Earth’s magnetic field is acting up and geologists don’t know why Erratic motion of north magnetic pole




Earth’s magnetic field is acting up and geologists don’t know why

Erratic motion of north magnetic pole forces experts to update model that aids global navigation.

Update, 9 January: The release of the World Magnetic Model has been postponed to 30 January due to the ongoing US government shutdown.

Something strange is going on at the top of the world. Earth’s north magnetic pole has been skittering away from Canada and towards Siberia, driven by liquid iron sloshing within the planet’s core. The magnetic pole is moving so quickly that it has forced the world’s geomagnetism experts into a rare move.

On 15 January, they are set to update the World Magnetic Model, which describes the planet’s magnetic field and underlies all modern navigation, from the systems that steer ships at sea to Google Maps on smartphones.

The most recent version of the model came out in 2015 and was supposed to last until 2020 — but the magnetic field is changing so rapidly that researchers have to fix the model now. “The error is increasing all the time,” says Arnaud Chulliat, a geomagnetist at the University of Colorado Boulder and the National Oceanic and Atmospheric Administration’s (NOAA’s) National Centers for Environmental Information.

The problem lies partly with the moving pole and partly with other shifts deep within the planet. Liquid churning in Earth’s core generates most of the magnetic field, which varies over time as the deep flows change. In 2016, for instance, part of the magnetic field temporarily accelerated deep under northern South America and the eastern Pacific Ocean. Satellites such as the European Space Agency’s Swarm mission tracked the shift.

By early 2018, the World Magnetic Model was in trouble. Researchers from NOAA and the British Geological Survey in Edinburgh had been doing their annual check of how well the model was capturing all the variations in Earth’s magnetic field. They realized that it was so inaccurate that it was about to exceed the acceptable limit for navigational errors.

Wandering pole

“That was an interesting situation we found ourselves in,” says Chulliat. “What’s happening?” The answer is twofold, he reported last month at a meeting of the American Geophysical Union in Washington DC.

First, that 2016 geomagnetic pulse beneath South America came at the worst possible time, just after the 2015 update to the World Magnetic Model. This meant that the magnetic field had lurched just after the latest update, in ways that planners had not anticipated.

Source: World Data Center for Geomagnetism/Kyoto Univ.

Second, the motion of the north magnetic pole made the problem worse. The pole wanders in unpredictable ways that have fascinated explorers and scientists since James Clark Ross first measured it in 1831 in the Canadian Arctic. In the mid-1990s it picked up speed, from around 15 kilometres per year to around 55 kilometres per year. By 2001, it had entered the Arctic Ocean — where, in 2007, a team including Chulliat landed an aeroplane on the sea ice in an attempt to locate the pole.

In 2018, the pole crossed the International Date Line into the Eastern Hemisphere. It is currently making a beeline for Siberia.

The geometry of Earth’s magnetic field magnifies the model’s errors in places where the field is changing quickly, such as the North Pole. “The fact that the pole is going fast makes this region more prone to large errors,” says Chulliat.

To fix the World Magnetic Model, he and his colleagues fed it three years of recent data, which included the 2016 geomagnetic pulse. The new version should remain accurate, he says, until the next regularly scheduled update in 2020.

Core questions

In the meantime, scientists are working to understand why the magnetic field is changing so dramatically. Geomagnetic pulses, like the one that happened in 2016, might be traced back to ‘hydromagnetic’ waves arising from deep in the core1. And the fast motion of the north magnetic pole could be linked to a high-speed jet of liquid iron beneath Canada2.

The jet seems to be smearing out and weakening the magnetic field beneath Canada, Phil Livermore, a geomagnetist at the University of Leeds, UK, said at the American Geophysical Union meeting. And that means that Canada is essentially losing a magnetic tug-of-war with Siberia.

“The location of the north magnetic pole appears to be governed by two large-scale patches of magnetic field, one beneath Canada and one beneath Siberia,” Livermore says. “The Siberian patch is winning the competition.”

Which means that the world’s geomagnetists will have a lot to keep them busy for the foreseeable future.

