See Mars via images from ExoMars orbiter

A “frenzy” of dust devil tracks in the Terra Sabaea region of Mars, as seen by TGO. The image is a color-composite representation where features that are bluer compared to the average color of Mars are shown in bright blue hues. Image via ESA/Roscosmos/CaSSIS, CC BY-SA 3.0 IGO.

Far from being just a cratered desert, Mars is a scenic and beautiful planet, with stunningly diverse landscapes. Many thousands of images have been taken by both orbiters and landers, with some of the most recent ones shown on this page. They are from the Trace Gas Orbiter (TGO), part of the European Space Agency’s ExoMars mission.

The new images include everything from surreal landscapes, water-formed minerals and 3D stereo views, to NASA’s InSight lander sitting on the surface.

The image of InSight is of particular significance – it’s the first time that a European orbiter has photographed a lander on the surface of Mars. TGO and InSight are also working together, as explained last month by Nicolas Thomas, CaSSIS Principal Investigator, from the University of Bern in Switzerland:

The ExoMars Trace Gas Orbiter is being used to relay data from InSight to Earth. Because of this function, to avoid uncertainties in communications, we had not been able to point the camera towards the landing site so far – we had to wait until the landing site passed directly under the spacecraft to get this image.

NASA’s InSight lander as seen from orbit by ESA’s Trace Gas Orbiter. Image via ESA/Roscosmos/CaSSIS, CC BY-SA 3.0 IGO.

The image from TGO – in the Elysium Planitia region – covers an area of about 2.25 x 2.25 km in size; at that scale, InSight just looks like a bright dot on the relatively flat landscape. A dark patch surrounds the lander, caused by the retro rockets as the lander touched down. The heat shield and back shell are also visible in the image.

Various rovers have also been photographed from orbit, and even their wheel tracks can be seen. InSight is a stationary lander however, so it will always remain in the same spot.

The CaSSIS system can also monitor the region surrounding InSight, including keeping watch for things like meteorite impacts – another great way that completely different missions, from different countries, can work together in Mars exploration.

Sulphate deposits in Columbus Crater in the southern hemisphere of Mars. Image via ESA/Roscosmos/CaSSIS, CC BY-SA 3.0 IGO.

Digital terrain model of the volcanic caldera on Ascraeus Mons, in the Tharsis region. Image via ESA/Roscosmos/CaSSIS.

3-D view of dunes cascading over the edge of Green Crater in the Noachis Terra region. Image via ESA/Roscosmos/CaSSIS, CC BY-SA 3.0 IGO.

CaSSIS will also be used when the next part of the ExoMars mission arrives in 2021 – the Rosalind Franklin rover, for both imaging and data relay.

The new image of InSight is just one of many new images released; others cover a wide variety of landscape features, such as layered deposits in the polar regions, dynamic dunes and the effects of converging dust devils. The 3-D stereo images bring an extra sense of reality to the images, so that it is almost like actually being there. Color-composite images can better highlight the differences in surface features, helping scientists find regions that have been altered by water in the past and guide future exploration missions. All of these are valuable, as explained by Thomas:

The InSight landing site image is just one of many really high quality images that we have been receiving. All of the images we’re sharing today represent some of the best from the last few months. We’re also really pleased with the digital terrain models.

South polar layered terrains in Burroughs Crater near the south polar cap. Image via ESA/Roscosmos/CaSSIS, CC BY-SA 3.0 IGO.

As also noted by Håkan Svedhem, ESA’s TGO project scientist:

This stunning image showcase really demonstrates the scientific potential we have with TGO’s imaging system. Over the course of the mission we’ll be able to investigate dynamic surface processes, including those that might also help to constrain the atmospheric gas inventory that TGO’s spectrometers have been analyzing, as well as characterise future landing sites.

TGO’s primary mission is to search for trace gases in the martian atmosphere – including methane, which could be a sign of either active geology or biology. Oddly, it hasn’t found any methane yet, although the gas has been confirmed previously by the Curiosity rover and multiple telescopes on Earth. The answer may lie in the fact that Curiosity documented a seasonal variation in the methane at its location in Gale Crater. TGO may have just looked at the wrong time, but it will continue to monitor the atmosphere in the months and years ahead.

The entire TGO image library can be seen here.

Bottom line: This fantastic collection of new images from TGO – like others – helps to show Mars as it really is, a world of diverse landscapes that in some ways are reminiscent of Earth, while also uniquely alien.

Via ESA

from EarthSky https://ift.tt/2WJ6pBr

A “frenzy” of dust devil tracks in the Terra Sabaea region of Mars, as seen by TGO. The image is a color-composite representation where features that are bluer compared to the average color of Mars are shown in bright blue hues. Image via ESA/Roscosmos/CaSSIS, CC BY-SA 3.0 IGO.

Far from being just a cratered desert, Mars is a scenic and beautiful planet, with stunningly diverse landscapes. Many thousands of images have been taken by both orbiters and landers, with some of the most recent ones shown on this page. They are from the Trace Gas Orbiter (TGO), part of the European Space Agency’s ExoMars mission.

The new images include everything from surreal landscapes, water-formed minerals and 3D stereo views, to NASA’s InSight lander sitting on the surface.

The image of InSight is of particular significance – it’s the first time that a European orbiter has photographed a lander on the surface of Mars. TGO and InSight are also working together, as explained last month by Nicolas Thomas, CaSSIS Principal Investigator, from the University of Bern in Switzerland:

The ExoMars Trace Gas Orbiter is being used to relay data from InSight to Earth. Because of this function, to avoid uncertainties in communications, we had not been able to point the camera towards the landing site so far – we had to wait until the landing site passed directly under the spacecraft to get this image.

NASA’s InSight lander as seen from orbit by ESA’s Trace Gas Orbiter. Image via ESA/Roscosmos/CaSSIS, CC BY-SA 3.0 IGO.

The image from TGO – in the Elysium Planitia region – covers an area of about 2.25 x 2.25 km in size; at that scale, InSight just looks like a bright dot on the relatively flat landscape. A dark patch surrounds the lander, caused by the retro rockets as the lander touched down. The heat shield and back shell are also visible in the image.

Various rovers have also been photographed from orbit, and even their wheel tracks can be seen. InSight is a stationary lander however, so it will always remain in the same spot.

