Moon sweeps through Leo July 25 and 26

The bright star shining close to the waxing crescent moon on June 25, 2020 is Regulus, Heart of the Lion in the constellation Leo. The following night – June 26 – the moon will have moved some 14 degrees (14 moon-diameters) east on the sky’s dome, following its endless orbit around Earth. It’ll be closer to Denebola, the Lion’s Tail.

If you look carefully and have a dark-enough sky, you can make out patterns in the stars near both Denebola and Regulus. Denebola is part of a triangle of stars. Regulus is part of a pattern that looks like a backwards question mark, with Regulus – the brightest star in Leo – marking the bottom of this question mark pattern. This pattern of stars is called the Sickle. It’s not a constellation but instead an asterism, or recognizable pattern on the sky’s dome.

Regulus is part of a backwards question mark pattern known as the Sickle in Leo. Image via Derekscope.

As the moon continues to move from night to night, shifting eastward in front of the constellations of the zodiac, it’ll move onward away from Leo. How can you find Regulus then? One way is to look for the stars of the Sickle. Another way is to use the bowl of the Big Dipper to find your way to Regulus.

An imaginary line drawn between the pointer stars in the Big Dipper – the two outer stars in the Dipper’s bowl – points in one direction toward Polaris, the North Star, and in the opposite direction toward Leo.

Regulus is considered to be one of the four Royal Stars of ancient Persia. These Royal Stars mark the four quadrants of the heavens. They are Regulus, Antares, Fomalhaut, and Aldebaran.

Four to five thousand years ago, the Royal Stars defined the approximate positions of equinoxes and solstices in the sky. Regulus reigned as the summer solstice star, Antares as the autumn equinox star, Fomalhaut as the winter solstice star, and Aldebaran as the spring equinox star. Regulus is often portrayed as the most significant Royal Star, possibly because it symbolized the height and glory of the summer solstice sun. Although the Royal Stars as seasonal signposts change over the long coarse of time, they still mark the four quadrants of the heavens.

Chart of the constellation Leo via the IAU. The ecliptic depicts the annual pathway of the sun in front of the constellations of the zodiac. The sun passes in front of the constellation Leo each year from around August 10 to September 17, and has its yearly conjunction with the star Regulus on or near August 23.

Regulus is the only bright star to reside almost squarely on the ecliptic, that is, Earth’s orbital plane projected onto the sphere of stars. Regulus coincided with the summer solstice point some 4,300 years ago. In our time, the sun has its annual conjunction with Regulus on or near August 23, or about two months after the summer solstice, or alternatively, one month before the autumn equinox. Regulus will mark the autumn equinox point some 2,100 years into the future.

What is the ecliptic?

Eight years ago, in 2012, Regulus reached a place on the zodiac where it was precisely 150 degrees east of the March equinox point (and 30 degrees west of the September equinox point). Before that juncture, Regulus and the March equinox point were a little less than 150 degrees apart, and Regulus and the September equinox point were a little more than 30 degrees apart. For some astrologers, this instant at which Regulus was precisely 30 degrees west of the September equinox point marked the end of the Age of Pisces and the beginning of the Age of Aquarius. Click here to find out why.

Whether you enjoy the arcane speculation on the Royal Star Regulus and the Age of Aquarius – or not – that star now close to the moon has given definition to the ecliptic and the zodiac since time immemorial!

When does the Age of Aquarius begin?

Bottom line: Regulus is the brightest star in the constellation Leo the Lion.  The moon can help you find it – and maybe the planets Jupiter and Venus – on the night of July 7, 2016.

A planisphere is virtually indispensable for beginning stargazers. Order your EarthSky planisphere today.

Help support EarthSky! Visit the EarthSky store for to see the great selection of educational tools and team gear we have to offer.

Leo? Here’s your constellation

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The bright star shining close to the waxing crescent moon on June 25, 2020 is Regulus, Heart of the Lion in the constellation Leo. The following night – June 26 – the moon will have moved some 14 degrees (14 moon-diameters) east on the sky’s dome, following its endless orbit around Earth. It’ll be closer to Denebola, the Lion’s Tail.

If you look carefully and have a dark-enough sky, you can make out patterns in the stars near both Denebola and Regulus. Denebola is part of a triangle of stars. Regulus is part of a pattern that looks like a backwards question mark, with Regulus – the brightest star in Leo – marking the bottom of this question mark pattern. This pattern of stars is called the Sickle. It’s not a constellation but instead an asterism, or recognizable pattern on the sky’s dome.

Regulus is part of a backwards question mark pattern known as the Sickle in Leo. Image via Derekscope.

As the moon continues to move from night to night, shifting eastward in front of the constellations of the zodiac, it’ll move onward away from Leo. How can you find Regulus then? One way is to look for the stars of the Sickle. Another way is to use the bowl of the Big Dipper to find your way to Regulus.

An imaginary line drawn between the pointer stars in the Big Dipper – the two outer stars in the Dipper’s bowl – points in one direction toward Polaris, the North Star, and in the opposite direction toward Leo.

Regulus is considered to be one of the four Royal Stars of ancient Persia. These Royal Stars mark the four quadrants of the heavens. They are Regulus, Antares, Fomalhaut, and Aldebaran.

Four to five thousand years ago, the Royal Stars defined the approximate positions of equinoxes and solstices in the sky. Regulus reigned as the summer solstice star, Antares as the autumn equinox star, Fomalhaut as the winter solstice star, and Aldebaran as the spring equinox star. Regulus is often portrayed as the most significant Royal Star, possibly because it symbolized the height and glory of the summer solstice sun. Although the Royal Stars as seasonal signposts change over the long coarse of time, they still mark the four quadrants of the heavens.

Chart of the constellation Leo via the IAU. The ecliptic depicts the annual pathway of the sun in front of the constellations of the zodiac. The sun passes in front of the constellation Leo each year from around August 10 to September 17, and has its yearly conjunction with the star Regulus on or near August 23.

