A mystery solved? Fast Radio Burst detected within Milky Way

Not the Fast Radio Burst. Radio waves aren’t visible to the eye. This is something else, from the Hubble Space Telescope. See a spectrum of the burst below. Image via NASA/ ESA/ Hubble/ ScienceAlert.

Fast Radio Bursts (FRBs) are short, intense bursts of radio waves lasting perhaps a thousandth of a second, coming from all over the sky and of unknown origin. In a shock discovery that could help to solve one of astronomy’s greatest mysteries – on April 28, 2020 – astronomers used an Astronomer’s Telegram to announce a Fast Radio Burst originating from inside our Milky Way galaxy. That’s a first. All other FRBs have been extragalactic, that is to say outside our galaxy. Even more importantly, the astronomers think they’ve also identified the source of the burst.

Explanations have ranged from neutron stars to supernovae to the inevitable aliens.

Dynamic spectrum – a range frequencies over time – from the April 28, 2020, Fast Radio Burst, via Astronomer’s Telegram.

FRBs were first detected in 2007. This new detection of an FRB is, in astronomical terms, very close to home. Astronomers found it using the CHIME (Canadian Hydrogen Intensity Mapping Experiment) radio telescope in Canada, an instrument designed specifically to study phenomena such as FRBs in order to answer major questions in astrophysics. This particular telescope has greatly increased the bursts’ detection rate since its first light in September 2017.

At the time of the April 28 signal, the telescope was not pointing straight at the source. But the signal was so strong the telescope captured it, so to speak, out of the corner of its eye. The signal was of sufficient strength to be detected from another galaxy (indicating it is the same phenomenon as those earlier extragalactic bursts detected from our galaxy), and it had the typical duration of a Fast Radio Burst.

The day before, on April 27, 2020, the Swift Burst Alert Telescope had detected a series of gamma-ray bursts originating from the same point in the sky as the FRB. Those gamma rays are associated with a known object, labeled SGR 1935+2154, a so-called Soft Gamma Repeater. This object is a type of stellar remnant known for periodically generating bursts of gamma rays. The distance to this object has been estimated at about 30,000 light-years. For comparison, the Milky Way galaxy is over 150,000 light-years across.

Excitingly, at the same time there was a burst of high-energy X-rays from the same point in the sky. The X-ray burst was observed by ground- and space-based X-ray telescopes. No FRB had ever been associated with gamma- or X-rays before, making this observation, if indeed it was of a FRB, something completely new.

Now you need to know that X-ray and gamma-ray bursts are not unusual in observations of magnetars.

Artist’s concept of an eruption on a magnetar. The Fast Radio Burst detected in our galaxy may be associated with these sorts of eruptions. Image via NASA Goddard Visualization Studio.

SGR 1935+2154 is believed to be a magnetar, a type of neutron star with a hypermagnetic field strong enough to pull the keys from your pocket from as far away as the moon!

While the reason for this ultra-strong magnetic field – a thousand times stronger than that of a normal neutron star – is unknown, astronomers theorize that FRBs might be produced when the crust of the neutron star suffers a starquake as a result of tension between the neutron star’s intense gravity and its magnetic field. This tension may be suddenly, and incomprehensibly violently, released in the starquake.

This may mean that the neutron star’s crust, thought to be a million times stronger than steel, slips by just a millimeter; however, this tiny shift may be sufficient to generate a brief burst of radio energy so powerful it can be detected from other galaxies, which we detect as an FRB.

Maybe! It seems possible, anyway, and, in astrophysics, what’s possible is the name of the game.

However, this detection does not mean that astronomers are ready to confirm that all FRBs originate from magnetars. The burst received by CHIME was at the low end of the signal strength historically associated with FRBs, which may or may not be of significance. As yet, astronomers have not analyzed the waveform of the signal to see if it matches that from FRBs. However, if this analysis and ongoing observations of magnetar SGR 1935+2154 do demonstrate conclusively that magnetars are the origin of Fast Radio Bursts, one of astronomy’s greatest mysteries will have been solved.

The CHIME radio telescope in Canada. It’s specifically designed to study objects such as Fast Radio Bursts. Image via CHIME.

Bottom line: Fast Radio Bursts are mysterious, short, intense bursts of radio waves coming from locations all over the sky. Before April 28, all the FRBs we knew were thought to come from outside our galaxy. The April 28 FRB, which apparently originated within our galaxy, will help astronomers unravel thorny questions in astrophysics.

from EarthSky https://ift.tt/3b2m5q0

Not the Fast Radio Burst. Radio waves aren’t visible to the eye. This is something else, from the Hubble Space Telescope. See a spectrum of the burst below. Image via NASA/ ESA/ Hubble/ ScienceAlert.

Fast Radio Bursts (FRBs) are short, intense bursts of radio waves lasting perhaps a thousandth of a second, coming from all over the sky and of unknown origin. In a shock discovery that could help to solve one of astronomy’s greatest mysteries – on April 28, 2020 – astronomers used an Astronomer’s Telegram to announce a Fast Radio Burst originating from inside our Milky Way galaxy. That’s a first. All other FRBs have been extragalactic, that is to say outside our galaxy. Even more importantly, the astronomers think they’ve also identified the source of the burst.

