Magnetars Trip The Light Fantastic!
Come, knit hands, and beat the ground, In a light fantastic round.
--Comus, John Milton (1637).
Over a thousand years ago, the record of a mysterious occurrence was hidden like a buried treasure in the tattle-tale tree-rings of a cedar forest in Japan.
One study suggests that a solar flare was the source of this mysterious event, but more recently a team of researchers has put the blame on a gamma-ray burst (GRB)--a monumental blast that occurs in Space.
The very old cedar trees, growing in this ancient Japanese forest, preserve a record of this strange event that occurred as early as 774 A.
D.
This weird record reveals itself as a dramatic rise in the quantity of radioactive carbon-14 and beryllium-10 that shows up in the cedar-rings.
This sort of thing can happen as a result of particles plummeting down to Earth from Space.
According to astronomers Dr.
Valeri Hambaryan and Dr.
Ralph Neuhauser of the Astrophysics Institute of the University of Jena in Germany, the most likely cause was a GRB that blew up at a distance of 3,000 to 12,000 light-years from Earth.
"If the gamma-ray burst had been much closer to Earth it would have caused significant harm to the biosphere.
But even thousands of light-years away, a similar event today could cause havoc with the sensitive electronic systems that advanced societies have come to depend on," Dr.
Neuhauser said in a January 21, 2013 statement to Space.
com.
GRBs are enormous explosions that frolic through the Universe in a fantastic dance.
The phenomenon was discovered back in 1967, when the VELA satellites were first launched.
The purpose of the VELA satellites was not to search for new and weird natural occurrences in Space--they were designed to enforce the Nuclear Test Ban Treaty by keeping a careful look-out for secret nuclear blasts from their vantage point in orbit around the Earth.
But, in a nice little piece of "scientific serendipity"--serendipity means you are looking for one thing, but find something else--the VELA satellites spotted the first GRB, even though their spying eye in the sky was looking for something else--something much more sinister.
At first, astronomers could not tell if the GRBs were coming from the Solar System--or beyond.
The very first paper on the discovery of GRBs came in 1973.
Magnetars are one of several possible sources for these monumental blasts that dazzle the sky in immense numbers.
Magnetars are the strange, super-dense relics of dead, massive stars that went supernova--and they generate the most powerful magnetic fields in the Cosmos! A magnetar is a type of neutron star that possesses an extremely strong magnetic field.
Neutron stars, in general, are massive stellar-corpses--the dense remnants of stars whose cores have attained 1.
4 times the mass of our Sun.
Such massive stars die in tremendous supernova blasts that leave the core of the now-dead star (the neutron star) behind as a relic testimony of their former existence.
Neutron stars have been studied by astronomers for decades.
The common, garden-variety of this bizarre entity forms when a main-sequence, massive star has finished devouring its supply of hydrogen fuel, and has none left to burn in its core.
All main-sequence stars, regardless of their masses, are unambiguously "living stars", that are still happily burning their rich supply of hydrogen into heavier elements by way of a process termed stellar nucleosynthesis.
A main-sequence star is able to keep itself bouncy against the force of gravity by exerting pressure derived from its hydrogen-burning eating habits.
Stars of all masses keep themselves bouncy against the force of gravity through the process of nuclear fusion going on within them.
They dwell in a delicate equilibrium between the immense quantity of energy output of the fusion derived from stellar nucleosynthesis--which is attempting to force everything out--and the immense power of their gravity, which attempts to pull everything in! Stars of all masses maintain this delicate balance as long as they are on the main-sequence--until they finally run out of hydrogen fuel, collapse, and then either experience a deadly,but relatively peaceful, burn-out, or go supernova.
Our own Sun is a small, main-sequence star that has "lived" out approximately half of its life.
It is about 4.
56 billion years old, and in about 5 billion years it will run out of most of its hydrogen fuel.
Our Sun, being a small star, will first swell into an enormous Red Giant star, and devour Mercury, Venus, and possibly Earth, before it gently puffs off its outer layers and leaves behind a White Dwarf as its corpse--its former core.
Stars of our Sun's relatively puny size do not go supernova like the big guys.
White Dwarfs are very dense, but not as dense as neutron stars, that are the sad remains of much more massive stars.