Nature 565, 143-144 (2019)

doi: 10.1038/d41586-019-00007-1

Astronomers Detected Planets Outside Our Galaxy in 2018



For The First Time Ever, Astronomers Detected Planets Outside Our Galaxy in 2018

23 DEC 2018

In an incredible world first, astrophysicists detected multiple planets in another galaxy earlier this year, ranging from masses as small as the Moon to ones as great as Jupiter.

Given how difficult it is to find exoplanets even within our Milky Way galaxy, this is no mean feat. Researchers at the University of Oklahoma achieved this in February thanks to clever use of gravitational microlensing.

The technique, first predicted by Einstein’s theory of general relativity, has been used to find exoplanets within Milky Way, and it’s the only known way of finding the smallest and most distant planets, thousands of light-years from Earth.

As a planet orbits a star, the gravitational field of the system can bend the light of a distant star behind it.

We know what this looks like when it’s just two stars, so when a planet enters the mix, it creates a further disturbance in the light that reaches us – a recognisable signature for the planet.

So far, 53 exoplanets within the Milky Way have been detected using this method. To find planets farther afield, though, something a little bit more powerful than a single star was required.

Oklahoma University astronomers Xinyu Dai and Eduardo Guerras studied a quasar 6 billion light-years away called RX J1131-1231, one of the best gravitationally lensed quasars in the sky.

The gravitational field of a galaxy 3.8 billion light-years away between us and the quasar bends light in such a way that it creates four images of the quasar, which is an active supermassive black hole that’s extremely bright in X-ray, thanks to the intense heat of its accretion disc.

Using data from NASA’s Chandra X-ray observatory, the researchers found that there were peculiar line energy shifts in the quasar’s light that could only be explained by planets in the galaxy lensing the quasar.

It turned out to be around 2,000 unbound planets with masses ranging between the Moon and Jupiter, between the galaxy’s stars.

“We are very excited about this discovery. This is the first time anyone has discovered planets outside our galaxy,” Dai said.

Of course, we haven’t seen the planets directly, and are unlikely to in the lifetime of anyone alive today. But being able to detect them at all is an incredible testament to the power of microlensing, not to mention being evidence that there are planets in other galaxies.

Of course, common sense would dictate that planets are out there – but evidence is always nice.

“This is an example of how powerful the techniques of analysis of extragalactic microlensing can be,” said Guerras.

“This galaxy is located 3.8 billion light years away, and there is not the slightest chance of observing these planets directly, not even with the best telescope one can imagine in a science fiction scenario.

“However, we are able to study them, unveil their presence and even have an idea of their masses. This is very cool science.”

The research was published in The Astrophysical Journal.

Magnetic fields may be the key to black hole activity



Magnetic fields may be the key to black hole activity

October 17, 2018, NASA
Magnetic fields may be the key to black hole activity
Artist’s conception of the core of Cygnus A, including the dusty donut-shaped surroundings, called a torus, and jets launching from its center. Magnetic fields are illustrated trapping the dust in the torus. These magnetic fields could be …more

Collimated jets provide astronomers with some of the most powerful evidence that a supermassive black hole lurks in the heart of most galaxies. Some of these black holes appear to be active, gobbling up material from their surroundings and launching jets at ultra-high speeds, while others are quiescent, even dormant. Why are some black holes feasting and others starving? Recent observations from the Stratospheric Observatory for Infrared Astronomy, or SOFIA, are shedding light on this question.

SOFIA data indicate that magnetic fields are trapping and confining dust near the center of the active galaxy, Cygnus A, and feeding material onto the supermassive black hole at its center.

The , which attempts to explain the different properties of active galaxies, states that the core is surrounded by a donut-shaped dust cloud, called a torus. How this obscuring structure is created and sustained has never been clear, but these new results from SOFIA indicate that magnetic fields may be responsible for keeping the dust close enough to be devoured by the hungry black hole. In fact, one of the fundamental differences between active galaxies like Cygnus A and their less active cousins, like our own Milky Way, may be the presence or absence of a  around the black hole.

