| Original enclosures: |
Sunday, May 15, 2016
Hubble Spies a Spiral Snowflake
Hubble Spies a Spiral Snowflake: Hubble Spies a Spiral Snowflake: Together with irregular galaxies, spiral galaxies make up approximately 60 percent of the galaxies in the local universe. However, despite their prevalence, each spiral galaxy is unique — like snowflakes, no two are alike. This is demonstrated by the striking face-on spiral galaxy NGC 6814.
From Science Alert: “WATCH: Here are the limits of humanity’s space exploration”
From Science Alert: “WATCH: Here are the limits of humanity’s space exploration”:
Science Alert
13 MAY 2016
JOSH HRALA
Access mp4 video here .
When it comes to space exploration, how far can we actually go? Is there a true limit, even with the sci-fi tech of the future, to humanity’s reach beyond Earth?
As the Kurzgesagt – In a Nutshell video above explains, humanity lives in a small area of the Milky Way – an average spiral galaxy that’s about 100,000 light-years across.
Milky Way NASA/JPL-Caltech /ESO R. Hurt
Like many other spiral galaxies, it’s full of stars, planets, gases, and dark energy, with a supermassive black hole in the centre.
Sag A* NASA Chandra X-Ray Observatory 23 July 2014
NASA/Chandra Telescope
Though we might think of our galaxy as crowded, most of it is actually empty space.
Scaling up from there, the Milky Way and Andromeda galaxies, along with about 50 dwarf galaxies, belong to our ‘local group’, which spans roughly 10 million light-years. Our local group is just one out of hundreds of other groups that make up the Laniakea Supercluster, which, in turn, is just a tiny part of the observable Universe.
Local Group. Andrew Z. Colvin 3 March 2011
Laniakea supercluster. No image credit
Now that we know where we stand spatially, let’s assume that humanity’s future rockets will meet a science fiction level of interstellar travel. With all of these advances, how far from Earth could we possibly get?
Sadly, not that far. In fact, humanity will only ever get to explore the local group.
But that’s okay, though, right? The local group is 10 million light-years in diameter. Surely that’s a considerable amount of Universe? Nope! According to the video, our local group is just 0.00000000001 percent of the observable Universe. That’s 100 billionth of a percent! In other words, humanity’s reach miniscule, which is a total bummer.
Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey
So what’s holding us back? In short: space itself. Space isn’t truly empty like it appears – it’s actually full of energy and different parts of the Universe have denser pockets than others. To understand this, we have to go all the way back to the Big Bang, which inflated the Universe from the size of a marble to an unimaginable size.
Inflationary Universe. NASA/WMAP
During this event, quantum fluctuations stretched out, making denser areas of the Universe. Since then, gravity has been pulling everything back together because that’s just what gravity likes to do. In smaller areas, like our local group, gravity formed galaxies and everything that comes along with them.
Over time, these groups grew apart, thanks to mysterious nature of dark energy, which researchers say is responsible for the expansion of the Universe, though they know almost nothing about it. This means that our local group isn’t bound to other groups by gravity, causing them to float away from us.
Since these galaxies are traveling at breakneck speeds away from us, even if we were to enter intergalactic space, we’d never move fast enough to reach them. In the future, this expansion will continue, and we’ll eventually lose the ability to even see these other groups.
While these groups move away, the galaxies inside our group will come together to form ‘Milkdromeda’, a combination of our galaxy and Andromeda (if you couldn’t tell by that name). All of this means that, if there are still people around when Milkdromeda forms, they’ll look out at the Universe and see nothing but darkness (sorry for the existential crisis).
Sounds pretty bleak, right? In a way, sure, but it’s important to remember that we haven’t even made it to Mars properly yet. There’s still a lot out there to explore before local groups separate enough for us to not see them. We’re talking billions of years – plenty of time!
Check out the video above to learn more.
See the full article here .
Please help promote STEM in your local schools.
Stem Education Coalition
Science Alert
13 MAY 2016
JOSH HRALA
Access mp4 video here .
When it comes to space exploration, how far can we actually go? Is there a true limit, even with the sci-fi tech of the future, to humanity’s reach beyond Earth?
As the Kurzgesagt – In a Nutshell video above explains, humanity lives in a small area of the Milky Way – an average spiral galaxy that’s about 100,000 light-years across.
Milky Way NASA/JPL-Caltech /ESO R. Hurt
Like many other spiral galaxies, it’s full of stars, planets, gases, and dark energy, with a supermassive black hole in the centre.
Sag A* NASA Chandra X-Ray Observatory 23 July 2014
NASA/Chandra Telescope
Though we might think of our galaxy as crowded, most of it is actually empty space.
Scaling up from there, the Milky Way and Andromeda galaxies, along with about 50 dwarf galaxies, belong to our ‘local group’, which spans roughly 10 million light-years. Our local group is just one out of hundreds of other groups that make up the Laniakea Supercluster, which, in turn, is just a tiny part of the observable Universe.
Local Group. Andrew Z. Colvin 3 March 2011
Laniakea supercluster. No image credit
Now that we know where we stand spatially, let’s assume that humanity’s future rockets will meet a science fiction level of interstellar travel. With all of these advances, how far from Earth could we possibly get?
Sadly, not that far. In fact, humanity will only ever get to explore the local group.
But that’s okay, though, right? The local group is 10 million light-years in diameter. Surely that’s a considerable amount of Universe? Nope! According to the video, our local group is just 0.00000000001 percent of the observable Universe. That’s 100 billionth of a percent! In other words, humanity’s reach miniscule, which is a total bummer.
Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey
So what’s holding us back? In short: space itself. Space isn’t truly empty like it appears – it’s actually full of energy and different parts of the Universe have denser pockets than others. To understand this, we have to go all the way back to the Big Bang, which inflated the Universe from the size of a marble to an unimaginable size.
Inflationary Universe. NASA/WMAP
During this event, quantum fluctuations stretched out, making denser areas of the Universe. Since then, gravity has been pulling everything back together because that’s just what gravity likes to do. In smaller areas, like our local group, gravity formed galaxies and everything that comes along with them.
Over time, these groups grew apart, thanks to mysterious nature of dark energy, which researchers say is responsible for the expansion of the Universe, though they know almost nothing about it. This means that our local group isn’t bound to other groups by gravity, causing them to float away from us.
Since these galaxies are traveling at breakneck speeds away from us, even if we were to enter intergalactic space, we’d never move fast enough to reach them. In the future, this expansion will continue, and we’ll eventually lose the ability to even see these other groups.
While these groups move away, the galaxies inside our group will come together to form ‘Milkdromeda’, a combination of our galaxy and Andromeda (if you couldn’t tell by that name). All of this means that, if there are still people around when Milkdromeda forms, they’ll look out at the Universe and see nothing but darkness (sorry for the existential crisis).
Sounds pretty bleak, right? In a way, sure, but it’s important to remember that we haven’t even made it to Mars properly yet. There’s still a lot out there to explore before local groups separate enough for us to not see them. We’re talking billions of years – plenty of time!
Check out the video above to learn more.
See the full article here .
Please help promote STEM in your local schools.
Stem Education Coalition
Hercules Galaxy Cluster: Going Deep
Hercules Galaxy Cluster: Going Deep:
In the Going Deep column in the July 2016 issue Sky & Telescope Contributing Editor Steve Gottlieb shared his expert knowledge, gathered through multiple observing sessions and outside research, of the Hercules Galaxy Cluster, cataloged as Abell 2151. The central 18' × 6' region, called Abell 2151C, is the richest region of the cluster and contains over 15 member galaxies from 14th- to 15th-magnitude. Steve first tackled the cluster in 1983, using a 13.1-inch reflector. More recently, he surveyed the region using his 18-inch f/4.3 reflector.
As Ken Crawford's image shows, Abell 2151 contains an abundant number of spiral galaxies (some 50% of the total) and includes a number of interacting pairs and trios. These galaxies are typically quite small, so Steve recommends using a magnification of 250x or higher if the seeing allows. The higher power will increase visibility and help to resolve the close pairs.
To aid your observing endeavor, Steve has provided an expanded table of galaxies, with their position angles, visual magnitudes, size, and positions. The table is available for download as an Excel file and as a PDF. The galaxies listed in boldface type are discussed in the July issue.
In the Going Deep column in the July 2016 issue Sky & Telescope Contributing Editor Steve Gottlieb shared his expert knowledge, gathered through multiple observing sessions and outside research, of the Hercules Galaxy Cluster, cataloged as Abell 2151. The central 18' × 6' region, called Abell 2151C, is the richest region of the cluster and contains over 15 member galaxies from 14th- to 15th-magnitude. Steve first tackled the cluster in 1983, using a 13.1-inch reflector. More recently, he surveyed the region using his 18-inch f/4.3 reflector.
As Ken Crawford's image shows, Abell 2151 contains an abundant number of spiral galaxies (some 50% of the total) and includes a number of interacting pairs and trios. These galaxies are typically quite small, so Steve recommends using a magnification of 250x or higher if the seeing allows. The higher power will increase visibility and help to resolve the close pairs.
To aid your observing endeavor, Steve has provided an expanded table of galaxies, with their position angles, visual magnitudes, size, and positions. The table is available for download as an Excel file and as a PDF. The galaxies listed in boldface type are discussed in the July issue.
