Archive for the ‘Magnetic Fields’ Category

Rings And Loops In The Stars: Planck’s Stunning New Images

Credit: M. Peel / JCBA / Planck / ESA

Credit: M. Peel / JCBA / Planck / ESA

A ring of dust 200 light years across and a loop covering a third of the sky: two of the results in a new map from the Planck satellite. Dr Mike Peel and Dr Paddy Leahy of the Jodrell Bank Centre for Astrophysics (JCBA) presented the images today at the National Astronomy Meeting (NAM 2015) at Venue Cymru, Llandudno, Wales.

The European Space Agency (ESA) Planck satellite, launched in 2009 to study the ancient light of the Big Bang, has also given us maps of our own Galaxy, the Milky Way, in microwaves (radiation at cm- to mm-wavelengths). Microwaves are generated by electrons spiralling in the Galaxy’s magnetic field at nearly the speed of light (the synchrotron process); by collisions in interstellar plasma, by thermal vibration of interstellar dust grains, and by “anomalous” microwave emission (AME), which may be from spinning dust grains.

The relative strength of these processes changes with wavelength, and are separated using multi-wavelength measurements from Planck, from NASA’s WMAP satellite, and from ground-based radio telescopes, giving maps of each component.

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Left-Handed Cosmic Magnetic Field Could Explain Missing Antimatter

An artist’s concept of the Fermi Gamma ray Space Telescope (FGST) in orbit. Credit: NASA

An artist’s concept of the Fermi Gamma ray Space Telescope (FGST) in orbit. Credit: NASA

The discovery of a ‘left-handed’ magnetic field that pervades the universe could help explain a long standing mystery – the absence of cosmic antimatter. A group of scientists, led by Prof Tanmay Vachaspati from Arizona State University in the United States, with collaborators at the University of Washington and Nagoya University, announce their result in Monthly Notices of the Royal Astronomical Society.

Planets, stars, gas and dust are almost entirely made up of ‘normal’ matter of the kind we are familiar with on Earth. But theory predicts that there should be a similar amount of antimatter, like normal matter, but with the opposite charge. For example, an antielectron or positron has the same mass as its conventional counterpart, but a positive rather than negative charge.

In 2001 Prof Vachaspati published theoretical models to try to solve this puzzle, which predict that the entire universe is filled with helical (screw-like) magnetic fields. He and his team were inspired to search for evidence of these fields in data from the NASA Fermi Gamma ray Space Telescope (FGST).

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The Origin Of The Magnetic Field Covering The Sun Has Been Discovered

February 20, 2015 1 comment

The magnetic field that covers the Sun and determines its behavior –the eleven year cycles no less than such conspicuous phenomena as solar spots and solar storms– also has another side to it: a magnetic web that covers the entire surface of the Sun at rest and whose net magnetic flow is greater than that of the active areas. A study led by the Institute of Astrophysics of Andalusia (IAA-CSIC) has revealed where the flow that feeds this web comes from.

The outline of the solar magnetic web coincides with the boundaries of the so-called supergranules, structures linked to the existence of hot gas rising to the surface (similar to the bubbles made by boiling water) some twenty thousand kilometers in diameter.

“We have discovered that inside these supergranules, in what is known as intranetwork, small magnetic elements appear which travel toward the outer boundaries and interact with the web”, says Milan Gosic, IAA researcher in charge of the study.

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Researchers Find That Earth’s “Plasmaspheric Hiss” Protects Against A Harmful Radiation Belt

February 18, 2015 Leave a comment

Courtesy of the reasearchers/Haystack Observatory

Courtesy of the reasearchers/Haystack Observatory

High above Earth’s atmosphere, electrons whiz past at close to the speed of light. Such ultrarelativistic electrons, which make up the outer band of the Van Allen radiation belt, can streak around the planet in a mere five minutes, bombarding anything in their path. Exposure to such high-energy radiation can wreak havoc on satellite electronics, and pose serious health risks to astronauts.

