Ancient cold front in Perseus

Image via ESA.

The European Space Agency (ESA) said on October 29, 2018 that a trio of X-ray telescopes – Chandra, XMM-Newton and ROSAT – observed this gigantic structure in the Perseus galaxy cluster. It described the feature as a cold front, but the word cold is relative here; in fact, the X-ray satellites are sensitive to extremely hot gases. In this case, they’re being used to study interstellar gas heated to millions of degrees around the extreme environment of colliding galaxies. ESA said:

The ancient cold front can be seen at the left of the image, drifting away from the inner, younger front closer to the center. Galactic cold fronts are nothing like the cold fronts we experience on Earth – instead they are caused by galaxy clusters colliding into one another. The gravitational pull of a larger cluster tugs a smaller cluster closer, resulting in gas in the core of the cluster being sloshed around like liquid in a glass. This creates a cold front in a spiral pattern moving outwards from the core and these sloshing cold fronts can provide a probe of the intercluster medium.

Cold fronts are the oldest coherent structures in cool core clusters and this one has been moving away from the center of the cluster for over five billion years – longer than our solar system has been in existence. The long curving structure spans around 2 million light years and is travelling at around 30 miles (50 km) per second.

The image combines data from NASA’s Chandra X-Ray observatory, ESA’s XMM-Newton and the German Aerospace Centre-led ROSAT satellite. Chandra also took a separate close-up of the upper left of the cold front, revealing some unexpected details.

The Perseus galaxy cluster contains thousands of galaxies and a supermassive black hole at the centre. The black hole is responsible for creating a harsh environment of sound waves and turbulence that should erode a cold front over time, smoothing out the previously sharp edges and creating gradual changes in density and temperature. Instead, the high-resolution Chandra image showed a surprisingly sharp edge on the cold front, and a temperature map revealed that the upper left of the cold front is split in two.

The sharpness of the cold front suggests it has been preserved by strong magnetic fields wrapped around it, essentially acting as a shield against the harsh environment. This magnetic ‘draping’ prevents the cold front from diffusing and is what has allowed it to survive so well for over five billion years as it drifts away from the center of the cluster.

Read the discovery announcement about this cold front, from 2017, here: Scientists Find Giant Wave Rolling Through the Perseus Galaxy Cluster.

The 2019 lunar calendars are here! Order yours before they’re gone. Makes a great gift.

Bottom line: A gigantic cold front in the Perseus galaxy cluster, in an image that combines data from NASA’s Chandra X-Ray observatory, ESA’s XMM-Newton and the German Aerospace Centre-led ROSAT satellite.

Via ESA

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

Image via ESA.

The European Space Agency (ESA) said on October 29, 2018 that a trio of X-ray telescopes – Chandra, XMM-Newton and ROSAT – observed this gigantic structure in the Perseus galaxy cluster. It described the feature as a cold front, but the word cold is relative here; in fact, the X-ray satellites are sensitive to extremely hot gases. In this case, they’re being used to study interstellar gas heated to millions of degrees around the extreme environment of colliding galaxies. ESA said:

The ancient cold front can be seen at the left of the image, drifting away from the inner, younger front closer to the center. Galactic cold fronts are nothing like the cold fronts we experience on Earth – instead they are caused by galaxy clusters colliding into one another. The gravitational pull of a larger cluster tugs a smaller cluster closer, resulting in gas in the core of the cluster being sloshed around like liquid in a glass. This creates a cold front in a spiral pattern moving outwards from the core and these sloshing cold fronts can provide a probe of the intercluster medium.

Cold fronts are the oldest coherent structures in cool core clusters and this one has been moving away from the center of the cluster for over five billion years – longer than our solar system has been in existence. The long curving structure spans around 2 million light years and is travelling at around 30 miles (50 km) per second.

The image combines data from NASA’s Chandra X-Ray observatory, ESA’s XMM-Newton and the German Aerospace Centre-led ROSAT satellite. Chandra also took a separate close-up of the upper left of the cold front, revealing some unexpected details.

The Perseus galaxy cluster contains thousands of galaxies and a supermassive black hole at the centre. The black hole is responsible for creating a harsh environment of sound waves and turbulence that should erode a cold front over time, smoothing out the previously sharp edges and creating gradual changes in density and temperature. Instead, the high-resolution Chandra image showed a surprisingly sharp edge on the cold front, and a temperature map revealed that the upper left of the cold front is split in two.

The sharpness of the cold front suggests it has been preserved by strong magnetic fields wrapped around it, essentially acting as a shield against the harsh environment. This magnetic ‘draping’ prevents the cold front from diffusing and is what has allowed it to survive so well for over five billion years as it drifts away from the center of the cluster.

Read the discovery announcement about this cold front, from 2017, here: Scientists Find Giant Wave Rolling Through the Perseus Galaxy Cluster.

The 2019 lunar calendars are here! Order yours before they’re gone. Makes a great gift.

Bottom line: A gigantic cold front in the Perseus galaxy cluster, in an image that combines data from NASA’s Chandra X-Ray observatory, ESA’s XMM-Newton and the German Aerospace Centre-led ROSAT satellite.

Via ESA

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

Halloween ghost of the summer sun

Every Halloween – and a few days before and after – the brilliant star Arcturus, brightest star in Bootes the Herdsman, sets at the same time and on the same spot on the west-northwest horizon as the summer sun. This star rises at the same time and at the same place on the east-northeast horizon as the summer sun. That’s why – every year at this time – you can consider Arcturus as a ghost of the summer sun.

At mid-northern latitudes, Arcturus now sets about 2 hours after sunset and rises about 2 hours before sunrise.