From SA: “Godless Universe: A Physicist Searches for Meaning in Nature”
From SA: “Godless Universe: A Physicist Searches for Meaning in Nature”:
Scientific American
May 10, 2016
Clara Moskowitz
The natural world is the only world, theoretical physicist Sean Carroll argues in a new book.
Inflationary Universe. NASA/WMAP
Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey
It is time to face reality, California Institute of Technology theoretical physicist Sean Carroll says: There is just no such thing as God, or ghosts, or human souls that reside outside of the body. Everything in existence belongs to the natural world and is accessible to science, he argues. In his new book “The Big Picture: On the Origin of Life, Meaning, and the Universe Itself,” out this week from Dutton, Carroll describes a guiding philosophy along these lines that he calls poetic naturalism. It excludes a supernatural or spiritual realm but still allows plenty of room for life to have a purpose.
Sean M. Carroll
“I think we can bring ideas like meaning and morality into our discussions of the natural world,” Carroll says. “The ways that we talk about the universe are what make it meaningful.” He eloquently argues that point in his far-ranging book, which takes on the origins of consciousness, the likeliness of God based on a rigorous application of Bayesian probability statistics, and many other “big” questions that scientists are often loath to tackle.
Scientific American spoke with Carroll about his philosophy and how we can all take a closer look at just what we truly, deeply believe.
[An edited transcript of the conversation follows.]
Naturalism is the viewpoint that everything arises from natural causes and that there is no supernatural realm. You coin the term “poetic naturalism” for your own particular brand of this guiding philosophy. Why the need for a new term?
Naturalism has been certainly been around for a very long time, but as more people become naturalists and talk to each other, their disagreements within naturalism are interesting. I thought there was a judicious middle ground, which I call poetic, between “the world is just a bunch of particles,” and “science can be used to discover meaning and morality.”
To me the connotations of “poetic” are that there’s some human choice that comes into how we talk about the world. In particular, when it comes to questions of morality and meaning, the way we go about deciding what is right and wrong, and meaningful or not, is not the same as the way we discover what is true and false.
Just because we have no evidence of another realm of reality beyond the physical world, how can we conclude it doesn’t exist?
It’s not a matter of certainty, ever. I would make the argument that if there were a supernatural element that played a role in our everyday life in some noticeable way, it’s very, very likely we would have noticed it. It just seems weird that this kind of thing would be so crucial and yet so difficult to notice in any controlled scientific way. I would make the case that it is sufficiently unlikely in a fair Bayesian accounting that we don’t need to spend any time thinking about it anymore. Five hundred years ago it would have been a possibility. I think these days we’re ready to move on.
All I can say at the end of the day is we should all be trying as hard as we can to guard against our individual cognitive biases, the things we want to be true. The existence of life after death, for example, I would love that to be true. My cognitive bias is in favor of that. And yet I don’t think it is true. The best we can do is try to be honest.
So do you think it’s impossible for a religious person to believe in poetic naturalism?
Of course that depends on what you mean by religious. There’s actually a movement called religious naturalism. Religion involves a whole bunch of things—practices, casts of mind, morals, etc., so you can certainly imagine calling yourself religious, reading the Bible, going to church and just not believing in God. I suspect the number of people who do that is much larger than the number of people who admit to it.
The mistake comes when we try to pretend that it doesn’t matter what our view of the ontology of the world is. I think it does matter. But having made those decisions [about your worldview], there are many ways you can live a life that’s meaningful and socially relevant and familial. I think we have a misunderstanding of meaning because we relate it to something outside the natural world, when it doesn’t have to be that.
This argument for naturalism feels particularly timely, when politicians and many in society are increasingly hostile to science and evidence-based thinking. How receptive to the approach of naturalism do you think most people are?
I think that scientists have a sort of professional level of understanding of the universe, and scientists are overwhelmingly naturalists. Whereas people on the street, or in Washington, D.C., still don’t admit to this. There aren’t a lot of naturalists in Congress. The way we talk about these things in the public sphere has not caught up with the way we understand the universe as it really is.
As a physicist, what inspired you to write a book essentially on philosophy?
It evolved over a very long time. I’ve always been interested in not only physics directly, but also the wider consequences. I was a philosophy minor as an undergraduate. I always have thought that doing physics was part of a larger intellectual project of trying to understand the whole world in different ways.
What do you hope readers take away from this book?
I think there’s a bunch of people who still, because they just haven’t thought about it that much, have the informal idea that science can explain what happens when two atoms bump into each other, but it can’t explain how the universe started or how life began. I hope people get the idea that we’re well on our way to answering those questions. There’s no obstacle in our way that says we’re just not going to be able to.
See the full article here .
Please help promote STEM in your local schools.
Stem Education Coalition
Scientific American, the oldest continuously published magazine in the U.S., has been bringing its readers unique insights about developments in science and technology for more than 160 years.
From SA: “Godless Universe: A Physicist Searches for Meaning in Nature”
Scientific American
May 10, 2016
Clara Moskowitz
The natural world is the only world, theoretical physicist Sean Carroll argues in a new book.
Inflationary Universe. NASA/WMAP
Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey
It is time to face reality, California Institute of Technology theoretical physicist Sean Carroll says: There is just no such thing as God, or ghosts, or human souls that reside outside of the body. Everything in existence belongs to the natural world and is accessible to science, he argues. In his new book “The Big Picture: On the Origin of Life, Meaning, and the Universe Itself,” out this week from Dutton, Carroll describes a guiding philosophy along these lines that he calls poetic naturalism. It excludes a supernatural or spiritual realm but still allows plenty of room for life to have a purpose.
Sean M. Carroll
“I think we can bring ideas like meaning and morality into our discussions of the natural world,” Carroll says. “The ways that we talk about the universe are what make it meaningful.” He eloquently argues that point in his far-ranging book, which takes on the origins of consciousness, the likeliness of God based on a rigorous application of Bayesian probability statistics, and many other “big” questions that scientists are often loath to tackle.
Scientific American spoke with Carroll about his philosophy and how we can all take a closer look at just what we truly, deeply believe.
[An edited transcript of the conversation follows.]
Naturalism is the viewpoint that everything arises from natural causes and that there is no supernatural realm. You coin the term “poetic naturalism” for your own particular brand of this guiding philosophy. Why the need for a new term?
Naturalism has been certainly been around for a very long time, but as more people become naturalists and talk to each other, their disagreements within naturalism are interesting. I thought there was a judicious middle ground, which I call poetic, between “the world is just a bunch of particles,” and “science can be used to discover meaning and morality.”
To me the connotations of “poetic” are that there’s some human choice that comes into how we talk about the world. In particular, when it comes to questions of morality and meaning, the way we go about deciding what is right and wrong, and meaningful or not, is not the same as the way we discover what is true and false.
Just because we have no evidence of another realm of reality beyond the physical world, how can we conclude it doesn’t exist?
It’s not a matter of certainty, ever. I would make the argument that if there were a supernatural element that played a role in our everyday life in some noticeable way, it’s very, very likely we would have noticed it. It just seems weird that this kind of thing would be so crucial and yet so difficult to notice in any controlled scientific way. I would make the case that it is sufficiently unlikely in a fair Bayesian accounting that we don’t need to spend any time thinking about it anymore. Five hundred years ago it would have been a possibility. I think these days we’re ready to move on.
All I can say at the end of the day is we should all be trying as hard as we can to guard against our individual cognitive biases, the things we want to be true. The existence of life after death, for example, I would love that to be true. My cognitive bias is in favor of that. And yet I don’t think it is true. The best we can do is try to be honest.
So do you think it’s impossible for a religious person to believe in poetic naturalism?
Of course that depends on what you mean by religious. There’s actually a movement called religious naturalism. Religion involves a whole bunch of things—practices, casts of mind, morals, etc., so you can certainly imagine calling yourself religious, reading the Bible, going to church and just not believing in God. I suspect the number of people who do that is much larger than the number of people who admit to it.
The mistake comes when we try to pretend that it doesn’t matter what our view of the ontology of the world is. I think it does matter. But having made those decisions [about your worldview], there are many ways you can live a life that’s meaningful and socially relevant and familial. I think we have a misunderstanding of meaning because we relate it to something outside the natural world, when it doesn’t have to be that.
This argument for naturalism feels particularly timely, when politicians and many in society are increasingly hostile to science and evidence-based thinking. How receptive to the approach of naturalism do you think most people are?
I think that scientists have a sort of professional level of understanding of the universe, and scientists are overwhelmingly naturalists. Whereas people on the street, or in Washington, D.C., still don’t admit to this. There aren’t a lot of naturalists in Congress. The way we talk about these things in the public sphere has not caught up with the way we understand the universe as it really is.
As a physicist, what inspired you to write a book essentially on philosophy?
It evolved over a very long time. I’ve always been interested in not only physics directly, but also the wider consequences. I was a philosophy minor as an undergraduate. I always have thought that doing physics was part of a larger intellectual project of trying to understand the whole world in different ways.
What do you hope readers take away from this book?
I think there’s a bunch of people who still, because they just haven’t thought about it that much, have the informal idea that science can explain what happens when two atoms bump into each other, but it can’t explain how the universe started or how life began. I hope people get the idea that we’re well on our way to answering those questions. There’s no obstacle in our way that says we’re just not going to be able to.