Regulus is the only bright star to reside almost squarely on the ecliptic, that is, Earth’s orbital plane projected onto the sphere of stars. Regulus coincided with the summer solstice point some 4,300 years ago. In our time, the sun has its annual conjunction with Regulus on or near August 23, or about two months after the summer solstice, or alternatively, one month before the autumn equinox. Regulus will mark the autumn equinox point some 2,100 years into the future.

What is the ecliptic?

Eight years ago, in 2012, Regulus reached a place on the zodiac where it was precisely 150 degrees east of the March equinox point (and 30 degrees west of the September equinox point). Before that juncture, Regulus and the March equinox point were a little less than 150 degrees apart, and Regulus and the September equinox point were a little more than 30 degrees apart. For some astrologers, this instant at which Regulus was precisely 30 degrees west of the September equinox point marked the end of the Age of Pisces and the beginning of the Age of Aquarius. Click here to find out why.

Whether you enjoy the arcane speculation on the Royal Star Regulus and the Age of Aquarius – or not – that star now close to the moon has given definition to the ecliptic and the zodiac since time immemorial!

When does the Age of Aquarius begin?

Bottom line: Regulus is the brightest star in the constellation Leo the Lion.  The moon can help you find it – and maybe the planets Jupiter and Venus – on the night of July 7, 2016.

A planisphere is virtually indispensable for beginning stargazers. Order your EarthSky planisphere today.

Help support EarthSky! Visit the EarthSky store for to see the great selection of educational tools and team gear we have to offer.

Leo? Here’s your constellation

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Imanda watching the eclipse

View at EarthSky Community Photos. | Image via Christopher Kipkemei.

Christopher Kipkemei captured his daughter, Imanda, viewing the annular solar eclipse of June 21, 2020 as it developed over Syokimau, Kenya (just south of the Equator). Thanks Christoper.

And … check out Imanda’s eclipse glasses. We love them! You can get yours here.

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View at EarthSky Community Photos. | Image via Christopher Kipkemei.

Christopher Kipkemei captured his daughter, Imanda, viewing the annular solar eclipse of June 21, 2020 as it developed over Syokimau, Kenya (just south of the Equator). Thanks Christoper.

And … check out Imanda’s eclipse glasses. We love them! You can get yours here.

from EarthSky https://ift.tt/3dqrwQR

Study reveals biggest Yellowstone supervolcano eruption

Explosions from volcanic super-eruptions have been some of the most extreme events in Earth’s history, ejecting enormous volumes of material – at least 1,000 times more than the 1980 eruption of Mount St. Helens – with the potential to alter the planet’s climate.

Now, in a study published June 1, 2020 in the peer-reviewed journal Geology, researchers have announced the discovery of two newly identified super-eruptions that occurred 9.0 and 8.7 million years ago, associated with the Yellowstone hotspot track – a volcanic hotspot responsible for large scale volcanism in Idaho, Montana, Nevada, Oregon, and Wyoming. The researchers believe the younger of the two – known as the Grey’s Landing super-eruption – was the volcanic province’s largest and most cataclysmic event. Volcanologist Thomas Knott of University of Leicester is the paper’s lead author. Knott said in a statement:

Based on the most recent collations of super-eruption sizes, it is one of the top five eruptions of all time.

Yellowstone hotspot track. Image via Kelvin Case/ Wikimedia Commons.

The results indicate the hotspot, which today fuels the famous geysers, mudpots, and fumaroles in Yellowstone National Park, may be waning in intensity. Knott told Scientific American that although the current rate of eruptions suggests that another explosion will not occur for roughly 900,000 years, this estimate is simply a historical average, and it doesn’t forecast how and when nature will act. He said:

We don’t want to encourage complacency—nor do we want to fearmonger.

Fountain Paint Pot. Image via National Park Service/ GSA.

The team used a combination of techniques to correlate volcanic deposits scattered across tens of thousands of square kilometers. Knott said:

We discovered that deposits previously believed to belong to multiple, smaller eruptions were in fact colossal sheets of volcanic material from two previously unknown super-eruptions at about 9.0 and 8.7 million years ago.

The younger of the two, the Grey’s Landing super-eruption, is now the largest recorded event of the entire Snake-River–Yellowstone volcanic province.

The team estimates the Grey’s Landing super-eruption was 30% larger than the previous record-holder (the well-known Huckleberry Ridge Tuff) and had devastating local and global effects. Knotts said:

The Grey’s Landing eruption enameled an area the size of New Jersey in searing-hot volcanic glass that instantly sterilized the land surface. Anything located within this region would have been buried and most likely vaporized during the eruption.

Particulates would have choked the stratosphere, raining fine ash over the entire United States and gradually encompassing the globe.

Both of the newly discovered super-eruptions occurred during the Miocene, the interval of geologic time spanning 23–5.3 million years ago. Knott said:

These two new eruptions bring the total number of recorded Miocene super-eruptions at the Yellowstone–Snake River volcanic province to six. This means that the recurrence rate of Yellowstone hotspot super-eruptions during the Miocene was, on average, once every 500,000 years.

By comparison, Knott says, two super-eruptions have — so far — taken place in what is now Yellowstone National Park during the past three million years. He said:

It therefore seems that the Yellowstone hotspot has experienced a three-fold decrease in its capacity to produce super-eruption events. This is a very significant decline.

But the new findings, says Knott, have little bearing on assessing the risk of another super-eruption occurring today in Yellowstone.

We have demonstrated that the recurrence rate of Yellowstone super-eruptions appears to be once every 1.5 million years. The last super-eruption there was 630,000 years ago, suggesting we may have up to 900,000 years before another eruption of this scale occurs.

Bottom line: A new study has identified the biggest eruption in the history of the Yellowstone supervolcano and also suggests that its activity might be slowing.

