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

LIGO and Virgo find a mystery object in the “mass gap”

In August of 2019, the LIGO-Virgo gravitational-wave network witnessed the merger of a black hole with 23 times the mass of our sun and a mystery object 2.6 times the mass of the sun. Scientists do not know if the mystery object was a neutron star or black hole, but either way it set a record as being either the heaviest-known neutron star … or the lightest-known black hole. Image via LIGO/ Caltech/ MIT/ R. Hurt (IPAC).

Originally published June 23, 2020 by the international LIGO-Virgo collaboration.

When the most massive stars die, they collapse under their own gravity and leave behind black holes; when stars that are a bit less massive die, they explode in supernovas and leave behind dense, dead remnants of stars called neutron stars. For decades, astronomers have been puzzled by a gap that lies between neutron stars and black holes: the heaviest known neutron star is no more than 2.5 times the mass of our Sun, or 2.5 solar masses, and the lightest known black hole is about 5 solar masses. The question remained: does anything lie in this so-called mass gap?

Now, in a new study from the National Science Foundation’s Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Virgo detector in Europe, scientists have announced the discovery of an object of 2.6 solar masses, placing it firmly in the mass gap. The object was found on August 14, 2019, as it merged with a black hole of 23 solar masses, generating a splash of gravitational waves detected back on Earth by LIGO and Virgo. A paper about the detection is being published today, June 23, in The Astrophysical Journal Letters.

“We’ve been waiting decades to solve this mystery” says Vicky Kalogera, a professor at Northwestern University. “We don’t know if this object is the heaviest known neutron star, or the lightest known black hole, but either way it breaks a record.”

“This is going to change how scientists talk about neutron stars and black holes,” says co-author Patrick Brady, a professor at the University of Wisconsin, Milwaukee, and the LIGO Scientific Collaboration spokesperson. “The mass gap may in fact not exist at all but may have been due to limitations in observational capabilities. Time and more observations will tell.”

The cosmic merger described in the study, an event dubbed GW190814, resulted in a final black hole about 25 times the mass of the Sun (some of the merged mass was converted to a blast of energy in the form of gravitational waves). The newly formed black hole lies about 800 million light-years away from Earth.

Before the two objects merged, their masses differed by a factor of 9, making this the most extreme mass ratio known for a gravitational-wave event. Another recently reported LIGO-Virgo event, called GW190412, occurred between two black holes with a mass ratio of about 4:1.

“It’s a challenge for current theoretical models to form merging pairs of compact objects with such a large mass ratio in which the low-mass partner resides in the mass gap. This discovery implies these events occur much more often than we predicted, making this a really intriguing low-mass object,” explains Kalogera. “The mystery object may be a neutron star merging with a black hole, an exciting possibility expected theoretically but not yet confirmed observationally. However, at 2.6 times the mass of our Sun, it exceeds modern predictions for the maximum mass of neutron stars, and may instead be the lightest black hole ever detected.”

When the LIGO and Virgo scientists spotted this merger, they immediately sent out an alert to the astronomical community. Dozens of ground- and space-based telescopes followed up in search of light waves generated in the event, but none picked up any signals. So far, such light counterparts to gravitational-wave signals have been seen only once, in an event called GW170817. That event, discovered by the LIGO-Virgo network in August of 2017, involved a fiery collision between two neutron stars that was subsequently witnessed by dozens of telescopes on Earth and in space. Neutron star collisions are messy affairs with matter flung outward in all directions and are thus expected to shine with light. Conversely, black hole mergers, in most circumstances, are thought not to produce light.

According to the LIGO and Virgo scientists, the August 2019 event was not seen by light-based telescopes for a few possible reasons. First, this event was six times farther away than the merger observed in 2017, making it harder to pick up any light signals. Secondly, if the collision involved two black holes, it likely would have not shone with any light. Thirdly, if the object was in fact a neutron star, its 9-fold more massive black-hole partner might have swallowed it whole; a neutron star consumed whole by a black hole would not give off any light.

“I think of Pac-Man eating a little dot,” says Kalogera. “When the masses are highly asymmetric, the smaller neutron star can be eaten in one bite.”

How will researchers ever know if the mystery object was a neutron star or a black hole? Future observations with LIGO, Virgo, and possibly other telescopes may catch similar events that would help reveal whether additional objects exist in the mass gap.

“This is the first glimpse of what could be a whole new population of compact binary objects,” says Charlie Hoy, a member of the LIGO Scientific Collaboration and a graduate student at Cardiff University. “What is really exciting is that this is just the start. As the detectors get more and more sensitive, we will observe even more of these signals, and we will be able to pinpoint the populations of neutron stars and black holes in the universe.”

“The mass gap has been an interesting puzzle for decades, and now we’ve detected an object that fits just inside it,” says Pedro Marronetti, program director for gravitational physics at the National Science Foundation (NSF). “That cannot be explained without defying our understanding of extremely dense matter or what we know about the evolution of stars. This observation is yet another example of the transformative potential of the field of gravitational-wave astronomy, which brings novel insights with every new detection.”

Bottom line:

Source: GW190814: Gravitational Waves from the Coalescence of a 23 Solar Mass Black Hole with a 2.6 Solar Mass Compact Object

Via LIGO/ Caltech

from EarthSky https://ift.tt/2BBFxOl

In August of 2019, the LIGO-Virgo gravitational-wave network witnessed the merger of a black hole with 23 times the mass of our sun and a mystery object 2.6 times the mass of the sun. Scientists do not know if the mystery object was a neutron star or black hole, but either way it set a record as being either the heaviest-known neutron star … or the lightest-known black hole. Image via LIGO/ Caltech/ MIT/ R. Hurt (IPAC).

Originally published June 23, 2020 by the international LIGO-Virgo collaboration.

When the most massive stars die, they collapse under their own gravity and leave behind black holes; when stars that are a bit less massive die, they explode in supernovas and leave behind dense, dead remnants of stars called neutron stars. For decades, astronomers have been puzzled by a gap that lies between neutron stars and black holes: the heaviest known neutron star is no more than 2.5 times the mass of our Sun, or 2.5 solar masses, and the lightest known black hole is about 5 solar masses. The question remained: does anything lie in this so-called mass gap?

Now, in a new study from the National Science Foundation’s Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Virgo detector in Europe, scientists have announced the discovery of an object of 2.6 solar masses, placing it firmly in the mass gap. The object was found on August 14, 2019, as it merged with a black hole of 23 solar masses, generating a splash of gravitational waves detected back on Earth by LIGO and Virgo. A paper about the detection is being published today, June 23, in The Astrophysical Journal Letters.