Although celestial magnetic fields are notoriously difficult to observe, astronomers have used polarized light—optical light from scattering and radio light from accelerating electrons—to study magnetic fields in galaxies. But optical wavelengths are too short and the radio wavelengths are too long to observe the torus directly. The infrared wavelengths observed by SOFIA are just right, allowing scientists, for the first time, to target and isolate the dusty torus.

Magnetic fields may be the key to black hole activity
Two images of Cygnus A layered over each other to show the galaxy’s jets glowing with radio radiation (shown in red). Quiescent galaxies, like our own Milky Way, do not have jets like this, which may be related to magnetic fields. The …more

SOFIA’s new instrument, the High-resolution Airborne Wideband Camera-plus (HAWC+), is especially sensitive to the infrared emission from aligned dust grains. This has proven to be a powerful technique to study magnetic fields and test a fundamental prediction of the unified model: the role of the dusty torus in the active-galaxy phenomena.

“It’s always exciting to discover something completely new,” noted Enrique Lopez-Rodriguez, a scientist at the SOFIA Science Center, and the lead author on the report of this new discovery. “These observations from HAWC+ are unique. They show us how infrared polarization can contribute to the study of galaxies.”

Recent observations of the heart of Cygnus A made with HAWC+ show infrared radiation dominated by a well-aligned dusty structure. Combining these results with archival data from the Herschel Space Observatory, the Hubble Space Telescope and the Gran Telescopio Canarias, the research team found that this powerful active galaxy, with its iconic large-scale jets, is able to confine the obscuring torus that feeds the supermassive black hole using a strong .

The results of this study were published in the July 10th issue of The Astrophysical Journal Letters.

Cygnus A is in the perfect location to learn about the role magnetic fields play in confining the dusty torus and channeling material onto the supermassive black hole because it is the closest and most powerful active galaxy. More observations of different types of galaxies are necessary to get the full picture of how magnetic fields affect the evolution of the environment surrounding . If, for example, HAWC+ reveals highly polarized  from the centers of active galaxies but not from quiescent , it would support the idea that magnetic fields regulate black hole feeding and reinforce astronomers’ confidence in the unified model of .

 Explore further: Black holes play hide-and-seek in low-luminosity radio galaxies

More information: Enrique Lopez-Rodriguez et al. The Highly Polarized Dusty Emission Core of Cygnus A, The Astrophysical Journal (2018). DOI: 10.3847/2041-8213/aacff5

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Stunning Pinwheel Nebula Is a Cosmic Cataclysm in the Making



Stunning Pinwheel Nebula Is a Cosmic Cataclysm in the Making

Apep, the first Wolf-Rayet star system to be discovered in the Milky Way.
Image: ESO/Callingham et al.

This image of a dusty, gas-rich nebula looks pretty, but appearances can be deceiving. Known as a Wolf-Rayet star system, it’s poised to unleash a catastrophic gamma-ray burst when it finally goes supernova. What’s remarkable about this particular Wolf-Rayet system, however, is that it’s the first to be discovered in our own galaxy. Cue the ominous music…

This Wolf-Rayet star system is formally known as 2XMM J160050.7-514245, but to the researchers who recently investigated this enigmatic object, it’s simply “Apep”—an exotic object named for the serpentine ancient Egyptian god of chaos. In a press release, Joseph Callingham, the lead author of the new study and an astronomer at the Netherlands Institute for Radio Astronomy (ASTRON), said “it’s the first such system to be discovered in our own galaxy”—a system he never expected to find “in our own backyard.” The details of this research were published today in Nature Astronomy.

Indeed, astronomers have observed Wolf-Rayet stars before, but only in other galaxies. These massive star systems are on the verge of entering into their death throes, at which time they’ll generate a type of supernova that emits an extremely powerful and narrow jet of plasma—the dreaded gamma-ray burst.

Apep is one such gamma-ray progenitor system, featuring a massive triple star system at its core—a binary pair and a lone star—and vast spiral arms composed of gas and dust. The system is located around 8,000 light-years from Earth, which is uncomfortably close given its explosive potential.

