If you don't often look at the moon, tonight is just the night to do it.
It's a kind of lunar triad, and it's all the rage. This month's full moon is called a “super blue moon.”
Don't know what this is? Read on.
What is a supermoon?
The Moon makes one revolution around the Earth once every 27.3 dayswith the phases of the Moon occurring every 29.5 days. However, the orbit is not circular, but elliptical, something like an elongated circle. This means that the Moon changes its distance from the Earth. When it is closest, this is called perigee, and when it is furthest, this is called apogee.
So, because the Moon is closer, brighter, and slightly larger in the sky, it is now colloquially referred to as a “supermoon.”
WATCH | What makes a supermoon a supermoon?
Supermoons occur about three to four times a year. The last one was on the day of a total solar eclipse, April 8.
The term “supermoon” is not scientific. It comes not from astronomy, but from astrology. It was invented in 1979 by astrologer Richard Nollewho claimed that the supermoon would cause earthquakes and an increase in severe weather. However, no connection was found. In fact, 2018 study found that there is no connection between supermoons and earthquakes.
What is a blue moon?
There are several definitions of the term “blue moon”.
The first is when there are two full moons in a month; the second is when there are four full moons in a season instead of the usual three. And the blue moon is not the fourth, but the third, as is the case with the full moon of this month.
Since the beginning of summer on June 20, there have been full moons on June 21, July 21 and today. The next full moon will be on September 17, and yes, it will be super too.
Why do we call it a blue moon? According to BritannicaThe term comes from the word “rarity”, which originated in the 16th century.
A supermoon and a blue moon together are rare. This is because approximately 25 percent of all full moons are supermoons.and only three percent of all full moons are blue moons. On average, super blue moons occur every 10 years or so.
Will it look different?
Yes… and no.
When the full moon is at perigee (its closest point), it can appear up to 14 percent larger and 30 percent brighter. However, unless you compare it to any other full moon, you'll be hard-pressed to tell the difference. And no: it won't look blue.
“If you look at the sky tonight, if you look at the moon, you wouldn't realize it's about 10 percent larger than usual. You just don't have a frame of reference,” said Paul Delaney, an astronomer and professor emeritus in the department of physics and astronomy at York University in Toronto.
“Because of this apparent increase in angular size, it means that it is also brighter – in this case, about 20 percent or so brighter. But again, you won't be able to perceive it because it will be bright, like all full moons.”
If you want to compare, one way is to take a photo of the full moon at perigee in a month when it is not closest to the Earth, then take a photo in a month when it is closest to the Earth and compare.
But if you really want to visually see a bigger moon, there is a way. When the moon rises or sets on the horizon, it appears much larger, especially when there are other objects around as a frame of reference.
It's called moon illusionand it's not entirely clear why this happens. But overall, it has to do with a few factors, including how our brains perceive the size of things that are closer to us or further away.
There are several ways to make sure that the Moon on the horizon is not actually larger than it is when it is in the sky.
You can try holding up a round aspirin when the moon is on the horizon and when it is higher in the sky and compare. You can also hold up a fingernail to it and do the same. You will find that the moon is always the same size.
Even if you can't tell the difference yourself, the moon is always a beautiful sight. Use binoculars, and the plane of the moon will disappear. Instead, you'll be able to discern craters and other beautiful features.
“The full moon is really eye-catching. Usually, everyone stops and looks and says, 'Oh my God, that's beautiful,' mainly because it's so close to the horizon,” Delaney said.
“And, you know, the perspective really does open up some great photography opportunities.”