Quad-Cities Popular Astronomy Club: May Features a ‘Blood Flower Moon’ | Local News
By Alan Sheidler People’s Astronomy Club
I must admit that I have always been interested in speed. The speed at which things move has always fascinated me.
What is the speed of an airliner, an automobile, a galloping horse, a snail or a horsefly? Granted, a jet airliner is faster than a garden snail on a miles per hour (or kilometers per hour) basis – but is that the best way to compare their speeds? What if we consider the size of the object and compare the time it takes for the accelerating object to move its own length?
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For example, let’s say a Boeing 747 (which is 70.6 meters long) is cruising at 900 kilometers per hour. If you divide the length of this airliner by its speed, you find that it takes just under three tenths of a second to travel its own length. Seems pretty quick to me.
But compare the 747 to a horse. I won’t bore you with the math, but a galloping horse can cover its own length in less than two-tenths of a second. Therefore, a horse is actually faster than the 747 when you factor in speed versus size.
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And a gadfly? I was surprised to learn that a male gadfly pursuing a female was measured at 145 km/h! Absolutely, it’s fast. But considering its small size (1 inch or 25 millimeters), this male gadfly moves its own length in an incredibly fast 0.00063 seconds. Now it’s really fast!
So now consider the modest garden snail. We’ve all seen one of these little guys go at a breakneck speed of one hundredth (0.01) km/h. It is indeed slow on an absolute basis, but considering that the average size of a snail is maybe 1.2 inches, and dividing its length by its speed, we see that a garden snail moves over its own length in just under 11 seconds, which is faster than I thought.
Now consider a very fast moving object – the moon. The moon’s actual speed varies a bit because its orbit is slightly elliptical. But its average speed in orbit around the Earth is about 3,660 km/h, or more than 2,200 miles per hour.
Everyone would agree that it’s fast, right? But now consider that the moon is 3,475 kilometers in diameter. Adjusting the moon’s speed to its size, we find that it travels its own diameter in just under an hour – about 57 minutes, to be exact. Compared to a garden snail, the moon is downright quiet. In fact, the moon is one of the few objects that moves by its own diameter in about an hour.
We will have the opportunity on Sunday May 15 to see the movement of the moon in real time. A lunar eclipse will begin that evening around 9:28 p.m. Central Time.
At this time – assuming the sky is clear – we will see the moon enter the darkest part of Earth’s shadow, called the umbra. At around 9:45 p.m. you should see a “bite” on one side of the moon’s disk and watch it gradually grow larger as the eclipse progresses.
This partial eclipse phase will continue as the moon dips deeper and deeper into Earth’s shadow for about an hour. At 10:29 p.m., the moon will be completely in shadow and will continue to be fully eclipsed for about 85 minutes as it gradually passes through Earth’s dark shadow.
The moon will be deepest in shadow at 11:12 p.m. Totality will end at 11:54 p.m. when the moon begins to re-emerge from the shadows. The remaining partial phase of the eclipse will continue until 12:56 a.m. Monday morning as the moon leaves the shadow and is gradually re-illuminated by sunlight.
During partial eclipse phases, the moon will move its own diameter from light to shadow and then back again. The time needed to do this is just over an hour because the moon’s path is slightly offset from the center of the Earth’s shadow. This means that the moon will have to travel a bit further to go from light to dark and vice versa.
Nevertheless, a lunar eclipse is a good opportunity to observe the movement of the moon in real time and prove to yourself that the moon indeed moves by its own diameter in about an hour.
This month’s lunar eclipse will also be a great opportunity for anyone who wants to enjoy one of nature’s most interesting and beautiful astronomical events. As the lunar eclipses go, this will be one of the best in a long time.
During the eclipse, Earth’s dark shadow will cover the moon’s surface for 85 minutes, during which time there will be no direct sunlight on the moon’s surface. The moon should theoretically be invisibly dark during the time it is in shadow; however, there will still be refracted light from Earth’s atmosphere that will make its way to the lunar surface.
As a result, we’ll see a dimly lit moon that can take on a very interesting color – a dull shade of red, brick red, orange, copper, or even gray. We won’t know the colors we will actually see until the eclipse occurs.
Imagine you are an astronaut standing on the surface of the moon and looking up at the sky during the eclipse. What you would see would be something beautiful and miraculous.
Watching the Earth pass in front of the Sun, you would always see the Earth’s atmosphere glow like a reddish halo as sunlight is refracted or bent around the Earth. This reddish halo is caused the same way we have red sunsets or sunrises on Earth.
Sunlight refracted from Earth’s atmospheric halo dimly illuminates the moon’s surface. So even if there is no direct sunlight falling on the part of the moon in shadow, it will still be visible to us as a pale reddish color.
The colors seen on the moon can be very different depending on whether there were recent volcanic eruptions, thick clouds, or thunderstorms on Earth before the eclipse. Dust particles and clouds can filter sunlight, causing dramatic shades of red.
A total lunar eclipse is called a “blood moon” because it can look almost blood red. The May full moon is sometimes referred to as the “flower moon” because May is the month when flowers bloom.
This month’s Lunar Eclipse might be called the “Blood Flower Moon” but whatever we call it, it should be good. Look for a spot with a clear view of the southwest sky and bring a pair of binoculars or a small telescope.
Often when we hear or read the word “eclipse” it is followed by some sort of warning to protect your eyes. This warning, however, only applies to solar eclipses. During a lunar eclipse there is no danger to your eyes, so you can safely view it without any eye protection and use binoculars or a telescope without a filter.
As you may have understood, a lunar eclipse is only possible when the moon is full. Because the full moon is very bright, its light drowns out darker deep sky objects.
As the lunar eclipse unfolds, however, the moon darkens and allows other nearby objects to shine through. Watch the moon darken and other nearby stars appear.
You won’t want to miss this event. Let’s hope for clear skies and keep looking up.
PAC invites the public to its next viewing session at Niabi Zoo on May 21 at sunset and on the third Saturday of each month until November. To learn more, visit the PAC website at popularastronomyclub.org or search for the club on Facebook.
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