If you live as far north as Barrow, Alaska, the star Arcturus shines all night long now, mimicking the midnight sun of summer.

If you live in the Southern Hemisphere, you can’t see Arcturus right now. South of the equator, Arcturus sets at the same time and on the same place on the horizon as the winter sun. In other words, Arcturus sets before the sun and rises after the sun at southerly latitudes at this time of year.

If you are in the Northern Hemisphere, try watching this star in the October evening chill. You can envision the absent summer sun radiating its extra hours of sunlight. Not till after dark does this star set, an echo of long summer afternoons. Similarly, Arcturus rises in the east before dawn, a phantom reminder of early morning daybreaks.

At northerly latitudes, Arcturus sets in the west after sunset and rises in the east before sunrise. You can verify that you’re looking at Arcturus once the Big Dipper comes out. Its handle always points to Arcturus.

Halloween – also known as All Hallows’ Eve or All Saints’ Eve – is observed in various countries on October 31, especially in the United States. It’s a big deal for America children, who roam from house to house trick or treating, hoping for candy and other treats.

This modern holiday is based on a much older tradition, that of cross-quarter days.

Cover of ‘Star Arcturus, ghost of summer sun’ coloring book

Bottom line: At mid-northern latitudes, Arcturus sets about 2 hours after sunset around Halloween, at the same point on the horizon as the summer sun. It’s a Halloween ghost of the summer sun and an echo of long summer afternoons.

Donate: Your support means the world to us

Halloween derived from ancient Celtic cross-quarter day

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from EarthSky https://ift.tt/2O94dP3

Every Halloween – and a few days before and after – the brilliant star Arcturus, brightest star in Bootes the Herdsman, sets at the same time and on the same spot on the west-northwest horizon as the summer sun. This star rises at the same time and at the same place on the east-northeast horizon as the summer sun. That’s why – every year at this time – you can consider Arcturus as a ghost of the summer sun.

At mid-northern latitudes, Arcturus now sets about 2 hours after sunset and rises about 2 hours before sunrise.

If you live as far north as Barrow, Alaska, the star Arcturus shines all night long now, mimicking the midnight sun of summer.

If you live in the Southern Hemisphere, you can’t see Arcturus right now. South of the equator, Arcturus sets at the same time and on the same place on the horizon as the winter sun. In other words, Arcturus sets before the sun and rises after the sun at southerly latitudes at this time of year.

If you are in the Northern Hemisphere, try watching this star in the October evening chill. You can envision the absent summer sun radiating its extra hours of sunlight. Not till after dark does this star set, an echo of long summer afternoons. Similarly, Arcturus rises in the east before dawn, a phantom reminder of early morning daybreaks.

At northerly latitudes, Arcturus sets in the west after sunset and rises in the east before sunrise. You can verify that you’re looking at Arcturus once the Big Dipper comes out. Its handle always points to Arcturus.

Halloween – also known as All Hallows’ Eve or All Saints’ Eve – is observed in various countries on October 31, especially in the United States. It’s a big deal for America children, who roam from house to house trick or treating, hoping for candy and other treats.

This modern holiday is based on a much older tradition, that of cross-quarter days.

Cover of ‘Star Arcturus, ghost of summer sun’ coloring book

Bottom line: At mid-northern latitudes, Arcturus sets about 2 hours after sunset around Halloween, at the same point on the horizon as the summer sun. It’s a Halloween ghost of the summer sun and an echo of long summer afternoons.

Donate: Your support means the world to us

Halloween derived from ancient Celtic cross-quarter day

Enjoying EarthSky so far? Sign up for our free daily newsletter today!

from EarthSky https://ift.tt/2O94dP3

Canada passed a carbon tax that will give most Canadians more money

Note: this will be our final entry on Climate Consensus - the 97%. The Guardian has decided to discontinue its Science and Environment blogging networks. We would like to thank this great paper for hosting us over the past five years, and to our readers for making it a worthwhile and rewarding endeavor.

Last week, Prime Minister Justin Trudeau announced that under the Greenhouse Gas Pollution Pricing Act, Canada will implement a revenue-neutral carbon tax starting in 2019, fulfilling a campaign pledge he made in 2015.

The federal carbon pollution price will start low at $20 per ton in 2019, rising at $10 per ton per year until reaching $50 per ton in 2022. The carbon tax will stay at that level unless the legislation is revisited and revised.

This is a somewhat modest carbon tax – after all, the social cost of carbon is many times higher – but it’s a higher carbon price than has been implemented in most countries. Moreover, a carbon tax doesn’t necessarily have to reflect the social cost of carbon. The question is whether it will be sufficiently high to meet the country’s climate targets.

Paris was a key motivator behind the Canadian carbon tax

The Preamble in the Act is worth reading. It begins by noting “there is broad scientific consensus that anthropogenic greenhouse gas emissions contribute to global climate change” (this is somewhat understated – carbon pollution is the dominant factor). It also notes that Canada is already feeling the impacts of climate change through factors like “coastal erosion, thawing permafrost, increases in heat waves, droughts and flooding, and related risks to critical infrastructures and food security.”

The Preamble also notes that in 1992, Canada signed the UNFCCC whose objectives include “the stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system,” and that Canada ratified the Paris Agreement, whose aims include limiting global warming to less than 2°C above pre-industrial temperatures.

Canada’s Paris commitment requires cutting its carbon pollution by 30% below 2005 levels by 2030. Prior to the implementation of the carbon tax, its policies were rated Highly Insufficient to meet that goal. Instead Canada’s emissions were on track to fall only about 4% below 2005 levels by 2030. So, the carbon tax is an important policy to close that gap.

