JUST IN: New NASA Mission Explores ‘Cosmic Rain’

A new experiment set for an Aug. 14 launch to the International Space Station will provide an unprecedented look at a rain of particles from deep space, called cosmic rays, that constantly showers our planet. The Cosmic Ray Energetics And Mass mission destined for the International Space Station (ISS-CREAM) is designed to measure the highest-energy particles of any detector yet flown in space.

Cosmic Ray Energetics And Mass

The ISS-CREAM experiment will be delivered to the space station as part of the 12th SpaceX commercial resupply service mission. Once there, ISS-CREAM will be moved to the Exposed Facility platform extending from Kibo, the Japanese Experiment Module. “High-energy cosmic rays carry a great deal of information about our interstellar neighborhood and our galaxy, but we haven’t been able to read these messages very clearly,” said co-investigator John Mitchell at Goddard. “ISS-CREAM represents one significant step in this direction.”

At energies above about 1 billion electron volts, most cosmic rays come to us from beyond our solar system. Various lines of evidence, including observations from NASA’s Fermi Gamma-ray Space Telescope, support the idea that shock waves from the expanding debris of stars that exploded as supernovas accelerate cosmic rays up to energies of 1,000 trillion electron volts (PeV). That’s 10 million times the energy of medical proton beams used to treat cancer. ISS-CREAM data will allow scientists to examine how sources other than supernova remnants contribute to the population of cosmic rays.

Protons are the most common cosmic ray particles, but electrons, helium nuclei and the nuclei of heavier elements make up a small percentage. All are direct samples of matter from interstellar space. But because the particles are electrically charged, they interact with galactic magnetic fields, causing them to wander in their journey to Earth. This scrambles their paths and makes it impossible to trace cosmic ray particles back to their sources.

JUST IN: New Study Affirms Mantle Plumes Source of Heated Surface

As outlined in my article Cosmic Ray Penetration More Prevalent Than Realized, a new study published July 27th in the journal ‘Science’, identifies mantle plumes – viscous molten rock coming from the Earth’s outer core – as the source heated surfaces which include volcanoes and ocean bottom fissures.

For more than 2 decades, scientists have pondered the nature of these mysterious regions, sometimes called Ultra Low Velocity Zones (ULVZs). Researchers examining one below Iceland at a depth of nearly 3000 kilometers, now have their answer. This discovery shows molten plumes that shoot out as roots of hot rock that slowly rise through the mantle to feeding a system of volcanoes and fissures.

Earth scientists have long suspected that upwellings in these mantle convection currents would manifest themselves as the plumes responsible for Earth’s volcanic hot spots. Now we have started to see them with sophisticated computer models that use the waves from large earthquakes to create CT scan–like tomographic pictures of Earth’s interior; says Barbara Romanowicz, a seismologist at the University of California, Berkeley, and led author of the study.

Thank you for your continued support. We’re now about half way there.

Coming Next: History of War and Quakes

New Study Indicates Many Scientists Clueless to Cause of Climate Cycles

Now, two first-of-their-kind studies provide new insight into the deep history of the Greenland Ice Sheet, looking back millions of years farther than previous techniques allowed. However, the two studies present some strongly contrasting evidence about how Greenland‘s ice sheet may have responded to past climate change – bringing new urgency to the need to understand if and how the giant ice sheet might dramatically accelerate its melt-off in the near future.

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The two new studies were published in the journal Nature on December 8, including one led by University of Vermont geologist Paul Bierman. The other led by Joerg Schaefer of Lamont-Doherty Earth Observatory and Columbia University.

Bierman and four colleagues – from UVM, Boston College, Lawrence Livermore Laboratory, and Imperial College London – studied deep cores of ocean-bottom mud containing bits of bedrock that eroded off of the east side of Greenland. Their results show that East Greenland has been actively scoured by glacial ice for much of the last 7.5 million years – and indicate that the ice sheet on this eastern flank of the island has not completely melted for long, if at all, in the past several million years. This result is consistent with existing computer models. Since the data the team collected only came from samples off the east side of Greenland, their results do not provide a definitive picture of the Greenland ice sheet.

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The other study in Nature – led by Joerg Schaefer of Lamont-Doherty Earth Observatory and Columbia University, and colleagues – looked at a small sample of bedrock from one location beneath the middle of the existing ice sheet and came to what appears to be a different conclusion: Greenland was nearly ice-free for at least 280,000 years during the middle Pleistocene – about 1.1 million years ago. This possibility is in contrast to existing computer models.