The CaSSIS system can also monitor the region surrounding InSight, including keeping watch for things like meteorite impacts – another great way that completely different missions, from different countries, can work together in Mars exploration.

Sulphate deposits in Columbus Crater in the southern hemisphere of Mars. Image via ESA/Roscosmos/CaSSIS, CC BY-SA 3.0 IGO.

Digital terrain model of the volcanic caldera on Ascraeus Mons, in the Tharsis region. Image via ESA/Roscosmos/CaSSIS.

3-D view of dunes cascading over the edge of Green Crater in the Noachis Terra region. Image via ESA/Roscosmos/CaSSIS, CC BY-SA 3.0 IGO.

CaSSIS will also be used when the next part of the ExoMars mission arrives in 2021 – the Rosalind Franklin rover, for both imaging and data relay.

The new image of InSight is just one of many new images released; others cover a wide variety of landscape features, such as layered deposits in the polar regions, dynamic dunes and the effects of converging dust devils. The 3-D stereo images bring an extra sense of reality to the images, so that it is almost like actually being there. Color-composite images can better highlight the differences in surface features, helping scientists find regions that have been altered by water in the past and guide future exploration missions. All of these are valuable, as explained by Thomas:

The InSight landing site image is just one of many really high quality images that we have been receiving. All of the images we’re sharing today represent some of the best from the last few months. We’re also really pleased with the digital terrain models.

South polar layered terrains in Burroughs Crater near the south polar cap. Image via ESA/Roscosmos/CaSSIS, CC BY-SA 3.0 IGO.

As also noted by Håkan Svedhem, ESA’s TGO project scientist:

This stunning image showcase really demonstrates the scientific potential we have with TGO’s imaging system. Over the course of the mission we’ll be able to investigate dynamic surface processes, including those that might also help to constrain the atmospheric gas inventory that TGO’s spectrometers have been analyzing, as well as characterise future landing sites.

TGO’s primary mission is to search for trace gases in the martian atmosphere – including methane, which could be a sign of either active geology or biology. Oddly, it hasn’t found any methane yet, although the gas has been confirmed previously by the Curiosity rover and multiple telescopes on Earth. The answer may lie in the fact that Curiosity documented a seasonal variation in the methane at its location in Gale Crater. TGO may have just looked at the wrong time, but it will continue to monitor the atmosphere in the months and years ahead.

The entire TGO image library can be seen here.

Bottom line: This fantastic collection of new images from TGO – like others – helps to show Mars as it really is, a world of diverse landscapes that in some ways are reminiscent of Earth, while also uniquely alien.

Via ESA

from EarthSky https://ift.tt/2WJ6pBr

Astronomers find 2nd galaxy lacking dark matter

See-through galaxy NGC 1052-DF2 is what’s known as an ultra-diffuse galaxy, or UDG. See the galaxies behind it? This was the 1st galaxy said by astronomers to contain little to no dark matter. Now the same team has found another one. Image via NASA/ESA/P. Van Dokkum/Keck Observatory.

A year ago, astronomers announced they’d found the first known galaxy without dark matter. Called NGC 1052-DF2 – or just DF2 for short – this object is 6.5 million light-years away and roughly the same size as our Milky Way galaxy, but with 200 times fewer stars. Now the same team of astronomers is back with what they say is “stronger evidence” about DF2’s bizarre nature. Plus the team says it has found a second galaxy without dark matter. The astronomers have published their studies in two separate papers in the peer-reviewed Astrophysical Journal Letters. One study was published in the March 20, 2019, issue, and the other was published on March 27.

Shany Danieli, an astronomy graduate student at Yale University and lead author of one of the studies, commented in a statement:

The fact that we’re seeing something that’s just completely new is what’s so fascinating. No one knew that such galaxies existed, and the best thing in the world for an astronomy student is to discover an object, whether it’s a planet, a star, or a galaxy, that no one knew about or even thought about.

When astronomers think about dark matter, the observed motions of space objects often come to mind. In the 1970s, Vera Rubin and Kent Ford of the Carnegie Institution of Washington realized that stars at the outskirts of the large spiral galaxy next to ours, the Andromeda galaxy, were moving just as fast as the stars near the center. This observation apparently violated Newton’s Laws of Motion, which explain, for example, why Mars moves more slowly in orbit than Earth (because it is farther from the sun). And so the idea was born that “something” unseen must exist beyond the visible boundaries of the Andromeda galaxy, and, by extension, all galaxies. That something is what we call dark matter.

The Yale astronomers are studying the motions of space objects, too. In the first of the two new studies, they used the W. M. Keck Observatory’s Keck Cosmic Web Imager (KCWI) to gather high-precision measurements of globular star clusters inside the galaxy DF2. They said they found that – unlike the stars in Rubin and Ford’s 1970s study – these clusters are moving at a speed consistent with the mass of the galaxy’s normal matter. Their statement explained:

If there were dark matter in DF2, the clusters would be moving much faster … [thus] the team confirmed its initial observations of NGC 1052-DF2, or DF2 for short, which show dark matter is practically absent in the galaxy.

In the second study, the team used Keck Observatory’s Low Resolution Imaging Spectrometer (LRIS) to find the second galaxy devoid of dark matter, named NGC 1052-DF4, or DF4 for short. Astronomer Pieter van Dokkum at Yale University – lead author of the DF4 study – said:

Discovering a second galaxy with very little to no dark matter is just as exciting as the initial discovery of DF2. This means the chances of finding more of these galaxies are now higher than we previously thought. Since we have no good ideas for how these galaxies were formed, I hope these discoveries will encourage more scientists to work on this puzzle.

Both DF2 and DF4 belong to a relatively new class of galaxies called ultra-diffuse galaxies (UDGs). They are as large as the Milky Way but have between 100 to 1000 times fewer stars, making them appear fluffy and translucent, therefore difficult to observe.

Ironically, these astronomers said, the lack of dark matter in these UDGs strengthens the dark matter theory. Their statement explained:

It proves that dark matter is a substance that is not coupled to ‘normal’ matter, as both can be found separately. The discovery of these galaxies is difficult to explain in theories that change the laws of gravity on large scales as an alternative to the dark matter hypothesis.