Some provinces already have carbon pricing in place

Several Canadian provinces have already implemented or plan to implement carbon pricing systems. British Columbia, Alberta, and Quebec already have such systems in place; the Canadian government noted that these provinces were “among the top performers in GDP growth across Canada in 2017.”

Provinces whose carbon prices meet the federal standards are already in compliance, so the new law won’t apply to them. Several other provinces (Northwest Territories, Nova Scotia, Prince Edward Island, Newfoundland and Labrador) have planned or proposed carbon pricing systems that will meet the federal requirements. The federal carbon tax will be applied to the remaining provinces.

 Green indicates that the province’s own carbon pricing system meets the federal standards. Purple and orange indicate a province’s planned or proposed carbon pricing will meet the federal standards, respectively. Red indicates that the federal carbon pricing will apply to the province. Illustration: Dana Nuccitelli

Energy prices will rise

A $20/ton carbon tax translates into a 16.6 cent per gallon surcharge on gasoline. So, in 2022, the $50/ton carbon tax will increase Canadian gasoline prices by about 42 cents per gallon (11 cents per liter). For comparison, the average price of gasoline in Canada is $1.43 per liter, so that would be about an 8% gasoline price increase in 2022.

The price of coal would more than double, with a carbon tax surcharge of about $100 per ton in 2022. Natural gas prices will rise by about 10 cents per cubic meter in 2022 compared to current prices of around 13 cents per cubic meter – about a 75% increase. This will increase demand for cheaper carbon-free electricity. However, Canada already supplies about 60% of its electricity through hydroelectric generation and 16% from nuclear – only about 20–25% comes from fossil fuels.

For that reason, only 11% of Canada’s carbon pollution comes from generating electricity. The industrial sector is responsible for the biggest chunk of Canadian carbon pollution (40%). It will not be subjected to the carbon tax, but rather to an Output-Based Allocations system (similar to cap and trade).

But rebates will more than offset higher fuel costs

One key component of the federal carbon tax is that it’s revenue-neutral, similar to the policy proposal from Citizens’ Climate Lobby. All the taxed money will be distributed back to the provinces from which they were generated. The provinces will in turn rebate about 90% the revenues back to individual taxpayers. The rebates are anticipated to exceed the increased energy costs for about 70% of Canadian households.

For example, a Manitoba family will receive a $336 rebate in 2019 compared to its increased costs of $232. A similar family in Saskatchewan will receive $598 compared to its higher costs of $403. In Ontario, families will receive $300 to offset its $244 in carbon taxes. And in New Brunswick a $248 rebate more than offsets the average household cost of $202. The rebates will more than double by 2022 as the carbon tax rises, and the net financial benefit to households will grow over time.

Click here to read the rest

from Skeptical Science https://ift.tt/2Jlm0lb

Note: this will be our final entry on Climate Consensus - the 97%. The Guardian has decided to discontinue its Science and Environment blogging networks. We would like to thank this great paper for hosting us over the past five years, and to our readers for making it a worthwhile and rewarding endeavor.

Last week, Prime Minister Justin Trudeau announced that under the Greenhouse Gas Pollution Pricing Act, Canada will implement a revenue-neutral carbon tax starting in 2019, fulfilling a campaign pledge he made in 2015.

The federal carbon pollution price will start low at $20 per ton in 2019, rising at $10 per ton per year until reaching $50 per ton in 2022. The carbon tax will stay at that level unless the legislation is revisited and revised.

This is a somewhat modest carbon tax – after all, the social cost of carbon is many times higher – but it’s a higher carbon price than has been implemented in most countries. Moreover, a carbon tax doesn’t necessarily have to reflect the social cost of carbon. The question is whether it will be sufficiently high to meet the country’s climate targets.

Paris was a key motivator behind the Canadian carbon tax

The Preamble in the Act is worth reading. It begins by noting “there is broad scientific consensus that anthropogenic greenhouse gas emissions contribute to global climate change” (this is somewhat understated – carbon pollution is the dominant factor). It also notes that Canada is already feeling the impacts of climate change through factors like “coastal erosion, thawing permafrost, increases in heat waves, droughts and flooding, and related risks to critical infrastructures and food security.”

The Preamble also notes that in 1992, Canada signed the UNFCCC whose objectives include “the stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system,” and that Canada ratified the Paris Agreement, whose aims include limiting global warming to less than 2°C above pre-industrial temperatures.

Canada’s Paris commitment requires cutting its carbon pollution by 30% below 2005 levels by 2030. Prior to the implementation of the carbon tax, its policies were rated Highly Insufficient to meet that goal. Instead Canada’s emissions were on track to fall only about 4% below 2005 levels by 2030. So, the carbon tax is an important policy to close that gap.

Some provinces already have carbon pricing in place

Several Canadian provinces have already implemented or plan to implement carbon pricing systems. British Columbia, Alberta, and Quebec already have such systems in place; the Canadian government noted that these provinces were “among the top performers in GDP growth across Canada in 2017.”

Provinces whose carbon prices meet the federal standards are already in compliance, so the new law won’t apply to them. Several other provinces (Northwest Territories, Nova Scotia, Prince Edward Island, Newfoundland and Labrador) have planned or proposed carbon pricing systems that will meet the federal requirements. The federal carbon tax will be applied to the remaining provinces.

