What’s up? March 2021
The month starts with a waning Moon just before quarter that becomes new on the 13th, with the first crescent becoming visible the following evening. The autumn equinox occurs on the 20th and is the time when there are as many hours of darkness (night) as there are daylight hours. Many regard this as the beginning of autumn, but we all know that the best days of the year are still ahead of us!
Also from this day on, the Sun rises and sets progressively further north of east, and is lower in the midday sky each day, till the solstice in
June. It is the time of the year when the rate at which we lose daylight is decreasing at its fastest. At the beginning of the month sunrise and sunset are at 06:20 and 19:07, while on the 31st they are at 06:45 and 18:29 respectively: we lose a little over an hour in the course of the month.
Away from the city lights, the evening sky is really good! The Milky Way stretches across the sky from north-west to south-east and is to me still a spectacular sight. Of course we are a part of that “city of stars” and thus can only see a part of it. Our Sun is one of over 200 billion others and is about 30 thousand light years away from the centre of our galaxy, which is hidden by dust, in the constellation of Sagittarius. After a short time when your eyes have adapted to the darkness, large, black dust bands are visible in the Milky
Way. Interestingly, the Australian Aborigines focus on these bands and “see” an emu! isiLimela is now low above the north-western horizon and Orion is losing its dominance in the northern sky. By month’s end it will be lying on its side just above the western horizon, with Sirius unmistakably bright above it. If you look at the sky around 19:15, only the brightest stars will be visible and this is an ideal time to try and identify them. The rectangular shape formed by Rigel, Sirius, Procyon and Betelgeuse was known as Magakala to the Tswana. When this grouping was visible in the early evening, it was time to start harvesting crops. Another geometric shape, an equilateral triangle known as the Great Southern Triangle, is formed by Sirius, very bright and high up in the north; the red giant Betelgeuse, rightmost star in Orion; and Procyon, the little Dog Star, to the right of Betelgeuse. Aldebaran, the reddish orange star to the upper right of isiLimela (Pleiades) is also easily visible. Take a look an hour later and see how many more stars there are and how easy it is to recognise the brighter ones.
Betelgeuse, which features in the geometry above, is the largest star visible to the naked eye and is about 645 light years away; if it were to replace the Sun, then the planets Mercury, Venus, Earth, Mars and possibly Jupiter would be inside it! It has recently undergone some variations in its brightness. It is a supergiant red star with a semi-regular variance in brightness. The recent dimming of Betelgeuse is probably due to it emitting vast amounts of hot gas and dust, that cooled and so blocked its light from view. By January 2020 it appeared 2,5 times fainter than usual, but it is now returning to normal.
For the entire month there is a mini celestial dance between Mercury, Jupiter and Saturn, looking east, before sunrise. They will be joined by the Moon from 8 to 12 March. Make a cup of coffee and enjoy some of Nature’s beauty!