Source:
Discovery of two new super-eruptions from the Yellowstone hotspot track (USA): Is the Yellowstone hotspot waning?

Via Geological Society of America

from EarthSky https://ift.tt/3ewNjrv

Explosions from volcanic super-eruptions have been some of the most extreme events in Earth’s history, ejecting enormous volumes of material – at least 1,000 times more than the 1980 eruption of Mount St. Helens – with the potential to alter the planet’s climate.

Now, in a study published June 1, 2020 in the peer-reviewed journal Geology, researchers have announced the discovery of two newly identified super-eruptions that occurred 9.0 and 8.7 million years ago, associated with the Yellowstone hotspot track – a volcanic hotspot responsible for large scale volcanism in Idaho, Montana, Nevada, Oregon, and Wyoming. The researchers believe the younger of the two – known as the Grey’s Landing super-eruption – was the volcanic province’s largest and most cataclysmic event. Volcanologist Thomas Knott of University of Leicester is the paper’s lead author. Knott said in a statement:

Based on the most recent collations of super-eruption sizes, it is one of the top five eruptions of all time.

Yellowstone hotspot track. Image via Kelvin Case/ Wikimedia Commons.

The results indicate the hotspot, which today fuels the famous geysers, mudpots, and fumaroles in Yellowstone National Park, may be waning in intensity. Knott told Scientific American that although the current rate of eruptions suggests that another explosion will not occur for roughly 900,000 years, this estimate is simply a historical average, and it doesn’t forecast how and when nature will act. He said:

We don’t want to encourage complacency—nor do we want to fearmonger.

Fountain Paint Pot. Image via National Park Service/ GSA.

The team used a combination of techniques to correlate volcanic deposits scattered across tens of thousands of square kilometers. Knott said:

We discovered that deposits previously believed to belong to multiple, smaller eruptions were in fact colossal sheets of volcanic material from two previously unknown super-eruptions at about 9.0 and 8.7 million years ago.

The younger of the two, the Grey’s Landing super-eruption, is now the largest recorded event of the entire Snake-River–Yellowstone volcanic province.

The team estimates the Grey’s Landing super-eruption was 30% larger than the previous record-holder (the well-known Huckleberry Ridge Tuff) and had devastating local and global effects. Knotts said:

The Grey’s Landing eruption enameled an area the size of New Jersey in searing-hot volcanic glass that instantly sterilized the land surface. Anything located within this region would have been buried and most likely vaporized during the eruption.

Particulates would have choked the stratosphere, raining fine ash over the entire United States and gradually encompassing the globe.

Both of the newly discovered super-eruptions occurred during the Miocene, the interval of geologic time spanning 23–5.3 million years ago. Knott said:

These two new eruptions bring the total number of recorded Miocene super-eruptions at the Yellowstone–Snake River volcanic province to six. This means that the recurrence rate of Yellowstone hotspot super-eruptions during the Miocene was, on average, once every 500,000 years.

By comparison, Knott says, two super-eruptions have — so far — taken place in what is now Yellowstone National Park during the past three million years. He said:

It therefore seems that the Yellowstone hotspot has experienced a three-fold decrease in its capacity to produce super-eruption events. This is a very significant decline.

But the new findings, says Knott, have little bearing on assessing the risk of another super-eruption occurring today in Yellowstone.

We have demonstrated that the recurrence rate of Yellowstone super-eruptions appears to be once every 1.5 million years. The last super-eruption there was 630,000 years ago, suggesting we may have up to 900,000 years before another eruption of this scale occurs.

Bottom line: A new study has identified the biggest eruption in the history of the Yellowstone supervolcano and also suggests that its activity might be slowing.

Source:
Discovery of two new super-eruptions from the Yellowstone hotspot track (USA): Is the Yellowstone hotspot waning?

Via Geological Society of America

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Latest dusk for northerly latitudes

Twilight over Manhattan.

Tonight – June 24, 2020 – if you’re located around 40 degrees north latitude, it’s your latest evening twilight for the year. The longest evening twilights always happen around the summer solstice. Although the Northern Hemisphere’s summer solstice, and longest day, happened a few days ago on June 20, the latest twilight at 40 degrees north latitude always occurs several days afterwards, on or near June 24.

The parallel 40 degrees north passes through Philadelphia, Pennsylvania, and the northern suburbs of Denver, Colorado. Worldwide the 40th parallel runs through Beijing, China; Turkey; Japan and Spain.

Want to know for your latitude? Click here and check the “astronomical twilight” box.

The year’s latest sunsets don’t come exactly on the solstice either. For 40 degrees north latitude, the latest sunset happens about a week after the summer solstice, on or near June 27.

Let us introduce you to the three different kinds of twilight:

Civil twilight starts at sundown and ends when the sun is 6 degrees below the horizon.

Nautical twilight occurs when the sun is 6 to 12 degrees below the horizon.

Astronomical twilight happens when the sun is 12 to 18 degrees below the horizon.

North of 50 degrees north latitude, there’s no true night in the month of June. In June, that far north, the sun never gets far enough below the horizon for true night to occur.

It’s the land of the midnight twilight from 50 degrees north latitude to the Arctic Circle (66.5 degrees north latitude).

It’s the land of the midnight sun from the Arctic Circle to the North Pole (90 degrees north latitude).

At the temperate zones and the tropics, the longest period of twilight after sunset or before sunrise happens around the summer solstice, and the shortest period around the equinoxes. At 40 degrees latitude, astronomical twilight ends about 2 hours after sunset on the summer solstice; and on the equinoxes, astronomical twilight ends about 1 1/2 hours after sunset. Believe it or not, the duration of astronomical twilight reaches a secondary peak around the winter solstice, lasting about 1 2/3 hours after the sun goes down at 40 degrees latitude.

Read more: What exactly is twilight?

True night doesn’t begin until the sun sinks 18 degrees beneath the horizon.