“We’ve been waiting decades to solve this mystery” says Vicky Kalogera, a professor at Northwestern University. “We don’t know if this object is the heaviest known neutron star, or the lightest known black hole, but either way it breaks a record.”

“This is going to change how scientists talk about neutron stars and black holes,” says co-author Patrick Brady, a professor at the University of Wisconsin, Milwaukee, and the LIGO Scientific Collaboration spokesperson. “The mass gap may in fact not exist at all but may have been due to limitations in observational capabilities. Time and more observations will tell.”

The cosmic merger described in the study, an event dubbed GW190814, resulted in a final black hole about 25 times the mass of the Sun (some of the merged mass was converted to a blast of energy in the form of gravitational waves). The newly formed black hole lies about 800 million light-years away from Earth.

Before the two objects merged, their masses differed by a factor of 9, making this the most extreme mass ratio known for a gravitational-wave event. Another recently reported LIGO-Virgo event, called GW190412, occurred between two black holes with a mass ratio of about 4:1.

“It’s a challenge for current theoretical models to form merging pairs of compact objects with such a large mass ratio in which the low-mass partner resides in the mass gap. This discovery implies these events occur much more often than we predicted, making this a really intriguing low-mass object,” explains Kalogera. “The mystery object may be a neutron star merging with a black hole, an exciting possibility expected theoretically but not yet confirmed observationally. However, at 2.6 times the mass of our Sun, it exceeds modern predictions for the maximum mass of neutron stars, and may instead be the lightest black hole ever detected.”

When the LIGO and Virgo scientists spotted this merger, they immediately sent out an alert to the astronomical community. Dozens of ground- and space-based telescopes followed up in search of light waves generated in the event, but none picked up any signals. So far, such light counterparts to gravitational-wave signals have been seen only once, in an event called GW170817. That event, discovered by the LIGO-Virgo network in August of 2017, involved a fiery collision between two neutron stars that was subsequently witnessed by dozens of telescopes on Earth and in space. Neutron star collisions are messy affairs with matter flung outward in all directions and are thus expected to shine with light. Conversely, black hole mergers, in most circumstances, are thought not to produce light.

According to the LIGO and Virgo scientists, the August 2019 event was not seen by light-based telescopes for a few possible reasons. First, this event was six times farther away than the merger observed in 2017, making it harder to pick up any light signals. Secondly, if the collision involved two black holes, it likely would have not shone with any light. Thirdly, if the object was in fact a neutron star, its 9-fold more massive black-hole partner might have swallowed it whole; a neutron star consumed whole by a black hole would not give off any light.

“I think of Pac-Man eating a little dot,” says Kalogera. “When the masses are highly asymmetric, the smaller neutron star can be eaten in one bite.”

How will researchers ever know if the mystery object was a neutron star or a black hole? Future observations with LIGO, Virgo, and possibly other telescopes may catch similar events that would help reveal whether additional objects exist in the mass gap.

“This is the first glimpse of what could be a whole new population of compact binary objects,” says Charlie Hoy, a member of the LIGO Scientific Collaboration and a graduate student at Cardiff University. “What is really exciting is that this is just the start. As the detectors get more and more sensitive, we will observe even more of these signals, and we will be able to pinpoint the populations of neutron stars and black holes in the universe.”

“The mass gap has been an interesting puzzle for decades, and now we’ve detected an object that fits just inside it,” says Pedro Marronetti, program director for gravitational physics at the National Science Foundation (NSF). “That cannot be explained without defying our understanding of extremely dense matter or what we know about the evolution of stars. This observation is yet another example of the transformative potential of the field of gravitational-wave astronomy, which brings novel insights with every new detection.”

Bottom line:

Source: GW190814: Gravitational Waves from the Coalescence of a 23 Solar Mass Black Hole with a 2.6 Solar Mass Compact Object

Via LIGO/ Caltech

from EarthSky https://ift.tt/2BBFxOl

A tribute to Professor Anne Charlton

Professor Anne Charlton was a much-loved colleague who blazed a research trail in cancer education and smoking prevention in schools.

Anne, who died in April aged 84 after contracting COVID-19, was a passionate advocate of the importance of public knowledge about cancer. She combined academic rigour with a down-to-earth and empathetic approach and her contribution to where we are today – in speaking in an open and informed manner about cancer and in driving down youth smoking rates – cannot be overstated.

Anne was a naturally inquisitive child, a trait that followed her throughout her life – from her early interest in botany research to her training and career as a biology teacher in schools in Barrow-in-Furness and Manchester.

It’s a testament to Anne’s energy and enthusiasm that she began her career in cancer research at the age of 39, focusing on cancer education, smoking prevention and the impact of cancer on children.

Cancer education

In the 1970s, cancer was still a taboo subject for many and the fear and misunderstanding it evoked often led to delays in seeking treatment. In 1974, Anne left teaching to take up a research post with the Manchester Regional Committee for Cancer Education.

With the first of many grants from Cancer Research Campaign, a forerunner of Cancer Research UK, Anne began to survey children and teachers’ opinions about cancer. The work led to a master’s degree and a lectureship at Manchester University and set Anne’s course for the next few decades.

Anne went on to explore the possibility of introducing cancer into the curriculum of secondary schools. This project opened up a whole new area of work and led to the development and rigorous evaluation of resources for schools, colleges and teachers – including teaching guides like ‘Cells, Cancers and Communities’ and the ‘Topic of Cancer’.

Through this work, hundreds if not thousands of teachers and education systems around the world were inspired to teach science to children in new ways that made both teaching and learning easier.

This work not only changed the conversation about cancer in schools, it also opened up conversations about smoking.

Children and smoking

By the early 1980s, Cancer Research Campaign (CRC) was beginning to fund research into young people and smoking, Anne conducted a major survey of children and young people in northern England. The research provided a wealth of information about the factors that influence children to take up smoking and revealed that a quarter of 15-16 year-old girls were already regular smokers.

With further funding from the CRC, Anne began to develop new approaches to teaching about cancer, health and tobacco to help delay uptake of smoking and support young smokers to quit.

Anne’s group developed and evaluated many resources for schools and teachers, including a smoking prevention programme for 9-10 year-old children that was also targeted at parents and teachers and a stop-smoking course for young people aged 15-19 years, which was based on the identification of 9 different types of smoker.