Explanations have ranged from neutron stars to supernovae to the inevitable aliens.

Dynamic spectrum – a range frequencies over time – from the April 28, 2020, Fast Radio Burst, via Astronomer’s Telegram.

FRBs were first detected in 2007. This new detection of an FRB is, in astronomical terms, very close to home. Astronomers found it using the CHIME (Canadian Hydrogen Intensity Mapping Experiment) radio telescope in Canada, an instrument designed specifically to study phenomena such as FRBs in order to answer major questions in astrophysics. This particular telescope has greatly increased the bursts’ detection rate since its first light in September 2017.

At the time of the April 28 signal, the telescope was not pointing straight at the source. But the signal was so strong the telescope captured it, so to speak, out of the corner of its eye. The signal was of sufficient strength to be detected from another galaxy (indicating it is the same phenomenon as those earlier extragalactic bursts detected from our galaxy), and it had the typical duration of a Fast Radio Burst.

The day before, on April 27, 2020, the Swift Burst Alert Telescope had detected a series of gamma-ray bursts originating from the same point in the sky as the FRB. Those gamma rays are associated with a known object, labeled SGR 1935+2154, a so-called Soft Gamma Repeater. This object is a type of stellar remnant known for periodically generating bursts of gamma rays. The distance to this object has been estimated at about 30,000 light-years. For comparison, the Milky Way galaxy is over 150,000 light-years across.

Excitingly, at the same time there was a burst of high-energy X-rays from the same point in the sky. The X-ray burst was observed by ground- and space-based X-ray telescopes. No FRB had ever been associated with gamma- or X-rays before, making this observation, if indeed it was of a FRB, something completely new.

Now you need to know that X-ray and gamma-ray bursts are not unusual in observations of magnetars.

Artist’s concept of an eruption on a magnetar. The Fast Radio Burst detected in our galaxy may be associated with these sorts of eruptions. Image via NASA Goddard Visualization Studio.

SGR 1935+2154 is believed to be a magnetar, a type of neutron star with a hypermagnetic field strong enough to pull the keys from your pocket from as far away as the moon!

While the reason for this ultra-strong magnetic field – a thousand times stronger than that of a normal neutron star – is unknown, astronomers theorize that FRBs might be produced when the crust of the neutron star suffers a starquake as a result of tension between the neutron star’s intense gravity and its magnetic field. This tension may be suddenly, and incomprehensibly violently, released in the starquake.

This may mean that the neutron star’s crust, thought to be a million times stronger than steel, slips by just a millimeter; however, this tiny shift may be sufficient to generate a brief burst of radio energy so powerful it can be detected from other galaxies, which we detect as an FRB.

Maybe! It seems possible, anyway, and, in astrophysics, what’s possible is the name of the game.

However, this detection does not mean that astronomers are ready to confirm that all FRBs originate from magnetars. The burst received by CHIME was at the low end of the signal strength historically associated with FRBs, which may or may not be of significance. As yet, astronomers have not analyzed the waveform of the signal to see if it matches that from FRBs. However, if this analysis and ongoing observations of magnetar SGR 1935+2154 do demonstrate conclusively that magnetars are the origin of Fast Radio Bursts, one of astronomy’s greatest mysteries will have been solved.

The CHIME radio telescope in Canada. It’s specifically designed to study objects such as Fast Radio Bursts. Image via CHIME.

Bottom line: Fast Radio Bursts are mysterious, short, intense bursts of radio waves coming from locations all over the sky. Before April 28, all the FRBs we knew were thought to come from outside our galaxy. The April 28 FRB, which apparently originated within our galaxy, will help astronomers unravel thorny questions in astrophysics.

from EarthSky https://ift.tt/3b2m5q0

Red rainbow over Bellingham, Washington

View at EarthSky Community Photos. | Lawrence Wong caught this photo on May 2, 2020 and wrote: “Just minutes before sunset and after raining, this double rainbow showed up on the eastern side of the sky. I gripped my camera and went outside and took several photos. This is one of them showing orange and red color inside the rainbow.”

Lawrence, you’ve caught a double red rainbow – a cousin to an ordinary multi-colored rainbow – that happens when the sun is low in the sky.

See how tall your rainbows are? The height of a rainbow corresponds (inversely) to the height of the sun in your sky. High sun, low rainbow. Low sun, high rainbow. So rainbow-watchers would know, without your having mentioned it, that the sun was low.

Now think about low suns for a moment. They typically appear reddish. That’s because – around sunset – you’re looking at the sun through a greater thickness of atmosphere than when the sun is high in the sky. At such times, the blue and green components of multi-colored sunrays are weakened by scattering during their long journey through the atmosphere to your eyes.

So red sunsets and red rainbows go hand-in-hand.

Thank you, Lawrence!

Read more and see more photos: What makes a red rainbow?

