Thursday, 8 October 2015

Moon and Supermoon

I have always been fascinated by the moon.  I live by the sea and have known since childhood that the lunar cycle controls the high and low tides. Pink Floyd's, Dark Side of the Moon blared out from my older brothers' bedroom during my formative years and of course, I saw Neil Armstrong set his feet safely on the surface in 1969, hoisting the star-spangled banner.  Of this stuff dreams are made.  I was not destined to become an astro-physicist but take a keen interest in the teachings of Professor Brian Cox, (who reminds a little of Simon Armitage), and I love to watch the Sky at Night. One day I may buy a telescope but not yet.  At the moment, I only seem to be in one place long enough to write my contribution to this blog once a week. 

This September, our earth became a viewing platform for an unusual astronomical event: A supermoon combined with a lunar eclipse that produced what is known as a blood moon.  Many people sat up into the early hours to watch the climatic eclipse and many incredible photographs were taken and posted online from vantage points all over the world.

Supermoon is not an official astronomical term.  It was first coined by astronomer Richard Nolle in 1979 and his definition of the supermoon is a new or a full Moon that occurs when the Moon is at or near (within 90% of) its closest approach to Earth in its orbit’. The technical term for a supermoon is perigee-syzygy of the Earth-Moon-Sun system.  On average the moon is 238,000 miles away from earth but the moon’s orbit around the earth is in an elliptical orbit. This means that the moon’s proximity to the earth varies from 225,000 miles at its closest (perigee) and 251,000 miles at its furthest distance (apogee). 
 
Of course this means that our moon passes through a perigee and apogee stage at least once every calendar month, the time it takes to travel from perigee to perigee. The transition between these  points is not synchronized,  sometimes the closest point is when the full moon is visible and this is what Nolle called a supermoon.  When it occurs as on Monday 28 September 2015 we on earth see the moon 12 – 14% bigger.  Up to 30% bigger than at apogee when it is called a mini or micro moon.  

A supermoon can also happen when the moon is ‘new ‘. In November 1997, I was with my family at The Epcot Centre in Florida. It was a beautiful clear evening.  I was standing at a food stall, (there was a world cuisine event taking place), when I looked up at the sky and saw a huge thin smile of light in the sky. It took me by surprise having always lived at a latitude where the moon phases change vertically. It looked like the grin of Lewis Carroll’s Cheshire Cat.  I asked the young American lady at the counter lady, “Is that your new moon?”  She looked at me for a while with a puzzled expression and then confidently declared, “Mam, we only have one moon.”  It was a truly unforgettable moment.

What made this September’s super moon so spectacular was that it occurred during syzygy. In astronomy, the term syzygy refers to the straight-line configuration of three celestial bodies: in this case earth, moon and sun all aligned. When the Moon is close to the lunar nodes of its path during syzygy, it causes a total solar or a total lunar eclipse. We were able to witness a vivid red, ‘blood moon’ very close to the earth, a reasonably rare event in the possibly, never-ending,  astronomical calendar. 

Okay but what about a blue moon?  “It only happens once every blue moon,” is a very well know English expression. Songs have been written to the blue moon but does it ever happen? Well technically it does.  The astronomical calendar is divided into four three monthly seasons; Spring, Summer, Autumn and Winter.  A lunar cycle is 28 days, (the time it takes for the moon to orbit the earth), so sometimes there will be two full moons during one calendar month and therefore, four full moons in one astronomcal season.  When this happens, the third full moon is called a ‘blue moon’ but it doesn’t look blue in colour.

A blue coloured moon is a bad sign. It only happens when the atmosphere is filled with dust particles of larger than 0.7 microns, after a major catastrophic event on earth such as a major volcanic eruption or a bush fire.  The dust particles refract the light making the moon appear blue in the sky. The moon is reported as appearing blue in colour after the volcanic eruption of Krakatoa, Indonesia in 1883, Mount St Helen’s, Washington State,  USA in 1980, El Chichon, Mexico 1982 and Mount Pinatubo, Luzon, Philippines 1991. So if you see a blue coloured moon, then you see trouble on the way. 






Blue Moon Blues

"Hey there big Moma," said Stegosaurus Junior,
"that shiny disc in the sky
 is lookin' kinda blue."
"Yeh Baby," Moma told him,
I can see the moon is changing,
let's ask your Papasaurus, 
he'll know what to do." 
Big ole Papasaurus, sat his son down on the plain, 
he though it might be somethin'
but he didn't get much brain, 
"It may be a bad moon rising son,
Ii could be trouble on the way,
but I'm no astro-physicist,
that's just my point of view.
Maybe we should tell someone 
but I'm hungry anyway,
let's just keep our heads down son,
maybe it'll fade away." 


The rest, Dead Good readers, is Jurassic history. 
Thanks for reading  - Adele

Reactions:

2 comments:

Steve Rowland said...

Informative blog and amusing poem. Thank you.

Lady Curt said...

Very interesting Adele ..get you telescope...life is too short !