 Green indicates that the province’s own carbon pricing system meets the federal standards. Purple and orange indicate a province’s planned or proposed carbon pricing will meet the federal standards, respectively. Red indicates that the federal carbon pricing will apply to the province. Illustration: Dana Nuccitelli

Energy prices will rise

A $20/ton carbon tax translates into a 16.6 cent per gallon surcharge on gasoline. So, in 2022, the $50/ton carbon tax will increase Canadian gasoline prices by about 42 cents per gallon (11 cents per liter). For comparison, the average price of gasoline in Canada is $1.43 per liter, so that would be about an 8% gasoline price increase in 2022.

The price of coal would more than double, with a carbon tax surcharge of about $100 per ton in 2022. Natural gas prices will rise by about 10 cents per cubic meter in 2022 compared to current prices of around 13 cents per cubic meter – about a 75% increase. This will increase demand for cheaper carbon-free electricity. However, Canada already supplies about 60% of its electricity through hydroelectric generation and 16% from nuclear – only about 20–25% comes from fossil fuels.

For that reason, only 11% of Canada’s carbon pollution comes from generating electricity. The industrial sector is responsible for the biggest chunk of Canadian carbon pollution (40%). It will not be subjected to the carbon tax, but rather to an Output-Based Allocations system (similar to cap and trade).

But rebates will more than offset higher fuel costs

One key component of the federal carbon tax is that it’s revenue-neutral, similar to the policy proposal from Citizens’ Climate Lobby. All the taxed money will be distributed back to the provinces from which they were generated. The provinces will in turn rebate about 90% the revenues back to individual taxpayers. The rebates are anticipated to exceed the increased energy costs for about 70% of Canadian households.

For example, a Manitoba family will receive a $336 rebate in 2019 compared to its increased costs of $232. A similar family in Saskatchewan will receive $598 compared to its higher costs of $403. In Ontario, families will receive $300 to offset its $244 in carbon taxes. And in New Brunswick a $248 rebate more than offsets the average household cost of $202. The rebates will more than double by 2022 as the carbon tax rises, and the net financial benefit to households will grow over time.

Click here to read the rest

from Skeptical Science https://ift.tt/2Jlm0lb

This morning’s moon, over Hong Kong

Photo by Matthew Chin.

Matthew Chin posted this photo to EarthSky Facebook this morning (October 29, 2018).

Thanks, Matthew!

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

Photo by Matthew Chin.

Matthew Chin posted this photo to EarthSky Facebook this morning (October 29, 2018).

Thanks, Matthew!

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

New species of missing link between dinos and birds

Artist’s concept of Archaeopteryx albersdoerferi. Image via Zhao Chuang/Martin Kundrát/PNSO/University of Manchester.

The 2019 lunar calendars are here! Order yours before they’re gone. Makes a great gift.

Known as “the missing link” between dinosaurs and birds, Archaeopteryx lived lived in the Late Jurassic around 150 million years ago. Now, an international team of scientists has identified a new species of Archaeopteryx that they say is closer to modern birds in evolutionary terms and distinctive and different enough to be described as a new species – Archaeopteryx albersdoerferi.

Archaeopteryx lived in what is now southern Germany during a time when Europe was an archipelago of islands in a warm, shallow tropical sea. It was about the size of a magpie, with the largest individuals possibly attaining the size of a raven. Archaeopteryx was first described as the “missing link” between reptiles and birds in 1861. Only 12 fossil specimens have ever been found.

For the study, the team re-examined one of these 12 fossil specimens by carrying out the first ever synchrotron examination, a form of 3-D X-ray analysis. The researchers concluded that that this individual Archaeopteryx fossil, known as specimen number eight, was physically much closer to a modern bird than it is to a reptile.

John Nudds, from the University of Manchester’s School of Earth and Environmental Sciences, is co-author of the study, published October 24, 2018, in the peer-reviewed journal Historical Biology. Nudds said in a statement:

Whenever a missing link is discovered, this merely creates two further missing links – what came before, and what came after! What came before was discovered in 1996 with the feathered dinosaurs in China. Our new species is what came after. It confirms Archaeopteryx as the first bird, and not just one of a number of feathered theropod dinosaurs, which some authors have suggested recently. You could say that it puts Archaeopteryx back on its perch as the first bird!

The researcher said that some of the differing skeletal characteristics of Archaeopteryx albersdoerferi include the fusion of cranial bones, different pectoral girdle (chest) and wing elements, and a reinforced configuration of carpals and metacarpals (hand) bones. These characteristics are seen more in modern flying birds and are not found in the older Archaeopteryx lithographica species, which more resembles reptiles and dinosaurs.

Specimen number eight is the newest of all the 12 known specimens by approximately half a million years. This age difference in comparison to the other specimens is a key factor in describing it as a new species. Nudds said:

By digitally dissecting the fossil we found that this specimen differed from all of the others. It possessed skeletal adaptations which would have resulted in much more efficient flight. In a nutshell we have discovered what Archaeopteryx lithographica evolved into – i.e., a more advanced bird, better adapted to flying – and we have described this as a new species of Archaeopteryx.

Bottom line: A study identifies a new species of Archaeopteryx, called the missing link between dinosaurs and birds.

Source: The first specimen of Archaeopteryx from the Upper Jurassic Mörnsheim Formation of Germany

Via University of Manchester

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

Artist’s concept of Archaeopteryx albersdoerferi. Image via Zhao Chuang/Martin Kundrát/PNSO/University of Manchester.

The 2019 lunar calendars are here! Order yours before they’re gone. Makes a great gift.

Known as “the missing link” between dinosaurs and birds, Archaeopteryx lived lived in the Late Jurassic around 150 million years ago. Now, an international team of scientists has identified a new species of Archaeopteryx that they say is closer to modern birds in evolutionary terms and distinctive and different enough to be described as a new species – Archaeopteryx albersdoerferi.

