Welcome to the September night sky. This is the month of the Autumn Equinox in the Northern Hemisphere, where the Sun crosses the celestial equator heading southwards.
Currently, the days and nights all over the planet are of approximately the same length. At the Equinox time, the rate of change of length of day is at its maximum, so this means that by the last week in September the days are getting shorter by three or four minutes every day at our latitudes.
This month does not have any major meteor showers to compare with August’s Perseids, but we do have a minor shower from the same area of the sky. This is the Epsilon Perseids visible on the night of the 7th. Unlike most meteor showers, this one is best observed in the early evening before midnight over in the north-eastern sky.
Directly overhead during September evenings, a summer triangle of bright stars is visible consisting of Deneb and Vega at the top and Altair at the lower point. This triangle of stars points due south and is a useful navigation aid at this time of year.
It is well known that the Sun goes through an 11-year sunspot cycle, but what is not well known to the public is that the amplitude of the cycle varies considerably, with some cycles having hardly any visible spots.
When the spot count is low, the Earth temperature falls, and the two last examples of this low spot count were the Maunder minimum from 1645 to 1750 and the Dalton minimum from 1790 to 1830.
The sunspot count has been directly recorded every day from the mid-1700s and, until now, 24 total sunspot cycles have been recorded. 2019 marks the end of cycle 24 and the start of number 25 that is expected to last until 2031.
The last three cycles had shown a considerable fall in sunspot numbers like the start of the Maunder and Dalton minimums.
Russian and Chinese climate scientists are forecasting that cycle 25 will be one of the lowest spot counts since records began, possibly leading to a little Ice Age starting in 2020. Predictably, western climate scientists are saying the opposite.
As long cold winters do much more harm than long hot summers, I will be making sure my central heating system works to be ready for the former rather than the latter.
The Moon is first quarter on the 6th, full on the 14th, last quarter on the 22nd and new on September 28.
To see the September Sky Map click on the pdf link below