Bottom line: Photo of a red rainbow over Bellingham, Washington on May 5, 2020.

from EarthSky https://ift.tt/2z3RGum

View at EarthSky Community Photos. | Lawrence Wong caught this photo on May 2, 2020 and wrote: “Just minutes before sunset and after raining, this double rainbow showed up on the eastern side of the sky. I gripped my camera and went outside and took several photos. This is one of them showing orange and red color inside the rainbow.”

Lawrence, you’ve caught a double red rainbow – a cousin to an ordinary multi-colored rainbow – that happens when the sun is low in the sky.

See how tall your rainbows are? The height of a rainbow corresponds (inversely) to the height of the sun in your sky. High sun, low rainbow. Low sun, high rainbow. So rainbow-watchers would know, without your having mentioned it, that the sun was low.

Now think about low suns for a moment. They typically appear reddish. That’s because – around sunset – you’re looking at the sun through a greater thickness of atmosphere than when the sun is high in the sky. At such times, the blue and green components of multi-colored sunrays are weakened by scattering during their long journey through the atmosphere to your eyes.

So red sunsets and red rainbows go hand-in-hand.

Thank you, Lawrence!

Read more and see more photos: What makes a red rainbow?

Bottom line: Photo of a red rainbow over Bellingham, Washington on May 5, 2020.

from EarthSky https://ift.tt/2z3RGum

Coronavirus and cancer – May updates

• 29 April – NHS England announces second phase of NHS response to COVID-19
• 27 April – NHS campaign urges people to get help if they need it
• 21 April – Urgent cancer referrals fall across the UK
• 17 April – Cancer care needs mass COVID-19 testing, says charity.
• 21 March – Shielding measures introduced to protect people at high risk of COVID-19
• For coronavirus and cancer updates from March and April, please see our previous blog post.

With news about the coronavirus pandemic developing daily, we want to make sure everyone affected by cancer gets the information they need during this time.

We’ll be monitoring the latest government and NHS health updates from across the UK and updating this blog post regularly as new guidance emerges. But for the most up to date guidance, please visit government and NHS websites. You can find a full list of links on our coronavirus information page.

We’d also recommend speaking to your cancer team if you have any questions or worries about coronavirus.

1 May – Health and Social Care Committee launch inquiry into delivering NHS services in England

The inquiry will cover issues such as balancing coronavirus and ‘ordinary’ health and care demand as well as addressing the potential backlog of tests and treatments that have been delayed because of the coronavirus pandemic. The committee held an oral evidence session on 1 May, where cancer care was one of the areas of focus. We’ve submitted our initial response to the inquiry to ensure that cancer services are prioritised.

Nobody knows the full impact yet of COVID-19 on people affected by cancer. But with over 350,000 people hearing the words “you have cancer” annually, it’s clear that continuing cancer diagnosis and treatment must be a government priority. pic.twitter.com/QGdCYExVhQ

— Cancer Research UK (@CR_UK) May 1, 2020

For coronavirus and cancer updates from March and April, please visit our previous blog post.

Katie 

If you have questions about cancer, you can talk to our nurses Monday to Friday, 9-5pm, on freephone 0808 800 4040.

from Cancer Research UK – Science blog https://ift.tt/2VYt27t

• 29 April – NHS England announces second phase of NHS response to COVID-19
• 27 April – NHS campaign urges people to get help if they need it
• 21 April – Urgent cancer referrals fall across the UK
• 17 April – Cancer care needs mass COVID-19 testing, says charity.
• 21 March – Shielding measures introduced to protect people at high risk of COVID-19
• For coronavirus and cancer updates from March and April, please see our previous blog post.

With news about the coronavirus pandemic developing daily, we want to make sure everyone affected by cancer gets the information they need during this time.

We’ll be monitoring the latest government and NHS health updates from across the UK and updating this blog post regularly as new guidance emerges. But for the most up to date guidance, please visit government and NHS websites. You can find a full list of links on our coronavirus information page.

We’d also recommend speaking to your cancer team if you have any questions or worries about coronavirus.

1 May – Health and Social Care Committee launch inquiry into delivering NHS services in England

The inquiry will cover issues such as balancing coronavirus and ‘ordinary’ health and care demand as well as addressing the potential backlog of tests and treatments that have been delayed because of the coronavirus pandemic. The committee held an oral evidence session on 1 May, where cancer care was one of the areas of focus. We’ve submitted our initial response to the inquiry to ensure that cancer services are prioritised.

Nobody knows the full impact yet of COVID-19 on people affected by cancer. But with over 350,000 people hearing the words “you have cancer” annually, it’s clear that continuing cancer diagnosis and treatment must be a government priority. pic.twitter.com/QGdCYExVhQ

— Cancer Research UK (@CR_UK) May 1, 2020

For coronavirus and cancer updates from March and April, please visit our previous blog post.