Archaeopteryx lived in what is now southern Germany during a time when Europe was an archipelago of islands in a warm, shallow tropical sea. It was about the size of a magpie, with the largest individuals possibly attaining the size of a raven. Archaeopteryx was first described as the “missing link” between reptiles and birds in 1861. Only 12 fossil specimens have ever been found.

For the study, the team re-examined one of these 12 fossil specimens by carrying out the first ever synchrotron examination, a form of 3-D X-ray analysis. The researchers concluded that that this individual Archaeopteryx fossil, known as specimen number eight, was physically much closer to a modern bird than it is to a reptile.

John Nudds, from the University of Manchester’s School of Earth and Environmental Sciences, is co-author of the study, published October 24, 2018, in the peer-reviewed journal Historical Biology. Nudds said in a statement:

Whenever a missing link is discovered, this merely creates two further missing links – what came before, and what came after! What came before was discovered in 1996 with the feathered dinosaurs in China. Our new species is what came after. It confirms Archaeopteryx as the first bird, and not just one of a number of feathered theropod dinosaurs, which some authors have suggested recently. You could say that it puts Archaeopteryx back on its perch as the first bird!

The researcher said that some of the differing skeletal characteristics of Archaeopteryx albersdoerferi include the fusion of cranial bones, different pectoral girdle (chest) and wing elements, and a reinforced configuration of carpals and metacarpals (hand) bones. These characteristics are seen more in modern flying birds and are not found in the older Archaeopteryx lithographica species, which more resembles reptiles and dinosaurs.

Specimen number eight is the newest of all the 12 known specimens by approximately half a million years. This age difference in comparison to the other specimens is a key factor in describing it as a new species. Nudds said:

By digitally dissecting the fossil we found that this specimen differed from all of the others. It possessed skeletal adaptations which would have resulted in much more efficient flight. In a nutshell we have discovered what Archaeopteryx lithographica evolved into – i.e., a more advanced bird, better adapted to flying – and we have described this as a new species of Archaeopteryx.

Bottom line: A study identifies a new species of Archaeopteryx, called the missing link between dinosaurs and birds.

Source: The first specimen of Archaeopteryx from the Upper Jurassic Mörnsheim Formation of Germany

Via University of Manchester

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

Why don’t Europa’s plumes have heat signatures?

Artist’s concept of a water vapor plume on Europa. New research shows that, if they do exist, Europa’s plumes aren’t as dynamic as those on Saturn’s moon Enceladus. Image via NASA/ESA/K. Retherford/SwRI.

Does Jupiter’s moon Europa have water vapor plumes? A growing body of evidence in the last few years suggests the answer is yes, but a final confirmation has remained elusive. If the plumes do exist on Europa, they seem to be less active than those on Saturn’s moon Enceladus, where huge geyser-like plumes erupt from the moon’s south pole on a regular basis. Data from the Hubble Space Telescope has strengthened the case for plumes on Europa. But a new finding – presented on October 22, 2018, at the Division of Planetary Sciences meeting in Knoxville, Tennessee – has thrown a wrench into the possibility.

The 2019 lunar calendars are here! Order yours before they’re gone. Makes a great gift.

Researchers led by Julie Rathbun of the Planetary Science Institute said they found a lack of the expected heat signatures at locations where Europa’s plumes should originate. In other words … no hot spots.

The new peer-reviewed findings were just published.

Jupiter’s moon Europa as captured by the Galileo spacecraft, which orbited Jupiter from 1995 to 2003. Galileo found the 1st evidence that a global ocean of liquid water exists under Europa’s icy crust. Image via NASA/Galileo.

Rathbun explained in a statement:

We searched through the available Galileo thermal data at the locations proposed as the sites of potential plumes. Reanalysis of temperature data from the Galileo mission does not show anything special in the locations where plumes have possibly been observed. There are no hotspot signatures at either of the sites.

This is surprising because the Enceladus plumes have a clear thermal signature at their site of origin, so this suggests that either the Europa plumes are very different, or the plumes are only occasional, or that they don’t exist, or that their thermal signature is too small to have been detected by current data.

Composite photos from the Hubble Space Telescope and the Galileo spacecraft, showing a suspected plume erupting on Europa in 2014 and 2016. Image via NASA/ESA/W. Sparks (STScI)/USGS Astrogeology Science Center.

Previous observations had suggested a plume originating from an area north of Pwyll Crater on Europa, and reanalysis of Galileo magnetometer and plasma data also supported the existence of a plume source about 600 miles (1,000 km) northeast of the first site.

But if the plume locations on Europa don’t show any heat signatures – as they do on Enceladus – that result suggests that either Europa’s are different from those on Enceladus, or that Europa’s plumes don’t even exist. Rathbun put it simply when she said:

Europa was expected to be active.

Rathbun said there are four possible explanations for the lack of heat signatures on Europa. The plumes may be intermittent. They may be fundamentally different from those on Enceladus and not be associated with anything hot. They may be smaller than expected. Or, they don’t exist; however, other data from Hubble provide strong evidence that they do exist.

Artist’s concept of the global subsurface ocean thought to lie beneath Europa’s icy crust. The plumes on Europa, if they exist, stem from there. Image via NASA/JPL-Caltech.

On Enceladus, the plumes originate from a salty global subsurface ocean, where the water makes its way to the surface through large cracks called “Tiger Stripes” in the outer ice shell near the south pole. Data from the Cassini spacecraft, which orbited Saturn until September of 2017, also showed that there is likely geothermal activity on the ocean floor. That’s intriguing because, on Earth, geothermal vents on the sea floor provide conditions suitable for life.

