The Streetlights in an Entire County Were Swapped to LEDs. Light Pollution got Worse
“The best laid plans of mice and men often go awry” – this famous paraphrase of Scottish poet Robert Burns sometimes sums up human ingenuity. That is exactly what happened when a county in Washington State decided to replace all of its county-owned streetlights with LEDs at least partially in an effort to combat light pollution. New research shows that they actually made the light pollution worse.
Dr. Li-Wei Hung and her colleagues at the National Park Service recently released a paper currently available on arXiv that details work that they did to monitor the night sky both before and after Chelan County replaced their streetlights with LEDs.
Map of Chelan County and where its street lights are located.
Credit – Hung et al.
Chelan County is located in the north-central part of the state and serves as a gateway to several outdoor recreational areas nearby, including North Cascades National Park. Given this interest in the outdoors, less light pollution would seem like a benefit to stargazing hoping to catch a glimpse of the Milky Way.
So the county decided to replace all 3,693 of the county-owned streetlights (60% of the total outdoor streetlights in Chelan County) with “full cutoff” light emitting diodes for bulbs. About 80% of these new LEDs were “3000K” or “warm white light”, while the other 20% were slightly brighter “4000K” bulbs that were installed to meet lighting requirements set by the Washington State Department of Transportation.
NG video on Light Pollution.
Credit – National Geographic YouTube Channel
The retrofit process took place between 2018 and 2019, and Dr. Hung and her team took measurements both before the install and after all of the new lights were in place. What they found was…surprising to say the least. The sky actually got brighter in the county after the LEDs were installed.
Such a result is only counterintuitive because LEDs are generally thought of as being much more energy efficient and better for light pollution. An experiment in Flagstaff, Arizona attempted to leverage LEDs to create the world’s first “International Dark Sky City” in 2018, though results are still out on its effectiveness.
Video discussing the some of the best places to stargaze in the US.
Credit – Check Facts 360 YouTube Channel
If the results in Chelan County are anything to go by that experiment might not be successful. Dr. Hung and her colleagues looked at three different metrics of calculating how dark the sky is – how bright the skyglow in the county was, how high it went, and “upward radiance” which measures the light directed upward.
Several tools were needed to comprehensively calculate the differences in light pollution. First, the National Park Service has a “night sky camera system”, which allowed the researchers to take simple before and after pictures of the night sky in the Chelan County area. More data was then collected by the Visible Infrared Imaging Radiometer Suite (VIIRS), which is located on the Suomi National Polar-orbiting Partnership Satellite.
Description of Suomi and it’s associated data.
Credit – USGS
Of the three metrics measured by these instrument, the brightness and height of the skyglow increased, while the upward radiance actually decreased. The explanation the authors put forward for why exactly the light pollution got worse is that there was an increase in light emissions shorter than 500 nm, closer to the blue end of the visible spectrum. As for why the amount of light directed upward decreased, it was most likely due to a combination of the directionality of the LEDs as well as better shielding on the lamppost themselves.
Despite actually making light pollution slightly worse, the LED retrofit can still be considered a success for its other two goals – decreasing energy consumption and cost. The LEDs are undeniably more energy efficient than the high pressure sodium lamps they replaced, and will last much longer, decreasing their overall cost to the county. While the energy and cost savings are great, astronomy enthusiasts everywhere can hope that other municipal authorities that are considering similar upgrades can take into account how new LEDs might affect their night skies. Utilizing all of the best aspects of LEDs could lead to happy humans and mice all around.
Learn More –
arXiv – Changes in night sky brightness after a countywide LED retrofit
Chelan County – Sharing the Night Sky
UT – Most light pollution isn’t coming
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I love the holidays, partly because I make a point of spending a lot of time outside with family and friends. But it’s also a time when I reflect on how much I enjoy my lifestyle—and how much I appreciate readers like you who follow and support my blog. To show my appreciation, I have a special gift for you.
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Michael Lanza of The Big Outside above Macon Lake and Washakie Lake on the Washakie Pass Trail in the Wind River Range, Wyoming.
” data-image-caption=”Me above Macon Lake and Washakie Lake on the Washakie Pass Trail in the Wind River Range, Wyoming; and in Death Hollow in southern Utah (lead photo, above).
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The Early Universe Had No Problem Making Barred Spiral Galaxies
Spiral galaxies like the Milky Way are like cosmic snowflakes—no two are exactly alike. For many years, astronomers thought spirals couldn’t exist until the universe was about half its present age. Now, a newly discovered galaxy in the early Universe is challenging that idea.
CEERS-2112 is an early “cosmic snowflake” with spiral arms and a bar across its middle. The amazing thing is that it’s showing this structure when the Universe was only 2 billion years old. That’s about five billion years earlier than astronomers expected something like that to exist. The fact that a perfectly formed spiral exists so early tells us that our ideas about galaxy formation in early cosmic history need some re-tuning.
