make it almost impossible to locate the planet.

Venus

Venus remains the brightest speck of light in the west after sunset. The planet dazzles at a magnitude of -4.03 in the constellation of Virgo. It sets around an hour and a half after sunset.

Mars

The Red Planet will be at its apogee (farthest point from Earth) on September 20. After putting up a great show in the night sky in September last year, Mars’ orbit has taken the planet to the far side of the solar system with respect to the Earth. Mars will remain hidden in the Sun’s glare for a couple of months.

Jupiter

Jupiter opposition 2021

Having passed its opposition on August 20, Jupiter dazzles in the night sky. After Venus, Jupiter is the brightest speck of light in the sky. Soon after sunset, the gas giant rises in the east, reaches its highest point in the sky around midnight, and sets in the west at dawn.

Saturn

Just like Jupiter, Saturn was at opposition last month. Both the gas giants lie close to each other in Capricornus. Also, look for the Moon passing by them on September 17-18.

Uranus

Uranus is heading for its opposition later this year. Uranus is currently visible as an early morning object in Aries. Since it has an apparent magnitude of 5.84, it won’t be visible with naked eyes. You will need a telescope to spot the planet.

Neptune

Neptune will be at opposition on September 14 and rises soon after dusk in Aries. At mag +7.06, it remains invisible to naked eyes. Hence, you will need a telescope to locate the planet.

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