“These results appear to be contradictory” UVM’s Bierman says. He notes that both studies have “some blurriness,” he says, in what they are able to resolve about short-term changes and the size of the ancient ice sheet. “Their study is a bit like one needle in a haystack,” he says, “and ours is like having the whole haystack, but not being sure how big it is.”

Both Studies Analyze Cosmic Ray Bombardment in Bedrock

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Both teams of scientists used, “a powerful new tool for Earth scientists,” says Dylan Rood, a scientist at Imperial College London and a co-author on the Bierman-led study: isotopes within grains of quartz, produced when bedrock is bombarded by cosmic rays from space. The isotopes come into being when rock is at or near Earth’s surface – but not when it’s buried under an overlying ice sheet. By looking at the ratio of two of these cosmic-ray-made elements – aluminum-26 and beryllium-10 caught in crystals of quartz, and measured in an accelerator mass spectrometer – the scientists were able to calculate how long the rocks in their samples had been exposed to the sky versus covered by ice.

UPDATE: New Study Suggest Cosmic Ray Origin Now Include ‘Dark Matter’

Observing the constant rain of cosmic rays hitting Earth can provide information on the “magnetic weather” in other parts of the Galaxy. A new high-precision measurement of two cosmic-ray elements, boron and carbon, supports a specific model of the magnetic turbulence that deflects cosmic rays on their journey through the Galaxy.

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The data, which come from the Alpha Magnetic Spectrometer (AMS) aboard the International Space Station, appear to rule out alternative models for cosmic-ray propagation. By ruling out these models, the AMS results support the alternative explanation – a new primary cosmic ray source that emits positrons. Candidates include pulsars and dark matter, but a lot of mystery still surrounds the unexplained positron data.

The majority of cosmic rays are particles or nuclei produced in supernovae or other astrophysical sources. However, as these so-called primary cosmic rays travel through the Galaxy to Earth, they collide with gas atoms in the interstellar medium. The collisions produce a secondary class of cosmic rays with masses and energies that differ from primary cosmic rays.

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To investigate the relationship of the two classes, astrophysicists often look at the ratio of the number of detection’s of two nuclei, such as boron and carbon. For the most part, carbon cosmic rays have a primary origin, whereas boron is almost exclusively created in secondary processes. A relatively high boron-to-carbon (B/C) ratio in a certain energy range implies that the relevant cosmic rays are traversing a lot of gas before reaching us. “The B/C ratio tells you how cosmic rays propagate through space,” says AMS principal investigator Samuel Ting of MIT.

Previous measurements of the B/C ratio have had large errors of 15% or more, especially at high energy, mainly because of the brief data collection time available for balloon-based detectors. But the AMS has been operating on the Space Station for five years, and over this time it has collected more than 80 billion cosmic rays. The AMS detectors measure the charges of these cosmic rays, allowing the elements to be identified. The collaboration has detected over ten million carbon and boron nuclei, with energies per nucleon ranging from a few hundred MeV up to a few TeV.

The B/C ratio decreases with energy because higher-energy cosmic rays tend to take a more direct path to us (and therefore experience fewer collisions producing boron). By contrast, lower-energy cosmic rays are diverted more strongly by magnetic fields, so they bounce around like pinballs among magnetic turbulence regions in the Galaxy. Several theories have been proposed to describe the size and spacing of these turbulent regions, and these theories lead to predictions for the energy dependence of the B/C ratio. However, previous B/C observations have not been precise enough to favor one theory over another. The AMS data show very clearly that the B/C ratio is proportional to the energy raised to the -1/3 power. This result matches a prediction based on a theory of magnetohydrodynamics developed in 1941 by the Russian mathematician Andrey Kolmogorov.

These results conflict with models that predict that the B/C ratio should exhibit some more complex energy dependence, such as kinks in the B/C spectrum at specific energies. Theorists proposed these models to explain anomalous observations – by AMS and other experiments – that showed an increase in the number of positrons (anti-electrons) reaching Earth relative to electrons at high energy. The idea was that these “excess” positrons are – like boron – produced in collisions between cosmic rays and interstellar gas. But such a scenario would require that cosmic rays encounter additional scattering sites, not just magnetically turbulent regions. By ruling out these models, the AMS results support the alternative explanation – a new primary cosmic ray source that emits positrons. Candidates include pulsars and dark matter, but a lot of mystery still surrounds the unexplained positron data.