A star that is much more massive than our Sun, and is going out of the main-sequence because it has devoured its hydrogen fuel, suffers an avalanche of horrific events which ultimately result in its outer envelope exploding as a dazzling supernova, leaving behind the very dense neutron star.
During this catastrophic sequence of events, the magnetic field of the doomed star increases due to a principle in physics termed flux conservation.
Basically, this means that the collapse of the star-that-was into a considerably more compact, dense area, causes the magnetic field strength to become more powerful so that a constant field strength can be maintained far away from the star.
Magnetars, however, form a bit differently from other neutron stars.
The specific mix of temperature, spin, and magnetic field strength cook up a strange stew that alters some of the expiring star's heat and rotational energy into additional magnetic field energy.
However, it may be a bit more complicated than this--some recent data indicates that the formation of a magnetar is not quite this simple and straightforward.
Magnetars may form in a more exotic way than "normal" neutron stars.
Perhaps interactions with companion stars add an additional ingredient to the weird stew.
Flash Bulbs Of The Cosmos Extremely energetic and mysterious--as well as exquisitely brief--gamma-ray bursts have been called the "flash bulbs of the Cosmos," because the most brilliant of their kind can actually outshine a million galaxies! These bursts then fade and vanish within minutes or hours.
Only extremely high-energy and localized occurrences could give rise to such brilliant and brief flashes.
Astronomers think that the majority of GRBs pop-off due to the merger or collapse of stars to form black holes.
When the most massive stars in the Universe die, they form stellar-mass black holes, rather than neutron stars.
This is because their extremely heavy mass cannot withstand the pull of gravity at all.
The brief timescales and great variety observed among GRBs has made it difficult for astronomers to calculate the physical processes that give rise to them.
However, observations derived from NASA's Fermi Gamma-ray Space Telescope, launched in 2008, and the Swift satellite, launched in 2004, have enabled astronomers to scrutinize the true nature of these mysterious bursts of fantastic light.
Findings derived from these missions point to the formation of magnetars as a culprit.
These highly magnetized and rapidly spinning objects are now thought to be at the heart of GRB formation.
A GRB consists of an initial high-energy gamma-ray and X-ray signal, termed prompt emission.
The prompt emission is then followed by an afterglow of X-rays.
"Long" GRBs last for more than two seconds, and they are believed to be set-off when a very massive star has finished devouring its fuel and collapses.
Jets of star-stuff rambling out from the collapsed star-that-was generate flashlight beams of radiation, which can sometimes be seen from our planet..
The evidence that points the finger at magnetars is derived from the prompt emission.
This usually fades very rapidly.
However, back in 2007, Dr.
Paul O'Brien of the University of Leicester in the UK, and his team, reported on a GRB spotted by Swift in which the X-ray emission remained steady for hundreds of seconds before it began to dim.
This type of signal had been predicted by theorists as the sign of a magnetar that forms within the GRB conflagration and, for a brief time, spins so wildly that it can resist collapsing into a black hole.
One example was insufficient evidence to convict magnetars as an elusive culprit behind GRBs.
However, many more similar observations followed suit.
Dr.
Brian Metzger of Princeton University in New Jersey, who is working on the magnetar scenario, explained in the November 3, 2010 Nature.
com that the emission from the formation of a black hole would be expected to flicker because the amount of material, falling in from the collapsed star, varies.
By contrast, the emission from a magnetar is caused by material being hurled out from its surface by a wild rotation rate that can be as much as one thousand whirls per second, collimated by a magnetic field that can reach an unbelievable one quadrillion times that of Earth.
Both the magnetic field and the wild rotation rate are expected to stay constant for several hundred seconds before the magnetar stops its wild pirouette, and finally meets its final doom as it collapses to form a stellar-mass black hole.
However, GRBs may be born as the result of some other events, as well.
Dr.
Chryssa Kouveliotou, an astrophysicist at Marshall Space Flight Center in Huntsville, Alabama, is an expert on GRBs and their relation to magnetars.
When Dr.
Kouveliotou was asked in a June 2009 interview published in Science Watch about what she had learned about GRBs during her investigations, she answered: "When we look at these high-energy transients, we can expect anything.
There are a lot of different objects out there and there are probably phenomena we've yet to identify.
