February begins, named after Februa, the Roman Festival of purification.
Look out early on February evenings for a couple of brilliant stars, Rigel in the foot of Orion and Capella in Auriga.
Last week our almanac featured the star chart and the way they are usually designed as a circular map, and marked by latitude and longitude in degrees and minutes. The origins of degrees and minutes lies with ancient Sumerians.
The ‘degree’ was devised by the ancient Sumerians of the middle-east. It was they who divided the circle into 360 degrees. Their word for a degree was ‘gesh’ which meant man, or one, or one degree.
The Sumerians of ancient Mesopotamia (2100 BC) had a calendar of 360 days. This came from rounding off the lunar month of 28 days to 30 days. Our almanac will explain more about what a lunar month in a future post.
This number of 360 fitted their mathematical and astronomical system that was based on the numbers 6 and 60.
Multiplying 6 x 60 equals 360, and 360 is the number we still use to divide the sky and any circular plane, and to this very day we divide all circles into 360 degrees.
The number 60 is also important for us and our astronomical clock because clock faces are usually divided into the familiar 60 units that we use to mark both minutes and seconds.
The word ‘second’ comes from the Latin secunda, meaning ‘second’ as in coming after the first, and being a shorter way of saying “secunda minuta”, or the second minute that comes after the first minute.
There has been lots of speculation as to why the number 60 was so important to the Sumerians. The fourth-century Greek scholar Theon supposed that the reason 60 was chosen as the base number for their numbering system was that 60 was the lowest number into which their first 6 numbers divided. Even with our number system you can see that 60 divides by 1, 2, 3, 4, 5, 6, 10, 12, 15, 20 and 30!
The Sumerian gods were given numbers. Anu, the great god of the heavens was given the number 60, Anatu, the earth-god has the number 50, Abyss is given 40, the moon-god is 30, and the sun-god is given 20. As we have noted already, the Sumerian word for 1 is the same word as is used for ‘man’.
For the Sumerians, the most mystical number of all was 60 x 60, which comes to 3,600. This number was called ‘sas’, a word that means ‘everything’, ‘whole’ and ‘cosmos’. The Sumerian written symbol for this word looks a bit like a circle!
Perseus is one of the most important figures of ancient Greek mythology and the legendary founder of Mycenae and of the Perseid dynasty there. He was the first of the mythic heroes of Greek mythology whose exploits in defeating various monsters left over from the mythic beginning of the world. Perseus was the hero who killed Medusa and claimed Andromeda, having rescued her from a sea monster.
In the constellation of Perseus it his bravery in killing the gorgon Medusa that is drawn out in the sky amongst the stars.
The star called Algol may not be the brightest star of this constellation, but it definitely is its most famous star. Algol (from Arabic al-Ghul, which means The Ghoul or The Demon Star) represents the eye of the gorgon Medusa. This star is the prototype of a whole group of eclipsing variable stars.
The first variable star was identified in 1638 when Johannes Holwarda noticed that Omicron Ceti (later named Mira) pulsated in a cycle taking 11 months. The second to be described variable star was the eclipsing variable Algol by Geminiano Montanari in 1669; John Goodricke in 1784 gave an explanation of its variability. Until relatively recently Algol was understood to be an eclipsing binary star is a binary star in which the orbit plane of the two stars lies so nearly in the line of sight of the observer that the stars eclipse each other so it looks like a blinking star. However Algol turns out to be a multiple star, a ternary star with three stars forming a star system