Now researchers at MIT, the University of Colorado, and elsewhere have found there’s a hard limit to how close ultrarelativistic electrons can get to the Earth. The team found that no matter where these electrons are circling around the planet’s equator, they can get no further than about 11,000 kilometers from the Earth’s surface — despite their intense energy.

What’s keeping this high-energy radiation at bay seems to be neither the Earth’s magnetic field nor long-range radio waves, but rather a phenomenon termed “plasmaspheric hiss” — very low-frequency electromagnetic waves in the Earth’s upper atmosphere that, when played through a speaker, resemble static, or white noise.

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Mystery Of Planet-forming Disks Explained By Magnetism

Artist's conception. Image credit: NASA/JPL-Caltech

Artist’s conception. Image credit: NASA/JPL-Caltech

Astronomers say that magnetic storms in the gas orbiting young stars may explain a mystery that has persisted since before 2006.

Researchers using NASA’s Spitzer Space Telescope to study developing stars have had a hard time figuring out why the stars give off more infrared light than expected. The planet-forming disks that circle the young stars are heated by starlight and glow with infrared light, but Spitzer detected additional infrared light coming from an unknown source.

A new theory, based on three-dimensional models of planet-forming disks, suggests the answer: Gas and dust suspended above the disks on gigantic magnetic loops like those seen on the sun absorb the starlight and glow with infrared light.

“If you could somehow stand on one of these planet-forming disks and look at the star in the center through the disk atmosphere, you would see what looks like a sunset,” said Neal Turner of NASA’s Jet Propulsion Laboratory, Pasadena, Calif.

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Glimpsing The Infrastructure Of A Gamma-Ray Burst Jet

December 6, 2013 Leave a comment

A new study using observations from a novel instrument provides the best look to date at magnetic fields at the heart of gamma-ray bursts, the most energetic explosions in the universe. An international team of astronomers from Britain, Slovenia and Italy has glimpsed the infrastructure of a burst’s high-speed jet.

Gamma-ray bursts are the most luminous explosions in the cosmos. Most are thought to be triggered when the core of a massive star runs out of nuclear fuel, collapses under its own weight, and forms a black hole. The black hole then drives jets of particles that drill all the way through the collapsing star and erupt into space at nearly the speed of light.

On March 8, 2012, NASA’s Swift satellite detected a 100-second pulse of gamma rays from a source in the constellation Ursa Minor. The spacecraft immediately forwarded the location of the gamma-ray burst, dubbed GRB 120308A, to observatories around the globe.

The world’s largest fully autonomous robotic optical telescope, the 2-meter Liverpool Telescope located at Roque de los Muchachos Observatory on La Palma in the Canary Islands, automatically responded to Swift’s notification.

“Just four minutes after it received Swift’s trigger, the telescope found the burst’s visible afterglow and began making thousands of measurements,” said lead researcher Carole Mundell, who heads the gamma-ray burst team at the Astrophysics Research Institute at Liverpool John Moores University in the U.K.

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Stanford Physicists Monitoring Huge Solar Event

November 13, 2013 Leave a comment

Every 11 years, the sun undergoes a complete makeover when the polarity of its magnetic field – its magnetic north and south – flips. The effects of this large-scale event ripple throughout the solar system.

Although the exact internal mechanism that drives the shift is not entirely understood, researchers at Stanford’s Wilcox Solar Observatory have monitored the sun’s magnetic field on a daily basis since 1975 and can identify the process as it occurs on the sun’s surface. This will be the fourth shift the observatory has monitored.

New polarity builds up throughout the 11-year solar cycle as sunspots – areas of intense magnetic activity – appear as dark blotches near the equator of the sun’s surface. Over the course of a month, a sunspot spreads out, and gradually that magnetic field migrates from the equator to one of the sun’s poles.

As the polarity moves toward the pole, it erodes the existing, opposite polarity, said Todd Hoeksema, a solar physicist at Stanford since 1978 and director of the Wilcox Solar Observatory. The magnetic field gradually reduces toward zero, and then rebounds with the opposite polarity.

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