The team acknowledge their work drew criticism from other astronomers, who did not believe their result, when they first announced their results in March of 2018. Van Dokkum commented:

It was a little stressful at times. On one hand, this is how the scientific process is supposed to work; you see something interesting, other people disagree, you obtain new data, and in the end you learn more about the universe. On the other hand, although the majority of the critiques were constructive and polite, not all of them were. Every time a new critique came out we had to scramble and figure out if we had missed something.

Now the team plans for look for more galaxies of this type. Danieli is leading a wide area survey with the Dragonfly Telephoto Array in New Mexico to look for more examples in a systematic way, then observe candidates again using the Keck telescopes. She said:

We hope to next find out how common these galaxies are and whether they exist in other areas of the universe. We want to find more evidence that will help us understand how the properties of these galaxies work with our current theories. Our hope is that this will take us one step further in understanding one of the biggest mysteries in our universe – the nature of dark matter.

A survey image taken with the Dragonfly Telephoto Array shows objects within the field of the elliptical galaxy NGC 1052 (center). Among these objects are DF2 (bottom left) and DF4 (top right); both are dark matter-deficient galaxies that are similar in size, luminosity, morphology, globular cluster population, and velocity dispersion. Image via P. Van Dokkum/STScI/ACS/Keck Observatory.

Bottom line: Astronomers based at Yale say they’ve confirmed their 2018 observation of an ultra-diffuse galaxy, or UDG, that, they say, contains little or no dark matter. And they say they’ve found a second galaxy lacking in dark matter.

Source (DF2 study): Still Missing Dark Matter: KCWI High-resolution Stellar Kinematics of NGC1052-DF2

Source (DF4 study): A Second Galaxy Missing Dark Matter in the NGC 1052 Group

Via Keck Observatory

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

See-through galaxy NGC 1052-DF2 is what’s known as an ultra-diffuse galaxy, or UDG. See the galaxies behind it? This was the 1st galaxy said by astronomers to contain little to no dark matter. Now the same team has found another one. Image via NASA/ESA/P. Van Dokkum/Keck Observatory.

A year ago, astronomers announced they’d found the first known galaxy without dark matter. Called NGC 1052-DF2 – or just DF2 for short – this object is 6.5 million light-years away and roughly the same size as our Milky Way galaxy, but with 200 times fewer stars. Now the same team of astronomers is back with what they say is “stronger evidence” about DF2’s bizarre nature. Plus the team says it has found a second galaxy without dark matter. The astronomers have published their studies in two separate papers in the peer-reviewed Astrophysical Journal Letters. One study was published in the March 20, 2019, issue, and the other was published on March 27.

Shany Danieli, an astronomy graduate student at Yale University and lead author of one of the studies, commented in a statement:

The fact that we’re seeing something that’s just completely new is what’s so fascinating. No one knew that such galaxies existed, and the best thing in the world for an astronomy student is to discover an object, whether it’s a planet, a star, or a galaxy, that no one knew about or even thought about.

When astronomers think about dark matter, the observed motions of space objects often come to mind. In the 1970s, Vera Rubin and Kent Ford of the Carnegie Institution of Washington realized that stars at the outskirts of the large spiral galaxy next to ours, the Andromeda galaxy, were moving just as fast as the stars near the center. This observation apparently violated Newton’s Laws of Motion, which explain, for example, why Mars moves more slowly in orbit than Earth (because it is farther from the sun). And so the idea was born that “something” unseen must exist beyond the visible boundaries of the Andromeda galaxy, and, by extension, all galaxies. That something is what we call dark matter.

The Yale astronomers are studying the motions of space objects, too. In the first of the two new studies, they used the W. M. Keck Observatory’s Keck Cosmic Web Imager (KCWI) to gather high-precision measurements of globular star clusters inside the galaxy DF2. They said they found that – unlike the stars in Rubin and Ford’s 1970s study – these clusters are moving at a speed consistent with the mass of the galaxy’s normal matter. Their statement explained:

If there were dark matter in DF2, the clusters would be moving much faster … [thus] the team confirmed its initial observations of NGC 1052-DF2, or DF2 for short, which show dark matter is practically absent in the galaxy.

In the second study, the team used Keck Observatory’s Low Resolution Imaging Spectrometer (LRIS) to find the second galaxy devoid of dark matter, named NGC 1052-DF4, or DF4 for short. Astronomer Pieter van Dokkum at Yale University – lead author of the DF4 study – said:

Discovering a second galaxy with very little to no dark matter is just as exciting as the initial discovery of DF2. This means the chances of finding more of these galaxies are now higher than we previously thought. Since we have no good ideas for how these galaxies were formed, I hope these discoveries will encourage more scientists to work on this puzzle.

Both DF2 and DF4 belong to a relatively new class of galaxies called ultra-diffuse galaxies (UDGs). They are as large as the Milky Way but have between 100 to 1000 times fewer stars, making them appear fluffy and translucent, therefore difficult to observe.

Ironically, these astronomers said, the lack of dark matter in these UDGs strengthens the dark matter theory. Their statement explained:

It proves that dark matter is a substance that is not coupled to ‘normal’ matter, as both can be found separately. The discovery of these galaxies is difficult to explain in theories that change the laws of gravity on large scales as an alternative to the dark matter hypothesis.

The team acknowledge their work drew criticism from other astronomers, who did not believe their result, when they first announced their results in March of 2018. Van Dokkum commented:

It was a little stressful at times. On one hand, this is how the scientific process is supposed to work; you see something interesting, other people disagree, you obtain new data, and in the end you learn more about the universe. On the other hand, although the majority of the critiques were constructive and polite, not all of them were. Every time a new critique came out we had to scramble and figure out if we had missed something.

Now the team plans for look for more galaxies of this type. Danieli is leading a wide area survey with the Dragonfly Telephoto Array in New Mexico to look for more examples in a systematic way, then observe candidates again using the Keck telescopes. She said:

We hope to next find out how common these galaxies are and whether they exist in other areas of the universe. We want to find more evidence that will help us understand how the properties of these galaxies work with our current theories. Our hope is that this will take us one step further in understanding one of the biggest mysteries in our universe – the nature of dark matter.