Her studies also highlighted external influences that reinforced children’s smoking, including tobacco industry sponsorship of Formula 1 racing and snooker, and contributed to the big push to transform UK government policy to de-normalise smoking.

Impact of cancer on children

With the rapid progress in treatment of many children’s cancers, increasing numbers of children were starting school for the first time or returning to the classroom after a cancer diagnosis and treatment.

Working closely with children’s cancer specialists at the Christie Hospital in Manchester, Anne initiated a detailed study of the experiences of a small group of children and their parents and teachers. This research revealed a number of physical, psychological and academic issues that could impact a child’s return to the classroom.

The success of this pilot led to a much larger study, which showed that teachers needed specific information about a child’s cancer, their treatment and the type of problems that might arise to fully support their pupil in the classroom. Following on from the research, a resource for teachers, ‘Welcome back’, was developed by colleagues in Bristol and Exeter and widely distributed.

Anne’s contribution to cancer education cannot be overstated, but her impact extended far beyond her research projects. She was not a world-renowned expert in her field, she was also a mentor to many researchers, thanks to her undeniable strengths in communication and networking.

Her zest for living was irrepressible. She never retired, continuing to travel, publish and present her research, and to enjoy Shakespeare plays and flower shows to the end of her life.

A good friend and colleague to many, Anne was always ready to offer encouragement and support. She will be greatly missed.

Jean King, Cancer Research UK’s former director of tobacco control and Lesley Walker, Cancer Research UK’s former director of cancer information

from Cancer Research UK – Science blog https://ift.tt/2NnKltw

Professor Anne Charlton was a much-loved colleague who blazed a research trail in cancer education and smoking prevention in schools.

Anne, who died in April aged 84 after contracting COVID-19, was a passionate advocate of the importance of public knowledge about cancer. She combined academic rigour with a down-to-earth and empathetic approach and her contribution to where we are today – in speaking in an open and informed manner about cancer and in driving down youth smoking rates – cannot be overstated.

Anne was a naturally inquisitive child, a trait that followed her throughout her life – from her early interest in botany research to her training and career as a biology teacher in schools in Barrow-in-Furness and Manchester.

It’s a testament to Anne’s energy and enthusiasm that she began her career in cancer research at the age of 39, focusing on cancer education, smoking prevention and the impact of cancer on children.

Cancer education

In the 1970s, cancer was still a taboo subject for many and the fear and misunderstanding it evoked often led to delays in seeking treatment. In 1974, Anne left teaching to take up a research post with the Manchester Regional Committee for Cancer Education.

With the first of many grants from Cancer Research Campaign, a forerunner of Cancer Research UK, Anne began to survey children and teachers’ opinions about cancer. The work led to a master’s degree and a lectureship at Manchester University and set Anne’s course for the next few decades.

Anne went on to explore the possibility of introducing cancer into the curriculum of secondary schools. This project opened up a whole new area of work and led to the development and rigorous evaluation of resources for schools, colleges and teachers – including teaching guides like ‘Cells, Cancers and Communities’ and the ‘Topic of Cancer’.

Through this work, hundreds if not thousands of teachers and education systems around the world were inspired to teach science to children in new ways that made both teaching and learning easier.

This work not only changed the conversation about cancer in schools, it also opened up conversations about smoking.

Children and smoking

By the early 1980s, Cancer Research Campaign (CRC) was beginning to fund research into young people and smoking, Anne conducted a major survey of children and young people in northern England. The research provided a wealth of information about the factors that influence children to take up smoking and revealed that a quarter of 15-16 year-old girls were already regular smokers.

With further funding from the CRC, Anne began to develop new approaches to teaching about cancer, health and tobacco to help delay uptake of smoking and support young smokers to quit.

Anne’s group developed and evaluated many resources for schools and teachers, including a smoking prevention programme for 9-10 year-old children that was also targeted at parents and teachers and a stop-smoking course for young people aged 15-19 years, which was based on the identification of 9 different types of smoker.

Her studies also highlighted external influences that reinforced children’s smoking, including tobacco industry sponsorship of Formula 1 racing and snooker, and contributed to the big push to transform UK government policy to de-normalise smoking.

Impact of cancer on children

With the rapid progress in treatment of many children’s cancers, increasing numbers of children were starting school for the first time or returning to the classroom after a cancer diagnosis and treatment.

Working closely with children’s cancer specialists at the Christie Hospital in Manchester, Anne initiated a detailed study of the experiences of a small group of children and their parents and teachers. This research revealed a number of physical, psychological and academic issues that could impact a child’s return to the classroom.

The success of this pilot led to a much larger study, which showed that teachers needed specific information about a child’s cancer, their treatment and the type of problems that might arise to fully support their pupil in the classroom. Following on from the research, a resource for teachers, ‘Welcome back’, was developed by colleagues in Bristol and Exeter and widely distributed.

Anne’s contribution to cancer education cannot be overstated, but her impact extended far beyond her research projects. She was not a world-renowned expert in her field, she was also a mentor to many researchers, thanks to her undeniable strengths in communication and networking.

Her zest for living was irrepressible. She never retired, continuing to travel, publish and present her research, and to enjoy Shakespeare plays and flower shows to the end of her life.

A good friend and colleague to many, Anne was always ready to offer encouragement and support. She will be greatly missed.

Jean King, Cancer Research UK’s former director of tobacco control and Lesley Walker, Cancer Research UK’s former director of cancer information

from Cancer Research UK – Science blog https://ift.tt/2NnKltw

Hummingbirds see colors we can only imagine

Male broad-tailed hummingbird. Researchers trained birds like these to perform experiments that revealed that the birds see colors invisible to human eyes. Image via Noah Whiteman (UC-Berkeley)/ Princeton University.

You know the old idea that dogs see only in shades of gray? Studies have shown that’s not true. Dogs do see some colors, though their color vision doesn’t reveal a world as richly or intensely colored as the world we see. Now a new study by scientists, published this month in the peer-reviewed journal Proceedings of the National Academy of Sciences, shows that our human color vision can’t compete with that of wild hummingbirds. These fleet little birds perceive a world far more richly hued than ours, full of visual cues humans never notice, via colors we can’t imagine. In fact, said evolutionary biologist Mary (Cassie) Stoddard at Princeton:

Humans are color-blind compared to birds and many other animals.

To other hummingbirds, this male’s magenta throat feathers likely appear as an ultraviolet+purple combination color. Image via David Inouye (U. of Maryland-College Park)/ Princeton University.