Bottom line: Although the latest sunset won’t happen at 40 degrees north latitude for another few days, the latest twilight happens on June 24.

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Twilight over Manhattan.

Tonight – June 24, 2020 – if you’re located around 40 degrees north latitude, it’s your latest evening twilight for the year. The longest evening twilights always happen around the summer solstice. Although the Northern Hemisphere’s summer solstice, and longest day, happened a few days ago on June 20, the latest twilight at 40 degrees north latitude always occurs several days afterwards, on or near June 24.

The parallel 40 degrees north passes through Philadelphia, Pennsylvania, and the northern suburbs of Denver, Colorado. Worldwide the 40th parallel runs through Beijing, China; Turkey; Japan and Spain.

Want to know for your latitude? Click here and check the “astronomical twilight” box.

The year’s latest sunsets don’t come exactly on the solstice either. For 40 degrees north latitude, the latest sunset happens about a week after the summer solstice, on or near June 27.

Let us introduce you to the three different kinds of twilight:

Civil twilight starts at sundown and ends when the sun is 6 degrees below the horizon.

Nautical twilight occurs when the sun is 6 to 12 degrees below the horizon.

Astronomical twilight happens when the sun is 12 to 18 degrees below the horizon.

North of 50 degrees north latitude, there’s no true night in the month of June. In June, that far north, the sun never gets far enough below the horizon for true night to occur.

It’s the land of the midnight twilight from 50 degrees north latitude to the Arctic Circle (66.5 degrees north latitude).

It’s the land of the midnight sun from the Arctic Circle to the North Pole (90 degrees north latitude).

At the temperate zones and the tropics, the longest period of twilight after sunset or before sunrise happens around the summer solstice, and the shortest period around the equinoxes. At 40 degrees latitude, astronomical twilight ends about 2 hours after sunset on the summer solstice; and on the equinoxes, astronomical twilight ends about 1 1/2 hours after sunset. Believe it or not, the duration of astronomical twilight reaches a secondary peak around the winter solstice, lasting about 1 2/3 hours after the sun goes down at 40 degrees latitude.

Read more: What exactly is twilight?

True night doesn’t begin until the sun sinks 18 degrees beneath the horizon.

Bottom line: Although the latest sunset won’t happen at 40 degrees north latitude for another few days, the latest twilight happens on June 24.

from EarthSky https://ift.tt/3fUcB3i

How much oxygen comes from the ocean?

The surface layer of the ocean is teeming with photosynthetic plankton. Though they’re invisible to the naked eye, they produce more oxygen than the largest redwoods. Image via Cindy Chai.

Via National Ocean Service/ NOAA

Scientists estimate that 50-80% of the oxygen production on Earth comes from the ocean. The majority of this production is from oceanic plankton — drifting plants, algae, and some bacteria that can photosynthesize – convert sunlight into energy. One particular species, Prochlorococcus, is the smallest photosynthetic organism on Earth. But this little bacteria produces up to 20% of the oxygen in our entire biosphere. That’s a higher percentage than all of the tropical rainforests on land combined.

Calculating the exact percentage of oxygen produced in the ocean is difficult because the amounts are constantly changing. Scientists can use satellite imagery to track photosynthesizing plankton and estimate the amount of photosynthesis occurring in the ocean, but satellite imagery cannot tell the whole story. The amount of plankton changes seasonally and in response to changes in the water’s nutrient load, temperature, and other factors. Studies have shown that the amount of oxygen in specific locations varies with time of day and with the tides.

It’s important to remember that although the ocean produces at least 50% of the oxygen on Earth, roughly the same amount is consumed by marine life. Like animals on land, marine animals use oxygen to breathe, and both plants and animals use oxygen for cellular respiration. Oxygen is also consumed when dead plants and animals decay in the ocean.

This is particularly problematic when algal blooms die and the decomposition process uses oxygen faster than it can be replenished. This can create areas of extremely low oxygen concentrations, or hypoxia These areas are often called dead zones, because the oxygen levels are too low to support most marine life.

Overlooking the Atlantic Ocean from the Georgia coast, by Greg Hogan.

Bottom line: How much of Earth’s oxygen comes from the ocean?

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The surface layer of the ocean is teeming with photosynthetic plankton. Though they’re invisible to the naked eye, they produce more oxygen than the largest redwoods. Image via Cindy Chai.

Via National Ocean Service/ NOAA

Scientists estimate that 50-80% of the oxygen production on Earth comes from the ocean. The majority of this production is from oceanic plankton — drifting plants, algae, and some bacteria that can photosynthesize – convert sunlight into energy. One particular species, Prochlorococcus, is the smallest photosynthetic organism on Earth. But this little bacteria produces up to 20% of the oxygen in our entire biosphere. That’s a higher percentage than all of the tropical rainforests on land combined.

Calculating the exact percentage of oxygen produced in the ocean is difficult because the amounts are constantly changing. Scientists can use satellite imagery to track photosynthesizing plankton and estimate the amount of photosynthesis occurring in the ocean, but satellite imagery cannot tell the whole story. The amount of plankton changes seasonally and in response to changes in the water’s nutrient load, temperature, and other factors. Studies have shown that the amount of oxygen in specific locations varies with time of day and with the tides.

It’s important to remember that although the ocean produces at least 50% of the oxygen on Earth, roughly the same amount is consumed by marine life. Like animals on land, marine animals use oxygen to breathe, and both plants and animals use oxygen for cellular respiration. Oxygen is also consumed when dead plants and animals decay in the ocean.

This is particularly problematic when algal blooms die and the decomposition process uses oxygen faster than it can be replenished. This can create areas of extremely low oxygen concentrations, or hypoxia These areas are often called dead zones, because the oxygen levels are too low to support most marine life.

Overlooking the Atlantic Ocean from the Georgia coast, by Greg Hogan.

Bottom line: How much of Earth’s oxygen comes from the ocean?

from EarthSky https://ift.tt/3fPUECM

Iridescent cloud? Or circumhorizon arc?