Igor Moskalenko from Stanford University is very surprised at the close match between the data and the Kolmogorov model. He expected that the ratio would deviate from a single power law in a way that might provide clues to the origin of the excess positrons. “This is a dramatic result that should lead to much better understanding of interstellar magnetohydrodynamic turbulence and propagation of cosmic rays,” he says. “On the other hand, it is very much unexpected in that it makes recent discoveries in astrophysics of cosmic rays even more puzzling.”

More Hints of Exotic Cosmic-Ray Origin

Observing the constant rain of cosmic rays hitting Earth can provide information on the “magnetic weather” in other parts of the Galaxy. A new high-precision measurement of two cosmic-ray elements, boron and carbon, supports a specific model of the magnetic turbulence that deflects cosmic rays on their journey through the Galaxy.

dark-matter3-science-of-cycles

The data, which come from the Alpha Magnetic Spectrometer (AMS) aboard the International Space Station, appear to rule out alternative models for cosmic-ray propagation. By ruling out these models, the AMS results support the alternative explanation – a new primary cosmic ray source that emits positrons. Candidates include pulsars and dark matter, but a lot of mystery still surrounds the unexplained positron data.

The majority of cosmic rays are particles or nuclei produced in supernovae or other astrophysical sources. However, as these so-called primary cosmic rays travel through the Galaxy to Earth, they collide with gas atoms in the interstellar medium. The collisions produce a secondary class of cosmic rays with masses and energies that differ from primary cosmic rays.

interstellar-collision-science_of_cycles

To investigate the relationship of the two classes, astrophysicists often look at the ratio of the number of detection’s of two nuclei, such as boron and carbon. For the most part, carbon cosmic rays have a primary origin, whereas boron is almost exclusively created in secondary processes. A relatively high boron-to-carbon (B/C) ratio in a certain energy range implies that the relevant cosmic rays are traversing a lot of gas before reaching us. “The B/C ratio tells you how cosmic rays propagate through space,” says AMS principal investigator Samuel Ting of MIT.

Previous measurements of the B/C ratio have had large errors of 15% or more, especially at high energy, mainly because of the brief data collection time available for balloon-based detectors. But the AMS has been operating on the Space Station for five years, and over this time it has collected more than 80 billion cosmic rays. The AMS detectors measure the charges of these cosmic rays, allowing the elements to be identified. The collaboration has detected over ten million carbon and boron nuclei, with energies per nucleon ranging from a few hundred MeV up to a few TeV.

The B/C ratio decreases with energy because higher-energy cosmic rays tend to take a more direct path to us (and therefore experience fewer collisions producing boron). By contrast, lower-energy cosmic rays are diverted more strongly by magnetic fields, so they bounce around like pinballs among magnetic turbulence regions in the Galaxy. Several theories have been proposed to describe the size and spacing of these turbulent regions, and these theories lead to predictions for the energy dependence of the B/C ratio. However, previous B/C observations have not been precise enough to favor one theory over another. The AMS data show very clearly that the B/C ratio is proportional to the energy raised to the -1/3 power. This result matches a prediction based on a theory of magnetohydrodynamics developed in 1941 by the Russian mathematician Andrey Kolmogorov.

These results conflict with models that predict that the B/C ratio should exhibit some more complex energy dependence, such as kinks in the B/C spectrum at specific energies. Theorists proposed these models to explain anomalous observations – by AMS and other experiments – that showed an increase in the number of positrons (anti-electrons) reaching Earth relative to electrons at high energy. The idea was that these “excess” positrons are – like boron – produced in collisions between cosmic rays and interstellar gas. But such a scenario would require that cosmic rays encounter additional scattering sites, not just magnetically turbulent regions. By ruling out these models, the AMS results support the alternative explanation – a new primary cosmic ray source that emits positrons. Candidates include pulsars and dark matter, but a lot of mystery still surrounds the unexplained positron data.

Igor Moskalenko from Stanford University is very surprised at the close match between the data and the Kolmogorov model. He expected that the ratio would deviate from a single power law in a way that might provide clues to the origin of the excess positrons. “This is a dramatic result that should lead to much better understanding of interstellar magnetohydrodynamic turbulence and propagation of cosmic rays,” he says. “On the other hand, it is very much unexpected in that it makes recent discoveries in astrophysics of cosmic rays even more puzzling.”

Powerful Punch of Gamma Rays Found in Mysterious Fast Radio Bursts

Penn State University astronomers have discovered that the mysterious “cosmic whistles” known as fast radio bursts can pack a serious punch, in some cases releasing a billion times more energy in gamma-rays than they do in radio waves and rivaling the stellar cataclysms known as supernovae in their explosive power. The discovery, the first-ever finding of non-radio emission from any fast radio burst, drastically raises the stakes for models of fast radio bursts and is expected to further energize efforts by astronomers to chase down and identify long-lived counterparts to fast radio bursts using X-ray, optical, and radio telescopes.