Katie 

If you have questions about cancer, you can talk to our nurses Monday to Friday, 9-5pm, on freephone 0808 800 4040.

from Cancer Research UK – Science blog https://ift.tt/2VYt27t

Milky Way could be catapulting stars into its outer halo

This isn’t a real galaxy. Instead, it’s part of a super-powerful computer simulation of our own galaxy, the Milky Way. In this simulated image, the “arm” you see extending out from the center spans more than 200,000 light-years. That’s wider than the Milky Way itself! The structure shows the prominent plumes of young blue stars, born in gas that was blown outward by supernova explosions. Read more. Image via Sijie Yu/ UCI.

Though mighty, the Milky Way and galaxies of similar mass are not without scars chronicling turbulent histories.

So say scientists at the University of California, Irvine, who used the “hyper-realistic, cosmologically self-consistent” computer simulations generated via the FIRE-2 collaboration (FIRE stands for Feedback in Realistic Environments) to model our Milky Way galaxy’s rotation over time. In this way, they’ve learned that our galaxy may sometimes launch newly forming stars into the space around itself – that is, into the halo of our galaxy – via outflows triggered by supernova explosions.

UC Irvine physicist Sijie Yu is lead author of this new study, which was published in March 2020 in the peer-reviewed Monthly Notices of the Royal Astronomical Society. Yu said the findings were made possible partly by the availability of a powerful new set of computing tools. She said in a statement:

The FIRE-2 simulations allow us to generate movies that make it seem as though you’re observing a real galaxy.

They show us that as the galaxy center is rotating, a bubble driven by supernova[s] is developing, with stars forming at its edge. It looks as though the stars are being kicked out from the center.

Here’s an example of one of the movies from the FIRE-2 simulations:

Visualization of one of the outflow events discovered in one of the FIRE-2 simulations. Left is the mock starlight movie, consisting of mock Hubble Space Telescope-type images (blue shows sites of young star formation, red/brown shows where dust has obscured the starlight). The right one shows the gas distribution. These gas images are a mock 3-color composite showing the cold neutral gas.

James Bullock of UCI is a study co-author. He commented:

These highly accurate numerical simulations have shown us that it’s likely the Milky Way has been launching stars in circumgalactic space in outflows triggered by supernova explosions. It’s fascinating, because when multiple big stars die, the resulting energy can expel gas from the galaxy, which in turn cools, causing new stars to be born.

The statement explained:

Astronomers have long assumed that galaxies are assembled over lengthy periods of time as smaller star groupings come in and are dismembered by the larger body, a process that ejects some stars into distant orbits. But the UCI team is proposing ‘supernova feedback’ as a different source for as many as 40% of these outer-halo stars.

A typical spiral galaxy, like our Milky Way, has a faint, extended stellar halo. The new FIRE-2 study proposes that outflows from more central regions of the galaxy – triggered by supernova explosions – account for as many of 40% of the outer-halo stars. Image via COSMOS.

Bullock said he did not expect to see such an arrangement because stars are such “tight, incredibly dense balls” that, he said, are generally not subject to being moved relative to the background of space:

Instead, what we’re witnessing is gas being pushed around, and that gas subsequently cools and makes stars on its way out.

The researchers said that while their conclusions have been drawn from simulations of galaxies forming, growing and evolving to the present day, there is actually a fair amount of observational evidence that stars are forming in outflows from galactic centers to their halos. Yu said:

In plots that compare data from the European Space Agency’s Gaia mission – which provides a 3-D velocity chart of stars in the Milky Way – with other maps that show stellar density and metallicity, we can see structures similar to those produced by outflow stars in our simulations.

Bullock added that mature, heavier, metal-rich stars like our sun rotate around the center of the galaxy at a predictable speed and trajectory. But the low-metallicity stars, which have been subjected to fewer generations of fusion than our sun, can be seen rotating in the opposite direction.

He said that over the lifespan of a galaxy, the number of stars produced in supernova bubble outflows is small, around 2%. But things change when the galaxy is undergoing starburst events, that is, events where the galaxy begins undergoing furious rates of star formation. Yu added:

There are some current projects looking at galaxies that are considered to be very ‘starbursting’ right now. Some of the stars in these observations also look suspiciously like they’re getting ejected from the center.

This mock Hubble Space Telescope image shows how star formation happens at the edges of a supernova bubble. The portion highlighted in pink shows the stellar birth region. Blue shaded areas show young stars; red/brown shows where dust has obscured the starlight. The simulation shows clearly where stellar outflow shells are being generated. Image via Sijie Yu/ UCI.

Bottom line: Scientists used computer simulations from the FIRE-2 collaboration to learn that our Milky Way galaxy may sometimes launch newly forming stars into the space around itself – that is, into the halo of our galaxy – via outflows triggered by supernova explosions.

Source: Stars made in outflows may populate the stellar halo of the Milky Way

Via University of California, Irvine

from EarthSky https://ift.tt/2VXWJp9

This isn’t a real galaxy. Instead, it’s part of a super-powerful computer simulation of our own galaxy, the Milky Way. In this simulated image, the “arm” you see extending out from the center spans more than 200,000 light-years. That’s wider than the Milky Way itself! The structure shows the prominent plumes of young blue stars, born in gas that was blown outward by supernova explosions. Read more. Image via Sijie Yu/ UCI.