A survey image taken with the Dragonfly Telephoto Array shows objects within the field of the elliptical galaxy NGC 1052 (center). Among these objects are DF2 (bottom left) and DF4 (top right); both are dark matter-deficient galaxies that are similar in size, luminosity, morphology, globular cluster population, and velocity dispersion. Image via P. Van Dokkum/STScI/ACS/Keck Observatory.

Bottom line: Astronomers based at Yale say they’ve confirmed their 2018 observation of an ultra-diffuse galaxy, or UDG, that, they say, contains little or no dark matter. And they say they’ve found a second galaxy lacking in dark matter.

Source (DF2 study): Still Missing Dark Matter: KCWI High-resolution Stellar Kinematics of NGC1052-DF2

Source (DF4 study): A Second Galaxy Missing Dark Matter in the NGC 1052 Group

Via Keck Observatory

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

2018 global CO2 growth 4th highest on record

Image via HuffPost.

By the end of 2018, NOAA’s atmospheric observatory at Mauna Loa, Hawaii, recorded the fourth-highest annual growth in the concentration of atmospheric carbon dioxide (CO2) in 60 years of record-keeping.

Carbon dioxide grew by 2.87 parts per million (ppm) at the mountaintop observatory during 2018, jumping from an average of 407.05 ppm on January 1, 2018, to 409.92 on January 1, 2019, according to a new analysis of air samples collected by NOAA’s Global Monitoring Division (GMD).

That means three of the four highest annual increases have occurred in the past four years, said Pieter Tans, senior scientist with GMD. Tans said:

At a time when there’s all this talk about how we should be decreasing CO2 emissions, the amount of CO2 we’re putting into the atmosphere is clearly accelerating. It’s no coincidence that the last four years also had the highest CO2 emissions on record.

A chart showing the steadily increasing concentrations of carbon dioxide in the atmosphere (in parts per million) observed at NOAA’s Mauna Loa Observatory over the course of 60 years. Measurements of the greenhouse gas began in 1959. Image via NOAA.

NOAA captures and analyzes air samples from a network of observatories and collecting stations around the world. Situated close to the top of Hawaii’s Mauna Loa volcano, NOAA’s Mauna Loa Observatory samples “background” samples of Northern Hemisphere air. Mauna Loa is the oldest in the network and has the longest record of CO2 measurements.

The increase observed in 2018 ranks behind only 2016’s record jump of 3.01 ppm, 2015’s near-record increase of 2.98 ppm and 1998’s growth of 2.93 ppm/yr in the modern record. The record dates to March 1958 when David Keeling of the Scripps Institution of Oceanography started measuring atmospheric CO2 in what’s known as the Keeling Curve.

Globally averaged CO2 levels increased by a similar amount to what was observed on Mauna Loa during 2018.

Carbon dioxide is by far the most important of the five primary greenhouse gases – carbon dioxide, methane, nitrous oxide, carbon monoxide and ozone – both in total amount and the rate of increase. When the first Mauna Loa samples were analyzed in 1958, CO2 had already risen 35 ppm from the pre-industrial level of 280 ppm. In the past 60 years, CO2 has increased by an additional 95 ppm to 410 ppm today.

In the last two decades, the rate of increase has been roughly 100 times faster than previous natural increases, such as those that occurred at the end of the last ice age 11,000-17,000 years ago. Tans said:

Today’s rise of CO2 is dominated by human activities. It’s not from natural causes.

About NOAA greenhouse gas monitoring

NOAA tracks five primary greenhouse gases that warm the planet by trapping heat from Earth’s surface that would otherwise escape into space, including two chlorofluorocarbons controlled by the Montreal Protocol that damage Earth’s ozone layer. All five gases account for about 96 percent of the atmosphere’s increased heat-trapping capacity since 1750, another climate indicator tracked by NOAA.

Bottom line: A NOAA report showed the 4th-highest growth in global atmospheric CO2 in 60 years of record-keeping.

Via NOAA

from EarthSky https://ift.tt/2CP0Vh0

Image via HuffPost.

By the end of 2018, NOAA’s atmospheric observatory at Mauna Loa, Hawaii, recorded the fourth-highest annual growth in the concentration of atmospheric carbon dioxide (CO2) in 60 years of record-keeping.

Carbon dioxide grew by 2.87 parts per million (ppm) at the mountaintop observatory during 2018, jumping from an average of 407.05 ppm on January 1, 2018, to 409.92 on January 1, 2019, according to a new analysis of air samples collected by NOAA’s Global Monitoring Division (GMD).

That means three of the four highest annual increases have occurred in the past four years, said Pieter Tans, senior scientist with GMD. Tans said:

At a time when there’s all this talk about how we should be decreasing CO2 emissions, the amount of CO2 we’re putting into the atmosphere is clearly accelerating. It’s no coincidence that the last four years also had the highest CO2 emissions on record.

A chart showing the steadily increasing concentrations of carbon dioxide in the atmosphere (in parts per million) observed at NOAA’s Mauna Loa Observatory over the course of 60 years. Measurements of the greenhouse gas began in 1959. Image via NOAA.

NOAA captures and analyzes air samples from a network of observatories and collecting stations around the world. Situated close to the top of Hawaii’s Mauna Loa volcano, NOAA’s Mauna Loa Observatory samples “background” samples of Northern Hemisphere air. Mauna Loa is the oldest in the network and has the longest record of CO2 measurements.

The increase observed in 2018 ranks behind only 2016’s record jump of 3.01 ppm, 2015’s near-record increase of 2.98 ppm and 1998’s growth of 2.93 ppm/yr in the modern record. The record dates to March 1958 when David Keeling of the Scripps Institution of Oceanography started measuring atmospheric CO2 in what’s known as the Keeling Curve.

Globally averaged CO2 levels increased by a similar amount to what was observed on Mauna Loa during 2018.

Carbon dioxide is by far the most important of the five primary greenhouse gases – carbon dioxide, methane, nitrous oxide, carbon monoxide and ozone – both in total amount and the rate of increase. When the first Mauna Loa samples were analyzed in 1958, CO2 had already risen 35 ppm from the pre-industrial level of 280 ppm. In the past 60 years, CO2 has increased by an additional 95 ppm to 410 ppm today.

