Once in a blue moon

It’s been quite some time since I’ve posted anything(around two months) hence the title. But the title has a purpose apart it’s idiomatic meaning. It has something to do with last night’s magnificent event which was something too good to be missed. While some of you may know and some don’t, last night was the night of a “Super Blue Blood Moon”. This name is the result of the spectacular trifecta of events that took place last evening.

The three events that make tonight’s moon so special are:

• The moon was a supermoon.
• It was a blue moon.
• It was a blood moon.

Let us talk about the three events separately.

Supermoon

 Firstly, let’s talk about what a “Supermoon” is.  A supermoon is a full moon or a new moon when the moon is the closest to the earth.  This is a result of the moon’s elliptical orbit around the Earth. At times when the closest to the Earth or at the “perigee”, we get a supermoon. When it’s farthest from the Earth, or at an “apogee”, we get a “Micromoon”. The difference between the distances between the Earth and The Moon at perigee(356,355 km) and an apogee(407,725 km) is almost about fifty thousand kilometers. Last night, however, was a full moon night. The moon was approximately at the closest point to Earth on its orbit. This causes the moon appearing bigger and brighter. A supermoon is roughly 14% bigger in diameter than a micromoon and almost 40% brighter. However, the apparent change in size is so small, it is almost unnoticeable to most skygazers. The first Supermoon of 2018 was seen on January 1st. This was the second supermoon of the year and also in January which was the reason for the second factor of last night’s event.

(The supermoon of January 1, 2018. Captured by Amrita Baruah)

Blue Moon

The name “Blue Moon”, does not have anything to do with the color of the moon. A blue moon in this context refers to the second full moon of a calendar month. The original use of the term was to define a rare incident or something which was never going to happen at all and was often used in a humorous way and hence the phrase “once in a blue moon”. Eventually, this use was associated with this event(two full moons in a month) to emphasize it’s rarity.

But a literal “blue moon” is also possible. Again, it’s even rarer. A literal blue moon occurs due to the presence of dust or particles of a specific size in the atmosphere. There have been quite a few incidents in history when the moon actually appeared blue. However, last night, the moon appeared red due to the “Blood Moon”.

Blood Moon

Last night’s eclipsed moon gets it’s name “Blood Moon” due to the fact that a totally eclipsed moon appears red. This occurs due to a phenomenon called “Rayleigh scattering”. In simpler words, the sunlight is filtered and refracted by the Earth’s atmosphere in such a way that the red section of the spectrum undergoes minimum refraction which makes the moon appear red. The moon can also appear red due to other factors like certain atmospheric phenomena.

A Blood Moon has had a very strong impact on traditional folklore. An eclipsed moon was believed to be a sign of an upcoming disease or famine. Though such superstitions have been proven wrong now, thanks to advancements in science, there are still some who believe in them. But you can rest assured that there is nothing harmful about an eclipse, it is just a natural phenomenon.

I hope you enjoyed the event last evening. Here are some pictures from last night’s spectacular event.

 

(Photos taken by 4 inches telescope of Assam University)