It’s thought that conditions similar to those on Enceladus probably exist in Europa’s global subsurface ocean as well. But finding out for sure will require a return mission to the vicinity of Jupiter. Europa’s subsurface ocean has given it a powerful allure for space scientists, and a future planetary mission is already bound there. NASA’s upcoming Europa Clipper mission, to be launched in the early-mid 2020s, will be able to study the marine environment in Europa’s ocean better than ever before. It will be able to examine deposits left on the moon’s surface by evaporating ocean water. Some water may simply seep to the surface, but if there are plumes, they could deposit a large amount of minerals on the surface, which Europa Clipper could analyze.

It’s even possible that Europa Clipper could fly directly through the plumes and analyze their composition, much as Cassini did at Enceladus, when that spacecraft discovered complex organic molecules in Enceladus’ plumes.

Geyser-like water vapor plumes on Saturn’s moon Enceladus, as seen by the Cassini spacecraft. Analysis by the spacecraft showed they contain water vapor, ice particles, organics and salts. Image via NASA/JPL/SSI.

Whatever the explanation for Europa’s plumes turns out to be, it will provide scientists with valuable insight into how plumes occur on other worlds, including the nitrogen gas ones on Neptune’s moon Triton. Those plumes have nothing to do with water, but are active geysers of extremely cold nitrogen gas – something not seen anywhere else in the solar system.

Bottom line: New research shows that Europa’s plumes may be significantly different from those on Saturn’s moon Enceladus, since they don’t exhibit the same heat signatures. The upcoming Europa Clipper mission should be able to help finally determine what is happening (or not) on Europa.

Source: A closer look at Galileo Thermal data from a Possible Plume Source North of Pwyll, Europa

Via Planetary Science Institute

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Artist’s concept of a water vapor plume on Europa. New research shows that, if they do exist, Europa’s plumes aren’t as dynamic as those on Saturn’s moon Enceladus. Image via NASA/ESA/K. Retherford/SwRI.

Does Jupiter’s moon Europa have water vapor plumes? A growing body of evidence in the last few years suggests the answer is yes, but a final confirmation has remained elusive. If the plumes do exist on Europa, they seem to be less active than those on Saturn’s moon Enceladus, where huge geyser-like plumes erupt from the moon’s south pole on a regular basis. Data from the Hubble Space Telescope has strengthened the case for plumes on Europa. But a new finding – presented on October 22, 2018, at the Division of Planetary Sciences meeting in Knoxville, Tennessee – has thrown a wrench into the possibility.

The 2019 lunar calendars are here! Order yours before they’re gone. Makes a great gift.

Researchers led by Julie Rathbun of the Planetary Science Institute said they found a lack of the expected heat signatures at locations where Europa’s plumes should originate. In other words … no hot spots.

The new peer-reviewed findings were just published.

Jupiter’s moon Europa as captured by the Galileo spacecraft, which orbited Jupiter from 1995 to 2003. Galileo found the 1st evidence that a global ocean of liquid water exists under Europa’s icy crust. Image via NASA/Galileo.

Rathbun explained in a statement:

We searched through the available Galileo thermal data at the locations proposed as the sites of potential plumes. Reanalysis of temperature data from the Galileo mission does not show anything special in the locations where plumes have possibly been observed. There are no hotspot signatures at either of the sites.

This is surprising because the Enceladus plumes have a clear thermal signature at their site of origin, so this suggests that either the Europa plumes are very different, or the plumes are only occasional, or that they don’t exist, or that their thermal signature is too small to have been detected by current data.

Composite photos from the Hubble Space Telescope and the Galileo spacecraft, showing a suspected plume erupting on Europa in 2014 and 2016. Image via NASA/ESA/W. Sparks (STScI)/USGS Astrogeology Science Center.

Previous observations had suggested a plume originating from an area north of Pwyll Crater on Europa, and reanalysis of Galileo magnetometer and plasma data also supported the existence of a plume source about 600 miles (1,000 km) northeast of the first site.

But if the plume locations on Europa don’t show any heat signatures – as they do on Enceladus – that result suggests that either Europa’s are different from those on Enceladus, or that Europa’s plumes don’t even exist. Rathbun put it simply when she said:

Europa was expected to be active.

Rathbun said there are four possible explanations for the lack of heat signatures on Europa. The plumes may be intermittent. They may be fundamentally different from those on Enceladus and not be associated with anything hot. They may be smaller than expected. Or, they don’t exist; however, other data from Hubble provide strong evidence that they do exist.

Artist’s concept of the global subsurface ocean thought to lie beneath Europa’s icy crust. The plumes on Europa, if they exist, stem from there. Image via NASA/JPL-Caltech.

On Enceladus, the plumes originate from a salty global subsurface ocean, where the water makes its way to the surface through large cracks called “Tiger Stripes” in the outer ice shell near the south pole. Data from the Cassini spacecraft, which orbited Saturn until September of 2017, also showed that there is likely geothermal activity on the ocean floor. That’s intriguing because, on Earth, geothermal vents on the sea floor provide conditions suitable for life.

It’s thought that conditions similar to those on Enceladus probably exist in Europa’s global subsurface ocean as well. But finding out for sure will require a return mission to the vicinity of Jupiter. Europa’s subsurface ocean has given it a powerful allure for space scientists, and a future planetary mission is already bound there. NASA’s upcoming Europa Clipper mission, to be launched in the early-mid 2020s, will be able to study the marine environment in Europa’s ocean better than ever before. It will be able to examine deposits left on the moon’s surface by evaporating ocean water. Some water may simply seep to the surface, but if there are plumes, they could deposit a large amount of minerals on the surface, which Europa Clipper could analyze.