When it comes to color vision, you can thank the cone cells in the retina of your eye. Humans have three types of color cones, making us sensitive to red, green and blue light. Birds have a fourth color cone that can detect ultraviolet light. The tiny hummingbirds also see combination colors like ultraviolet+green and ultraviolet+red, according to the new research. The hummingbirds rely on their heightened color sense to find food, dazzle mates, escape predators and navigate diverse terrain, these scientists said.

To investigate how birds perceive color, Stoddard and her research team explored bird color vision in a natural setting. They worked at the Rocky Mountain Biological Laboratory in Gothic, Colorado, training wild broad-tailed hummingbirds (Selasphorus platycercus) to participate in color vision experiments. In the scientists’ statement, Stoddard explained:

Most detailed perceptual experiments on birds are performed in the lab, but we risk missing the bigger picture of how birds really use color vision in their daily lives.

Hummingbirds are perfect for studying color vision in the wild. These sugar fiends have evolved to respond to flower colors that advertise a nectar reward, so they can learn color associations rapidly and with little training.

The team said it was particularly interested in nonspectral color combinations, which involve hues from widely separated parts of the color spectrum. That’s as opposed, they said:

… to blends of neighboring colors like teal (blue-green) or yellow (green-red). For humans, purple is the clearest example of a nonspectral color. Technically, purple is not in the rainbow: it arises when our blue (short-wave) and red (long-wave) cones are stimulated, but not green (medium-wave) cones.

While humans have just one nonspectral color – purple – birds can theoretically see up to five: purple, ultraviolet+red, ultraviolet+green, ultraviolet+yellow and ultraviolet+purple.

View larger. | Infographic by the Stoddard Lab/ Princeton University.

Stoddard and her colleagues designed a series of experiments to test whether hummingbirds can see these nonspectral colors. They performed outdoor experiments each summer for three years, starting with a pair of custom “bird vision” LED tubes programmed to display a broad range of colors, including nonspectral colors like ultraviolet+green. Next, they performed experiments in an alpine meadow frequently visited by local broad-tailed hummingbirds. Their statement said:

Each morning, the researchers rose before dawn and set up two feeders: one containing sugar water and the other plain water. Beside each feeder, they placed an LED tube. The tube beside the sugar water emitted one color, while the one next to the plain water emitted a different color. The researchers periodically swapped the positions of the rewarding and unrewarding tubes, so the birds could not simply use location to pinpoint a sweet treat. They also performed control experiments to ensure that the tiny birds were not using smell or another inadvertent cue to find the reward. Over the course of several hours, wild hummingbirds learned to visit the rewarding color. Using this setup, the researchers recorded over 6,000 feeder visits in a series of 19 experiments.

The experiments revealed that hummingbirds can see a variety of nonspectral colors, including purple, ultraviolet+green, ultraviolet+red and ultraviolet+yellow. For example, hummingbirds readily distinguished ultraviolet+green from pure ultraviolet or pure green, and they discriminated between two different mixtures of ultraviolet+red light – one redder, one less so.

Harold Eyster, a UBC Ph.D. student and a co-author of the study, commented:

It was amazing to watch. The ultraviolet+green light and green light looked identical to us, but the hummingbirds kept correctly choosing the ultraviolet+green light associated with sugar water. Our experiments enabled us to get a sneak peek into what the world looks like to a hummingbird.

Even though hummingbirds can perceive nonspectral colors, appreciating how these colors appear to birds can be difficult, the scientists said. Ben Hogan, a postdoctoral research associate at Princeton and a co-author of the study, commented:

It’s impossible to really know how the birds perceive these colors. Is ultraviolet+red a mix of those colors, or an entirely new color? We can only speculate.

Stoddard added:

To imagine an extra dimension of color vision – that is the thrill and challenge of studying how avian perception works. Fortunately, the hummingbirds reveal that they can see things we cannot.

David Inouye, who is affiliated with the University of Maryland and the center where the study took place, added:

The colors that we see in the fields of wildflowers at our study site, the wildflower capital of Colorado, are stunning to us, but just imagine what those flowers look like to birds with that extra sensory dimension.

The scientists said the wide variety of nonspectral colors available to birds is the result of their ancient four color-cone visual system. Stoddard explained:

Tetrachromacy – having four color cone types – evolved in early vertebrates. This color vision system is the norm for birds, many fish and reptiles, and it almost certainly existed in dinosaurs. We think the ability to perceive many nonspectral colors is not just a feat of hummingbirds but a widespread feature of animal color vision.

The research team studied hummingbirds at the Rocky Mountain Biological Laboratory in Gothic, Colorado. The high-altitude site, at an elevation of nearly 10,000 feet (3,000 meters), is home to many broad-tailed hummingbirds. The research team included (from left): Prof. Mary “Cassie” Stoddard; Cole Morokhovich of the Class of 2020; Harold Eyster, a Ph.D. student at the University of British Columbia; and postdoctoral research associate Ben Hogan. Stoddard, Eyster and Hogan are authors on the paper appearing this week in PNAS. Photo via Princeton University.

Bottom line: A new series of experiments shows that wild hummingbirds perceive a world far more richly colored than ours, full of visual cues humans can never perceive via colors we can’t imagine.

Source: Wild hummingbirds discriminate non-spectral colors

Via Princeton University

from EarthSky https://ift.tt/37QDvGq

Male broad-tailed hummingbird. Researchers trained birds like these to perform experiments that revealed that the birds see colors invisible to human eyes. Image via Noah Whiteman (UC-Berkeley)/ Princeton University.

You know the old idea that dogs see only in shades of gray? Studies have shown that’s not true. Dogs do see some colors, though their color vision doesn’t reveal a world as richly or intensely colored as the world we see. Now a new study by scientists, published this month in the peer-reviewed journal Proceedings of the National Academy of Sciences, shows that our human color vision can’t compete with that of wild hummingbirds. These fleet little birds perceive a world far more richly hued than ours, full of visual cues humans never notice, via colors we can’t imagine. In fact, said evolutionary biologist Mary (Cassie) Stoddard at Princeton:

Humans are color-blind compared to birds and many other animals.

To other hummingbirds, this male’s magenta throat feathers likely appear as an ultraviolet+purple combination color. Image via David Inouye (U. of Maryland-College Park)/ Princeton University.

