The Moon appears 12% bigger when it is closest to Earth compared with its appearance when it's farthest away. (Tomruen/WikimediaCommons, CC BY-SA)
What's a super moon?
A supermoon occurs when a full or new moon coincides with the Moon's closest approach to the Earth.
The Moon's orbit is not a perfect circle as it slowly rotates around Earth. (Rfassbind/WikimediaCommons)
The Moon's orbit around Earth is not perfectly circular. This means the Moon's distance from Earth varies as it goes around the planet. The closest point in the orbit, called the perigee, is roughly 28,000 miles closer to Earth than the farthest point of the orbit. A full moon that happens near the perigee is called a supermoon.
So why is it super? The relatively close proximity of the Moon makes it seem a little bit bigger and brighter than usual, though the difference between a supermoon and a normal moon is usually hard to notice unless you're looking at two pictures side by side.
The phases of the Moon correspond to how much of the lit–up side you can see from Earth. (Orion 8/WikimediaCommons, CC BY-SA)
How does a lunar eclipse work?
A lunar eclipse happens when the Earth's shadow covers all or part of the Moon. This can only happen during a full moon, so first, it helps to understand what makes a full moon.
Like the Earth, half of the Moon is illuminated by the sun at any one time. A full moon happens when the Moon and the Sun are on opposite sides of the Earth. This allows you see the entire lit-up side, which looks like a round disc in the night sky.
If the Moon had a totally flat orbit, every full moon would be a lunar eclipse. But the Moon's orbit is tilted by about 5 degrees relative to Earth's orbit. So, most of the time a full moon ends up a little above or below the shadow cast by the Earth.
A lunar eclipse occurs when the Moon passes through Earth's shadow. (Sagredo/WikimediaCommons)
But twice in each lunar orbit, the Moon is on the same horizontal plane as both the Earth and Sun. If this corresponds to a full moon, the Sun, the Earth and the Moon will form a straight line and the Moon will pass through the Earth's shadow. This results in a total lunar eclipse.
To see a lunar eclipse, you need to be on the night side of the Earth while the Moon passes through the shadow. The best place to see the eclipse on May 26, 2021, will be the middle of the Pacific Ocean, Australia, the East Coast of Asia and the West Coast of the Americas. It will be visible on the eastern half of the U.S., but only the very earliest stages before the Moon sets.
The Earth's atmosphere gives the Moon a blood-red glow during total lunar eclipses. (Irvin Calicut/WikimediaCommons, CC BY-SA)
Why does the moon look red?
When the Moon is completely covered by Earth's shadow it will darken, but doesn't go completely black. Instead, it takes on a red color, which is why total lunar eclipses are sometimes called red or blood moons.
Sunlight contains all colors of visible light. The particles of gas that make up Earth's atmosphere are more likely to scatter blue wavelengths of light while redder wavelengths pass through. This is called Rayleigh scattering, and it's why the sky is blue and sunrises and sunsets are often red.
In the case of a lunar eclipse, red light can pass through the Earth's atmosphere and is refracted – or bent – toward the Moon, while blue light is filtered out. This leaves the moon with a pale reddish hue during an eclipse.
Hopefully you will be able to go see this super lunar eclipse. When you do, now you will know exactly what makes for such a special sight.
Portions of this story originally appeared in a previous article published on Jan. 24, 2018.
Shannon Schmoll, Director, Abrams Planetarium, Department of Physics and Astronomy, Michigan State University
This article is republished from The Conversation under a Creative Commons license. Read the original article.
In 2007, the Japan Aerospace Exploration Agency (JAXA) launched the SELENE lunar orbiter, better known by its nickname Kaguya. As the most ambitious moon mission since the Apollo program, Kaguya spent 20 months surveying the moon and photographing its surface, until JAXA instructed the orbiter to impact near the Gill crater in 2009.
Using those images, video artist Seán Doran recently published two videos depicting a "real-time" lunar orbit that spans more than eight hours.
Kaguya was the first spacecraft to capture high-definition images of the moon. The orbiter was outfitted with two 2.2 megapixel CCD HDTV cameras, one equipped with a telephoto lens, the other a wide-angle. These cameras helped JAXA construct a detailed topography of the moon, with "data points 10 orders larger than the previous model of the lunar surface," NASA noted.