It’s even possible that Europa Clipper could fly directly through the plumes and analyze their composition, much as Cassini did at Enceladus, when that spacecraft discovered complex organic molecules in Enceladus’ plumes.

Geyser-like water vapor plumes on Saturn’s moon Enceladus, as seen by the Cassini spacecraft. Analysis by the spacecraft showed they contain water vapor, ice particles, organics and salts. Image via NASA/JPL/SSI.

Whatever the explanation for Europa’s plumes turns out to be, it will provide scientists with valuable insight into how plumes occur on other worlds, including the nitrogen gas ones on Neptune’s moon Triton. Those plumes have nothing to do with water, but are active geysers of extremely cold nitrogen gas – something not seen anywhere else in the solar system.

Bottom line: New research shows that Europa’s plumes may be significantly different from those on Saturn’s moon Enceladus, since they don’t exhibit the same heat signatures. The upcoming Europa Clipper mission should be able to help finally determine what is happening (or not) on Europa.

Source: A closer look at Galileo Thermal data from a Possible Plume Source North of Pwyll, Europa

Via Planetary Science Institute

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Large and Small Magellanic Clouds collided!

The video above simulates an interaction between the Small Magellanic Cloud and Large Magellanic Cloud, starting 1 billion years ago. It shows a collision about 100 million years ago. And indeed astronomers now think this happened.

Just a few years ago, astronomer Gurtina Besla at University of Arizona used a computer to model what would have happened if, sometime in the past, the Large and Small Magellanic Clouds collided. The simulation above comes from her work. She and her team predicted at that time that a direct collision would cause the southeast region of the Small Magellanic Cloud – which astronomers call the Wing – to move toward the Large Magellanic Cloud. On the other hand, if the two galaxies simply passed near each other, the Wing stars should be moving in a perpendicular direction. This past week (October 25, 2018) – thanks to ESA’s Gaia space observatory – Michigan astronomers were able to confirm that what Besla and team predicted is in fact occurring. The Wing is moving away from the main body of the Small Magellanic. They said this observation provides:

… the first unambiguous evidence that the Small and Large Magellanic Clouds recently collided.

The Magellanic Clouds, visible from Earth’s Southern Hemisphere, are known to be small satellite galaxies of our Milky Way. They’re located not far from each other on the sky’s dome. Star motions in the smaller Cloud provide evidence for the collision, but we didn’t have data on these motions prior to Gaia, whose second data release was last April. Astronomers have been mining the Gaia data to learn all sorts of interesting insights about our galaxy and its neighborhood of space, and now here’s another one. Astronomer Sally Oey of University of Michigan, lead author of the study said:

This is really one of our exciting results. You can actually see that the Wing is its own separate region that’s moving away from the rest of the Small Magellanic Cloud.

Oey and colleagues published their results in The Astrophysical Journal Letters.

Astrophotographer Justin Ng caught the edgewise view into our Milky Way galaxy, the bright star Canopus and the Large and Small Magellanic Clouds at sunrise, in September 2013, over East Java’s Mount Bromo. Read more about this image.

A statement from University of Michigan described some of the process these astronomers used to make their discovery:

Together with an international team, Oey and undergraduate researcher Johnny Dorigo Jones were examining the SMC for ‘runaway’ stars, or stars that have been ejected from clusters within the SMC. To observe this galaxy they were using a recent data release from Gaia …

Gaia is designed to image stars again and again over a period of several years in order to plot their movement in real time. That way, scientists can measure how stars move across the sky.

Artist’s concept of Gaia in space. Image via D. DUCROS/ESA.

Oey said:

We’ve been looking at very massive, hot young stars—the hottest, most luminous stars, which are fairly rare. The beauty of the Small Magellanic Cloud and the Large Magellanic Cloud is that they’re their own galaxies, so we’re looking at all of the massive stars in a single galaxy.

Examining stars in a single galaxy helps astronomers in two ways, these researchers said. First, it provides a statistically complete sample of stars in one parent galaxy. Second, this gives the astronomers a uniform distance to all the stars, which helps them measure their individual velocities. Dorigo Jones said:

It’s really interesting that Gaia obtained the proper motions of these stars. These motions contain everything we’re looking at. For example, if we observe someone walking in the cabin of an airplane in flight, the motion we see contains that of the plane, as well as the much slower motion of the person walking.

So we removed the bulk motion of the entire Small Magellanic Cloud in order to learn more about the velocities of individual stars. We’re interested in the velocity of individual stars because we’re trying to understand the physical processes occurring within the cloud.

Oey and Dorigo Jones study runaway stars to determine how they have been ejected from these clusters. In one mechanism, called the binary supernova scenario, one star in a gravitationally bound, binary pair explodes as a supernova, ejecting the other star like a slingshot. This mechanism produces X-ray-emitting binary stars.

Another mechanism is that a gravitationally unstable cluster of stars eventually ejects one or two stars from the group. This is called the dynamical ejection scenario, which produces normal binary stars. The researchers found significant numbers of runaway stars among both X-ray binaries and normal binaries, indicating that both mechanisms are important in ejecting stars from clusters.

In looking at this data, the team also observed that all the stars within the Wing—that southeast part of the SMC—are moving in a similar direction and speed. This demonstrates the SMC and LMC likely had a collision a few hundred million years ago.

The Magellanic Clouds – satellite galaxies of the Milky Way – via ESO/ Wikipedia.

Dorigo Jones commented:

We want as much information about these stars as possible to better constrain these ejection mechanisms.