When it comes to color vision, you can thank the cone cells in the retina of your eye. Humans have three types of color cones, making us sensitive to red, green and blue light. Birds have a fourth color cone that can detect ultraviolet light. The tiny hummingbirds also see combination colors like ultraviolet+green and ultraviolet+red, according to the new research. The hummingbirds rely on their heightened color sense to find food, dazzle mates, escape predators and navigate diverse terrain, these scientists said.

To investigate how birds perceive color, Stoddard and her research team explored bird color vision in a natural setting. They worked at the Rocky Mountain Biological Laboratory in Gothic, Colorado, training wild broad-tailed hummingbirds (Selasphorus platycercus) to participate in color vision experiments. In the scientists’ statement, Stoddard explained:

Most detailed perceptual experiments on birds are performed in the lab, but we risk missing the bigger picture of how birds really use color vision in their daily lives.

Hummingbirds are perfect for studying color vision in the wild. These sugar fiends have evolved to respond to flower colors that advertise a nectar reward, so they can learn color associations rapidly and with little training.

The team said it was particularly interested in nonspectral color combinations, which involve hues from widely separated parts of the color spectrum. That’s as opposed, they said:

… to blends of neighboring colors like teal (blue-green) or yellow (green-red). For humans, purple is the clearest example of a nonspectral color. Technically, purple is not in the rainbow: it arises when our blue (short-wave) and red (long-wave) cones are stimulated, but not green (medium-wave) cones.

While humans have just one nonspectral color – purple – birds can theoretically see up to five: purple, ultraviolet+red, ultraviolet+green, ultraviolet+yellow and ultraviolet+purple.

View larger. | Infographic by the Stoddard Lab/ Princeton University.

Stoddard and her colleagues designed a series of experiments to test whether hummingbirds can see these nonspectral colors. They performed outdoor experiments each summer for three years, starting with a pair of custom “bird vision” LED tubes programmed to display a broad range of colors, including nonspectral colors like ultraviolet+green. Next, they performed experiments in an alpine meadow frequently visited by local broad-tailed hummingbirds. Their statement said:

Each morning, the researchers rose before dawn and set up two feeders: one containing sugar water and the other plain water. Beside each feeder, they placed an LED tube. The tube beside the sugar water emitted one color, while the one next to the plain water emitted a different color. The researchers periodically swapped the positions of the rewarding and unrewarding tubes, so the birds could not simply use location to pinpoint a sweet treat. They also performed control experiments to ensure that the tiny birds were not using smell or another inadvertent cue to find the reward. Over the course of several hours, wild hummingbirds learned to visit the rewarding color. Using this setup, the researchers recorded over 6,000 feeder visits in a series of 19 experiments.

The experiments revealed that hummingbirds can see a variety of nonspectral colors, including purple, ultraviolet+green, ultraviolet+red and ultraviolet+yellow. For example, hummingbirds readily distinguished ultraviolet+green from pure ultraviolet or pure green, and they discriminated between two different mixtures of ultraviolet+red light – one redder, one less so.

Harold Eyster, a UBC Ph.D. student and a co-author of the study, commented:

It was amazing to watch. The ultraviolet+green light and green light looked identical to us, but the hummingbirds kept correctly choosing the ultraviolet+green light associated with sugar water. Our experiments enabled us to get a sneak peek into what the world looks like to a hummingbird.

Even though hummingbirds can perceive nonspectral colors, appreciating how these colors appear to birds can be difficult, the scientists said. Ben Hogan, a postdoctoral research associate at Princeton and a co-author of the study, commented:

It’s impossible to really know how the birds perceive these colors. Is ultraviolet+red a mix of those colors, or an entirely new color? We can only speculate.

Stoddard added:

To imagine an extra dimension of color vision – that is the thrill and challenge of studying how avian perception works. Fortunately, the hummingbirds reveal that they can see things we cannot.

David Inouye, who is affiliated with the University of Maryland and the center where the study took place, added:

The colors that we see in the fields of wildflowers at our study site, the wildflower capital of Colorado, are stunning to us, but just imagine what those flowers look like to birds with that extra sensory dimension.

The scientists said the wide variety of nonspectral colors available to birds is the result of their ancient four color-cone visual system. Stoddard explained:

Tetrachromacy – having four color cone types – evolved in early vertebrates. This color vision system is the norm for birds, many fish and reptiles, and it almost certainly existed in dinosaurs. We think the ability to perceive many nonspectral colors is not just a feat of hummingbirds but a widespread feature of animal color vision.

The research team studied hummingbirds at the Rocky Mountain Biological Laboratory in Gothic, Colorado. The high-altitude site, at an elevation of nearly 10,000 feet (3,000 meters), is home to many broad-tailed hummingbirds. The research team included (from left): Prof. Mary “Cassie” Stoddard; Cole Morokhovich of the Class of 2020; Harold Eyster, a Ph.D. student at the University of British Columbia; and postdoctoral research associate Ben Hogan. Stoddard, Eyster and Hogan are authors on the paper appearing this week in PNAS. Photo via Princeton University.

Bottom line: A new series of experiments shows that wild hummingbirds perceive a world far more richly colored than ours, full of visual cues humans can never perceive via colors we can’t imagine.

Source: Wild hummingbirds discriminate non-spectral colors

Via Princeton University

from EarthSky https://ift.tt/37QDvGq

What is a derecho? An atmospheric scientist explains these rare but dangerous storm systems

A derecho moves across central Kansas on July 3, 2005. Image via Jim Reed/ Corbis/ Getty Images.

By Russ Schumacher, Colorado State University

Thunderstorms are common across North America, especially in warm weather months. About 10% of them become severe, meaning they produce hail 1 inch (2.5 cm) or greater in diameter, winds gusting in excess of 50 knots (57.5 miles per hour, over 90 kph), or a tornado.

The U.S. recently has experienced two rarer events: organized lines of thunderstorms with widespread damaging winds, known as derechos.

Derechos occur mainly across the central and eastern U.S., where many locations are affected one to two times per year on average. They can produce significant damage to structures and sometimes cause “blowdowns” of millions of trees. Pennsylvania and New Jersey received the brunt of a derecho on June 3, 2020, that killed four people and left nearly a million without power across the mid-Atlantic region.

In the West, derechos are less common, but Colorado – where I serve as state climatologist and director of the Colorado Climate Center – experienced a rare and powerful derecho on June 6 that generated winds exceeding 100 miles per hour in some locations. Derechos have also been observed and analyzed in many other parts of the world, including Europe, Asia and South America.

Derechos are an important and active research area in meteorology. I expect that at least one or two more will occur somewhere in the U.S. this summer. Here’s what we know about these unusual storms.