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Fast radio bursts, which astronomers refer to as FRBs, were first discovered in 2007, and in the years since radio astronomers have detected a few dozen of these events. Although they last mere milliseconds at any single frequency, their great distances from Earth — and large quantities of intervening plasma — delay their arrival at lower frequencies, spreading the signal out over a second or more and yielding a distinctive downward-swooping “whistle” across the typical radio receiver band.

“This discovery revolutionizes our picture of FRBs, some of which apparently manifest as both a whistle and a bang,” said coauthor Derek Fox, a Penn State professor of astronomy and astrophysics. The radio whistle can be detected by ground-based radio telescopes, while the gamma-ray bang can be picked up by high-energy satellites like NASA’s Swift mission. “Rate and distance estimates for FRBs suggest that, whatever they are, they are a relatively common phenomenon, occurring somewhere in the universe more than 2,000 times a day.”

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Efforts to identify FRB counterparts began soon after their discovery but have all come up empty until now. In a paper recently published in Astrophysical Journal Letters the Penn State team, led by physics graduate student James DeLaunay, reports bright gamma-ray emission from the fast radio burst FRB 131104, named after the date it occurred, 4 November 2013. “I started this search for FRB counterparts without expecting to find anything,” said DeLaunay. “This burst was the first that even had useful data to analyse. When I saw that it showed a possible gamma-ray counterpart, I couldn’t believe my luck!”

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Discovery of the gamma-ray “bang” from FRB 131104, the first non-radio counterpart to any FRB, was made possible by NASA’s Earth-orbiting Swift satellite, which was observing the exact part of the sky where FRB 131104 occurred as the burst was detected by the Parkes Observatory radio telescope in Parkes, Australia. “Swift is always watching the sky for bursts of X-rays and gamma-rays,” said Neil Gehrels, the mission’s principal investigator and chief of the Astroparticle Physics Laboratory at NASA’s Goddard Space Flight Center. “What a delight it was to catch this flash from one of the mysterious fast radio bursts.”

“Although theorists had anticipated that FRBs might be accompanied by gamma rays, the gamma-ray emission we see from FRB 131104 is surprisingly long-lasting and bright,” Fox said. The duration of the gamma-ray emission, at two to six minutes, is many times the millisecond duration of the radio emission. And the gamma-ray emission from FRB 131104 outshines its radio emissions by more than a billion times, dramatically raising estimates of the burst’s energy requirements and suggesting severe consequences for the burst’s surroundings and host galaxy.

Two common models for gamma-ray emission from FRBs exist: one invoking magnetic flare events from magnetars — highly magnetized neutron stars that are the dense remnants of collapsed stars — and another invoking the catastrophic merger of two neutron stars, colliding to form a black hole. According to coauthor Kohta Murase, a Penn State professor and theorist, “The energy release we see is challenging for the magnetar model unless the burst is relatively nearby. The long timescale of the gamma-ray emission, while unexpected in both models, might be possible in a merger event if we observe the merger from the side, in an off-axis scenario.”

“In fact, the energy and timescale of the gamma-ray emission is a better match to some types of supernovae, or to some of the supermassive black hole accretion events that Swift has seen,” Fox said. “The problem is that no existing models predict that we would see an FRB in these cases.”

The bright gamma-ray emission from FRB 131104 suggests that the burst, and others like it, might be accompanied by long-lived X-ray, optical, or radio emissions. Such counterparts are dependably seen in the wake of comparably energetic cosmic explosions, including both stellar-scale cataclysms — supernovae, magnetar flares, and gamma-ray bursts — and episodic or continuous accretion activity of the supermassive black holes that commonly lurk in the centers of galaxies.

In fact, Swift X-ray and optical observations were carried out two days after FRB 131104, thanks to prompt analysis by radio astronomers (who were not aware of the gamma-ray counterpart) and a nimble response from the Swift mission operations team, headquartered at Penn State. In spite of this relatively well-coordinated response, no long-lived X-ray, ultraviolet, or optical counterpart was seen.

The authors hope to participate in future campaigns aimed at discovering more FRB counterparts, and in this way, finally revealing the sources responsible for these ubiquitous and mysterious events. “Ideally, these campaigns would begin soon after the burst and would continue for several weeks afterward to make sure nothing gets missed. Maybe we’ll get even luckier next time,” DeLaunay said.