Surveying the Early Universe
This galaxy showed up in a survey done by the JWST called “Cosmic Evolution Early Release Science” (CEERS). It uses JWST imaging and spectroscopy to do a survey of the early Universe to find the earliest galaxy. The analysis of the CEERS-2112 galaxy was done by an international team led by astronomer Luca Constantin of the Centro de Astrobiología in Spain.
CEERS results should show astronomers the early populations of galaxies at high redshifts (distances). They will also help them estimate related star-formation conditions and black hole growth. Finally, the work should give some insight into the formation of galaxy disks and bulges. Essentially, CEERS data should add to our store of knowledge about first light and reionization (which occurred after the Big Bang) and explain the formation and evolution of early galaxies.
Early deep-field images of very distant galaxies show shreds of galaxies and irregular clumps of stars in the early Universe. That was evident in some of the first Hubble Deep-Field images. The most distant ones in the images looked more blobby and indistinct. And, some of them appeared to be colliding, which fits into the collisional model of galaxy formation.
This view of nearly 10,000 galaxies is called the Hubble Ultra Deep Field. It shows some galaxies in the early Universe, (which appear as red blobs). Credit: NASA/ESA/HUDF
Forming Galaxies in the Early Universe
Prior to the Hubble and JWST eras, astronomers really felt that it would take a long time to form spiral galaxies. They often describe a hierarchical model of galaxy formation. That’s where smaller clumpy galaxies collide to form larger ones. Over time, those objects begin to develop structures like spiral arms and bars.
“In such galaxies, bars can form spontaneously due to instabilities in the spiral structure or gravitational effects from a neighboring galaxy,” according to astronomer and team member Alexander de la Vega. He is a post-doctoral researcher currently at the University of California Riverside. “In the past, when the Universe was very young, galaxies were unstable and chaotic. It was thought that bars could not form or last long in galaxies in the early universe.”
The spiral arms are likely the result of density waves moving through the galaxy. The bars also form from density waves radiating out from the center. That compresses material in the arms and bars, leading to bursts of star formation. That could explain why these regions in galaxies seem brighter, with their populations of hot young stars. All of this takes time to accomplish. That’s why astronomers suggested that it would take about half the age of the Universe to form spiral galaxies.
CEERS-2112 is Part of the Early Universe
CEERS-2112 upends the discussion about spiral formation, according to de la Vega. “Finding CEERS-2112 shows that galaxies in the early Universe could be as ordered as the Milky Way,” he said. “This is surprising because galaxies were much more chaotic in the early Universe and very few had similar structures to the Milky Way.”
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Apollo Samples Contain Hydrogen Hurled from the Sun
According to the U.S. National Academies of Sciences, Engineering, and Medicine, men should drink 3.7litres of water a day and women 2.7litres. Now imagine a crew of three heading to the Moon for a 3 week trip, that’s something of the order of 189 litres of water, that’s about 189 kilograms! Assuming you have to carry all the water rather than recycle some of it longer trips into space with more people are going to be logistically challenging for water carriage alone. Researchers from the U.S. Naval Research Laboratory (NRL) have discovered lunar rocks with hydrogen in them which, when combined with lunar oxygen provide a possibly supply for future explorers.
A total of 382 kilograms of rock was brought back from the Moon by the Apollo program (I weigh about 80kg so that’s almost five of me in weight – and its all muscle I promise!) Some of the samples were immediately studied while others were sealed for future research hoping that future instrumentation would be more sensitive.
A research team from NRL, led by Katherine D. Burgess and team members Brittany A. Cymes and Rhonda M. Stroud, have recently announced their findings whilst studying some of the lunar rock. They wanted to understand the source of water on the Moon and to understand its formation. Future lunar exploration especially permanent lunar bases will rely heavily upon existing lunar resources. The paper articulates “Effective use of the resource depends on developing an understanding of where and how within the regolith the water is formed and retained”.
Buzz Aldrin’s footprint in the lunar regolith – the soft powdery material found over the surface of the Moon (Credit – NASA)
Transmission electron microscopy was used as part of the study to explore lunar sample 79221. The technique utilises a particle beam of electrons to visualise specimens and generate a highly magnified image. In particular, the team looked at grains of the minerals apatite and merrillite and discovered signs of ‘space’ weathering due to the solar wind. The solar wind is a stream of charged particles that rush outward from the Sun at speeds of up to 1.6 million km per hour!
They found hydrogen signatures in samples in vesicles – small holes left behind after lava cools. The discovery confirms that solar wind is being trapped in detectable quantities proving a potential reservoir that could be accessible to future explorers.
Hydrogen itself is a tremendously useful resource and if that can be mined from the lunar surface material it can aide many aspects of exploration. The real buzz around the discovery is that it may finally resolve the mystery about the origins of lunar water and that it might well be the result of chemical interactions between the solar wind and lunar rocks. If we can understand the origins of the lunar water – and we may finally be close to that now – then we can be sure we use it effectively to reach out further into the Solar System.
Source : Hydrogen detected in lunar samples, points to resource availability for space exploration
The post Apollo Samples Contain Hydrogen Hurled from the Sun appeared first on Universe Today.
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