See the full article here .
Please help promote STEM in your local schools.
Stem Education Coalition
Scientific American, the oldest continuously published magazine in the U.S., has been bringing its readers unique insights about developments in science and technology for more than 160 years.
NASA Directly Observes Fundamental Process of Nature for 1st Time
NASA Directly Observes Fundamental Process of Nature for 1st Time:
Like sending sensors up into a hurricane, NASA has flown four spacecraft through an invisible maelstrom in space, called magnetic reconnection. Magnetic reconnection is one of the prime drivers of space radiation and so it is a key factor in the quest to learn more about our space environment and protect our spacecraft and astronauts as we explore farther and farther from our home planet.
Space is a better vacuum than any we can create on Earth, but it does contain some particles — and it’s bustling with activity. It overflows with energy and a complex system of magnetic fields. Sometimes, when two sets of magnetic fields connect, an explosive reaction occurs: As the magnetic fields re-align and snap into a new formation they send particles zooming off in jets.
The four Magnetospheric Multiscale, or MMS, spacecraft (shown here in an artist's concept) have now made more than 4,000 trips through the boundaries of Earth's magnetic field, gathering observations of our dynamic space environment. Credits: NASA/Goddard/Conceptual Image LabA new paper printed on May 12, 2016, in Science provides the first observations from inside a magnetic reconnection event. The research shows that magnetic reconnection is dominated by the physics of electrons — thus providing crucial information about what powers this fundamental process in nature.
The effects of this sudden release of particles and energy — such as giant eruptions on the sun, the aurora, radiation storms in near-Earth space, high energy cosmic particles that come from other galaxies — have been observed throughout the solar system and beyond. But we have never been able to witness the phenomenon of magnetic reconnection directly. Satellites have observed tantalizing glances of particles speeding by, but not the impetus — like seeing the debris flung out from a tornado, but never seeing the storm itself.
“We developed a mission, the Magnetospheric Multiscale mission, that for the first time would have the precision needed to gather observations in the heart of magnetic reconnection,” said Jim Burch, the principal investigator for MMS at the Southwest Research Institute in San Antonio, Texas, and the first author of the Science paper. “We received results faster than we could have expected. By seeing magnetic reconnection in action, we have observed one of the fundamental forces of nature.”
MMS is made of four identical spacecraft that launched in March 2015. They fly in a pyramid formation to create a full 3-D map of any phenomena they observe. On Oct. 16, 2015, the spacecraft traveled straight through a magnetic reconnection event at the boundary where Earth’s magnetic field bumps up against the sun’s magnetic field. In only a few seconds, the 25 sensors on each of the spacecraft collected thousands of observations. This unprecedented time cadence opened the door for scientists to track better than ever before how the magnetic and electric fields changed, as well as the speeds and direction of the various charged particles.
The science of reconnection springs from the basic science of electromagnetics, which dominates most of the universe and is a force as fundamental in space as gravity is on Earth. Any set of magnetic fields can be thought of as a row of lines. These field lines are always anchored to some body — a planet, a star — creating a giant magnetic network surrounding it. It is at the boundaries of two such networks where magnetic reconnection happens.
Magnetic reconnection — a phenomenon that happens throughout space — occurs when magnetic field lines come together, realign and send particles hurling outward. Credits: NASA/Goddard/Conceptual Image LabImagine rows of magnetic field lines moving toward each other at such a boundary. (The boundary that MMS travels through, for example, is the one where Earth’s fields meet the sun’s.) The field lines are sometimes traveling in the same direction, and don’t have much effect on each other, like two water currents flowing along side each other.
But if the two sets of field lines point in opposite directions, the process of realigning is dramatic. It can be hugely explosive, sending particles hurtling off at near the speed of light. It can also be slow and steady. Either way it releases a huge amount of energy.
“One of the mysteries of magnetic reconnection is why it’s explosive in some cases, steady in others, and in some cases, magnetic reconnection doesn’t occur at all,” said Tom Moore, the mission scientist for MMS at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
Whether explosive or steady, the local particles are caught up in the event, hurled off to areas far away, crossing magnetic boundaries they never could have crossed otherwise. At the edges of Earth’s magnetic environment, the magnetosphere, such events allow solar radiation to enter near-Earth space.
“From previous satellites’ measurements, we know that the magnetic fields act like a slingshot, sending the protons accelerating out,” said Burch. “The decades-old mystery is what do the electrons do, and how do the two magnetic fields interconnect. Satellite measurements of electrons have been too slow by a factor of 100 to sample the magnetic reconnection region. The precision and speed of the MMS measurements, however, opened up a new window on the universe, a new ‘microscope’ to see reconnection.”
With this new set of observations, MMS tracked what happens to electrons during magnetic reconnection. As the four spacecraft flew across the magnetosphere’s boundary they flew directly through what’s called the dissipation region where magnetic reconnection occurred. The observations were able to track how the magnetic fields suddenly shifted, and also how the particles moved away.
Space is a better vacuum than any we can create on Earth, but it's nonetheless bustling with activity, particles and magnetic field lines. NASA studies our space environment to protect our technology and astronauts as we explore farther and farther from our home planet. Credits: NASA/Goddard/Conceptual Image LabThe observations show that the electrons shot away in straight lines from the original event at hundreds of miles per second, crossing the magnetic boundaries that would normally deflect them. Once across the boundary, the particles curved back around in response to the new magnetic fields they encountered, making a U-turn. These observations align with a computer simulation known as the crescent model, named for the characteristic crescent shapes that the graphs show to represent how far across the magnetic boundary the electrons can be expected to travel before turning around again.
A surprising result was that at the moment of interconnection between the sun’s magnetic field lines and those of Earth the crescents turned abruptly so that the electrons flowed along the field lines. By watching these electron tracers, MMS made the first observation of the predicted breaking and interconnection of magnetic fields in space.
“The data showed the entire process of magnetic reconnection to be fairly orderly and elegant,” said Michael Hesse, a space scientist at Goddard who first developed the crescent model. “There doesn’t seem to be much turbulence present, or at least not enough to disrupt or complicate the process.”
Spotting the persistent characteristic crescent shape in the electron distributions suggests that it is the physics of electrons that is at the heart of understanding how magnetic field lines accelerate the particles.
“This shows us that the electrons move in such a way that electric fields are established and these electric fields in turn produce a flash conversion of magnetic energy,” said Roy Torbert, a scientist at the Space Science Center at the University of New Hampshire in Durham, who is a co-author on the paper. “The encounter that our instruments were able to measure gave us a clearer view of an explosive reconnection energy release and the role played by electron physics.”
Since it launched, MMS has made more than 4,000 trips through the magnetic boundaries around Earth, each time gathering information about the way the magnetic fields and particles move. After its first direct observation of magnetic reconnection, it has flown through such an event five more times, providing more information about this fundamental process.
As the mission continues, the team can adjust the formation of the MMS spacecraft bringing them closer together, which provides better viewing of electron paths, or further apart, which provides better viewing of proton paths. Each set of observations contributes to explaining different aspects of magnetic reconnection. Together, such information will help scientists map out the details of our space environment — crucial information as we journey ever farther beyond our home planet.
Like sending sensors up into a hurricane, NASA has flown four spacecraft through an invisible maelstrom in space, called magnetic reconnection. Magnetic reconnection is one of the prime drivers of space radiation and so it is a key factor in the quest to learn more about our space environment and protect our spacecraft and astronauts as we explore farther and farther from our home planet.
Space is a better vacuum than any we can create on Earth, but it does contain some particles — and it’s bustling with activity. It overflows with energy and a complex system of magnetic fields. Sometimes, when two sets of magnetic fields connect, an explosive reaction occurs: As the magnetic fields re-align and snap into a new formation they send particles zooming off in jets.
The four Magnetospheric Multiscale, or MMS, spacecraft (shown here in an artist's concept) have now made more than 4,000 trips through the boundaries of Earth's magnetic field, gathering observations of our dynamic space environment. Credits: NASA/Goddard/Conceptual Image Lab
The effects of this sudden release of particles and energy — such as giant eruptions on the sun, the aurora, radiation storms in near-Earth space, high energy cosmic particles that come from other galaxies — have been observed throughout the solar system and beyond. But we have never been able to witness the phenomenon of magnetic reconnection directly. Satellites have observed tantalizing glances of particles speeding by, but not the impetus — like seeing the debris flung out from a tornado, but never seeing the storm itself.
“We developed a mission, the Magnetospheric Multiscale mission, that for the first time would have the precision needed to gather observations in the heart of magnetic reconnection,” said Jim Burch, the principal investigator for MMS at the Southwest Research Institute in San Antonio, Texas, and the first author of the Science paper. “We received results faster than we could have expected. By seeing magnetic reconnection in action, we have observed one of the fundamental forces of nature.”
MMS is made of four identical spacecraft that launched in March 2015. They fly in a pyramid formation to create a full 3-D map of any phenomena they observe. On Oct. 16, 2015, the spacecraft traveled straight through a magnetic reconnection event at the boundary where Earth’s magnetic field bumps up against the sun’s magnetic field. In only a few seconds, the 25 sensors on each of the spacecraft collected thousands of observations. This unprecedented time cadence opened the door for scientists to track better than ever before how the magnetic and electric fields changed, as well as the speeds and direction of the various charged particles.