“This was a very fun project to do in some ways, in the sense that Joe found this object and first showed it to me in 2012 when we were officemates as undergrads in Sydney—and it took us six years to gather all the data to reveal this surprising story,” Benjamin Pope, a NASA Sagan fellow at New York University’s Center for Cosmology and Particle Physics and a co-author of the new study, told Gizmodo. “Sometimes science is slow! But I remember when last year, the day before my PhD defense in Oxford, he was visiting and showed me the picture of the Apep spiral—I literally gasped, it was so shocking. There’s really nothing quite like this.”

Using the VISIR mid-infrared camera on the European Southern Observatory’s Very Large Telescope, Pope, Callingham, and their colleagues measured the velocity of the dust within the spiral arms. At this end-stage of their brief life cycle (these systems only last a few hundred thousand years—a blink of the eye in cosmological terms), stars within Wolf-Rayet systems spin rapidly, producing stellar winds that move at horrendous speeds. These winds carry significant portions of stellar material into space, and they’re responsible for forming the majestic plumes of dust particles. In the case of Apep, its spiral arms measure several light-years across.

By measuring the rotational speeds within this nebula, the researchers concluded that at least one of the three stars within the system is spinning fast enough such that it’ll trigger a long-duration gamma-ray burst when it finally explodes as supernova (the exact timing is still impossible to predict). The speed of gas within the nebula was clocked at 12 million kilometers per hour, but the dust is moving at “just” 570 million kilometers per hour. The researchers say this discrepancy is indicative of a star approaching near-critical rotation.

“Apep’s dust pinwheel moves much slower than the wind in the system,” said Callingham. “One way this can occur is if one of the massive stars is rotating so quickly that it is nearly tearing itself apart. Such a rotation means that when it runs out of fuel and begins to explode as a supernova, it will collapse at the poles before the equator, producing a gamma-ray burst.”

The significance of this finding, said Pope, is that nobody had observed rapidly rotating Wolf-Rayet systems in our galaxy before. Moreover, many astronomers assumed these objects couldn’t even exist in a galaxy like ours; the Milky Way is old and metal-rich, containing an abundance of heavy stars that should spin down quickly. The new result suggests our understanding of how massive stars die is still incomplete.

“Wolf-Rayet star systems are thought to be the progenitors of long gamma-ray bursts, so if there’s one in our galaxy that’s an exciting find,” Pope told Gizmodo. “Even if not—something deeply weird is happening to this star system and this is the best explanation we have.”

Artist’s impression of a gamma-ray burst.
Image: NASA/Dana Berry/Skyworks Digital

As noted, gamma-ray bursts are among the most powerful explosions known to astronomers. Lasting from between two seconds and a few hours, long-duration gamma-ray bursts release as much energy as the Sun does over the course of its entire lifetime. Disturbingly, some scientists theorize that the Ordovician-Silurian extinction—a mass extinction event that happened on Earth some 440 million years ago—was caused by a gamma-ray burst within our own galaxy. Physicist Adrian Melott from the University of Kansas speculates that a “dangerously near GRB should occur on average two or more times per billion years.”

Pope said it would be “pretty bad” if one were to go off nearby, but he’s not particularly concerned.

“In terms of why we have nothing to worry about, the best I can offer is that it’s highly uncertain whether Apep will go off as a gamma-ray burst at all, and if it does, it is unlikely to be in the very near future.”

As another point of encouragement, gamma-ray bursters are highly directional, spewing their concentrated, high-energy rays in a specific direction. So for Apep to pose a threat, it would not only have to go supernova, it would also have to be pointed in our general direction.

Regardless, there’s nothing we can really do about it except to learn more about Wolf-Rayet systems. It might also be useful to speak the ancient Egyptian incantation to rid the world of Apep’s destructive powers:

Spitting upon Apep, Defiling Apep with the left foot, Taking a lance to smite Apep,Fettering Apep, Taking a knife to smite Apep, Putting fire upon Apep…

[Nature Astronomy]

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