Weather Outside Your Window: Final nights of summer to offer glimpse of distant galaxy

By Brian Lada, AccuWeather meteorologist and staff writer

Updated Sep. 1, 2021 1:26 PM EDT

Jupiter and Saturn took center stage in the night sky throughout August, and while the duo will remain prominent features in the sky throughout September, the ninth month of the year comes with a new slate of astronomical happenings to mark on the calendar.

Many big astronomical events throughout the year do not require anything other than a cloud-free sky, but a telescope or pair of binoculars will be needed this month to spot one of Earth's celestial neighbors.

The new month will also feature a full moon to illuminate the final nights of astronomical summer.

Here are three astronomical happenings to mark on your calendar as September gets underway.

1. Find the Andromedia Galaxy
When: Early September

The night sky is filled with countless stars, but with the help of a telescope, onlookers can see over 1 trillion stars bunched together in the depths of space.

The Andromeda Galaxy is the largest galaxy in our celestial neighborhood. It is comprised of more than twice as many stars as the Milky Way, the galaxy that is home to our solar system. Despite its size, it can be tricky to see as it swirls 2.5 million light-years away from Earth.

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To see the Andromeda Galaxy, stargazers can use a method called star-hopping. This is when you use a brighter star or constellation to help find the dimmer object.

Cassiopeia is a great constellation to help direct people toward the faint Andromeda. The upper angle of the w-shaped constellation forms an arrow that points directly at the galaxy. Cassiopeia rises in the northeast after sunset and is visible all night long.

Andromeda will look like a fuzzy cloud as opposed to a single point of light, but in that cloud is a sea of countless stars, planets, moons and potentially even alien life.

The Andromeda Galaxy glowing in the middle of a field of stars (Hans Braxmeier)

Since Andromeda is dim, it is best to look for the galaxy during the first part of the month when the crescent moon is below the horizon most of the night. It also helps to find a viewing spot away from disruptive light pollution.

2. Harvest Moon
When: Sept. 20

One of the final nights of astronomical summer will also feature one of the most popular full moons of the entire year.

Folks stepping outside shortly after sunset on Monday, Sept. 20, will be able to see the Harvest Moon, provided that it is not cloudy overhead.

The Harvest Moon is the full moon that rises closest to the September equinox, which this year, takes place just days after the month’s full moon.

A couple sits on a bluff overlooking the Missouri River as the full moon rises in the distance Monday, Sept. 8, 2014, in Kansas City, Mo. The full moon, also known as a Harvest Moon, was also third and final "supermoon" of 2014. The phenomenon, which scientists call a "perigee moon," occurs when the moon is near the horizon and appears larger and brighter than other full moons. (AP Photo/Charlie Riedel)

September’s full moon has other nicknames related to the changing of the seasons, including the Autumn Moon, the Falling Leaves Moon and the Yellow Leaf Moon.

3. September equinox
When: Sept. 22

September marks the changing of the seasons, but the official start of autumn varies depending on if you ask a meteorologist or an astronomer.

Astronomical autumn will officially begin in the Northern Hemisphere at 3:21 p.m. EDT on Sept. 22, while the Southern Hemisphere transitions to spring. This is different than meteorological autumn, which begins on Sept. 1. every year.

At the precise moment of the autumnal equinox, which marks the beginning of astronomical fall, the sun’s most direct rays are focused on the equator. As a result, the day and the following night will be about equal around the entire globe, both lasting around 12 hours.

After Sept. 22, the nights will be longer than the days across the Northern Hemisphere all the way until the next equinox, which takes place on March 20, 2022.

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