The science of reconnection springs from the basic science of electromagnetics, which dominates most of the universe and is a force as fundamental in space as gravity is on Earth. Any set of magnetic fields can be thought of as a row of lines. These field lines are always anchored to some body — a planet, a star — creating a giant magnetic network surrounding it. It is at the boundaries of two such networks where magnetic reconnection happens.
Magnetic reconnection — a phenomenon that happens throughout space — occurs when magnetic field lines come together, realign and send particles hurling outward. Credits: NASA/Goddard/Conceptual Image Lab
But if the two sets of field lines point in opposite directions, the process of realigning is dramatic. It can be hugely explosive, sending particles hurtling off at near the speed of light. It can also be slow and steady. Either way it releases a huge amount of energy.
“One of the mysteries of magnetic reconnection is why it’s explosive in some cases, steady in others, and in some cases, magnetic reconnection doesn’t occur at all,” said Tom Moore, the mission scientist for MMS at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
Whether explosive or steady, the local particles are caught up in the event, hurled off to areas far away, crossing magnetic boundaries they never could have crossed otherwise. At the edges of Earth’s magnetic environment, the magnetosphere, such events allow solar radiation to enter near-Earth space.
“From previous satellites’ measurements, we know that the magnetic fields act like a slingshot, sending the protons accelerating out,” said Burch. “The decades-old mystery is what do the electrons do, and how do the two magnetic fields interconnect. Satellite measurements of electrons have been too slow by a factor of 100 to sample the magnetic reconnection region. The precision and speed of the MMS measurements, however, opened up a new window on the universe, a new ‘microscope’ to see reconnection.”
With this new set of observations, MMS tracked what happens to electrons during magnetic reconnection. As the four spacecraft flew across the magnetosphere’s boundary they flew directly through what’s called the dissipation region where magnetic reconnection occurred. The observations were able to track how the magnetic fields suddenly shifted, and also how the particles moved away.
Space is a better vacuum than any we can create on Earth, but it's nonetheless bustling with activity, particles and magnetic field lines. NASA studies our space environment to protect our technology and astronauts as we explore farther and farther from our home planet. Credits: NASA/Goddard/Conceptual Image Lab
A surprising result was that at the moment of interconnection between the sun’s magnetic field lines and those of Earth the crescents turned abruptly so that the electrons flowed along the field lines. By watching these electron tracers, MMS made the first observation of the predicted breaking and interconnection of magnetic fields in space.
“The data showed the entire process of magnetic reconnection to be fairly orderly and elegant,” said Michael Hesse, a space scientist at Goddard who first developed the crescent model. “There doesn’t seem to be much turbulence present, or at least not enough to disrupt or complicate the process.”
Spotting the persistent characteristic crescent shape in the electron distributions suggests that it is the physics of electrons that is at the heart of understanding how magnetic field lines accelerate the particles.
“This shows us that the electrons move in such a way that electric fields are established and these electric fields in turn produce a flash conversion of magnetic energy,” said Roy Torbert, a scientist at the Space Science Center at the University of New Hampshire in Durham, who is a co-author on the paper. “The encounter that our instruments were able to measure gave us a clearer view of an explosive reconnection energy release and the role played by electron physics.”
Since it launched, MMS has made more than 4,000 trips through the magnetic boundaries around Earth, each time gathering information about the way the magnetic fields and particles move. After its first direct observation of magnetic reconnection, it has flown through such an event five more times, providing more information about this fundamental process.
As the mission continues, the team can adjust the formation of the MMS spacecraft bringing them closer together, which provides better viewing of electron paths, or further apart, which provides better viewing of proton paths. Each set of observations contributes to explaining different aspects of magnetic reconnection. Together, such information will help scientists map out the details of our space environment — crucial information as we journey ever farther beyond our home planet.
"The Milky Way's Dark Disk" --Did It Seed the Existence of the Central Supermassive Black Hole? (Weekend Most Popular)
"The Milky Way's Dark Disk" --Did It Seed the Existence of the Central Supermassive Black Hole? (Weekend Most Popular): “We have some genuinely new ideas,” Randall said. “I’ll say from the start that we don’t know if they’re going to turn out to be right, but what’s interesting is that this opens the door to a whole class of ideas that haven’t been tested before, and potentially have a great deal of interesting impacts.
Though the black-hole hypothesis adds additional complexity to a number of already-thorny questions about the nature of the universe, Randall believes it will be important to understand if a portion — even a relatively small portion — of dark matter behaves in unexpected ways.
Though the exact nature of dark matter remains unknown, physicists have been able to infer its existence based on the gravitational effect it exerts on ordinary matter. Though dark matter is otherwise believed to be non-interacting, two Harvard physics professors have suggested that a hypothetical type of dark matter could form a disk of material that runs through the center of the galaxy.
“If you were to look at our world and assume there was only one type of particle, you’d be pretty wrong,” said Randall. “I think it’s definitely a worthwhile theory to explore, because even if this is only a small fraction of dark matter, there is six times more dark matter in the universe than ordinary matter. We care a lot about ordinary matter, and that’s precisely because it has interactions. So if there is a small portion of dark matter that has those interactions, that may be what we should pay attention to, perhaps even more so than other dark matter.”
The composite Hubble Space Telescope, Spitzer Space Telescope, and the Chandra X-ray Observatory image of the central region of our Milky Way galaxy above shows the center of the galaxy, located within the bright white region to the right of and just below the middle of the image. Like the downtown of a large city, the center of our galaxy is a crowded, active, and vibrant place. The supermassive black hole -- some four million times more massive than the Sun -- resides within the bright region in the lower right. The diffuse X-ray light comes from gas heated to millions of degrees by outflows from the supermassive black hole, winds from giant stars, and stellar explosions. This central region is the most energetic place in our galaxy.
If the solar system, as it orbited the center of the galaxy, were to move through that disk, they theorized that the gravitational effects from the dark matter might be enough to dislodge comets and other objects from what’s known as the Oort Cloud and send them hurtling toward Earth. The solar system's orbit through Milky Way shown below, though exaggerated vertically for clarity, bobs up and down every 64 million years due to the gravity of the galactic disk.
“Those objects are only weakly gravitationaly bound,” Randall said. “With enough of a trigger, it’s possible to dislodge objects from their current orbit. While some will go out of the solar system, others may come into the inner solar system, which increases the likelihood that they may hit the Earth.”
The model described by Randall and colleague Matthew Reece suggests that those oscillations occur approximately every 32-35 million years, a figure that is on par with evidence collected from impact craters suggesting that increases in meteor strikes occur over similar periods. Reece's research centers around connecting theoretical particle physics with new experimental results, building models that attempt to extend the Standard Model of particle physics in ways that address various puzzles arising in quantum field theory and cosmology.
The extinction of the dinosaurs, however, is just one theory that will have to be re-examined if Randall and Reece’s theory proves true.”
Our Sun orbits around the Galactic center, taking approximately 250 million years to make a complete revolution. However, this trajectory is not a perfect circle. The Solar System weaves up and down, crossing the plane of the Milky Way approximately every 32 million years, which coincides with the presumed periodicity of the impact variations. This bobbing motion, which extends about 250 light years above and below the plane, is determined by the concentration of gas and stars in the disk of our Galaxy.
This ordinary “baryonic” matter is concentrated within about 1000 light years of the plane. Because the density drops off in the vertical direction, there is a gravitational gradient, or tide, that may perturb the orbits of comets in the Oort cloud, causing some comets to fly into the inner Solar System and periodically raise the chances of collision with Earth. However, the problem with this idea is that the estimated galactic tide is too weak to cause many waves in the Oort cloud.
In their study, Randall and Reece focus on this second hypothesis and suggest that the galactic tide could be made stronger with a thin disk of dark matter. Dark disks are a possible outcome of dark matter physics, as the authors and their colleagues recently showed. Here, the researchers consider a specific model, in which our Galaxy hosts a dark disk with a thickness of 30 light years and a surface density of around 1 solar mass per square light year (the surface density of ordinary baryonic matter is roughly 5 times that, but it’s less concentrated near the plane).
Although one has to stretch the observational constraints to make room, their thin disk of dark matter is consistent with astronomical data on our Galaxy. Focusing their analysis on large (>20km) craters created in the last 250 million years, Randall and Reece argue that their dark disk scenario can produce the observed pattern in crater frequency with a fair amount of statistical uncertainty.
Randall and Reece’s dark disk model is not made of an ordinary type of dark matter. The most likely candidate of dark matter—known as weakly interacting massive particles (WIMPs)—is expected to form a spherical halo around the Milky Way, instead of being concentrated in the disk. This WIMP dark matter scenario has been remarkably successful in explaining the large-scale distribution of matter in the Universe.
But there is a long-standing problem on small-scales—the theory generally predicts overly dense cores in the centers of galaxies and clusters of galaxies, and it predicts a larger number of dwarf galaxy satellites around the Milky Way than are observed. While some of these problems could be resolved by better understanding the physics of baryonic matter (as it relates, for example, to star formation and gas dynamics), it remains unclear whether a baryonic solution can work in the smallest mass galaxies (with very little stars and gas) where discrepancies are observed.