View at EarthSky Community Photos. | Henry Malinda took this photo in Spring Mountains National Park in Nevada on June 12, 2020. He asked us, what is it? This sky phenomenon is called an iridescent cloud. Notice how Henry placed the nearby sun behind a tree? That’s one clue that he saw a true iridescent cloud, and not another sky phenomenon called a circumhorizon arc. The rainbow-colored circumhorizon arcs are often mistaken for iridescent clouds. Here’s how to tell the difference. Thank you, Henry!

Here at EarthSky, we often receive photos of rainbow-like arcs and bands in the sky. Most aren’t true rainbows, but instead are other examples of the many sorts of optical phenomena you can see in the sky. Two that are commonly confused are iridescent clouds and circumhorizon arcs. It was an alert EarthSky reader – George Preoteasa, who responded to a photo we had mistakenly identified at our website – who set us straight. We hope this post will let you learn to tell the difference between these sky phenomena, too.

Mistaking one for the other is very common! But it’s also easy to learn which is which.

View at EarthSky Community Photos. | Eric Broneer in Marseille, France, caught this circumhorizon arc on June 3, 2019. He wrote, “Beautiful weather, very dry, sun behind me.” Notice how organized the colors are, red at the top, indigo at the bottom.

View at EarthSky Community Photos. | Karl Diefenderfer caught this image of a bird soaring in front of iridescent clouds on June 14, 2019, from Blue Bell, Pennsylvania. Notice that the colors in the cloud are randomly distributed. Thank you, Karl!

How can you tell the difference between an iridescent cloud and a circumhorizon arc in the sky, or in a picture?

George Preoteasa said he used to mistake one for the other, too, and had made a study of how to tell them apart. He wrote:

The circumhorizon arc is a band parallel to the horizon. So, to the extent that the horizon is an arc, this is one, too. The colors in a circumhorizon arc are well organized, red at the top, indigo at the bottom. With cloud iridescence, the colors are more randomly distributed.

Circumhorizon arcs have a certain fuzziness. They are caused by ice crystals in cirrus clouds, much as solar and lunar halos are. Iridescence, on the other hand, is caused by water droplets.

For a circumhorizon arc to occur, the sun must be high up, over 58 degrees above the horizon. Iridescence usually occurs close to the sun, which makes it difficult to photograph. You need to hide the sun so that sunlight does not overwhelm the colors in the cloud.

This is an iridescent cloud. The colors are not as organized as in a circumhorizon arc, and they tend to be seen near the sun. Best way to see one is to place the sun itself behind some foreground object, a building or mountain, for example. Duke Marsh captured this image in 2012 in New Albany, Indiana.

George continued:

It’s funny, but I made the same mistake. I was using the CloudSpotter app from the Cloud Appreciation Society. If you see clouds or cloud features or optical phenomena, you can take a picture and submit it for verification. I submitted the shot below as iridescence, and the moderator pointed out it’s not, but rather a fragment of a circumhorizon arc.

After that, I went to Les Cowley’s website – Atmospheric Optics – and immediately it became clear that the Cloud Appreciation Society moderator was right. So now I’m spreading the knowledge :-)

Thank you, George!

Here’s the image George Preoteasa captured, which he at first thought was an example of an iridescent cloud. Now he knows it’s a circumhorizon arc, and he described these arcs this way: “Imagine a horizontal band at the level where you see the colors. If you had cirrus clouds with the same properties as the one with the colors, you would get a nice colored arc parallel to the horizon. For a circumhorizon arc to occur, the sun must be high up in the sky, above 58 degrees. The fact that the sun does not appear in this picture is another clue it’s not iridescence.”

George also very kindly went into an EarthSky article about iridescent clouds and found three photos that are really circumhorizon arcs. We next sent those three photos to the world’s sky optics guru, Les Cowley of Atmospheric Optics, for confirmation. Les – who is a long-time friend of EarthSky and often helps us identify sky phenomena – confirmed that, yes, the photos below are all circumhorizon arcs. He also confirmed that:

… one key difference between a circumhorizon arc and iridescence is color structure. A circumhorizon arc has a spectral sequence of color with red at top and blue/violet lowest.

A circumhorizon arc is always about two outstretched hand-widths below the sun. Iridescent clouds are usually rather closer.

Thank you, Les.

Read more about circumhorizon arcs on Les Cowley’s website, Atmospheric Optics

Below are the three photos EarthSky had misidentified:

Circumhorizon arc. The band is parallel to the horizon with red at the top, indigo at the bottom. The sun is well out of the picture. For circumhorizon arcs, the sun is always at least twice the span from thumb to little finger of your outstretched hand, held at arm’s length. Photo taken May 31, 2016, by Laura Berry.

Circumhorizon arc. Parallel to horizon. Red at top, indigo at bottom. Sun well out of picture, at least 2 hand-spans away. A circumhorizon arc can look slightly curved in photographs, but the curvature isn’t real; it’s due to the distortion that camera lenses can make. In the sky, circumhorizon arcs are completely straight. Photo taken May 27, 2013, by Mike O’Neal.

Circumhorizon arc. If there were more cloud here, you could see more of the arc, which is parallel to the horizon with red at the top, indigo at the bottom. Photo taken May 24, 2017, by Zaneta Kosiba Vargas in Santa Barbara, California.

The Cloud Appreciation Society had this to say about the likelihood of seeing a circumhorizon arc:

The rarity of the circumhorizon arc depends on where you’re based. The lower the latitude, the greater your chance of spotting a circumhorizon arc when Cirrus or Cirrostratus clouds are in the sky. Les Cowley … reports in his Atmospheric Optics site that from most locations in the U.S. they can be observed about five times a year, but from locations in northern Europe you might see them only once or twice. Likewise, they’re more commonly seen in Australia than in New Zealand. You’ll never see a circumhorizon arc, however, from latitudes above 56 degrees – in the Northern Hemisphere, that’s anywhere north of Copenhagen, Denmark – since the sun never climbs high enough in the sky.