Though mighty, the Milky Way and galaxies of similar mass are not without scars chronicling turbulent histories.

So say scientists at the University of California, Irvine, who used the “hyper-realistic, cosmologically self-consistent” computer simulations generated via the FIRE-2 collaboration (FIRE stands for Feedback in Realistic Environments) to model our Milky Way galaxy’s rotation over time. In this way, they’ve learned that our galaxy may sometimes launch newly forming stars into the space around itself – that is, into the halo of our galaxy – via outflows triggered by supernova explosions.

UC Irvine physicist Sijie Yu is lead author of this new study, which was published in March 2020 in the peer-reviewed Monthly Notices of the Royal Astronomical Society. Yu said the findings were made possible partly by the availability of a powerful new set of computing tools. She said in a statement:

The FIRE-2 simulations allow us to generate movies that make it seem as though you’re observing a real galaxy.

They show us that as the galaxy center is rotating, a bubble driven by supernova[s] is developing, with stars forming at its edge. It looks as though the stars are being kicked out from the center.

Here’s an example of one of the movies from the FIRE-2 simulations:

Visualization of one of the outflow events discovered in one of the FIRE-2 simulations. Left is the mock starlight movie, consisting of mock Hubble Space Telescope-type images (blue shows sites of young star formation, red/brown shows where dust has obscured the starlight). The right one shows the gas distribution. These gas images are a mock 3-color composite showing the cold neutral gas.

James Bullock of UCI is a study co-author. He commented:

These highly accurate numerical simulations have shown us that it’s likely the Milky Way has been launching stars in circumgalactic space in outflows triggered by supernova explosions. It’s fascinating, because when multiple big stars die, the resulting energy can expel gas from the galaxy, which in turn cools, causing new stars to be born.

The statement explained:

Astronomers have long assumed that galaxies are assembled over lengthy periods of time as smaller star groupings come in and are dismembered by the larger body, a process that ejects some stars into distant orbits. But the UCI team is proposing ‘supernova feedback’ as a different source for as many as 40% of these outer-halo stars.

A typical spiral galaxy, like our Milky Way, has a faint, extended stellar halo. The new FIRE-2 study proposes that outflows from more central regions of the galaxy – triggered by supernova explosions – account for as many of 40% of the outer-halo stars. Image via COSMOS.

Bullock said he did not expect to see such an arrangement because stars are such “tight, incredibly dense balls” that, he said, are generally not subject to being moved relative to the background of space:

Instead, what we’re witnessing is gas being pushed around, and that gas subsequently cools and makes stars on its way out.

The researchers said that while their conclusions have been drawn from simulations of galaxies forming, growing and evolving to the present day, there is actually a fair amount of observational evidence that stars are forming in outflows from galactic centers to their halos. Yu said:

In plots that compare data from the European Space Agency’s Gaia mission – which provides a 3-D velocity chart of stars in the Milky Way – with other maps that show stellar density and metallicity, we can see structures similar to those produced by outflow stars in our simulations.

Bullock added that mature, heavier, metal-rich stars like our sun rotate around the center of the galaxy at a predictable speed and trajectory. But the low-metallicity stars, which have been subjected to fewer generations of fusion than our sun, can be seen rotating in the opposite direction.

He said that over the lifespan of a galaxy, the number of stars produced in supernova bubble outflows is small, around 2%. But things change when the galaxy is undergoing starburst events, that is, events where the galaxy begins undergoing furious rates of star formation. Yu added:

There are some current projects looking at galaxies that are considered to be very ‘starbursting’ right now. Some of the stars in these observations also look suspiciously like they’re getting ejected from the center.

This mock Hubble Space Telescope image shows how star formation happens at the edges of a supernova bubble. The portion highlighted in pink shows the stellar birth region. Blue shaded areas show young stars; red/brown shows where dust has obscured the starlight. The simulation shows clearly where stellar outflow shells are being generated. Image via Sijie Yu/ UCI.

Bottom line: Scientists used computer simulations from the FIRE-2 collaboration to learn that our Milky Way galaxy may sometimes launch newly forming stars into the space around itself – that is, into the halo of our galaxy – via outflows triggered by supernova explosions.

Source: Stars made in outflows may populate the stellar halo of the Milky Way

Via University of California, Irvine

from EarthSky https://ift.tt/2VXWJp9

These new maps show 16 years of ice sheet loss

A new study, published April 30, 2020 in Science, used an advanced Earth-observing laser instrument aboard a satellite to make precise, detailed measurements of how the elevation of the Greenland and Antarctic ice sheets have changed between 2003 and 2019.

The study results show that small gains of ice in East Antarctica are dwarfed by massive losses in West Antarctica. According to the scientists, the net loss of ice from Antarctica, along with Greenland’s shrinking ice sheet, has been responsible for 0.55 inches (14 millimeters) of sea level rise between 2003 and 2019 – slightly less than a third of the total amount of sea level rise observed in the world’s oceans.