Alternatively, this small-scale conflict could be evidence of more complex physics in the dark matter sector itself. One solution is to invoke strong electromagnetic-like interactions among dark matter particles, which could lead to the emission of “dark photons”. These self-interactions can redistribute momentum through elastic scattering, thereby altering the predicted distribution of dark matter in the innermost regions of galaxies and clusters of galaxies as well as the number of dwarf galaxies in the Milky Way.
Although self-interacting dark matter could resolve the tension between theory and observations at small-scales, large-scale measurements of galaxies and clusters of galaxies only allow a small fraction (less than 5%) of the dark matter to be self-interacting. Recently, Randall, Reece, and their collaborators showed that if a portion of the dark matter is self-interacting, then these particles will collapse into a dark galactic disk that overlaps with the ordinary baryonic disk .
So, did a thin disk of dark matter trigger extinction events like the one that snuffed out the dinosaurs? The evidence is still far from compelling. First, the periodicity in Earth’s cratering rate is not clearly established, because a patchy crater record makes it difficult to see a firm pattern. It is also unclear what role comets may have played in the mass extinctions. The prevailing view is that the Chicxulub crater, which has been linked to the dinosaur extinction 66 million years ago, was created by a giant asteroid, instead of a comet. Randall and Reece were careful in acknowledging at the outset that “statistical evidence is not overwhelming” and listing various limitations for using a patchy crater record. But the geological data is unlikely to improve in the near future, unfortunately.
On the other hand, advances in astronomical data are expected with the European Space Agency’s Gaia space mission, which was launched last year and is currently studying the Milky Way in unprecedented detail. Gaia will observe millions of stars and measure their precise distances and velocities. These measurements should enable astronomers to map out the surface-density of the dense galactic disk as a function of height. Close to the plane, astronomers could then directly see whether there is a “disk within the disk” that has much more mass than we could account for with the ordinary baryonic matter. Evidence of such a dark disk would allow better predictive modeling of the effects on comets and on the life of our planet.
Over the next several years, Randall said, the Gaia satellite will perform a precise survey of the position and velocity of as many as a billion stars, giving scientists far greater insights into the shape of the galaxy and into the potential presence of a disk of dark matter.
Source: Dark Matter as a Trigger for Periodic Comet Impacts, Lisa Randall and Matthew Reece,Phys. Rev. Lett. 112, 161301 (2014), Published April 21, 2014
The Daily Galaxy via news.harvard.edu and Daisuke Nagai, Department of Physics, Yale University and American Physical Society
Image credits: Solar Systems Milky Way Orbit with thanks to Chris Setter/Phil Plait; Top of Page image
Related articles
Though the black-hole hypothesis adds additional complexity to a number of already-thorny questions about the nature of the universe, Randall believes it will be important to understand if a portion — even a relatively small portion — of dark matter behaves in unexpected ways.
Though the exact nature of dark matter remains unknown, physicists have been able to infer its existence based on the gravitational effect it exerts on ordinary matter. Though dark matter is otherwise believed to be non-interacting, two Harvard physics professors have suggested that a hypothetical type of dark matter could form a disk of material that runs through the center of the galaxy.
“If you were to look at our world and assume there was only one type of particle, you’d be pretty wrong,” said Randall. “I think it’s definitely a worthwhile theory to explore, because even if this is only a small fraction of dark matter, there is six times more dark matter in the universe than ordinary matter. We care a lot about ordinary matter, and that’s precisely because it has interactions. So if there is a small portion of dark matter that has those interactions, that may be what we should pay attention to, perhaps even more so than other dark matter.”
The composite Hubble Space Telescope, Spitzer Space Telescope, and the Chandra X-ray Observatory image of the central region of our Milky Way galaxy above shows the center of the galaxy, located within the bright white region to the right of and just below the middle of the image. Like the downtown of a large city, the center of our galaxy is a crowded, active, and vibrant place. The supermassive black hole -- some four million times more massive than the Sun -- resides within the bright region in the lower right. The diffuse X-ray light comes from gas heated to millions of degrees by outflows from the supermassive black hole, winds from giant stars, and stellar explosions. This central region is the most energetic place in our galaxy.
If the solar system, as it orbited the center of the galaxy, were to move through that disk, they theorized that the gravitational effects from the dark matter might be enough to dislodge comets and other objects from what’s known as the Oort Cloud and send them hurtling toward Earth. The solar system's orbit through Milky Way shown below, though exaggerated vertically for clarity, bobs up and down every 64 million years due to the gravity of the galactic disk.
“Those objects are only weakly gravitationaly bound,” Randall said. “With enough of a trigger, it’s possible to dislodge objects from their current orbit. While some will go out of the solar system, others may come into the inner solar system, which increases the likelihood that they may hit the Earth.”
The model described by Randall and colleague Matthew Reece suggests that those oscillations occur approximately every 32-35 million years, a figure that is on par with evidence collected from impact craters suggesting that increases in meteor strikes occur over similar periods. Reece's research centers around connecting theoretical particle physics with new experimental results, building models that attempt to extend the Standard Model of particle physics in ways that address various puzzles arising in quantum field theory and cosmology.
The extinction of the dinosaurs, however, is just one theory that will have to be re-examined if Randall and Reece’s theory proves true.”
Our Sun orbits around the Galactic center, taking approximately 250 million years to make a complete revolution. However, this trajectory is not a perfect circle. The Solar System weaves up and down, crossing the plane of the Milky Way approximately every 32 million years, which coincides with the presumed periodicity of the impact variations. This bobbing motion, which extends about 250 light years above and below the plane, is determined by the concentration of gas and stars in the disk of our Galaxy.
This ordinary “baryonic” matter is concentrated within about 1000 light years of the plane. Because the density drops off in the vertical direction, there is a gravitational gradient, or tide, that may perturb the orbits of comets in the Oort cloud, causing some comets to fly into the inner Solar System and periodically raise the chances of collision with Earth. However, the problem with this idea is that the estimated galactic tide is too weak to cause many waves in the Oort cloud.
In their study, Randall and Reece focus on this second hypothesis and suggest that the galactic tide could be made stronger with a thin disk of dark matter. Dark disks are a possible outcome of dark matter physics, as the authors and their colleagues recently showed. Here, the researchers consider a specific model, in which our Galaxy hosts a dark disk with a thickness of 30 light years and a surface density of around 1 solar mass per square light year (the surface density of ordinary baryonic matter is roughly 5 times that, but it’s less concentrated near the plane).
Although one has to stretch the observational constraints to make room, their thin disk of dark matter is consistent with astronomical data on our Galaxy. Focusing their analysis on large (>20km) craters created in the last 250 million years, Randall and Reece argue that their dark disk scenario can produce the observed pattern in crater frequency with a fair amount of statistical uncertainty.
Randall and Reece’s dark disk model is not made of an ordinary type of dark matter. The most likely candidate of dark matter—known as weakly interacting massive particles (WIMPs)—is expected to form a spherical halo around the Milky Way, instead of being concentrated in the disk. This WIMP dark matter scenario has been remarkably successful in explaining the large-scale distribution of matter in the Universe.
But there is a long-standing problem on small-scales—the theory generally predicts overly dense cores in the centers of galaxies and clusters of galaxies, and it predicts a larger number of dwarf galaxy satellites around the Milky Way than are observed. While some of these problems could be resolved by better understanding the physics of baryonic matter (as it relates, for example, to star formation and gas dynamics), it remains unclear whether a baryonic solution can work in the smallest mass galaxies (with very little stars and gas) where discrepancies are observed.
Alternatively, this small-scale conflict could be evidence of more complex physics in the dark matter sector itself. One solution is to invoke strong electromagnetic-like interactions among dark matter particles, which could lead to the emission of “dark photons”. These self-interactions can redistribute momentum through elastic scattering, thereby altering the predicted distribution of dark matter in the innermost regions of galaxies and clusters of galaxies as well as the number of dwarf galaxies in the Milky Way.
Although self-interacting dark matter could resolve the tension between theory and observations at small-scales, large-scale measurements of galaxies and clusters of galaxies only allow a small fraction (less than 5%) of the dark matter to be self-interacting. Recently, Randall, Reece, and their collaborators showed that if a portion of the dark matter is self-interacting, then these particles will collapse into a dark galactic disk that overlaps with the ordinary baryonic disk .
So, did a thin disk of dark matter trigger extinction events like the one that snuffed out the dinosaurs? The evidence is still far from compelling. First, the periodicity in Earth’s cratering rate is not clearly established, because a patchy crater record makes it difficult to see a firm pattern. It is also unclear what role comets may have played in the mass extinctions. The prevailing view is that the Chicxulub crater, which has been linked to the dinosaur extinction 66 million years ago, was created by a giant asteroid, instead of a comet. Randall and Reece were careful in acknowledging at the outset that “statistical evidence is not overwhelming” and listing various limitations for using a patchy crater record. But the geological data is unlikely to improve in the near future, unfortunately.
On the other hand, advances in astronomical data are expected with the European Space Agency’s Gaia space mission, which was launched last year and is currently studying the Milky Way in unprecedented detail. Gaia will observe millions of stars and measure their precise distances and velocities. These measurements should enable astronomers to map out the surface-density of the dense galactic disk as a function of height. Close to the plane, astronomers could then directly see whether there is a “disk within the disk” that has much more mass than we could account for with the ordinary baryonic matter. Evidence of such a dark disk would allow better predictive modeling of the effects on comets and on the life of our planet.