In the last two decades, the rate of increase has been roughly 100 times faster than previous natural increases, such as those that occurred at the end of the last ice age 11,000-17,000 years ago. Tans said:

Today’s rise of CO2 is dominated by human activities. It’s not from natural causes.

About NOAA greenhouse gas monitoring

NOAA tracks five primary greenhouse gases that warm the planet by trapping heat from Earth’s surface that would otherwise escape into space, including two chlorofluorocarbons controlled by the Montreal Protocol that damage Earth’s ozone layer. All five gases account for about 96 percent of the atmosphere’s increased heat-trapping capacity since 1750, another climate indicator tracked by NOAA.

Bottom line: A NOAA report showed the 4th-highest growth in global atmospheric CO2 in 60 years of record-keeping.

Via NOAA

from EarthSky https://ift.tt/2CP0Vh0

Use the Big Dipper to find the Little Dipper

So you say you can find the Big Dipper, but not the Little Dipper? This post is for you. Here’s the view northward on April evenings. At present the Big Dipper is high in the north during the evening hours. Notice the two outer stars in the bowl of the Big Dipper. These two stars – called Duhbe and Merak – always point to Polaris, the North Star. Find Polaris, and you can find the Little Dipper.

Polaris is special because Earth’s northern axis nearly points to its location in the sky. It’s the star around which the entire northern sky appears to turn.

Polaris is also fun to locate for another reason. It’s part of a famous – though elusive – star pattern, known as the Little Dipper.

So here it is! The Little Dipper! The North Star, Polaris, marks the end of its handle.

View larger. | No matter where you see the Big Dipper, the two outer stars in its bowl point to Polaris. In this shot, Tom Wildoner caught the Big Dipper and Polaris at around 3:30 a.m. in July 2013. Thanks, Tom!

By the way, Polaris is less than a degree away from the true north celestial pole on the sky’s dome now. It’ll be closest to true north – less than half a degree away – in the year 2102. The change is due to a motion of Earth called “precession,” which causes Earth’s axis to trace out a circle among the stars every 26,000 years.

By the way, thousands of years ago, Polaris was an ordinary star in the northern sky, known to the Greeks by the name Phoenice.

Other ordinary stars in the northern sky now – Kochab and Pherkad, the two outermost stars in the bowl of the Little Dipper (see chart below) – have had the honor of being pole stars.

Kochab and Pherkad served as twin pole stars from about 1500 B.C. to about 500 B.C.

They’re still sometimes called the Guardians of the Pole.

Kochab is located about 126 light-years away. Pherkad is more distant, at about 480 light-years by some estimates. Meanwhile, Polaris is a bit more than 400 light-years away.

Kochab and Pherkad are the 2 outermost stars in the bowl of the Little Dipper.

Bottom line: The Big Dipper is usually pretty easy to find, but the Little Dipper is less easy. This post tells you how to use the Big Dipper to find Polaris and the Little Dipper, plus how to recognize the stars Kochab and Pherkad.

Thuban: Past North Star

Star Errai: Future North Star

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So you say you can find the Big Dipper, but not the Little Dipper? This post is for you. Here’s the view northward on April evenings. At present the Big Dipper is high in the north during the evening hours. Notice the two outer stars in the bowl of the Big Dipper. These two stars – called Duhbe and Merak – always point to Polaris, the North Star. Find Polaris, and you can find the Little Dipper.

Polaris is special because Earth’s northern axis nearly points to its location in the sky. It’s the star around which the entire northern sky appears to turn.

Polaris is also fun to locate for another reason. It’s part of a famous – though elusive – star pattern, known as the Little Dipper.

So here it is! The Little Dipper! The North Star, Polaris, marks the end of its handle.

View larger. | No matter where you see the Big Dipper, the two outer stars in its bowl point to Polaris. In this shot, Tom Wildoner caught the Big Dipper and Polaris at around 3:30 a.m. in July 2013. Thanks, Tom!

By the way, Polaris is less than a degree away from the true north celestial pole on the sky’s dome now. It’ll be closest to true north – less than half a degree away – in the year 2102. The change is due to a motion of Earth called “precession,” which causes Earth’s axis to trace out a circle among the stars every 26,000 years.

By the way, thousands of years ago, Polaris was an ordinary star in the northern sky, known to the Greeks by the name Phoenice.

Other ordinary stars in the northern sky now – Kochab and Pherkad, the two outermost stars in the bowl of the Little Dipper (see chart below) – have had the honor of being pole stars.

Kochab and Pherkad served as twin pole stars from about 1500 B.C. to about 500 B.C.

They’re still sometimes called the Guardians of the Pole.

Kochab is located about 126 light-years away. Pherkad is more distant, at about 480 light-years by some estimates. Meanwhile, Polaris is a bit more than 400 light-years away.

Kochab and Pherkad are the 2 outermost stars in the bowl of the Little Dipper.

Bottom line: The Big Dipper is usually pretty easy to find, but the Little Dipper is less easy. This post tells you how to use the Big Dipper to find Polaris and the Little Dipper, plus how to recognize the stars Kochab and Pherkad.

Thuban: Past North Star

Star Errai: Future North Star

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Speedy asteroid buzzed Earth last week, 1 day before being detected

via Gfycat

In 2013, a small asteroid entered Earth’s atmosphere above the city of Chelyabinsk in Russia. Its shock wave broke windows and knocked down parts of buildings in six Russian cities and caused some 1,500 people to seek medical attention for injuries, mostly from flying glass. Can a Chelyabinsk-type event occur again? Definitely.

Late last week (March 29, 2019), astronomers at Mt. Lemmon, Arizona, discovered a fast-moving space rock. After calculations of its orbit, it was realized that the asteroid had made its closest approach to Earth one day earlier, on March 28. The asteroid has been designated as 2019 FC1. According to The Watchers website, this is the 14th known asteroid to fly past Earth within one lunar distance since the start of 2019. It is the sixth this month. With an estimated size of around 98 feet (30 meters) in diameter, it’s the largest asteroid to pass closer to us than the moon since 2019 began.

It passed closer to us than the moon, at around 26.8 percent of the Earth-moon distance, or 64,102 miles (103,162 km) from our planet. According to NASA, closest approach occurred on March 28, 2019, at around 05:46 UTC (1:46 a.m. ET); translate UTC to your time.

