The night sky in September

Want to know what's up in the sky tonight? Our night sky chart will provide you with the information you need to locate the brightest planets, stars and deep-sky objects ...

The equinox occurs this month and signals the end of summer. Autumn is on the way and with the season comes shorter periods of daylight and ever-longer periods of nighttime.

september This month’s chart shows the night sky looking South in mid September at 2300. (click on image for larger view)

Pegasus, the Winged Horse – this month’s sky highlight

Pegasus contains the large recognizable pattern of stars called the Great Square of Pegasus. Pegasus was the winged horse of mythology, created by Neptune, born of sand, sea-foam and Medusa’s blood.

For ease, we start this observation at 2330. This is when the Great Square of Pegasus is exactly due South. It’s stars are not the brightest, but because they create a square-ish pattern 15 degrees wide and high, they’re recognisable. To find the Square, look approximately 60 degrees in elevation. If you’re struggling, but you can see Cassiopeia, use this as a guide. Set yourself traveling in a five o’clock direction for 30 degrees. This will bring you to the Square.

To the right of the Square is Andromeda. We’re now going to find a galaxy, which is 2.9 million light years from us. If you can see it with the unaided eye you are gazing upon one of the most distant objects visible without optical aid.

Take the uppermost left-hand star of the Square and travel for six degrees in a 10 o’clock direction and you will arrive at a bright-ish star. Move from here in an 11 o’clock direction for seven degrees and you will see a brighter star called Mirach. Stop here. Now, three degrees away in a 10 o’clock direction you will find another faint-ish star. Aim a pair of binoculars at this position. Slowly continue to move in the same direction for another three degrees. As you do you will sweep-up a fuzzy patch. This is the great Andromeda Galaxy – M31.

This is one of the most magnificent objects in the night sky and undoubtedly the most famous galaxy outside our own Milky Way. Its extent covers as much of the sky as five full moons put together. Binoculars will show M31 with a clear brightening towards the centre. They may also show one of two of Andromeda’s companion galaxies – M32. If you are lucky you may also see M110. Careful observation of the nuclear region with a telescope will reveal faint dust lanes and other structures. The Hubble Space Telescope has shown that the Andromeda Galaxy has a double nucleus, indicating that it may have cannibalised another galaxy. M31 was once thought to be a nebula inside our galaxy, but in 1923, astronomer Edwin Hubble showed that it lies outside the Milky Way. The galaxy is over 150000 light years across, and has a mass 1.2 trillion times that of our Sun.

In history …

Johann Galle of the Berlin Observatory saw and identified Neptune on the night of September 23rd 1846.

On September 1st 1859 Richard Carrington observed and recorded the first solar flare. The next night a beautiful aurora was witnessed by millions of people at northern latitudes.

Nearly a century later, on September 12th 1959, the USSR crash-landed Luna 2 onto the Moon, making it the first manmade object to strike another world.

On September 24 1970 the USSR’s unmanned vehicle, Luna 16, returned to Earth carrying three ounces of samples from the Moon. (Meanwhile, the crews of Apollo 11 and 12 had returned over 140 pounds of lunar materials.)

Viking 2 landed safely on Mars on the 3rd of September 1976. (Viking 1 had landed on Mars on July 20th, 1976.)

Top

© Macclesfield Astronomical Society 2017