No single model can describe the whole thing.
"
--Comus, John Milton (1637).
Over a thousand years ago, the record of a mysterious occurrence was hidden like a buried treasure in the tattle-tale tree-rings of a cedar forest in Japan.
One study suggests that a solar flare was the source of this mysterious event, but more recently a team of researchers has put the blame on a gamma-ray burst (GRB)--a monumental blast that occurs in Space.
The very old cedar trees, growing in this ancient Japanese forest, preserve a record of this strange event that occurred as early as 774 A.
D.
This weird record reveals itself as a dramatic rise in the quantity of radioactive carbon-14 and beryllium-10 that shows up in the cedar-rings.
This sort of thing can happen as a result of particles plummeting down to Earth from Space.
According to astronomers Dr.
Valeri Hambaryan and Dr.
Ralph Neuhauser of the Astrophysics Institute of the University of Jena in Germany, the most likely cause was a GRB that blew up at a distance of 3,000 to 12,000 light-years from Earth.
"If the gamma-ray burst had been much closer to Earth it would have caused significant harm to the biosphere.
But even thousands of light-years away, a similar event today could cause havoc with the sensitive electronic systems that advanced societies have come to depend on," Dr.
Neuhauser said in a January 21, 2013 statement to Space.
com.
GRBs are enormous explosions that frolic through the Universe in a fantastic dance.
The phenomenon was discovered back in 1967, when the VELA satellites were first launched.
The purpose of the VELA satellites was not to search for new and weird natural occurrences in Space--they were designed to enforce the Nuclear Test Ban Treaty by keeping a careful look-out for secret nuclear blasts from their vantage point in orbit around the Earth.
But, in a nice little piece of "scientific serendipity"--serendipity means you are looking for one thing, but find something else--the VELA satellites spotted the first GRB, even though their spying eye in the sky was looking for something else--something much more sinister.
At first, astronomers could not tell if the GRBs were coming from the Solar System--or beyond.
The very first paper on the discovery of GRBs came in 1973.
Magnetars are one of several possible sources for these monumental blasts that dazzle the sky in immense numbers.
Magnetars are the strange, super-dense relics of dead, massive stars that went supernova--and they generate the most powerful magnetic fields in the Cosmos! A magnetar is a type of neutron star that possesses an extremely strong magnetic field.
Neutron stars, in general, are massive stellar-corpses--the dense remnants of stars whose cores have attained 1.
4 times the mass of our Sun.
Such massive stars die in tremendous supernova blasts that leave the core of the now-dead star (the neutron star) behind as a relic testimony of their former existence.
Neutron stars have been studied by astronomers for decades.
The common, garden-variety of this bizarre entity forms when a main-sequence, massive star has finished devouring its supply of hydrogen fuel, and has none left to burn in its core.
All main-sequence stars, regardless of their masses, are unambiguously "living stars", that are still happily burning their rich supply of hydrogen into heavier elements by way of a process termed stellar nucleosynthesis.
A main-sequence star is able to keep itself bouncy against the force of gravity by exerting pressure derived from its hydrogen-burning eating habits.
Stars of all masses keep themselves bouncy against the force of gravity through the process of nuclear fusion going on within them.
They dwell in a delicate equilibrium between the immense quantity of energy output of the fusion derived from stellar nucleosynthesis--which is attempting to force everything out--and the immense power of their gravity, which attempts to pull everything in! Stars of all masses maintain this delicate balance as long as they are on the main-sequence--until they finally run out of hydrogen fuel, collapse, and then either experience a deadly,but relatively peaceful, burn-out, or go supernova.
Our own Sun is a small, main-sequence star that has "lived" out approximately half of its life.
It is about 4.
56 billion years old, and in about 5 billion years it will run out of most of its hydrogen fuel.
Our Sun, being a small star, will first swell into an enormous Red Giant star, and devour Mercury, Venus, and possibly Earth, before it gently puffs off its outer layers and leaves behind a White Dwarf as its corpse--its former core.
Stars of our Sun's relatively puny size do not go supernova like the big guys.
White Dwarfs are very dense, but not as dense as neutron stars, that are the sad remains of much more massive stars.