Derechos occur fairly regularly over large parts of the U.S. each year, most commonly from April through August. Image via Dennis Cain/ NOAA.

A massive derecho in June 2012 developed in northern Illinois and traveled to the mid-Atlantic coast, killing 22 and causing $4 billion to $5 billion in damages.

Walls of wind

Scientists have long recognized that organized lines of thunderstorms can produce widespread damaging winds. Gustav Hinrichs, a professor at the University of Iowa, analyzed severe winds in the 1870s and 1880s and identified that many destructive storms were produced by straight-line winds rather than by tornadoes, in which winds rotate. Because the word “tornado,” of Spanish origin, was already in common usage, Hinrichs proposed “derecho” – Spanish for “straight ahead” – for damaging windstorms not associated with tornadoes.

In 1987, meteorologists defined what qualified as a derecho. They proposed that for a storm system to be classified as a derecho, it had to produce severe winds – 57.5 mph (26 meters per second) or greater – and those intense winds had to extend over a path at least 250 miles (400 kilometers) long, with no more than three hours separating individual severe wind reports.

Derechos are almost always caused by a type of weather system known as a bow echo, which has the shape of an archer’s bow on radar images. These in turn are a specific type of mesoscale convective system, a term that describes large, organized groupings of storms.

A derecho affected the central Rockies and northern Plains on Saturday (6/6/20). Derechos are very rare for parts of UT, WY & CO. In fact, only two other derechos are well-documented west of the Rockies. Interested in learning more about derechos? Visit: https://t.co/Na0e8JB4bc pic.twitter.com/XcUI8j5pQQ

— NWS Storm Prediction Center (@NWSSPC) June 8, 2020

Researchers are studying whether and how climate change is affecting weather hazards from thunderstorms. Although some aspects of mesoscale convective systems, such as the amount of rainfall they produce, are very likely to change with continued warming, it’s not yet clear how future climate change may affect the likelihood or intensity of derechos.

Speeding across the landscape

The term “derecho” vaulted into public awareness in June 2012, when one of the most destructive derechos in U.S. history formed in the Midwest and traveled some 700 miles (1,100 km) in 12 hours, eventually making a direct impact on the Washington, D.C. area. This event killed 22 people and caused millions of power outages.

Top: Radar imagery every 2 hours, from 1600 UTC June 29 to 0400 UTC June 30, 2012, combined to show the progression of a derecho-producing bow echo across the central and eastern US. Bottom: Severe wind reports for the June 29-30, 2012, derecho, colored by wind speed. Image via Schumacher and Rasmussen, 2020/ Guastini and Bosart 2016/ Nature.

Only a few recorded derechos had occurred in the western U.S. prior to June 6, 2020. On that day, a line of strong thunderstorms developed in eastern Utah and western Colorado in the late morning. This was unusual in itself, as storms in this region tend to be less organized and occur later in the day.

The thunderstorms continued to organize and moved northeastward across the Rocky Mountains. This was even more unusual: Derecho-producing lines of storms are driven by a pool of cold air near the ground, which would typically be disrupted by a mountain range as tall as the Rockies. In this case, the line remained organized.

As the line of storms emerged to the east of the mountains, it caused widespread wind damage in the Denver metro area and northeastern Colorado. It then strengthened further as it proceeded north-northeastward across eastern Wyoming, western Nebraska and the Dakotas.

In total there were nearly 350 reports of severe winds, including 44 of 75 miles per hour (about 34 meters per second) or greater. The strongest reported gust was 110 mph at Winter Park ski area in the Colorado Rockies. Of these reports, 95 came from Colorado – by far the most severe wind reports ever from a single thunderstorm system.

Animation showing the development and evolution of the June 6-7, 2020, western derecho. Radar reflectivity is shown in the color shading, with National Weather Service warnings shown in the colored outlines (yellow polygons indicate severe thunderstorm warnings). Image via Iowa Environmental Mesonet.

Coloradans are accustomed to big weather, including strong winds in the mountains and foothills. Some of these winds are generated by flow down mountain slopes, localized thunderstorm microbursts, or even “bomb cyclones.” Western thunderstorms more commonly produce hailstorms and tornadoes, so it was very unusual to have a broad swath of the state experience damaging straight-line winds that extended from west of the Rockies all the way to the Dakotas.

Damage comparable to a hurricane

Derechos are challenging to predict. On days when derechos form, it is often uncertain whether any storms will form at all. But if they do, the chance exists for explosive development of intense winds. Forecasters did not anticipate the historic June 2012 derecho until it was already underway.

For the western derecho on June 6, 2020, outlooks showed an enhanced potential for severe storms in Nebraska and the Dakotas two to three days in advance. However, the outlooks didn’t highlight the potential for destructive winds farther south in Colorado until the morning that the derecho formed.

Once a line of storms has begun to develop, however, the National Weather Service routinely issues highly accurate severe thunderstorm warnings 30 to 60 minutes ahead of the arrival of intense winds, alerting the public to take precautions.

Communities, first responders and utilities may have only a few hours to prepare for an oncoming derecho, so it is important to know how to receive severe thunderstorm warnings, such as TV, radio and smartphone alerts, and to take these warnings seriously. Tornadoes and tornado warnings often get the most attention, but lines of severe thunderstorms can also pack a major punch.

Russ Schumacher, Associate Professor of Atmospheric Science and Colorado State Climatologist, Colorado State University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Bottom line: What is a derecho? An atmospheric scientist explains these rare but dangerous storm systems.

from EarthSky https://ift.tt/3fU0mU3

A derecho moves across central Kansas on July 3, 2005. Image via Jim Reed/ Corbis/ Getty Images.

By Russ Schumacher, Colorado State University

Thunderstorms are common across North America, especially in warm weather months. About 10% of them become severe, meaning they produce hail 1 inch (2.5 cm) or greater in diameter, winds gusting in excess of 50 knots (57.5 miles per hour, over 90 kph), or a tornado.

The U.S. recently has experienced two rarer events: organized lines of thunderstorms with widespread damaging winds, known as derechos.

Derechos occur mainly across the central and eastern U.S., where many locations are affected one to two times per year on average. They can produce significant damage to structures and sometimes cause “blowdowns” of millions of trees. Pennsylvania and New Jersey received the brunt of a derecho on June 3, 2020, that killed four people and left nearly a million without power across the mid-Atlantic region.