The findings compared the recent data from NASA’s Ice, Cloud and land Elevation Satellite 2 (ICESat-2), launched in 2018, with measurements taken by the original ICESat from 2003 to 2009.

Using data from the ICESat and ICESat-2 laser altimeters, scientists precisely measured how much ice has been lost from ice sheets in Antarctica and Greenland between 2003 and 2019. The Antarctic Peninsula, seen here, was one of the fastest changing regions of the continent. Image via NASA/ K. Ramsayer

The study found that Greenland’s ice sheet lost an average of 200 gigatons of ice per year, and Antarctica’s ice sheet lost an average of 118 gigatons of ice per year.

How much ice is that? One gigaton of ice is enough to fill 400,000 Olympic-sized swimming pools or cover New York’s Central Park in ice more than 1,000 feet (300 meters) thick, reaching higher than the Chrysler Building.

The new data comes from what NASA describes as its most advanced Earth-observing laser instrument ever flown in space:

ICESat-2’s instrument is a laser altimeter, which sends 10,000 pulses of light a second down to Earth’s surface, and times how long it takes to return to the satellite – to within a billionth of a second. The instrument’s pulse rate allows for a dense map of measurement over the ice sheet; its high precision allows scientists to determine how much an ice sheet changes over a year to within an inch.

The researchers took tracks of earlier ICESat measurements and overlaid the tracks of ICESat-2 measurements from 2019, and took data from the tens of millions of sites where the two data sets intersected. That gave them the elevation change, but to get to how much ice has been lost, the researchers developed a new model to convert volume change to mass change. The model calculated densities across the ice sheets to allow the total mass loss to be calculated.

Greenland. Image via NASA

Ben Smith is a glaciologist at the University of Washington and lead author of the new paper. Smith said in a statement:

If you watch a glacier or ice sheet for a month, or a year, you’re not going to learn much about what the climate is doing to it. We now have a 16-year span between ICESat and ICESat-2 and can be much more confident that the changes we’re seeing in the ice have to do with the long-term changes in the climate.

Bottom line: New maps made using satellite data show 16 years of ice sheet loss on Antarctic and Greenland.

Source: Pervasive ice sheet mass loss reflects competing ocean and atmosphere processes

Via NASA

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

A new study, published April 30, 2020 in Science, used an advanced Earth-observing laser instrument aboard a satellite to make precise, detailed measurements of how the elevation of the Greenland and Antarctic ice sheets have changed between 2003 and 2019.

The study results show that small gains of ice in East Antarctica are dwarfed by massive losses in West Antarctica. According to the scientists, the net loss of ice from Antarctica, along with Greenland’s shrinking ice sheet, has been responsible for 0.55 inches (14 millimeters) of sea level rise between 2003 and 2019 – slightly less than a third of the total amount of sea level rise observed in the world’s oceans.

The findings compared the recent data from NASA’s Ice, Cloud and land Elevation Satellite 2 (ICESat-2), launched in 2018, with measurements taken by the original ICESat from 2003 to 2009.

Using data from the ICESat and ICESat-2 laser altimeters, scientists precisely measured how much ice has been lost from ice sheets in Antarctica and Greenland between 2003 and 2019. The Antarctic Peninsula, seen here, was one of the fastest changing regions of the continent. Image via NASA/ K. Ramsayer

The study found that Greenland’s ice sheet lost an average of 200 gigatons of ice per year, and Antarctica’s ice sheet lost an average of 118 gigatons of ice per year.

How much ice is that? One gigaton of ice is enough to fill 400,000 Olympic-sized swimming pools or cover New York’s Central Park in ice more than 1,000 feet (300 meters) thick, reaching higher than the Chrysler Building.

The new data comes from what NASA describes as its most advanced Earth-observing laser instrument ever flown in space:

ICESat-2’s instrument is a laser altimeter, which sends 10,000 pulses of light a second down to Earth’s surface, and times how long it takes to return to the satellite – to within a billionth of a second. The instrument’s pulse rate allows for a dense map of measurement over the ice sheet; its high precision allows scientists to determine how much an ice sheet changes over a year to within an inch.

The researchers took tracks of earlier ICESat measurements and overlaid the tracks of ICESat-2 measurements from 2019, and took data from the tens of millions of sites where the two data sets intersected. That gave them the elevation change, but to get to how much ice has been lost, the researchers developed a new model to convert volume change to mass change. The model calculated densities across the ice sheets to allow the total mass loss to be calculated.

Greenland. Image via NASA

Ben Smith is a glaciologist at the University of Washington and lead author of the new paper. Smith said in a statement:

If you watch a glacier or ice sheet for a month, or a year, you’re not going to learn much about what the climate is doing to it. We now have a 16-year span between ICESat and ICESat-2 and can be much more confident that the changes we’re seeing in the ice have to do with the long-term changes in the climate.

Bottom line: New maps made using satellite data show 16 years of ice sheet loss on Antarctic and Greenland.

