The Blue Supermoon
Moonrise over the hills of Pilanesberg.
Whilst the world continued with its ‘busyness’ this week, the heavens quietly put on a spectacular show. In our part of the world, full Moon occurred at 03h35 on Thursday 31st August. But this was no ordinary Moon. It was a “Super Blue Moon”.
The Moon travels around the world in an elliptical orbit (an elongated circle), with earth closer to one side of the ellipse. Each month, the Moon passes through the point closest to earth (perigee) and the point farthest from earth (apogee). When it is full Moon at the same time that it is at or near its closest point to earth, it is called a “supermoon”, because it appears larger and brighter in the sky. These “supermoons” happen three to four times a year, appearing 14% larger, 30% brighter than when they are furthest from the earth (a ‘micro Moon’). According to NASA this Moon was about 357 000 km away from earth – which was 27 000 km closer than average.
The reflection of the Super Moon on Mankwe Lake in Pilanesberg.
This full Moon was the second full Moon in August, making it a Blue Moon (when we see the full Moon twice in a single month). This ‘newer’ definition was introduced by Sky & Telescope magazine in 1946, and happens approximately every 2.7 years. The older definition of a Blue Moon, dating back to at least the 1500s, is the name for the third full Moon in a season (between the solstice and the equinox) that has four Moons. The term “Blue Moon” originated from the 16th-century expression “the Moon is blue,” meaning something that was impossible. It has nothing to do with the colour of the Moon.
The time between Super Blue Moons is quite irregular. It can be as much as 20 years, but as a rule, 10 years is the average. Our next Super Blue Moons will occur in a pair, in January and March 2037. That was not, however, all that was happening last week. The planet Saturn, just a few days from its closest and brightest for the year, appeared near the Moon, appearing to swing clockwise around the Moon as the evening progressed.
Change your focus slightly, wait for the hippos to stop making ripples, and you get the reflection of the hills too…
A friend highlighted this event quite some time before it took place, and I was able to organise to view this phenomenon in the bush – Pilanesberg to be precise. Which got me to thinking about the relationship between full Moon and the wilderness. Sadly, in the wilderness, the full Moon is also known as “Poacher’s Moon”. Poachers love the full Moon as it makes it possible for them to move and see throughout the night without using artificial lights.
Moving to our oceans, each year, around the full Moon in November, the world’s largest synchronised coral spawning event happens along the Great Barrier Reef (larger in area than Italy – stretching 2,300 kilometres down the eastern coast of Australia, covering an incredible 348 700 km²). When corals release egg and sperm bundles into the water like this, they cause massive ‘spawn-slicks’. This rare and dramatic phenomenon lasts just a couple of nights. Inside the fertilized eggs, a tiny embryo develops within a day or so. The tiny baby coral is ready to settle after about five days, and drops down to the bottom. If it is lucky, it will find a good spot to grow for many decades. The visual effect of this coordinated lunar timing is so dramatic that it can be seen from space.
As an interesting aside, because coral reefs are under threat and dying (think climate change, declining water quality, overfishing, pollution and unsustainable coastal development), experiments are now being done to harvest these slicks of coral larvae to help restore the coral reefs. Our South African colonies of coral also spawn on a single night of the year, simultaneously, all over the reef.
The Moon always appears larger at a low angle when seen through the atmosphere.
The lunar cycle affects birds too. Two simple examples: Barau’s petrels (an endangered seabird that mates and breeds on the island of Réunion in the Indian Ocean) time their pre- and post-breeding migrations by the length of the day, waiting until it reaches 12.5 hours before setting off. Whilst their arrival dates at the breeding grounds vary each year, they always arrive together at the full Moon. This suggests they use both the Moon and the length of the day to synchronise their migrations. GPS tracking data reveals that the foraging activity of the European nightjar more than doubles during moon-lit nights (which makes sense as they are nocturnal insectivores that hunt by sight). The birds then migrate simultaneously about 10 days after the full Moon.
That magical moment just before the Moon rose.
Plants are also affected by the full Moon. The “joint pine” or Mormon tea (Ephedra foeminea) is widespread in the eastern Mediterranean area. The exact timing of pollination in E. foeminea varies considerably from year to year but is always correlated with the full Moon of July. This gymnosperm produces a clear sugary substance which oozes out of cone-shaped female organs, forming globules. When an insect lands on the globule, it carries with it pollen that sticks to the substance, and eventually the pollen makes its way to a seed at the base of the organ, fertilizing it. These globules apparently glisten brightly in the full moonlight, attracting insects. No other plant has been found to wait for the full Moon to activate a pollinator inducement.
The Super Blue Moon was incredibly bright.
Our final example comes straight from the plains of Africa. The dung beetle Scarabaeus zambesianus uses the polarisation pattern of moonlight and the way it scatters through the atmosphere to navigate in a straight line! As a dung beetle with a fresh dung pile, the best thing to do is to take your newly rolled dung ball and leave in a straight line, moving as quickly and efficiently as possible to your burrow. Hanging around could get you eaten by a predator. Or you could lose your dung ball to a competitor. In recent research done in a lab in Sweden, where scientists placed dung beetles under non-polarising artificial light, they apparently discovered that they travelled in circles – confirming the use of moonlight as a navigation aid.
And one last image looking towards the magical sunset of the African bushveld.
Whilst one can find endless facts about the Moon, sometimes it is worth simply appreciating it for its magic. There is something distinctly enchanting about the full Moon. Each time it arrives, I revel in its beauty. And when it starts to wane, I look forward to the next full Moon…
“Go slowly, my lovely Moon, go slowly.” Khaled Hosseini, The Kite Runner
Jacqui Ikin & the Cross Country Team