Over the next several years, Randall said, the Gaia satellite will perform a precise survey of the position and velocity of as many as a billion stars, giving scientists far greater insights into the shape of the galaxy and into the potential presence of a disk of dark matter.
Source: Dark Matter as a Trigger for Periodic Comet Impacts, Lisa Randall and Matthew Reece,Phys. Rev. Lett. 112, 161301 (2014), Published April 21, 2014
The Daily Galaxy via news.harvard.edu and Daisuke Nagai, Department of Physics, Yale University and American Physical Society
Image credits: Solar Systems Milky Way Orbit with thanks to Chris Setter/Phil Plait; Top of Page image
Related articles
One way trip to Mars #MarsNone
One way trip to Mars #MarsNone:
We speak with Mars One candidate Josh Richards about his views on Mars, Mars One and if this project can ever get off the ground. You can find more information on Josh at themightyginge.com
In Space News:
* Return of the Dragon
* NASA’s Kepler Mission Announces the Largest Collection of Exoplanets Ever Discovered
* Antares rolls out to pad for tests
* New limit on RD-180 Engines
* NASA and Roscosmos discuss ISS suicide plunge requirements
* Starliner’s First Complete Hull Mated At Kennedy, Crew Flight Delayed to 2018
TMRO Live Shows are crowd funded. If you like this episode consider contributing to help us to continue to improve. Head over to http://www.patreon.com/tmro for information, goals and reward levels. Don’t forget to check out our SpacePod campaign as well over at http://www.patreon.com/spacepod
We speak with Mars One candidate Josh Richards about his views on Mars, Mars One and if this project can ever get off the ground. You can find more information on Josh at themightyginge.com
In Space News:
* Return of the Dragon
* NASA’s Kepler Mission Announces the Largest Collection of Exoplanets Ever Discovered
* Antares rolls out to pad for tests
* New limit on RD-180 Engines
* NASA and Roscosmos discuss ISS suicide plunge requirements
* Starliner’s First Complete Hull Mated At Kennedy, Crew Flight Delayed to 2018
TMRO Live Shows are crowd funded. If you like this episode consider contributing to help us to continue to improve. Head over to http://www.patreon.com/tmro for information, goals and reward levels. Don’t forget to check out our SpacePod campaign as well over at http://www.patreon.com/spacepod
Hubble Spies a Spiral Snowflake
Hubble Spies a Spiral Snowflake: Together with irregular galaxies, spiral galaxies make up approximately 60 percent of the galaxies in the local universe. However, despite their prevalence, each spiral galaxy is unique — like snowflakes, no two are alike. This is demonstrated by the striking face-on spiral galaxy NGC 6814.
| Original enclosures: |
Mars' teeny, weird, moons, and it's strange eclipses..
Mars' teeny, weird, moons, and it's strange eclipses..:
Now, thanks to the Mars rover Curiosity, a fourth kind has been seen: Martian. Mars has two moons - far smaller than our Moon, but also a lot closer to Mars than the Moon is to Earth. So, although Martian eclipses aren't as dramtic as Earth's they do happen - and the Curiosity rover caught one on camera. Take a look:
It's one of the first times such a thing has been seen from the surface of another planet. Compare it to a total eclipse on Earth...
...and some of the differences between Earth's Moon and Mars's moons are pretty obvious: Our Moon is round, because it's big enough for gravity to pull it into a ball, whereas Mars's moons are so tiny that their gravity is barely noticeable. Still, for all their tiny size, Phobos and Deimos are pretty interesting little worlds. They present a major mystery: They seem to be incredibly ancient captured asteroids, but they've somehow ended up on nearly perfectly circular equatorial orbits - very unlikey for a random capture.
The innermost Moon, Phobos, is being gradually pulled closer and closer to Mars, and in about fifty million reas Martian gravity will rip the teeny moon apart. That might be a long way off, but the cracks are literally already showing.
Phobos would also be a great way to get samples of the Martian surface back to Earth on the cheap: The little moon gets sprayed with Martian rock every time a major impact hits the red planet. That means there's a lot of Martian rock on it's surface, and it's weak gravity would make a return trip to Earth much easier than the return trip from Mars.
Russia tried to send a probe there a few years back, but it malfunctioned before it could break Earth orbit. Beyond getting a cheap Mars return, Phobos' own geological makeup is a bit of a mystery, and it has some baffling surface features, like the infamous Phobos monolith.
Deimos, the smaller and further out moon, is much less well explored than Phobos. From the martian surface it's barely bigger than Venus in the sky, so it doesn't eclipse the Sun in any meaningful way... but aving two Moons does meran Mars gets a kind of eclipse we don't get on Earth at all: One Moon eclipsing another, which has also been seen by Mars rovers:
We may or may not one day land see humans on Mars, and I know I'll never see these sights in person - but I like knowing that they're out there - even if the only audience they ever get is robots....
A solar eclipse is one of nature's wonders, and they come in dfferent types:
- Total, where the Moon completely covers the Sun:
- Annular, where the moon is a bit further away and the Sun peeks out from around the edge:
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| Courtesy of astrobob |
- Partial, where the Moon only covers part of the Sun:
 |
| Courtesy of astrobob |
Now, thanks to the Mars rover Curiosity, a fourth kind has been seen: Martian. Mars has two moons - far smaller than our Moon, but also a lot closer to Mars than the Moon is to Earth. So, although Martian eclipses aren't as dramtic as Earth's they do happen - and the Curiosity rover caught one on camera. Take a look:
Above: A solar eclipse on Mars. The moon responsible is the twenty km wide Phobos.
It's one of the first times such a thing has been seen from the surface of another planet. Compare it to a total eclipse on Earth...
Above: A solar clipse seen from Earth. Ours is bigger Mars, neeeer!
...and some of the differences between Earth's Moon and Mars's moons are pretty obvious: Our Moon is round, because it's big enough for gravity to pull it into a ball, whereas Mars's moons are so tiny that their gravity is barely noticeable. Still, for all their tiny size, Phobos and Deimos are pretty interesting little worlds. They present a major mystery: They seem to be incredibly ancient captured asteroids, but they've somehow ended up on nearly perfectly circular equatorial orbits - very unlikey for a random capture.
The innermost Moon, Phobos, is being gradually pulled closer and closer to Mars, and in about fifty million reas Martian gravity will rip the teeny moon apart. That might be a long way off, but the cracks are literally already showing.
Above: Phobos, a teeny world just 20 Km long, with a plethora of odd surface features. Courtesy of NASA/JPL.
Phobos would also be a great way to get samples of the Martian surface back to Earth on the cheap: The little moon gets sprayed with Martian rock every time a major impact hits the red planet. That means there's a lot of Martian rock on it's surface, and it's weak gravity would make a return trip to Earth much easier than the return trip from Mars.
Russia tried to send a probe there a few years back, but it malfunctioned before it could break Earth orbit. Beyond getting a cheap Mars return, Phobos' own geological makeup is a bit of a mystery, and it has some baffling surface features, like the infamous Phobos monolith.
Above: The Phobos monolith - almost certainly just a big rock, and not an alien marker. But I'm only going with 'almost', just in case the first probe to reach it finds the words 'Earthlings suck' engraved on it or something. Courtesy of NASA/JPL.
Deimos, the smaller and further out moon, is much less well explored than Phobos. From the martian surface it's barely bigger than Venus in the sky, so it doesn't eclipse the Sun in any meaningful way... but aving two Moons does meran Mars gets a kind of eclipse we don't get on Earth at all: One Moon eclipsing another, which has also been seen by Mars rovers:
 |
| Above: Phobos eclipsing Deimos, as seen by the Curiosity rover. Courtesy of NASA/JPL |
Scientists Use Advanced Astronomical Software to Date 2,500 Year-old Lyric Poem
Scientists Use Advanced Astronomical Software to Date 2,500 Year-old Lyric Poem:
Physicists and astronomers from The University of Texas at Arlington (UTA) have used advanced astronomical software to accurately date lyric poet Sappho’s “Midnight Poem,” which describes the night sky over Greece more than 2,500 years ago. The scientists described their research in the article “Seasonal dating of Sappho’s ‘Midnight Poem’ revisited,” published in the Journal of Astronomical History and Heritage. Martin George, former president of the International Planetarium Society, now at the National Astronomical Research Institute of Thailand, also participated in the work.
“This is an example of where the scientific community can make a contribution to knowledge described in important ancient texts," said Manfred Cuntz, physics professor and lead author of the study. “Estimations had been made for the timing of this poem in the past, but we were able to scientifically confirm the season that corresponds to her specific descriptions of the night sky in the year 570 B.C.”
Sappho’s “Midnight Poem” describes a star cluster known as the Pleiades having set at around midnight, when supposedly observed by her from the Greek island of Lesbos.
The moon has set
And the Pleiades;
It is midnight,
The time is going by,
And I sleep alone.
(Henry Thornton Wharton, 1887:68)
Cuntz and co-author and astronomer Levent Gurdemir, director of the Planetarium at UTA, used advanced software called Starry Night version 7.3, to identify the earliest date that the Pleiades would have set at midnight or earlier in local time in 570 B.C. The Planetarium system Digistar 5 also allows creating the night sky of ancient Greece for Sappho’s place and time.