The asteroid that buzzed Earth on March 28 was travelling really fast. Its speed has been estimated at 57,973 miles per hour (93,298 km/h), or 25.9 km per second, relative to Earth.

Although most of the mass of an asteroid of its size would disintegrate during the passage through Earth’s protective atmosphere, it’s worth noting that this space rock was almost twice as wide as the asteroid that penetrated the atmosphere over the skies above Chelyabinsk, Russia, on February 15, 2013. For comparison, the Chelyabinsk asteroid was estimated to be 55 feet (17 meters) in diameter, before entering our atmosphere.

The Apollo-type asteroid has an orbit that brings it close to Earth’s orbit every 3.3 years, but, according to astronomers’ calculations, the 2019 approach was the closest for this particular asteroid for at least the next 89 years.

The green line indicates the object’s apparent motion relative to the Earth, and the bright green marks are the object’s location at approximately half-hour intervals. The moon’s orbit is gray. The blue arrow points in the direction of Earth’s motion and the yellow arrow points toward the sun. Image via Minor Planet Center/The Watchers.

Bottom line: A small asteroid – now designated as 2019 FC1 – flew closer to us than the moon (64,102 miles or 103,162 km) on March 28, 2019. Astronomers detected it one day later and calculated its orbit backwards. With an estimated size of around 98 feet (30 meters) in diameter, it’s the largest of 14 asteroids to pass closer to us than the moon since 2019 began.

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via Gfycat

In 2013, a small asteroid entered Earth’s atmosphere above the city of Chelyabinsk in Russia. Its shock wave broke windows and knocked down parts of buildings in six Russian cities and caused some 1,500 people to seek medical attention for injuries, mostly from flying glass. Can a Chelyabinsk-type event occur again? Definitely.

Late last week (March 29, 2019), astronomers at Mt. Lemmon, Arizona, discovered a fast-moving space rock. After calculations of its orbit, it was realized that the asteroid had made its closest approach to Earth one day earlier, on March 28. The asteroid has been designated as 2019 FC1. According to The Watchers website, this is the 14th known asteroid to fly past Earth within one lunar distance since the start of 2019. It is the sixth this month. With an estimated size of around 98 feet (30 meters) in diameter, it’s the largest asteroid to pass closer to us than the moon since 2019 began.

It passed closer to us than the moon, at around 26.8 percent of the Earth-moon distance, or 64,102 miles (103,162 km) from our planet. According to NASA, closest approach occurred on March 28, 2019, at around 05:46 UTC (1:46 a.m. ET); translate UTC to your time.

The asteroid that buzzed Earth on March 28 was travelling really fast. Its speed has been estimated at 57,973 miles per hour (93,298 km/h), or 25.9 km per second, relative to Earth.

Although most of the mass of an asteroid of its size would disintegrate during the passage through Earth’s protective atmosphere, it’s worth noting that this space rock was almost twice as wide as the asteroid that penetrated the atmosphere over the skies above Chelyabinsk, Russia, on February 15, 2013. For comparison, the Chelyabinsk asteroid was estimated to be 55 feet (17 meters) in diameter, before entering our atmosphere.

The Apollo-type asteroid has an orbit that brings it close to Earth’s orbit every 3.3 years, but, according to astronomers’ calculations, the 2019 approach was the closest for this particular asteroid for at least the next 89 years.

The green line indicates the object’s apparent motion relative to the Earth, and the bright green marks are the object’s location at approximately half-hour intervals. The moon’s orbit is gray. The blue arrow points in the direction of Earth’s motion and the yellow arrow points toward the sun. Image via Minor Planet Center/The Watchers.

Bottom line: A small asteroid – now designated as 2019 FC1 – flew closer to us than the moon (64,102 miles or 103,162 km) on March 28, 2019. Astronomers detected it one day later and calculated its orbit backwards. With an estimated size of around 98 feet (30 meters) in diameter, it’s the largest of 14 asteroids to pass closer to us than the moon since 2019 began.

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Today in science: Comet Hale-Bopp

Comet Hale-Bopp with its prominent dust (white) and plasma (blue) tails. Photo via E. Kolmhofer, H. Raab; Johannes-Kepler-Observatory, Linz, Austria.

April 1, 1997. On this date, Comet Hale-Bopp – probably the best-remembered bright comet for many in the Northern Hemisphere – reached its perihelion or closest point to the sun. It was 0.9 astronomical units (AU, or Earth-sun distances) away from the sun on that day. Its brightness – though dispersed across a wider area than stars – exceeded that of any star in the sky except for Sirius, the sky’s brightest star.

As seen from the Northern Hemisphere, Hale-Bopp was the brightest comet since Comet West, sometimes called the Great Comet of 1976.

It stayed visible with the unaided eye for a record of 18 months, twice as long as the previous record holder: the Great Comet of 1811.

Hale-Bopp – officially labeled C/1995 O1 – became one of the most-viewed comets in human history. There are over 5,000 images of this comet available via a webpage maintained by NASA’s Jet Propulsion Laboratory.

Some called Hale-Bopp the Great Comet of 1997 (although others disagreed that it met the criteria for a Great Comet).

It attracted so many not only because of its rarity and beauty, but also because it enabled people to jump – in their minds – back in time. Some 4,200 years ago, when Hale-Bopp last passed the Earth and sun, the Egyptian pyramids were newly being polished by sand, and the Epic of Gilgamesh, considered the first great work of Western literature, was not yet written.

Comet Hale-Bopp was discovered on July 23, 1995, by two independently observing amateur astronomers: Alan Hale and Thomas Bopp. At that time, the comet was a whopping 7.2 AU from the sun, which made it the most distant comet to ever be discovered by amateurs up until that time.

What made that discovery possible was that Hale-Bopp was so bright. It was literally a thousand times brighter than Comet Halley had been at that same distance; Halley, one of the most famous comets, had visited the inner solar system a decade earlier. It was clear that Hale-Bopp was a very special comet, because comets typically don’t shine so brightly when they are beyond Jupiter’s orbit.