To create the new videos, Doran synthesized the Kaguya images and polished them up by denoising, repairing, grading, retiming and upscaling them to 4k, as he wrote on Twitter.
As a self-taught artist, Doran has created dozens of space-art videos using images collected by instruments like the High Resolution Imaging Science Experiment (HiRISE) and the High Resolution Stereo Camera (HRSC).
"I use Photoshop for 2D work as well as batch processing frames for animation," Doran wrote in a blog post published on the HiRISE website. "I use 3DS Max and Blender for 3D work. I use After Effects, Premiere and Audition for video. I also use a plethora of plugins for each software stack as well as numerous apps for specific tasks. I'm always testing new methods and love trying out new software."
"Making content with HiRISE data has sparked a new chapter in my creative expression, bringing datasets to life through mosaics, animations, VR experiences and short films set to music."
Space has captured the imagination of artists for centuries. Humans living during the Paleolithic and Neolithic periods painted constellations on cave walls. In medieval Europe, artists often personified the planets, viewing the cosmos in a religious context, with Earth at the center of a divine universe. As science progressed, so did space art.
The 20th century saw artists from Pablo Picasso to Andy Warhol capture the cosmos in varying forms. The Russian painter Wassily Kandinsky hinted at the planets abstractly in his 1926 painting "Several Circles," while artists like Agnes Denes used a more mathematical approach to illustrate our own planet from outer space.
Doran's fascination with the cosmos was sparked by a luminary in science education.
"I've been interested in astronomy since being introduced to the concept watching Ann Druyan & Carl Sagan's Cosmos TV series," he wrote. "It was a welcome distraction from the civil war raging in Belfast during the 1980s."
You can check out more of Doran's work on his Flickr account and YouTube channel.
A new look at the Moon
A larger version of the same image.
Credit: NRAO/GBO/Raytheon/NSF/AU
The pictures were produced using radar imaging, a powerful if infrequently used tool in astronomy for creating detailed pictures of places from where visible light can't reach us.
According to a statement released by the NRAO, the Green Bank Telescope (GBT) in West Virginia had a powerful radio transmitter installed. This was used to transmit radio waves towards the Moon which then bounced back into the telescopes of the Very Long Baseline Array (VLBA), which produced the images. The transmission occurred in November of last year.
The image depicts the Hadley–Apennine region of the Moon, most noteworthy for being the Apollo 15 mission's landing site. Highlights include the 6km crater known as Hadley C and the remains of a collapsed lava tube known as Hadley Rille, which winds across the picture like a dried-out river.
The resolution of this image is tremendous. Objects as small as 5 meters (16.4 ft) can easily be seen.
Credit: Sophia Dagnello, NRAO/GBO/Raytheon/AUI/NSF/USGS
How does it work, exactly?
Using radio waves for astronomy has certain advantages. Visible light waves can have difficulty getting through the Earth's atmosphere. They can be drowned out by light pollution, and have to either be produced by or reflected off the object you want to look at. This can make things difficult for astronomers.
However, radio waves don't face these problems in the same way; waves emitted by extremely distant objects are picked up all the time. In radar astronomy, radio or microwaves are used to produce images of objects that visible light ways might struggle with. The first images of the surface of Venus, which is famously obscured by clouds, were captured this way.
For the most part, it works just like radar here on Earth. Radio waves are transmitted to the Moon, or whatever nearby cosmic object you want to see, and then bounce back to the Earth. Radio telescopes then record the returning waves. In this case, they were picked up by the telescopes of the VLBA, which stretch from Hawaii to the Virgin Islands. The vast distance between the receiving telescopes helps to improve their resolution.
The shape of things to come
This operation was just a proof of concept test. Having proven what the existing transmitter is capable of, efforts will now shift towards building a larger one that will be focused on other objects in the solar system.
Not only will this allow for extremely high-resolution images to be produced, but it may allow us to take closer looks than previously possible at objects which are too dark to show up in the visible light spectrum, such as certain asteroids.
Scientists involved with the project suggest it could be effective at viewing objects as far away as Neptune. Given that the strength of radar detection drops off exponentially with distance, this is quite the achievement.