A star that is much more massive than our Sun, and is going out of the main-sequence because it has devoured its hydrogen fuel, suffers an avalanche of horrific events which ultimately result in its outer envelope exploding as a dazzling supernova, leaving behind the very dense neutron star.
During this catastrophic sequence of events, the magnetic field of the doomed star increases due to a principle in physics termed flux conservation.
Basically, this means that the collapse of the star-that-was into a considerably more compact, dense area, causes the magnetic field strength to become more powerful so that a constant field strength can be maintained far away from the star.
Magnetars, however, form a bit differently from other neutron stars.
The specific mix of temperature, spin, and magnetic field strength cook up a strange stew that alters some of the expiring star's heat and rotational energy into additional magnetic field energy.
However, it may be a bit more complicated than this--some recent data indicates that the formation of a magnetar is not quite this simple and straightforward.
Magnetars may form in a more exotic way than "normal" neutron stars.
Perhaps interactions with companion stars add an additional ingredient to the weird stew.
Flash Bulbs Of The Cosmos Extremely energetic and mysterious--as well as exquisitely brief--gamma-ray bursts have been called the "flash bulbs of the Cosmos," because the most brilliant of their kind can actually outshine a million galaxies! These bursts then fade and vanish within minutes or hours.
Only extremely high-energy and localized occurrences could give rise to such brilliant and brief flashes.
Astronomers think that the majority of GRBs pop-off due to the merger or collapse of stars to form black holes.
When the most massive stars in the Universe die, they form stellar-mass black holes, rather than neutron stars.
This is because their extremely heavy mass cannot withstand the pull of gravity at all.
The brief timescales and great variety observed among GRBs has made it difficult for astronomers to calculate the physical processes that give rise to them.
However, observations derived from NASA's Fermi Gamma-ray Space Telescope, launched in 2008, and the Swift satellite, launched in 2004, have enabled astronomers to scrutinize the true nature of these mysterious bursts of fantastic light.
Findings derived from these missions point to the formation of magnetars as a culprit.
These highly magnetized and rapidly spinning objects are now thought to be at the heart of GRB formation.
A GRB consists of an initial high-energy gamma-ray and X-ray signal, termed prompt emission.
The prompt emission is then followed by an afterglow of X-rays.
"Long" GRBs last for more than two seconds, and they are believed to be set-off when a very massive star has finished devouring its fuel and collapses.
Jets of star-stuff rambling out from the collapsed star-that-was generate flashlight beams of radiation, which can sometimes be seen from our planet..
The evidence that points the finger at magnetars is derived from the prompt emission.
This usually fades very rapidly.
However, back in 2007, Dr.
Paul O'Brien of the University of Leicester in the UK, and his team, reported on a GRB spotted by Swift in which the X-ray emission remained steady for hundreds of seconds before it began to dim.
This type of signal had been predicted by theorists as the sign of a magnetar that forms within the GRB conflagration and, for a brief time, spins so wildly that it can resist collapsing into a black hole.
One example was insufficient evidence to convict magnetars as an elusive culprit behind GRBs.
However, many more similar observations followed suit.
Dr.
Brian Metzger of Princeton University in New Jersey, who is working on the magnetar scenario, explained in the November 3, 2010 Nature.
com that the emission from the formation of a black hole would be expected to flicker because the amount of material, falling in from the collapsed star, varies.
By contrast, the emission from a magnetar is caused by material being hurled out from its surface by a wild rotation rate that can be as much as one thousand whirls per second, collimated by a magnetic field that can reach an unbelievable one quadrillion times that of Earth.
Both the magnetic field and the wild rotation rate are expected to stay constant for several hundred seconds before the magnetar stops its wild pirouette, and finally meets its final doom as it collapses to form a stellar-mass black hole.
However, GRBs may be born as the result of some other events, as well.
Dr.
Chryssa Kouveliotou, an astrophysicist at Marshall Space Flight Center in Huntsville, Alabama, is an expert on GRBs and their relation to magnetars.
When Dr.
Kouveliotou was asked in a June 2009 interview published in Science Watch about what she had learned about GRBs during her investigations, she answered: "When we look at these high-energy transients, we can expect anything.
There are a lot of different objects out there and there are probably phenomena we've yet to identify.
No single model can describe the whole thing.
"