There were a few reasons explaining the comet’s unusual brightness. The main one is the enormous size of its nucleus, or core. Most cometary nuclei are thought to be no more than about 10 miles (16 km) across. The nucleus of Hale-Bopp had a diameter estimated to be between 25 and 40 miles across (40-60 km).

Giant Jupiter is thought to have affected this comet’s orbit. It’s been calculated that Hale-Bopp was last seen in Earth’s skies around 4,200 years ago. Now, though, the comet’s orbit is shorter. Astronomers think that – on what might’ve been its first voyage around the sun thousands of years ago – the comet almost collided with Jupiter. It passed very close to Jupiter again in April 1996, shortening its orbital period still more. The comet’s current orbital period is around 2,530 Earth years.

No records have been found of the comet’s passage 4,200 years ago, but that does not mean that no records were made. It most likely means that none survived. Around 2213 B.C., when the comet last was visible, civilizations had been using the sky to track seasonal changes and other phenomena for a long time. They could not have missed Hale-Bopp.

For more about the world at Hale-Bopp passage around 2213 B.C., click here.

Thus, in a way, Hale-Bopp is like a clock that measures time in millennia. It reminds us of the progress humankind has made since its last visit.

Imagine what the world will look like when Comet Hale-Bopp next crosses our skies, sometime around the year 4380.

A night under the stars and Comet Hale-Bopp. It remained visible to the unaided eye for 18 months. Photo ©1997 Jerry Lodriguss/www.astropix.com. Used with permission.

Bottom line: On April 1, 1997, Comet Hale-Bopp was at perihelion, its closest point to the sun. This comet – remembered by many – was the last widely seen comet from the Northern Hemisphere.

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Comet Hale-Bopp with its prominent dust (white) and plasma (blue) tails. Photo via E. Kolmhofer, H. Raab; Johannes-Kepler-Observatory, Linz, Austria.

April 1, 1997. On this date, Comet Hale-Bopp – probably the best-remembered bright comet for many in the Northern Hemisphere – reached its perihelion or closest point to the sun. It was 0.9 astronomical units (AU, or Earth-sun distances) away from the sun on that day. Its brightness – though dispersed across a wider area than stars – exceeded that of any star in the sky except for Sirius, the sky’s brightest star.

As seen from the Northern Hemisphere, Hale-Bopp was the brightest comet since Comet West, sometimes called the Great Comet of 1976.

It stayed visible with the unaided eye for a record of 18 months, twice as long as the previous record holder: the Great Comet of 1811.

Hale-Bopp – officially labeled C/1995 O1 – became one of the most-viewed comets in human history. There are over 5,000 images of this comet available via a webpage maintained by NASA’s Jet Propulsion Laboratory.

Some called Hale-Bopp the Great Comet of 1997 (although others disagreed that it met the criteria for a Great Comet).

It attracted so many not only because of its rarity and beauty, but also because it enabled people to jump – in their minds – back in time. Some 4,200 years ago, when Hale-Bopp last passed the Earth and sun, the Egyptian pyramids were newly being polished by sand, and the Epic of Gilgamesh, considered the first great work of Western literature, was not yet written.

Comet Hale-Bopp was discovered on July 23, 1995, by two independently observing amateur astronomers: Alan Hale and Thomas Bopp. At that time, the comet was a whopping 7.2 AU from the sun, which made it the most distant comet to ever be discovered by amateurs up until that time.

What made that discovery possible was that Hale-Bopp was so bright. It was literally a thousand times brighter than Comet Halley had been at that same distance; Halley, one of the most famous comets, had visited the inner solar system a decade earlier. It was clear that Hale-Bopp was a very special comet, because comets typically don’t shine so brightly when they are beyond Jupiter’s orbit.

There were a few reasons explaining the comet’s unusual brightness. The main one is the enormous size of its nucleus, or core. Most cometary nuclei are thought to be no more than about 10 miles (16 km) across. The nucleus of Hale-Bopp had a diameter estimated to be between 25 and 40 miles across (40-60 km).

Giant Jupiter is thought to have affected this comet’s orbit. It’s been calculated that Hale-Bopp was last seen in Earth’s skies around 4,200 years ago. Now, though, the comet’s orbit is shorter. Astronomers think that – on what might’ve been its first voyage around the sun thousands of years ago – the comet almost collided with Jupiter. It passed very close to Jupiter again in April 1996, shortening its orbital period still more. The comet’s current orbital period is around 2,530 Earth years.

No records have been found of the comet’s passage 4,200 years ago, but that does not mean that no records were made. It most likely means that none survived. Around 2213 B.C., when the comet last was visible, civilizations had been using the sky to track seasonal changes and other phenomena for a long time. They could not have missed Hale-Bopp.

For more about the world at Hale-Bopp passage around 2213 B.C., click here.

Thus, in a way, Hale-Bopp is like a clock that measures time in millennia. It reminds us of the progress humankind has made since its last visit.

Imagine what the world will look like when Comet Hale-Bopp next crosses our skies, sometime around the year 4380.

A night under the stars and Comet Hale-Bopp. It remained visible to the unaided eye for 18 months. Photo ©1997 Jerry Lodriguss/www.astropix.com. Used with permission.

Bottom line: On April 1, 1997, Comet Hale-Bopp was at perihelion, its closest point to the sun. This comet – remembered by many – was the last widely seen comet from the Northern Hemisphere.

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Saturn’s rings coat 5 tiny moons

This graphic shows the ring moons inspected by NASA’s Cassini spacecraft in super-close flybys. The rings and moons depicted are not to scale. Image via NASA-JPL/Caltech.

New findings have emerged about five tiny moons nestled in and near Saturn’s rings. Super-close flybys by NASA’s Cassini spacecraft – which orbited Saturn from 2004 to 2017 – reveal that the surfaces of these unusual moons are covered with material from the planet’s rings – and from icy particles blasting out of Saturn’s larger moon Enceladus.

Planet Saturn has 62 moons, ranging in size from tiny moonlets less than .6 miles (1 kilometer) across to the enormous Titan, which is larger than the planet Mercury. The five moons inspected by Cassini were Atlas, Epimetheus, Pandora, Daphnis and Pan.