Nor is it possible, unless you’re near the equator, to see a circumhorizon arc throughout the year. For most of us, the dependence of this vibrant optical effect on a such high sun means that its horizontal streak of pure, spectral color will only ever grace our skies during the summertime.

Here’s Joan Helle-Fasolo’s July 4, 2017, image, which EarthSky misidentified as an iridescent cloud. In fact, this is an entirely different sky phenomenon, called a circumhorizon arc.

Bottom line: It’s easy to confuse a circumhorizon arc with an iridescent cloud, and vice versa. Here’s how to tell these two elusive, colorful, beautiful daytime sky phenomena apart. As for frequency … we see many, many more photos of circumhorizon arcs than of true iridescent clouds.

from EarthSky https://ift.tt/3fQdo58

View at EarthSky Community Photos. | Henry Malinda took this photo in Spring Mountains National Park in Nevada on June 12, 2020. He asked us, what is it? This sky phenomenon is called an iridescent cloud. Notice how Henry placed the nearby sun behind a tree? That’s one clue that he saw a true iridescent cloud, and not another sky phenomenon called a circumhorizon arc. The rainbow-colored circumhorizon arcs are often mistaken for iridescent clouds. Here’s how to tell the difference. Thank you, Henry!

Here at EarthSky, we often receive photos of rainbow-like arcs and bands in the sky. Most aren’t true rainbows, but instead are other examples of the many sorts of optical phenomena you can see in the sky. Two that are commonly confused are iridescent clouds and circumhorizon arcs. It was an alert EarthSky reader – George Preoteasa, who responded to a photo we had mistakenly identified at our website – who set us straight. We hope this post will let you learn to tell the difference between these sky phenomena, too.

Mistaking one for the other is very common! But it’s also easy to learn which is which.

View at EarthSky Community Photos. | Eric Broneer in Marseille, France, caught this circumhorizon arc on June 3, 2019. He wrote, “Beautiful weather, very dry, sun behind me.” Notice how organized the colors are, red at the top, indigo at the bottom.

View at EarthSky Community Photos. | Karl Diefenderfer caught this image of a bird soaring in front of iridescent clouds on June 14, 2019, from Blue Bell, Pennsylvania. Notice that the colors in the cloud are randomly distributed. Thank you, Karl!

How can you tell the difference between an iridescent cloud and a circumhorizon arc in the sky, or in a picture?

George Preoteasa said he used to mistake one for the other, too, and had made a study of how to tell them apart. He wrote:

The circumhorizon arc is a band parallel to the horizon. So, to the extent that the horizon is an arc, this is one, too. The colors in a circumhorizon arc are well organized, red at the top, indigo at the bottom. With cloud iridescence, the colors are more randomly distributed.

Circumhorizon arcs have a certain fuzziness. They are caused by ice crystals in cirrus clouds, much as solar and lunar halos are. Iridescence, on the other hand, is caused by water droplets.

For a circumhorizon arc to occur, the sun must be high up, over 58 degrees above the horizon. Iridescence usually occurs close to the sun, which makes it difficult to photograph. You need to hide the sun so that sunlight does not overwhelm the colors in the cloud.

This is an iridescent cloud. The colors are not as organized as in a circumhorizon arc, and they tend to be seen near the sun. Best way to see one is to place the sun itself behind some foreground object, a building or mountain, for example. Duke Marsh captured this image in 2012 in New Albany, Indiana.

George continued:

It’s funny, but I made the same mistake. I was using the CloudSpotter app from the Cloud Appreciation Society. If you see clouds or cloud features or optical phenomena, you can take a picture and submit it for verification. I submitted the shot below as iridescence, and the moderator pointed out it’s not, but rather a fragment of a circumhorizon arc.

After that, I went to Les Cowley’s website – Atmospheric Optics – and immediately it became clear that the Cloud Appreciation Society moderator was right. So now I’m spreading the knowledge :-)

Thank you, George!

Here’s the image George Preoteasa captured, which he at first thought was an example of an iridescent cloud. Now he knows it’s a circumhorizon arc, and he described these arcs this way: “Imagine a horizontal band at the level where you see the colors. If you had cirrus clouds with the same properties as the one with the colors, you would get a nice colored arc parallel to the horizon. For a circumhorizon arc to occur, the sun must be high up in the sky, above 58 degrees. The fact that the sun does not appear in this picture is another clue it’s not iridescence.”

George also very kindly went into an EarthSky article about iridescent clouds and found three photos that are really circumhorizon arcs. We next sent those three photos to the world’s sky optics guru, Les Cowley of Atmospheric Optics, for confirmation. Les – who is a long-time friend of EarthSky and often helps us identify sky phenomena – confirmed that, yes, the photos below are all circumhorizon arcs. He also confirmed that:

… one key difference between a circumhorizon arc and iridescence is color structure. A circumhorizon arc has a spectral sequence of color with red at top and blue/violet lowest.

A circumhorizon arc is always about two outstretched hand-widths below the sun. Iridescent clouds are usually rather closer.

Thank you, Les.

Read more about circumhorizon arcs on Les Cowley’s website, Atmospheric Optics

Below are the three photos EarthSky had misidentified:

Circumhorizon arc. The band is parallel to the horizon with red at the top, indigo at the bottom. The sun is well out of the picture. For circumhorizon arcs, the sun is always at least twice the span from thumb to little finger of your outstretched hand, held at arm’s length. Photo taken May 31, 2016, by Laura Berry.

Circumhorizon arc. Parallel to horizon. Red at top, indigo at bottom. Sun well out of picture, at least 2 hand-spans away. A circumhorizon arc can look slightly curved in photographs, but the curvature isn’t real; it’s due to the distortion that camera lenses can make. In the sky, circumhorizon arcs are completely straight. Photo taken May 27, 2013, by Mike O’Neal.