Source: Pervasive ice sheet mass loss reflects competing ocean and atmosphere processes

Via NASA

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

Why more Eta Aquariid meteors in Southern Hemisphere?

Eta Aquarid meteor shower in 2015 from Chile’s Atacama Desert. Composite image by Yuri Beletsky.

The famous Eta Aquariid meteor shower – one of the year’s major meteor showers – peaks every year in early May. In 2020, the peak centers around May 5. This shower is known to be richer as seen from Earth’s Southern Hemisphere than from the Northern Hemisphere. Why?

If you traced the paths of Eta Aquarid meteors backward on the sky’s dome, you’d find that these meteors appear to stream from an asterism, or recognizable pattern of stars, known as the Water Jar in the constellation Aquarius.

This spot in the sky is the radiant point of the Eta Aquarid meteor shower. The meteors seem to emanate from the vicinity of the Water Jar, before spreading out and appearing in all parts of the sky.

The radiant point of the Eta Aquarid meteor shower is near the famous Water Jar asterism of the constellation Aquarius.

Because the Water Jar is on the celestial equator – an imaginary great circle directly above the Earth’s equator – the radiant of the Eta Aquarid shower rises due east as seen from all over the world. Moreover, the radiant rises at about the same time worldwide, around 1:40 a.m. local time (2:40 a.m. Daylight Saving Time) in early May, around the shower’s typical peak date.

So you’d think the shower would be about the same as seen from around the globe.

But it’s not. The reason it’s not is that sunrise comes later to the Southern Hemisphere (where it’s autumn in May) and earlier to the Northern Hemisphere (where it’s spring in May).

Later sunrise means more dark time to watch meteors. And it also means the radiant point of the Eta Aquarid shower has a chance to climb higher into the predawn sky as seen from more southerly latitudes. That’s why the tropics and southern temperate latitudes tend to see more Eta Aquarid meteors than we do at mid-northern latitudes.

Cruise to a southerly latitude, anyone?

Everything you need to know: Eta Aquarid meteor shower

Eta Aquarids in 2013 by Colin Legg in Australia.

Bottom line: Everyone around the globe can enjoy the Eta Aquariid meteor shower in early May. Best for the Southern Hemisphere! Peak in 2020 is on or near the morning of May 5.

Read more: EarthSky’s annual meteor shower guide

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

Eta Aquarid meteor shower in 2015 from Chile’s Atacama Desert. Composite image by Yuri Beletsky.

The famous Eta Aquariid meteor shower – one of the year’s major meteor showers – peaks every year in early May. In 2020, the peak centers around May 5. This shower is known to be richer as seen from Earth’s Southern Hemisphere than from the Northern Hemisphere. Why?

If you traced the paths of Eta Aquarid meteors backward on the sky’s dome, you’d find that these meteors appear to stream from an asterism, or recognizable pattern of stars, known as the Water Jar in the constellation Aquarius.

This spot in the sky is the radiant point of the Eta Aquarid meteor shower. The meteors seem to emanate from the vicinity of the Water Jar, before spreading out and appearing in all parts of the sky.

The radiant point of the Eta Aquarid meteor shower is near the famous Water Jar asterism of the constellation Aquarius.

Because the Water Jar is on the celestial equator – an imaginary great circle directly above the Earth’s equator – the radiant of the Eta Aquarid shower rises due east as seen from all over the world. Moreover, the radiant rises at about the same time worldwide, around 1:40 a.m. local time (2:40 a.m. Daylight Saving Time) in early May, around the shower’s typical peak date.

So you’d think the shower would be about the same as seen from around the globe.

But it’s not. The reason it’s not is that sunrise comes later to the Southern Hemisphere (where it’s autumn in May) and earlier to the Northern Hemisphere (where it’s spring in May).

Later sunrise means more dark time to watch meteors. And it also means the radiant point of the Eta Aquarid shower has a chance to climb higher into the predawn sky as seen from more southerly latitudes. That’s why the tropics and southern temperate latitudes tend to see more Eta Aquarid meteors than we do at mid-northern latitudes.

Cruise to a southerly latitude, anyone?

Everything you need to know: Eta Aquarid meteor shower

Eta Aquarids in 2013 by Colin Legg in Australia.

Bottom line: Everyone around the globe can enjoy the Eta Aquariid meteor shower in early May. Best for the Southern Hemisphere! Peak in 2020 is on or near the morning of May 5.

Read more: EarthSky’s annual meteor shower guide

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

This month’s full moon comes on May 6-7

A full moon is opposite the sun. We see all of its dayside. Illustration via Bob King.

The moon appears full to the eye for two to three nights. However, astronomers regard the moon as full at a precisely defined instant, when the moon is exactly 180 degrees opposite the sun in ecliptic longitude. This week, the moon will look full on Wednesday evening, but the instant of full moon happens Thursday morning at 10:45 UTC (5:45 a.m. CDT). Translate UTC to your time.

It’s that feature of a full moon – the fact that it’s opposite the sun as viewed from Earth – that causes a full moon to look full.