Bonnie Buratti of NASA’s Jet Propulsion Laboratory is lead author of the study, published in the journal Science on March 28, 2019. She said in a statement:

The daring, close flybys of these odd little moons let us peer into how they interact with Saturn’s rings. We’re seeing more evidence of how extremely active and dynamic the Saturn ring and moon system is.

The new research, from data gathered by Cassini’s instruments before the spacecraft plunged into Saturn’s atmosphere in 2017, suggests that dust and ice from the rings accretes onto the moons embedded within and near the rings.

Scientists also found the moon surfaces to be highly porous, which, the researchers say, helps confirm the theory that they were formed in multiple stages as ring material settled onto denser cores that might be remnants of a larger object that broke apart. The porosity also helps explain their shape: Rather than being spherical, these moons are blobby and ravioli-like, with material stuck around their equators. Buratti said:

We found these moons are scooping up particles of ice and dust from the rings to form the little skirts around their equators. A denser body would be more ball-shaped because gravity would pull the material in.

See the tiny moon Pandora, right, outside Saturn’s outermost ring, in this image by NASA’s Cassini spacecraft in 2014. Image via NASA/JPL-Caltech/Space Science Institute.

Cassini Project Scientist Linda Spilker said:

Perhaps this process is going on throughout the rings, and the largest ring particles are also accreting ring material around them. Detailed views of these tiny ring moons may tell us more about the behavior of the ring particles themselves.

This montage of views from the Cassini spacecraft shows 3 of Saturn’s small ring moons, Atlas, Daphnis and Pan, at the same scale for ease of comparison. The Atlas image was acquired on April 12, 2017, at a distance of 10,000 miles (16,000 km), the Pan image on March 7, 2017, at 16,000 miles (26,000 km) and Daphnis image on January. 16, 2017, at 17,000 miles (28,000 km). Image via NASA.

Of the satellites studied, the surfaces of those closest to Saturn – Daphnis and Pan – are the most altered by ring materials, according to the researchers. The surfaces of the moons Atlas, Epimetheus and Pandora, farther out from Saturn, have ring material as well – but they’re also coated with the bright icy particles and water vapor from the plume spraying out of Enceladus. (A broad outer ring of Saturn, known as the E ring, is formed by the icy material that fans out from Enceladus’ plume.)

Astronomers don’t know what triggered the moons to form.

Cassini’s mission ended in September 2017, when it was low on fuel. Mission controllers deliberately plunged Cassini into Saturn’s atmosphere rather than risk crashing the spacecraft into the planet’s moons.

Bottom line: New research using data from the Cassini spacecraft says that dust and ice from Saturn’s rings accumulate on moons orbiting in the rings’ vicinity.

Source: Close Cassini flybys of Saturn’s ring moons Pan, Daphnis, Atlas, Pandora, and Epimetheus

Via NASA

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This graphic shows the ring moons inspected by NASA’s Cassini spacecraft in super-close flybys. The rings and moons depicted are not to scale. Image via NASA-JPL/Caltech.

New findings have emerged about five tiny moons nestled in and near Saturn’s rings. Super-close flybys by NASA’s Cassini spacecraft – which orbited Saturn from 2004 to 2017 – reveal that the surfaces of these unusual moons are covered with material from the planet’s rings – and from icy particles blasting out of Saturn’s larger moon Enceladus.

Planet Saturn has 62 moons, ranging in size from tiny moonlets less than .6 miles (1 kilometer) across to the enormous Titan, which is larger than the planet Mercury. The five moons inspected by Cassini were Atlas, Epimetheus, Pandora, Daphnis and Pan.

Bonnie Buratti of NASA’s Jet Propulsion Laboratory is lead author of the study, published in the journal Science on March 28, 2019. She said in a statement:

The daring, close flybys of these odd little moons let us peer into how they interact with Saturn’s rings. We’re seeing more evidence of how extremely active and dynamic the Saturn ring and moon system is.

The new research, from data gathered by Cassini’s instruments before the spacecraft plunged into Saturn’s atmosphere in 2017, suggests that dust and ice from the rings accretes onto the moons embedded within and near the rings.

Scientists also found the moon surfaces to be highly porous, which, the researchers say, helps confirm the theory that they were formed in multiple stages as ring material settled onto denser cores that might be remnants of a larger object that broke apart. The porosity also helps explain their shape: Rather than being spherical, these moons are blobby and ravioli-like, with material stuck around their equators. Buratti said:

We found these moons are scooping up particles of ice and dust from the rings to form the little skirts around their equators. A denser body would be more ball-shaped because gravity would pull the material in.

See the tiny moon Pandora, right, outside Saturn’s outermost ring, in this image by NASA’s Cassini spacecraft in 2014. Image via NASA/JPL-Caltech/Space Science Institute.

Cassini Project Scientist Linda Spilker said:

Perhaps this process is going on throughout the rings, and the largest ring particles are also accreting ring material around them. Detailed views of these tiny ring moons may tell us more about the behavior of the ring particles themselves.

This montage of views from the Cassini spacecraft shows 3 of Saturn’s small ring moons, Atlas, Daphnis and Pan, at the same scale for ease of comparison. The Atlas image was acquired on April 12, 2017, at a distance of 10,000 miles (16,000 km), the Pan image on March 7, 2017, at 16,000 miles (26,000 km) and Daphnis image on January. 16, 2017, at 17,000 miles (28,000 km). Image via NASA.

Of the satellites studied, the surfaces of those closest to Saturn – Daphnis and Pan – are the most altered by ring materials, according to the researchers. The surfaces of the moons Atlas, Epimetheus and Pandora, farther out from Saturn, have ring material as well – but they’re also coated with the bright icy particles and water vapor from the plume spraying out of Enceladus. (A broad outer ring of Saturn, known as the E ring, is formed by the icy material that fans out from Enceladus’ plume.)

Astronomers don’t know what triggered the moons to form.

Cassini’s mission ended in September 2017, when it was low on fuel. Mission controllers deliberately plunged Cassini into Saturn’s atmosphere rather than risk crashing the spacecraft into the planet’s moons.

Bottom line: New research using data from the Cassini spacecraft says that dust and ice from Saturn’s rings accumulate on moons orbiting in the rings’ vicinity.

Source: Close Cassini flybys of Saturn’s ring moons Pan, Daphnis, Atlas, Pandora, and Epimetheus

Via NASA

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