In the West, derechos are less common, but Colorado – where I serve as state climatologist and director of the Colorado Climate Center – experienced a rare and powerful derecho on June 6 that generated winds exceeding 100 miles per hour in some locations. Derechos have also been observed and analyzed in many other parts of the world, including Europe, Asia and South America.

Derechos are an important and active research area in meteorology. I expect that at least one or two more will occur somewhere in the U.S. this summer. Here’s what we know about these unusual storms.

Derechos occur fairly regularly over large parts of the U.S. each year, most commonly from April through August. Image via Dennis Cain/ NOAA.

A massive derecho in June 2012 developed in northern Illinois and traveled to the mid-Atlantic coast, killing 22 and causing $4 billion to $5 billion in damages.

Walls of wind

Scientists have long recognized that organized lines of thunderstorms can produce widespread damaging winds. Gustav Hinrichs, a professor at the University of Iowa, analyzed severe winds in the 1870s and 1880s and identified that many destructive storms were produced by straight-line winds rather than by tornadoes, in which winds rotate. Because the word “tornado,” of Spanish origin, was already in common usage, Hinrichs proposed “derecho” – Spanish for “straight ahead” – for damaging windstorms not associated with tornadoes.

In 1987, meteorologists defined what qualified as a derecho. They proposed that for a storm system to be classified as a derecho, it had to produce severe winds – 57.5 mph (26 meters per second) or greater – and those intense winds had to extend over a path at least 250 miles (400 kilometers) long, with no more than three hours separating individual severe wind reports.

Derechos are almost always caused by a type of weather system known as a bow echo, which has the shape of an archer’s bow on radar images. These in turn are a specific type of mesoscale convective system, a term that describes large, organized groupings of storms.

A derecho affected the central Rockies and northern Plains on Saturday (6/6/20). Derechos are very rare for parts of UT, WY & CO. In fact, only two other derechos are well-documented west of the Rockies. Interested in learning more about derechos? Visit: https://t.co/Na0e8JB4bc pic.twitter.com/XcUI8j5pQQ

— NWS Storm Prediction Center (@NWSSPC) June 8, 2020

Researchers are studying whether and how climate change is affecting weather hazards from thunderstorms. Although some aspects of mesoscale convective systems, such as the amount of rainfall they produce, are very likely to change with continued warming, it’s not yet clear how future climate change may affect the likelihood or intensity of derechos.

Speeding across the landscape

The term “derecho” vaulted into public awareness in June 2012, when one of the most destructive derechos in U.S. history formed in the Midwest and traveled some 700 miles (1,100 km) in 12 hours, eventually making a direct impact on the Washington, D.C. area. This event killed 22 people and caused millions of power outages.

Top: Radar imagery every 2 hours, from 1600 UTC June 29 to 0400 UTC June 30, 2012, combined to show the progression of a derecho-producing bow echo across the central and eastern US. Bottom: Severe wind reports for the June 29-30, 2012, derecho, colored by wind speed. Image via Schumacher and Rasmussen, 2020/ Guastini and Bosart 2016/ Nature.

Only a few recorded derechos had occurred in the western U.S. prior to June 6, 2020. On that day, a line of strong thunderstorms developed in eastern Utah and western Colorado in the late morning. This was unusual in itself, as storms in this region tend to be less organized and occur later in the day.

The thunderstorms continued to organize and moved northeastward across the Rocky Mountains. This was even more unusual: Derecho-producing lines of storms are driven by a pool of cold air near the ground, which would typically be disrupted by a mountain range as tall as the Rockies. In this case, the line remained organized.

As the line of storms emerged to the east of the mountains, it caused widespread wind damage in the Denver metro area and northeastern Colorado. It then strengthened further as it proceeded north-northeastward across eastern Wyoming, western Nebraska and the Dakotas.

In total there were nearly 350 reports of severe winds, including 44 of 75 miles per hour (about 34 meters per second) or greater. The strongest reported gust was 110 mph at Winter Park ski area in the Colorado Rockies. Of these reports, 95 came from Colorado – by far the most severe wind reports ever from a single thunderstorm system.

Animation showing the development and evolution of the June 6-7, 2020, western derecho. Radar reflectivity is shown in the color shading, with National Weather Service warnings shown in the colored outlines (yellow polygons indicate severe thunderstorm warnings). Image via Iowa Environmental Mesonet.

Coloradans are accustomed to big weather, including strong winds in the mountains and foothills. Some of these winds are generated by flow down mountain slopes, localized thunderstorm microbursts, or even “bomb cyclones.” Western thunderstorms more commonly produce hailstorms and tornadoes, so it was very unusual to have a broad swath of the state experience damaging straight-line winds that extended from west of the Rockies all the way to the Dakotas.

Damage comparable to a hurricane

Derechos are challenging to predict. On days when derechos form, it is often uncertain whether any storms will form at all. But if they do, the chance exists for explosive development of intense winds. Forecasters did not anticipate the historic June 2012 derecho until it was already underway.

For the western derecho on June 6, 2020, outlooks showed an enhanced potential for severe storms in Nebraska and the Dakotas two to three days in advance. However, the outlooks didn’t highlight the potential for destructive winds farther south in Colorado until the morning that the derecho formed.

Once a line of storms has begun to develop, however, the National Weather Service routinely issues highly accurate severe thunderstorm warnings 30 to 60 minutes ahead of the arrival of intense winds, alerting the public to take precautions.

Communities, first responders and utilities may have only a few hours to prepare for an oncoming derecho, so it is important to know how to receive severe thunderstorm warnings, such as TV, radio and smartphone alerts, and to take these warnings seriously. Tornadoes and tornado warnings often get the most attention, but lines of severe thunderstorms can also pack a major punch.

Russ Schumacher, Associate Professor of Atmospheric Science and Colorado State Climatologist, Colorado State University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Bottom line: What is a derecho? An atmospheric scientist explains these rare but dangerous storm systems.

from EarthSky https://ift.tt/3fU0mU3

Will large parts of Earth be too hot for people in 50 years?

A moonlit night – and stars – above the Sahara Desert in northern Africa. Image via Sergey Pesterev/ Wikimedia Commons.

If greenhouse gas emissions continue unabated, land temperatures will rise so substantially that large areas of Earth will become inhabitable. That’s according to new research by an international team of scientists, published May 26, 2020 in the peer-reviewed journal Proceedings of the National Academy of Sciences.