“Use of Planetarium software permits us to simulate the night sky more accurately on any date, past or future, at any location,“ said Gurdemir. ”This is an example of how we are opening up the Planetarium to research into disciplines beyond astronomy, including geosciences, biology, chemistry, art, literature, architecture, history and even medicine."
The Starry Night software demonstrated that in 570 B.C., the Pleiades set at midnight on Jan. 25, which would be the earliest date that the poem could relate to. As the year progressed, the Pleiades set progressively earlier.
“The timing question is complex as at that time they did not have accurate mechanical clocks as we do, only perhaps water clocks” said Cuntz. “For that reason, we also identified the latest date on which the Pleiades would have been visible to Sappho from that location on different dates some time during the evening.”
The researchers also determined that the last date that the Pleiades would have been seen at the end of astronomical twilight – the moment when the sun’s altitude is -18 degrees and the sky is regarded as perfectly dark – was March 31.
“From there, we were able to accurately seasonally date this poem to mid-winter and early spring, scientifically confirming earlier estimations by other scholars,” Cuntz said.
Sappho was the leading female poet of her time and closely rivaled Homer. Her interest in astronomy was not restricted to the “Midnight Poem.” Other examples of her work make references to the sun, the moon, and planet Venus.
“Sappho should be considered an informal contributor to early Greek astronomy as well as to Greek society at large,” Cuntz added. “Not many ancient poets comment on astronomical observations as clearly as she does.”
Morteza Khaledi, dean of UTA’s College of Science, congratulated the researchers on their work, which forms part of UTA’s strategic focus on data-driven discovery within the Strategic Plan 2020: Bold Solutions | Global Impact.
“This research helps to break down the traditional silos between science and the liberal arts, by using high-precision technology to accurately date ancient poetry,” Khaledi said. ”It also demonstrates that the Planetarium’s reach can go way beyond astronomy into multiple fields of research."
Dr. Manfred Cuntz is a professor of physics at UTA and active researcher in solar and stellar astrophysics, as well as astrobiology. In recent years he has focused on extra-solar planets, including stellar habitable zones and orbital stability analyses. He received his Ph.D. from the University of Heidelberg, Germany, in 1988.
Levent Gurdemir received his master’s of science degree in physics from UTA and is the current director of the University’s Planetarium. UTA uses the facility for research, teaching and community outreach, serving large numbers of K-12 students and the public at this local facility.
Credit: uta.edu
Is Earth’s Magnetic Field Ready to Flip?
Is Earth’s Magnetic Field Ready to Flip?:
Although invisible to the eye, Earth's magnetic field plays a huge role in both keeping us safe from the ever-present solar and cosmic winds while making possible the opportunity to witness incredible displays of the northern lights. Like a giant bar magnet, if you could sprinkle iron filings around the entire Earth, the particles would align to reveal the nested arcs of our magnetic domain. The same field makes your compass needle align north to south.
We can picture our magnetic domain as a huge bubble, protecting us from cosmic radiation and electrically charged atomic particles that bombard Earth in solar winds. Satellites and instruments on the ground keep a constant watch over this bubble of magnetic energy surrounding our planet. For good reason: it's always changing.
The European Space Agency's Swarm satellite trio, launched at the end of 2013, has been busy measuring and untangling the different magnetic signals from Earth’s core, mantle, crust, oceans, ionosphere (upper atmosphere where the aurora occurs) and magnetosphere, the name given to the region of space dominated by Earth's magnetic field.
At this week’s Living Planet Symposium in Prague, Czech Republic, new results from the constellation of Swarm satellites show where our protective field is weakening and strengthening, and how fast these changes are taking place.
Based on results from ESA’s Swarm mission, the animation shows how the strength of Earth's magnetic field has changed between 1999 and mid-2016. Blue depicts where the field is weak and red shows regions where the field is strong. The field has weakened by about 3.5% at high latitudes over North America, while it has grown about 2% stronger over Asia. Watch also the migration of the north geomagnetic pole (white dot).
Between 1999 and May 2016 the changes are obvious. In the image above, blue depicts where the field is weak and red shows regions where it is strong. As well as recent data from the Swarm constellation, information from the CHAMP and Ørsted satellites were also used to create the map.
The animation shows changes in the rate at which Earth’s magnetic field strengthened and weakened between 2000 and 2015. Regions where changes in the field have slowed are shown in blue while red shows where changes sped up. For example, in 2015 changes in the field have slowed near South Africa but changes got faster over Asia. This map has been compiled using data from ESA’s Swarm mission.
The animation show that overall the field has weakened by about 3.5% at high latitudes over North America, while it has strengthened about 2% over Asia. The region where the field is at its weakest – the South Atlantic Anomaly – has moved steadily westward and weakened further by about 2%. Moreover, the magnetic north pole is also on the move east, towards Asia. Unlike the north and south geographic poles, the magnetic poles wander in an erratic way, obeying the movement of sloshing liquid iron and nickel in Earth's outer core. More on that in a minute.
The anomaly is a region over above South America, about 125-186 miles (200 - 300 kilometers) off the coast of Brazil, and extending over much of South America, where the inner Van Allen radiation belt dips just 125-500 miles (200 - 800 kilometers) above the Earth's surface. Satellites passing through the anomaly experience extra-strong doses of radiation from fast-moving, charged particles.
The magnetic field is thought to be produced largely by an ocean of molten, swirling liquid iron that makes up our planet’s outer core, 1,860 miles (3000 kilometers) under our feet. As the fluid churns inside the rotating Earth, it acts like a bicycle dynamo or steam turbine. Flowing material within the outer core generates electrical currents and a continuously changing electromagnetic field. It's thought that changes in our planet's magnetic field are related to the speed and direction of the flow of liquid iron and nickel in the outer core.
Chris Finlay, senior scientist at DTU Space in Denmark, said, “Swarm data are now enabling us to map detailed changes in Earth's magnetic field. Unexpectedly, we are finding rapid localized field changes that seem to be a result of accelerations of liquid metal flowing within the core.”
Further results are expected to yield a better understanding as why the field is weakening in some places, and globally. We know that over millions of years, magnetic poles can actually flip with north becoming south and south north. It's possible that the current speed up in the weakening of the global field might mean it's ready to flip.
Although there's no evidence previous flips affected life in a negative way, one thing's for sure. If you wake up one morning and find your compass needle points south instead of north, it's happened.
The post Is Earth’s Magnetic Field Ready to Flip? appeared first on Universe Today.
Although invisible to the eye, Earth's magnetic field plays a huge role in both keeping us safe from the ever-present solar and cosmic winds while making possible the opportunity to witness incredible displays of the northern lights. Like a giant bar magnet, if you could sprinkle iron filings around the entire Earth, the particles would align to reveal the nested arcs of our magnetic domain. The same field makes your compass needle align north to south.
We can picture our magnetic domain as a huge bubble, protecting us from cosmic radiation and electrically charged atomic particles that bombard Earth in solar winds. Satellites and instruments on the ground keep a constant watch over this bubble of magnetic energy surrounding our planet. For good reason: it's always changing.
The European Space Agency's Swarm satellite trio, launched at the end of 2013, has been busy measuring and untangling the different magnetic signals from Earth’s core, mantle, crust, oceans, ionosphere (upper atmosphere where the aurora occurs) and magnetosphere, the name given to the region of space dominated by Earth's magnetic field.
At this week’s Living Planet Symposium in Prague, Czech Republic, new results from the constellation of Swarm satellites show where our protective field is weakening and strengthening, and how fast these changes are taking place.
Based on results from ESA’s Swarm mission, the animation shows how the strength of Earth's magnetic field has changed between 1999 and mid-2016. Blue depicts where the field is weak and red shows regions where the field is strong. The field has weakened by about 3.5% at high latitudes over North America, while it has grown about 2% stronger over Asia. Watch also the migration of the north geomagnetic pole (white dot).
Between 1999 and May 2016 the changes are obvious. In the image above, blue depicts where the field is weak and red shows regions where it is strong. As well as recent data from the Swarm constellation, information from the CHAMP and Ørsted satellites were also used to create the map.
The animation shows changes in the rate at which Earth’s magnetic field strengthened and weakened between 2000 and 2015. Regions where changes in the field have slowed are shown in blue while red shows where changes sped up. For example, in 2015 changes in the field have slowed near South Africa but changes got faster over Asia. This map has been compiled using data from ESA’s Swarm mission.
The animation show that overall the field has weakened by about 3.5% at high latitudes over North America, while it has strengthened about 2% over Asia. The region where the field is at its weakest – the South Atlantic Anomaly – has moved steadily westward and weakened further by about 2%. Moreover, the magnetic north pole is also on the move east, towards Asia. Unlike the north and south geographic poles, the magnetic poles wander in an erratic way, obeying the movement of sloshing liquid iron and nickel in Earth's outer core. More on that in a minute.
The anomaly is a region over above South America, about 125-186 miles (200 - 300 kilometers) off the coast of Brazil, and extending over much of South America, where the inner Van Allen radiation belt dips just 125-500 miles (200 - 800 kilometers) above the Earth's surface. Satellites passing through the anomaly experience extra-strong doses of radiation from fast-moving, charged particles.