A kiss under the full moon of November 3, 2017, via our friend Steven Sweet of Lunar 101-Moon Book. He was at Port Credit, a neighborhood in the city of Mississauga, Ontario, Canada … at the mouth of the Credit River on the north shore of Lake Ontario.

Why does a full moon look full? Remember that half the moon is always illuminated by the sun. That lighted half is the moon’s day side. In order to appear full to us on Earth, we have to see the entire day side of the moon. That happens only when the moon is opposite the sun in our sky. So a full moon looks full because it’s opposite the sun.

That’s also why every full moon rises in the east around sunset – climbs highest up for the night midway between sunset and sunrise (around midnight) – and sets around sunrise. Stand outside tonight around sunset and look for the moon. Sun going down while the moon is coming up? That’s a full moon, or close to one.

Just be aware that the moon will look full for at least a couple of night around the instant of full moon.

Read more: What are the full moon names?

Often, you’ll find two different dates on calendars for the date of full moon. That’s because some calendars list moon phases in Coordinated Universal Time, also called Universal Time Coordinated (UTC). And other calendars list moon phases in local time, a clock time of a specific place, usually the place that made and distributed the calendars. Translate UTC to your local time.

Want to know the instant of full moon in your part of the world, as well as the moonrise and moonset times? Visit Sunrise Sunset Calendars, remembering to check the moon phases plus moonrise and moonset boxes.

If a full moon is opposite the sun, why doesn’t Earth’s shadow fall on the moon at every full moon? The reason is that the moon’s orbit is tilted by 5.1 degrees with respect to Earth’s orbit around the sun. At every full moon, Earth’s shadow sweeps near the moon. But, in most months, there’s no eclipse.

A full moon normally passes above or below Earth’s shadow, with no eclipse. Illustration by Bob King.

As the moon orbits Earth, it changes phase in an orderly way. Follow these links to understand the various phases of the moon.

New moon
Waxing crescent moon
First quarter moon
Waxing gibbous moon
Full moon
Waning gibbous moon
Last quarter moon
Waning crescent moon

Bottom line: A full moon looks full because it’s opposite the sun. Its lighted face is turned entirely in Earth’s direction. The next full moon is Thursday, May 7, at 10:45 UTC.

Read more: 4 keys to understanding moon phases

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

A full moon is opposite the sun. We see all of its dayside. Illustration via Bob King.

The moon appears full to the eye for two to three nights. However, astronomers regard the moon as full at a precisely defined instant, when the moon is exactly 180 degrees opposite the sun in ecliptic longitude. This week, the moon will look full on Wednesday evening, but the instant of full moon happens Thursday morning at 10:45 UTC (5:45 a.m. CDT). Translate UTC to your time.

It’s that feature of a full moon – the fact that it’s opposite the sun as viewed from Earth – that causes a full moon to look full.

A kiss under the full moon of November 3, 2017, via our friend Steven Sweet of Lunar 101-Moon Book. He was at Port Credit, a neighborhood in the city of Mississauga, Ontario, Canada … at the mouth of the Credit River on the north shore of Lake Ontario.

Why does a full moon look full? Remember that half the moon is always illuminated by the sun. That lighted half is the moon’s day side. In order to appear full to us on Earth, we have to see the entire day side of the moon. That happens only when the moon is opposite the sun in our sky. So a full moon looks full because it’s opposite the sun.

That’s also why every full moon rises in the east around sunset – climbs highest up for the night midway between sunset and sunrise (around midnight) – and sets around sunrise. Stand outside tonight around sunset and look for the moon. Sun going down while the moon is coming up? That’s a full moon, or close to one.

Just be aware that the moon will look full for at least a couple of night around the instant of full moon.

Read more: What are the full moon names?

Often, you’ll find two different dates on calendars for the date of full moon. That’s because some calendars list moon phases in Coordinated Universal Time, also called Universal Time Coordinated (UTC). And other calendars list moon phases in local time, a clock time of a specific place, usually the place that made and distributed the calendars. Translate UTC to your local time.

Want to know the instant of full moon in your part of the world, as well as the moonrise and moonset times? Visit Sunrise Sunset Calendars, remembering to check the moon phases plus moonrise and moonset boxes.

If a full moon is opposite the sun, why doesn’t Earth’s shadow fall on the moon at every full moon? The reason is that the moon’s orbit is tilted by 5.1 degrees with respect to Earth’s orbit around the sun. At every full moon, Earth’s shadow sweeps near the moon. But, in most months, there’s no eclipse.

A full moon normally passes above or below Earth’s shadow, with no eclipse. Illustration by Bob King.

As the moon orbits Earth, it changes phase in an orderly way. Follow these links to understand the various phases of the moon.

New moon
Waxing crescent moon
First quarter moon
Waxing gibbous moon
Full moon
Waning gibbous moon
Last quarter moon
Waning crescent moon

Bottom line: A full moon looks full because it’s opposite the sun. Its lighted face is turned entirely in Earth’s direction. The next full moon is Thursday, May 7, at 10:45 UTC.

Read more: 4 keys to understanding moon phases

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