For several thousands of years, human societies have prospered on lands with hospitable climates, within what scientists call our climate niche. According to the new research, the majority of people have lived within areas where the annual average temperature ranges from 52-59 degrees Fahrenheit (11-15 degrees Celsius), while fewer have inhabited lands with temperatures ranging from 68-77 degrees F (20-25 degrees C). For comparison, the Sahara Desert, one of the hottest regions around the world, has an annual average temperature of 30 degrees C (86 degrees F). Large areas of the Sahara are considered uninhabitable because of the hot and dry conditions, although a few nomadic tribes do live in the desert today.

According to the new research, 50 years from now, if greenhouse gas emissions continue unabated and as Earth’s land surface continues to warm, the area of uninhabitable land will expand drastically. Specifically, these scientists estimate that – without emission reductions – a 13.5 degrees F (7.5 degrees C) rise in land temperatures can be expected by 2070. The global temperature (land plus water) will only rise a bit a more than 5.4 degrees F (3 degrees C) by this time because water does not warm as much as land.

Correspondingly, according to this new research, the area of Earth’s land surface occupied by inhospitably hot temperatures greater than 29 degrees C on average can be expected to rise from a current level of 0.8% today to 19% in 2070.

Map showing the projected expansion in area of inhospitably hot lands caused by climate change. The small black areas represent the land with an average annual temperature of greater than 29 degrees Celsius (84 degrees Fahrenheit) at the present time. The large shaded areas represent the potential extent of such lands in 2070, according to the new research. This map was featured in the May 26, 2020, publication Future of the human climate niche. Image via Wageningen University.

By 2070, this large expansion in uninhabitable land could affect 30% of the projected human population. While some form of adaptation could occur in terms of new cooling technologies for homes, factors such as crop growth, livestock health, and water availability would all contribute to constraints on the livability of these super warm regions. Thus, the pressure for people to migrate would be very high, though the scientists caution that the complexity of migration makes such trends difficult to predict.

Lead author Chi Xu of Nanjing University commented on the findings in a statement:

We were frankly blown away by our own initial results. As our findings were so striking, we took an extra year to carefully check all assumptions and computations. We also decided to publish all data and computer codes for transparency and to facilitate follow-up work by others. The results are as important to China as they are to any other nation. Clearly we will need a global approach to safeguard our children against the potentially enormous social tensions the projected change could invoke.

As sobering as the new findings are, there is still a chance that we can avoid this bleak future by reducing greenhouse gas emissions. Tim Lenton, climate specialist at the University of Exeter and coauthor of the paper said:

The good news is that these impacts can be greatly reduced if humanity succeeds in curbing global warming. Our computations show that each degree warming above present levels corresponds to roughly one billion people falling outside of the climate niche. It is important that we can now express the benefits of curbing greenhouse gas emissions in something more human than just monetary terms.

Bottom line: New research by an international team of scientists indicates that inhospitably hot regions on Earth may expand from a current level of 0.8% to 19% by 2070 if greenhouse gas emissions continue unabated.

Source: Future of the human climate niche

Via Wageningen University

from EarthSky https://ift.tt/2NiYZCm

A moonlit night – and stars – above the Sahara Desert in northern Africa. Image via Sergey Pesterev/ Wikimedia Commons.

If greenhouse gas emissions continue unabated, land temperatures will rise so substantially that large areas of Earth will become inhabitable. That’s according to new research by an international team of scientists, published May 26, 2020 in the peer-reviewed journal Proceedings of the National Academy of Sciences.

For several thousands of years, human societies have prospered on lands with hospitable climates, within what scientists call our climate niche. According to the new research, the majority of people have lived within areas where the annual average temperature ranges from 52-59 degrees Fahrenheit (11-15 degrees Celsius), while fewer have inhabited lands with temperatures ranging from 68-77 degrees F (20-25 degrees C). For comparison, the Sahara Desert, one of the hottest regions around the world, has an annual average temperature of 30 degrees C (86 degrees F). Large areas of the Sahara are considered uninhabitable because of the hot and dry conditions, although a few nomadic tribes do live in the desert today.

According to the new research, 50 years from now, if greenhouse gas emissions continue unabated and as Earth’s land surface continues to warm, the area of uninhabitable land will expand drastically. Specifically, these scientists estimate that – without emission reductions – a 13.5 degrees F (7.5 degrees C) rise in land temperatures can be expected by 2070. The global temperature (land plus water) will only rise a bit a more than 5.4 degrees F (3 degrees C) by this time because water does not warm as much as land.

Correspondingly, according to this new research, the area of Earth’s land surface occupied by inhospitably hot temperatures greater than 29 degrees C on average can be expected to rise from a current level of 0.8% today to 19% in 2070.

Map showing the projected expansion in area of inhospitably hot lands caused by climate change. The small black areas represent the land with an average annual temperature of greater than 29 degrees Celsius (84 degrees Fahrenheit) at the present time. The large shaded areas represent the potential extent of such lands in 2070, according to the new research. This map was featured in the May 26, 2020, publication Future of the human climate niche. Image via Wageningen University.

By 2070, this large expansion in uninhabitable land could affect 30% of the projected human population. While some form of adaptation could occur in terms of new cooling technologies for homes, factors such as crop growth, livestock health, and water availability would all contribute to constraints on the livability of these super warm regions. Thus, the pressure for people to migrate would be very high, though the scientists caution that the complexity of migration makes such trends difficult to predict.

Lead author Chi Xu of Nanjing University commented on the findings in a statement:

We were frankly blown away by our own initial results. As our findings were so striking, we took an extra year to carefully check all assumptions and computations. We also decided to publish all data and computer codes for transparency and to facilitate follow-up work by others. The results are as important to China as they are to any other nation. Clearly we will need a global approach to safeguard our children against the potentially enormous social tensions the projected change could invoke.

As sobering as the new findings are, there is still a chance that we can avoid this bleak future by reducing greenhouse gas emissions. Tim Lenton, climate specialist at the University of Exeter and coauthor of the paper said:

The good news is that these impacts can be greatly reduced if humanity succeeds in curbing global warming. Our computations show that each degree warming above present levels corresponds to roughly one billion people falling outside of the climate niche. It is important that we can now express the benefits of curbing greenhouse gas emissions in something more human than just monetary terms.

Bottom line: New research by an international team of scientists indicates that inhospitably hot regions on Earth may expand from a current level of 0.8% to 19% by 2070 if greenhouse gas emissions continue unabated.

Source: Future of the human climate niche

Via Wageningen University

from EarthSky https://ift.tt/2NiYZCm