Case Rijsdijk’s What’s up?
This February has 29 days as 2020 is a leap year. Leap years were introduced to our calendar to keep our natural cycles, such as the seasons, in step. The Julian calendar, which added one day every four years, was used up to the 16th century, but as it did not correspond with the natural cycles, it was by this time out of step by about 10 days. To correct this, Pope Gregory implemented what is now known as the Gregorian calendar in 1582.
The Gregorian calendar made all century years - such as 1500 and 1900 - not leap years, but if the year was divisible by 400 it would be a leap year. So 2000 was a leap year. Simply put, years divisible by four are leap years, those divisible by 100 are not, but those divisible by 400 are, and finally, those divisible by 4000 are not! This should keep everything working nicely for at least another 20 000 years, by which time it will be someone else's problem! It is interesting to note that Omar Khayyam's calendar from the early 12th century was more accurate that our current one.
The month starts with a waxing crescent Moon that becomes full on the 9th with the new Moon following on the 23rd, and the first crescent becoming visible the following evening just after sunset. After this the Moon once again becomes an excellent marker for identifying planets, stars and clusters. After sunset on the 27th, the waxing crescent Moon is close to the bright planet Venus, often mistakenly called the "Evening Star". I say "mistakenly" because Venus is a planet, not a star, and it often appears before sunrise and is then called the "Morning Star". This month Venus is the only planet visible, and once set, no other planets are visible till well after midnight.
The northwestern evening sky this month is still dominated by the constellation of Orion, the Hunter, with the small bright cluster of isiLimela, the open cluster of the Hyades and the "belt" stars of Orion forming an almost vertical line with the horizon later in the evening.
To the south-east the Southern Cross and the Pointers are clearly visible, and high up, to the upper right, the Large and Small Magellanic Clouds can be seen if you are away from city lights. These are the two nearest galaxies to our own and both are a little smaller than our Milky Way. The former is about 160 000 light years away and the latter 180 000 light years. You should be able to find the small Magellanic Cloud with a pair of binoculars. On the lower righthand edge is the globular cluster 47 Tucana, looking rather like a fuzzy tennis ball, one of the biggest and brightest clusters. It consists of about a million of some of the oldest known stars (see sketch).
There are many of these globular clusters and they are found in what is called the "halo" surrounding our Milky Way galaxy. Many of the biggest and best of these globular clusters are visible in the southern skies.
The diagram also shows how to find "south" using the Cross and Pointers.
The easiest way to determine the Celestial South Pole is by taking an imaginary line through the long axis of the Cross and marking the point where it meets the imaginary bisector of the Pointers. The direction "south" is immediately below this point.