Everyone loves marveling at images of galaxies and nebulae that are incredibly far away. The Small Magellanic Cloud is so close to us, however, that we can see its beauty in the night sky with just our unaided eye. This fact, along with the data from Gaia, allow us to analyze the complex motions of stars within the Small Magellanic Cloud and even determine factors of its evolution.

Bottom line: The motions of stars in the Small Magellanic Cloud – as revealed by the Gaia space observatory – show that this small satellite galaxy of our Milky Way collided in the past with its larger neighbor, the Large Magellanic Cloud.

Read more … Gaia’s 2nd data release: 1.7 billion stars!

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

The video above simulates an interaction between the Small Magellanic Cloud and Large Magellanic Cloud, starting 1 billion years ago. It shows a collision about 100 million years ago. And indeed astronomers now think this happened.

Just a few years ago, astronomer Gurtina Besla at University of Arizona used a computer to model what would have happened if, sometime in the past, the Large and Small Magellanic Clouds collided. The simulation above comes from her work. She and her team predicted at that time that a direct collision would cause the southeast region of the Small Magellanic Cloud – which astronomers call the Wing – to move toward the Large Magellanic Cloud. On the other hand, if the two galaxies simply passed near each other, the Wing stars should be moving in a perpendicular direction. This past week (October 25, 2018) – thanks to ESA’s Gaia space observatory – Michigan astronomers were able to confirm that what Besla and team predicted is in fact occurring. The Wing is moving away from the main body of the Small Magellanic. They said this observation provides:

… the first unambiguous evidence that the Small and Large Magellanic Clouds recently collided.

The Magellanic Clouds, visible from Earth’s Southern Hemisphere, are known to be small satellite galaxies of our Milky Way. They’re located not far from each other on the sky’s dome. Star motions in the smaller Cloud provide evidence for the collision, but we didn’t have data on these motions prior to Gaia, whose second data release was last April. Astronomers have been mining the Gaia data to learn all sorts of interesting insights about our galaxy and its neighborhood of space, and now here’s another one. Astronomer Sally Oey of University of Michigan, lead author of the study said:

This is really one of our exciting results. You can actually see that the Wing is its own separate region that’s moving away from the rest of the Small Magellanic Cloud.

Oey and colleagues published their results in The Astrophysical Journal Letters.

Astrophotographer Justin Ng caught the edgewise view into our Milky Way galaxy, the bright star Canopus and the Large and Small Magellanic Clouds at sunrise, in September 2013, over East Java’s Mount Bromo. Read more about this image.

A statement from University of Michigan described some of the process these astronomers used to make their discovery:

Together with an international team, Oey and undergraduate researcher Johnny Dorigo Jones were examining the SMC for ‘runaway’ stars, or stars that have been ejected from clusters within the SMC. To observe this galaxy they were using a recent data release from Gaia …

Gaia is designed to image stars again and again over a period of several years in order to plot their movement in real time. That way, scientists can measure how stars move across the sky.

Artist’s concept of Gaia in space. Image via D. DUCROS/ESA.

Oey said:

We’ve been looking at very massive, hot young stars—the hottest, most luminous stars, which are fairly rare. The beauty of the Small Magellanic Cloud and the Large Magellanic Cloud is that they’re their own galaxies, so we’re looking at all of the massive stars in a single galaxy.

Examining stars in a single galaxy helps astronomers in two ways, these researchers said. First, it provides a statistically complete sample of stars in one parent galaxy. Second, this gives the astronomers a uniform distance to all the stars, which helps them measure their individual velocities. Dorigo Jones said:

It’s really interesting that Gaia obtained the proper motions of these stars. These motions contain everything we’re looking at. For example, if we observe someone walking in the cabin of an airplane in flight, the motion we see contains that of the plane, as well as the much slower motion of the person walking.

So we removed the bulk motion of the entire Small Magellanic Cloud in order to learn more about the velocities of individual stars. We’re interested in the velocity of individual stars because we’re trying to understand the physical processes occurring within the cloud.

Oey and Dorigo Jones study runaway stars to determine how they have been ejected from these clusters. In one mechanism, called the binary supernova scenario, one star in a gravitationally bound, binary pair explodes as a supernova, ejecting the other star like a slingshot. This mechanism produces X-ray-emitting binary stars.

Another mechanism is that a gravitationally unstable cluster of stars eventually ejects one or two stars from the group. This is called the dynamical ejection scenario, which produces normal binary stars. The researchers found significant numbers of runaway stars among both X-ray binaries and normal binaries, indicating that both mechanisms are important in ejecting stars from clusters.

In looking at this data, the team also observed that all the stars within the Wing—that southeast part of the SMC—are moving in a similar direction and speed. This demonstrates the SMC and LMC likely had a collision a few hundred million years ago.

The Magellanic Clouds – satellite galaxies of the Milky Way – via ESO/ Wikipedia.

Dorigo Jones commented:

We want as much information about these stars as possible to better constrain these ejection mechanisms.

Everyone loves marveling at images of galaxies and nebulae that are incredibly far away. The Small Magellanic Cloud is so close to us, however, that we can see its beauty in the night sky with just our unaided eye. This fact, along with the data from Gaia, allow us to analyze the complex motions of stars within the Small Magellanic Cloud and even determine factors of its evolution.

Bottom line: The motions of stars in the Small Magellanic Cloud – as revealed by the Gaia space observatory – show that this small satellite galaxy of our Milky Way collided in the past with its larger neighbor, the Large Magellanic Cloud.

Read more … Gaia’s 2nd data release: 1.7 billion stars!

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