Circumhorizon arc. If there were more cloud here, you could see more of the arc, which is parallel to the horizon with red at the top, indigo at the bottom. Photo taken May 24, 2017, by Zaneta Kosiba Vargas in Santa Barbara, California.

The Cloud Appreciation Society had this to say about the likelihood of seeing a circumhorizon arc:

The rarity of the circumhorizon arc depends on where you’re based. The lower the latitude, the greater your chance of spotting a circumhorizon arc when Cirrus or Cirrostratus clouds are in the sky. Les Cowley … reports in his Atmospheric Optics site that from most locations in the U.S. they can be observed about five times a year, but from locations in northern Europe you might see them only once or twice. Likewise, they’re more commonly seen in Australia than in New Zealand. You’ll never see a circumhorizon arc, however, from latitudes above 56 degrees – in the Northern Hemisphere, that’s anywhere north of Copenhagen, Denmark – since the sun never climbs high enough in the sky.

Nor is it possible, unless you’re near the equator, to see a circumhorizon arc throughout the year. For most of us, the dependence of this vibrant optical effect on a such high sun means that its horizontal streak of pure, spectral color will only ever grace our skies during the summertime.

Here’s Joan Helle-Fasolo’s July 4, 2017, image, which EarthSky misidentified as an iridescent cloud. In fact, this is an entirely different sky phenomenon, called a circumhorizon arc.

Bottom line: It’s easy to confuse a circumhorizon arc with an iridescent cloud, and vice versa. Here’s how to tell these two elusive, colorful, beautiful daytime sky phenomena apart. As for frequency … we see many, many more photos of circumhorizon arcs than of true iridescent clouds.

from EarthSky https://ift.tt/3fQdo58

Opinion: ‘UK cancer research could be set back years by COVID-19. We must act now’

Today, we announced that because of COVID-19 and the devastating impact it’s had on our income, we could be forced to cut £150 million per year from our research funding. 

Michelle Mitchell is our chief executive officer.

As an organisation whose sole mission is to beat cancer – to ensure that fewer people are diagnosed and those that are can face the future with more confidence – it’s not an announcement we ever wanted to make.  

These cuts would undoubtedly set back progress for cancer patients everywhere. To put the figure in context, £150 million is what Cancer Research UK would spend on clinical trials over the next 10 years. £150 million is approximately 35% of our total research spend  last year, and a cut like this could mean we have to close some of our sites around the country and leave thousands of early–career scientists unsupported. 

Figures like these, which are echoed by medical research charities across the UK, should be enough to ring alarm bells across the sector and for the Government. But the truth is the impact will be much bigger, and much broader, than a single number could ever convey.  

Because we don’t just fund over 50% of all publicly funded cancer research in the UK, we’re also a vital part of the country’s scientific ecosystem.  

Charities bring innovation and infrastructure to research across the country 

The UK is celebrated as a world leader in research and innovation, and one of the reasons for this success is the mix of government, private and charity-funded research.  

Medical research charities help to drive progress by funding early-stage, high risk research that wouldn’t otherwise be supported. And the insights that our researchers generate feed the pipeline of pharma companies all over the world. In fact, Cancer Research UK is the second biggest licensor of cancer drugs in the world, after MD Anderson in Texas. 

Take vemurafenib for example, a targeted cancer drug that by mid-2018 had been used to treat over 50,000 patients with malignant melanoma worldwide. This drug came from early research funded by Cancer Research UK and other charity partners, which revealed a particular mutation that cropped up in a lot of melanomas. The mutation was patented as a target for drug screens and patient tests. All 5 named inventors were UK-based scientists.  

As well as funding individual research projects, we also contribute a great deal to the research and innovation sector – through our work and our people.  

We’ve built a vibrant platform for cancer research across the UK through our Institutes and Clinical Trials Unit – funding 50% of the cancer research infrastructure in the UK.  

Our long-term investment in state-of-the-art facilities has helped to create a thriving network of research at 90 institutions in over 40 UK towns and cities.  

This infrastructure is part of what makes the UK a key player on the world stage, and an attractive place for cancer experts to bring their skills. It’s this infrastructure that’s at risk if we don’t get the support we need and, at a time when the Government is working to rebalance research investment across the UK, it’s an infrastructure that would be hard to recreate in our absence.  

Our ambitions rely on our dedicated researchers

But while our centres and clinical trials network are crucial pieces of our success, they’re brought to life by the scientists who work within them. We fund over 4,000 researchers in labs and hospitals across the UK. And as well as world leading experts, we’re helping to train the next generation of scientists, supporting over 500 PhD students, 160 fellows and 600 post-doctoral researchers.  

With COVID-19 delaying cancer research, diagnosis and treatment, these scientists have played a vital role in the UK’s response to the coronavirus pandemic, volunteering in COVID-19 testing facilities, redeploying to the front line and using their skills and expertise to help tackle the virus.  

And with the Chancellor highlighting research and innovation as a road to economic recovery, our researchers will also play a role in helping to rebuild the economy. Through our entrepreneurial programmes, we help the cancer research community to translate their discoveries into products and launch spinout companies that will improve the lives of people with cancer. Cancer Research UK has formed more than 40 spinout companies so far, which have collectively raised around £1 billion in third party investment and created thousands of jobs and many new treatments over the years.

We’re proud to be a part of the UK’s research and innovation sector, but we will never forget why we’re here, and what we’re here to do. Cancer Research UK exists because of the generosity of our supporters and the public’s commitment to our ambition of improving cancer diagnosis, treatment and care.  And it’s a responsibility we take very seriously.  

We fund research that will accelerate progress towards our goal of beating cancer. We’ve identified cancer types where progress has been slower – lung, pancreatic, brain and oesophageal cancers – and increased our efforts and our funding in these areas.

