Astronomy: What to look for in the sky this September

The Perseus Double Cluster circled in green on the map

Beneath the left hand star of the W is one of the best star clusters in the entire sky (location circled in green on the map) - the Perseus Double Cluster - Credit: James Abbott of North Essex Astronomical Society

James Abbott of North Essex Astronomical Society on what can be seen this month.

The Autumn Equinox takes place this year on Wednesday September 22, when the hours of daylight and night are broadly equal.

Although the Sun is getting lower in the sky each day, for several hours in the middle of the day, sunshine can feel warm through early Autumn as the Sun still attains over 30 degrees above the horizon when in the South.

Jupiter and Saturn remain prominent and in mid-month at around 10pm they are in the South, rather low down.

The waxing gibbous Moon will be just below and to the right of Jupiter on the night of the 17/18.

The September Full Moon can be seen on the night of the 20/21 and will be about twice as high in the sky as the mid-summer Full Moon.

Each successive Full Moon through Autumn and early Winter gets higher in the sky until January.

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Venus might be glimpsed low down in the West after sunset throughout the month.

The best period for dark skies stargazing will be in the first half of the month, with twilight ending by about 9.30pm.

Looking to the North East the familiar W shape of the constellation of Cassiopeia is about half way up the sky at 10pm.

Beneath the left hand star of the W is one of the best star clusters in the entire sky (location circled in green on the map).

Seen as a hazy patch to the unaided eye, binoculars or a small telescope reveal there are actually two distinct star clusters.

Known as the Perseus Double Cluster, the pair was first documented in 130 BC by the Greek astronomer Hipparchos.

The clusters appear to be side by side but in reality are separated in space, with distances from us of 7,100 and 7,400 light years.

They are both young in astronomical terms, being about 12 million years old.

Young clusters like these are tightly packed together, but as they age the stars will spread out into space.


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