Karen O'Neil, the Green Bank Observatory site director, explained how impressive this new system could be, "The planned system will be a leap forward in radar science, allowing access to never before seen features of the Solar System from right here on Earth."
Reports suggest the new system will come online no sooner than 2024 and cost millions of dollars if it is greenlit.
As many of you will know, despite the recent collapse of the Arecibo Observatory, it's been an exciting time in radio astronomy, with new discoveries being made on an almost regular basis. With new developments like this, the excitement can be expected to continue for some time.
It's a rhythm that preceded our presence on Earth: The moon's inexorable push and pull on our planet's oceans. According to researchers at University of Tromsø, The Arctic University of Norway, it turns out that the moon does more than move the tides—it also controls the release of methane into the atmosphere from below the Arctic Ocean. There's no reason to think it's not true in other seas as well.
This is yet another example of the complexity of global warming, methane being the other major greenhouse gas. All sorts of things are involved in keeping the environment in balance that one would never expect, like the moon. The study points out that it's not all bad news, however, since as the oceans rise they may help the moon in controlling methane's release.
The study is published in the journal Nature Communications.
Tidal methane
Screenshot of visualization from researchers' data
Credit: Andreia Plaza Faverola
Methane often takes second billing to carbon dioxide in discussions of climate change, likely because it dissipates much more quickly. However, its warming effect is actually far more intense that CO2's — it is 84 times more potent. Methane makes up about 25 percent of our greenhouse gases.
Says co-author of the study Andreia Plaza Faverola, "We noticed that gas accumulations, which are in the sediments within a meter from the seafloor, are vulnerable to even slight pressure changes in the water column. Low tide means less of such hydrostatic pressure and higher intensity of methane release. High tide equals high pressure and lower intensity of the release."
This phenomenon has not been previously observed. While significant gas hydrate concentrations have been sampled in the area, no methane release had been documented. "It is the first time that this observation has been made in the Arctic Ocean," says co-author Jochen Knies. "It means that slight pressure changes can release significant amounts of methane. This is a game-changer and the highest impact of the study."
Detecting the tidal story
Screenshot from video of piezometer out of the water
Credit: Przemyslaw Domel
The researchers buried a tool called a piezometer in the sediment on the ocean floor, and left it in place for four days. During that time, the instrument made hourly measurements of pressure and temperature in the sediments, and these indicated the presence of methane close to the sea floor, increasing at low tide and decreasing at high tide.
Their first notable observation was, of course, the presence of the gas on the Arctic Ocean floor despite a lack of other more visible indicators of its presence. "This tells us that gas release from the seafloor is more widespread than we can see using traditional sonar surveys," says Plaza Faverola. "We saw no bubbles or columns of gas in the water." She credits the watchful presence of the piezometer for making the discovery: "Gas burps that have a periodicity of several hours won't be identified unless there is a permanent monitoring tool in place, such as the piezometer."
Enthuses Knies, "What we found was unexpected and the implications are big. This is a deep-water site. Small changes in pressure can increase the gas emissions but the methane will still stay in the ocean due to the water depth."
Of course, not all the Earth's waters are equally deep, and there may not be enough water weight in some places to contain the methane below. "But what happens in shallower sites?" asks Knies. "This approach needs to be done in shallow Arctic waters as well, over a longer period. In shallow water, the possibility that methane will reach the atmosphere is greater."
The weight of water
The basic mechanics at play are simple. Higher tides mean more water pressing down on the methane, and this increased pressure keeps it from rising away from the sea floor. Low tide means less water, less pressure, and a greater opportunity for the methane to escape.
The researchers note in their study that this simple relationship may actually offer a silver lining to the rising of the world's ocean as the planet cools. There will be more water, and thus more pressure to keep methane from escaping up and into the atmosphere. In essence, higher sea levels may have something of a cooling effect by keeping methane out of the atmosphere.
In the end, there's not much we can do about the Moon and its tides, but the more knowledge we have of the mechanisms behind climate change the better.
As Plaza Faverola puts it:
"Earth systems are interconnected in ways that we are still deciphering, and our study reveals one of such interconnections in the Arctic: The moon causes tidal forces, the tides generate pressure changes, and bottom currents that in turn shape the seafloor and impact submarine methane emissions. Fascinating!"