It’s this kind of patient-centric, strategic research investment that’s at risk because of the COVID-19 pandemic.  

We must act now  

We’ve written before about how medical research charities are slipping through the cracks of Government support.  And with COVID-19’s impact on medical research charities still unfolding, we need the Government to rethink its strategy. 

Our mission is clear – to beat cancer. And with the impact of COVID-19 being keenly felt by people with cancer, it’s never been more important.  

We and other medical research charities urgently need support to ensure we can continue to support today and tomorrow’s patients and contribute to economic growth. This is why we’re working with other medical research charities to ask for targeted financial support from the Government, through a Government-charity co-investment scheme for life sciences research.  

Together we can still beat cancer, but we can’t do it alone.  We’ve partnered with government for many years, and we now need their support more than ever if we want to rebuild the UK as a leader in cancer research. 

Michelle Mitchell is the chief executive officer of Cancer Research UK 

from Cancer Research UK – Science blog https://ift.tt/3etMRdr

Today, we announced that because of COVID-19 and the devastating impact it’s had on our income, we could be forced to cut £150 million per year from our research funding. 

Michelle Mitchell is our chief executive officer.

As an organisation whose sole mission is to beat cancer – to ensure that fewer people are diagnosed and those that are can face the future with more confidence – it’s not an announcement we ever wanted to make.  

These cuts would undoubtedly set back progress for cancer patients everywhere. To put the figure in context, £150 million is what Cancer Research UK would spend on clinical trials over the next 10 years. £150 million is approximately 35% of our total research spend  last year, and a cut like this could mean we have to close some of our sites around the country and leave thousands of early–career scientists unsupported. 

Figures like these, which are echoed by medical research charities across the UK, should be enough to ring alarm bells across the sector and for the Government. But the truth is the impact will be much bigger, and much broader, than a single number could ever convey.  

Because we don’t just fund over 50% of all publicly funded cancer research in the UK, we’re also a vital part of the country’s scientific ecosystem.  

Charities bring innovation and infrastructure to research across the country 

The UK is celebrated as a world leader in research and innovation, and one of the reasons for this success is the mix of government, private and charity-funded research.  

Medical research charities help to drive progress by funding early-stage, high risk research that wouldn’t otherwise be supported. And the insights that our researchers generate feed the pipeline of pharma companies all over the world. In fact, Cancer Research UK is the second biggest licensor of cancer drugs in the world, after MD Anderson in Texas. 

Take vemurafenib for example, a targeted cancer drug that by mid-2018 had been used to treat over 50,000 patients with malignant melanoma worldwide. This drug came from early research funded by Cancer Research UK and other charity partners, which revealed a particular mutation that cropped up in a lot of melanomas. The mutation was patented as a target for drug screens and patient tests. All 5 named inventors were UK-based scientists.  

As well as funding individual research projects, we also contribute a great deal to the research and innovation sector – through our work and our people.  

We’ve built a vibrant platform for cancer research across the UK through our Institutes and Clinical Trials Unit – funding 50% of the cancer research infrastructure in the UK.  

Our long-term investment in state-of-the-art facilities has helped to create a thriving network of research at 90 institutions in over 40 UK towns and cities.  

This infrastructure is part of what makes the UK a key player on the world stage, and an attractive place for cancer experts to bring their skills. It’s this infrastructure that’s at risk if we don’t get the support we need and, at a time when the Government is working to rebalance research investment across the UK, it’s an infrastructure that would be hard to recreate in our absence.  

Our ambitions rely on our dedicated researchers

But while our centres and clinical trials network are crucial pieces of our success, they’re brought to life by the scientists who work within them. We fund over 4,000 researchers in labs and hospitals across the UK. And as well as world leading experts, we’re helping to train the next generation of scientists, supporting over 500 PhD students, 160 fellows and 600 post-doctoral researchers.  

With COVID-19 delaying cancer research, diagnosis and treatment, these scientists have played a vital role in the UK’s response to the coronavirus pandemic, volunteering in COVID-19 testing facilities, redeploying to the front line and using their skills and expertise to help tackle the virus.  

And with the Chancellor highlighting research and innovation as a road to economic recovery, our researchers will also play a role in helping to rebuild the economy. Through our entrepreneurial programmes, we help the cancer research community to translate their discoveries into products and launch spinout companies that will improve the lives of people with cancer. Cancer Research UK has formed more than 40 spinout companies so far, which have collectively raised around £1 billion in third party investment and created thousands of jobs and many new treatments over the years.

We’re proud to be a part of the UK’s research and innovation sector, but we will never forget why we’re here, and what we’re here to do. Cancer Research UK exists because of the generosity of our supporters and the public’s commitment to our ambition of improving cancer diagnosis, treatment and care.  And it’s a responsibility we take very seriously.  

We fund research that will accelerate progress towards our goal of beating cancer. We’ve identified cancer types where progress has been slower – lung, pancreatic, brain and oesophageal cancers – and increased our efforts and our funding in these areas.

It’s this kind of patient-centric, strategic research investment that’s at risk because of the COVID-19 pandemic.  

We must act now  

We’ve written before about how medical research charities are slipping through the cracks of Government support.  And with COVID-19’s impact on medical research charities still unfolding, we need the Government to rethink its strategy. 

Our mission is clear – to beat cancer. And with the impact of COVID-19 being keenly felt by people with cancer, it’s never been more important.  

We and other medical research charities urgently need support to ensure we can continue to support today and tomorrow’s patients and contribute to economic growth. This is why we’re working with other medical research charities to ask for targeted financial support from the Government, through a Government-charity co-investment scheme for life sciences research.  

Together we can still beat cancer, but we can’t do it alone.  We’ve partnered with government for many years, and we now need their support more than ever if we want to rebuild the UK as a leader in cancer research. 

Michelle Mitchell is the chief executive officer of Cancer Research UK 

from Cancer Research UK – Science blog https://ift.tt/3etMRdr