The magnetic field is thought to be produced largely by an ocean of molten, swirling liquid iron that makes up our planet’s outer core, 1,860 miles (3000 kilometers) under our feet. As the fluid churns inside the rotating Earth, it acts like a bicycle dynamo or steam turbine. Flowing material within the outer core generates electrical currents and a continuously changing electromagnetic field. It's thought that changes in our planet's magnetic field are related to the speed and direction of the flow of liquid iron and nickel in the outer core.
Chris Finlay, senior scientist at DTU Space in Denmark, said, “Swarm data are now enabling us to map detailed changes in Earth's magnetic field. Unexpectedly, we are finding rapid localized field changes that seem to be a result of accelerations of liquid metal flowing within the core.”
Further results are expected to yield a better understanding as why the field is weakening in some places, and globally. We know that over millions of years, magnetic poles can actually flip with north becoming south and south north. It's possible that the current speed up in the weakening of the global field might mean it's ready to flip.
Although there's no evidence previous flips affected life in a negative way, one thing's for sure. If you wake up one morning and find your compass needle points south instead of north, it's happened.
The post Is Earth’s Magnetic Field Ready to Flip? appeared first on Universe Today.
Rock Around the Comet Clock with Hubble
Rock Around the Comet Clock with Hubble:
Remember 252P/LINEAR? This comet appeared low in the morning sky last month and for a short time grew bright enough to see with the naked eye from a dark site. 252P swept closest to Earth on March 21, passing just 3.3 million miles away or about 14 times the distance between our planet and the moon. Since then, it's been gradually pulling away and fading though it remains bright enough to see in small telescope during late evening hours.
While amateurs set their clocks to catch the comet before dawn, astronomers using NASA's Hubble Space Telescope captured close-up photos of it two weeks after closest approach. The images reveal a narrow, well-defined jet of dust ejected by the comet's fragile, icy nucleus spinning like a water jet from a rotating lawn sprinkler. These observations also represent the closest celestial object Hubble has observed other than the moon.
Sunlight warms a comet's nucleus, vaporizing ices below the surface. In a confined space, the pressure of the vapor builds and builds until it finds a crack or weakness in the comet's crust and blasts into space like water from a whale's blowhole. Dust and other gases go along for the ride. Some of the dust drifts back down to coat the surface, some into space to be shaped by the pressure of sunlight into a dust tail.
You can still see 252P/LINEAR if you have a 4-inch or larger telescope. Right now it's a little brighter than magnitude +9 as it slowly arcs along the border of Ophiuchus and Hercules. With the moon getting brighter and brighter as it fills toward full, tonight and tomorrow night will be best for viewing the comet. After that you're best to wait till after the May 21st full moon when darkness returns to the evening sky. 252P will spend much of the next couple weeks near the 3rd magnitude star Kappa Ophiuchi, a convenient guidepost for aiming your telescope in the comet's direction.
While you probably won't see any jets in amateur telescopes, they're there all the same and helped created this comet's distinctive and large, fuzzy coma. Happy hunting!
The post Rock Around the Comet Clock with Hubble appeared first on Universe Today.
Remember 252P/LINEAR? This comet appeared low in the morning sky last month and for a short time grew bright enough to see with the naked eye from a dark site. 252P swept closest to Earth on March 21, passing just 3.3 million miles away or about 14 times the distance between our planet and the moon. Since then, it's been gradually pulling away and fading though it remains bright enough to see in small telescope during late evening hours.
While amateurs set their clocks to catch the comet before dawn, astronomers using NASA's Hubble Space Telescope captured close-up photos of it two weeks after closest approach. The images reveal a narrow, well-defined jet of dust ejected by the comet's fragile, icy nucleus spinning like a water jet from a rotating lawn sprinkler. These observations also represent the closest celestial object Hubble has observed other than the moon.
Sunlight warms a comet's nucleus, vaporizing ices below the surface. In a confined space, the pressure of the vapor builds and builds until it finds a crack or weakness in the comet's crust and blasts into space like water from a whale's blowhole. Dust and other gases go along for the ride. Some of the dust drifts back down to coat the surface, some into space to be shaped by the pressure of sunlight into a dust tail.
You can still see 252P/LINEAR if you have a 4-inch or larger telescope. Right now it's a little brighter than magnitude +9 as it slowly arcs along the border of Ophiuchus and Hercules. With the moon getting brighter and brighter as it fills toward full, tonight and tomorrow night will be best for viewing the comet. After that you're best to wait till after the May 21st full moon when darkness returns to the evening sky. 252P will spend much of the next couple weeks near the 3rd magnitude star Kappa Ophiuchi, a convenient guidepost for aiming your telescope in the comet's direction.
While you probably won't see any jets in amateur telescopes, they're there all the same and helped created this comet's distinctive and large, fuzzy coma. Happy hunting!
The post Rock Around the Comet Clock with Hubble appeared first on Universe Today.
A Transit of Mercury
A Transit of Mercury:
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2016 May 12
A Transit of Mercury
Image Credit & Copyright: Howard Brown-Greaves
Explanation: On May 9, the diminutive disk of Mercury spent about seven and a half hours crossing in front of the Sun as viewed from the general vicinity of Earth. It was the second of 14 transits of the Solar System's innermost planet in the 21st century. Captured from Fulham, London, England, planet Earth the tiny silhouette shares the enormous solar disk with prominences, filaments, and active regions in this sharp image. But Mercury's round disk (left of center) appears to be the only dark spot, despite the planet-sized sunspots scattered across the Sun. Made with an H-alpha filter that narrowly transmits the red light from hydrogen atoms, the image emphasizes the chromosphere, stretching above the photosphere or normally visible solar surface. In H-alpha pictures of the chromosphere, normally dark sunspot regions are dominated by bright splotches called plages.
Tomorrow's picture: ToMISS
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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
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NASA Web Privacy Policy and Important Notices
A service of: ASD at NASA / GSFC
& Michigan Tech. U.
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2016 May 12
A Transit of Mercury
Image Credit & Copyright: Howard Brown-Greaves
Explanation: On May 9, the diminutive disk of Mercury spent about seven and a half hours crossing in front of the Sun as viewed from the general vicinity of Earth. It was the second of 14 transits of the Solar System's innermost planet in the 21st century. Captured from Fulham, London, England, planet Earth the tiny silhouette shares the enormous solar disk with prominences, filaments, and active regions in this sharp image. But Mercury's round disk (left of center) appears to be the only dark spot, despite the planet-sized sunspots scattered across the Sun. Made with an H-alpha filter that narrowly transmits the red light from hydrogen atoms, the image emphasizes the chromosphere, stretching above the photosphere or normally visible solar surface. In H-alpha pictures of the chromosphere, normally dark sunspot regions are dominated by bright splotches called plages.
Tomorrow's picture: ToMISS
< | Archive | Submissions | Search | Calendar | RSS | Education | About APOD | Discuss | >
Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
NASA Official: Phillip Newman Specific rights apply.
NASA Web Privacy Policy and Important Notices
A service of: ASD at NASA / GSFC
& Michigan Tech. U.
ISS and Mercury Too
ISS and Mercury Too:
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2016 May 13
ISS and Mercury Too
Image Credit & Copyright: Thierry Legault
Explanation: Transits of Mercury are relatively rare. Monday's leisurely 7.5 hour long event was only the 2nd of 14 Mercury transits in the 21st century. If you're willing to travel, transits of the International Space Station can be more frequent though, and much quicker. This sharp video frame composite was taken from a well-chosen location in Philadelphia, USA. It follows the space station, moving from upper right to lower left, as it crossed the Sun's disk in 0.6 seconds. Mercury too is included as the small, round, almost stationary silhouette just below center. In apparent size, the International Space Station looms larger from low Earth orbit, about 450 kilometers from Philadelphia. Mercury was about 84 million kilometers away. (Editor's note: The stunning video includes another double transit, Mercury and a Pilatus PC12 aircraft. Even quicker than the ISS to cross the Sun, the aircraft was about 1 kilometer away.)
Tomorrow's picture: launch and landing
< | Archive | Submissions | Search | Calendar | RSS | Education | About APOD | Discuss | >
Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
NASA Official: Phillip Newman Specific rights apply.
NASA Web Privacy Policy and Important Notices
A service of: ASD at NASA / GSFC
& Michigan Tech. U.
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2016 May 13
ISS and Mercury Too
Image Credit & Copyright: Thierry Legault
Explanation: Transits of Mercury are relatively rare. Monday's leisurely 7.5 hour long event was only the 2nd of 14 Mercury transits in the 21st century. If you're willing to travel, transits of the International Space Station can be more frequent though, and much quicker. This sharp video frame composite was taken from a well-chosen location in Philadelphia, USA. It follows the space station, moving from upper right to lower left, as it crossed the Sun's disk in 0.6 seconds. Mercury too is included as the small, round, almost stationary silhouette just below center. In apparent size, the International Space Station looms larger from low Earth orbit, about 450 kilometers from Philadelphia. Mercury was about 84 million kilometers away. (Editor's note: The stunning video includes another double transit, Mercury and a Pilatus PC12 aircraft. Even quicker than the ISS to cross the Sun, the aircraft was about 1 kilometer away.)
Tomorrow's picture: launch and landing
< | Archive | Submissions | Search | Calendar | RSS | Education | About APOD | Discuss | >
Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
NASA Official: Phillip Newman Specific rights apply.
NASA Web Privacy Policy and Important Notices
A service of: ASD at NASA / GSFC
& Michigan Tech. U.
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