The Gray Whale is the 10th largest creature alive today, and the 9 creatures larger than it are all whales, too. Gray Whales are known for their epic migration routes, sometimes covering more than 16,000 km (10,000 miles) on their two-way trips between their feeding grounds and their breeding grounds. Researchers don’t have a complete understanding of how whales navigate these great distances, but some evidence suggests that Earth’s magnetism has something to do with it.Continue reading “Solar Storms Might Confuse Whale Navigation, and Make Them More Likely to Strand Themselves”
Electromagnetism is one of the fundamental forces of the universe, responsible for everything from electric and magnetic fields to light. Originally, scientists believed that magnetism and electricity were separate forces. But by the late 19th century, this view changed, as research demonstrated conclusively that positive and negative electrical charges were governed by one force (i.e. magnetism).
Since that time, scientists have sought to test and measure electromagnetic fields, and to recreate them. Towards this end, they created electromagnets, a device that uses electrical current to induce a magnetic field. And since their initial invention as a scientific instrument, electromagnets have gone on to become a regular feature of electronic devices and industrial processes.
Over the course of April 28–29 a gigantic filament, briefly suspended above the surface* of the Sun, broke off and created an enormous snakelike eruption of plasma that extended millions of miles out into space. The event was both powerful and beautiful, another demonstration of the incredible energy and activity of our home star…and it was all captured on camera by two of our finest Sun-watching spacecraft.
Watch a video of the event below.
Made from data acquired by both NASA’s Solar Dynamics Observatory (SDO) and the joint ESA/NASA SOHO spacecraft, the video was compiled by astronomer and sungrazing comet specialist Karl Battams. It shows views of the huge filament before and after detaching from the Sun, and gives a sense of the enormous scale of the event.
At one point the plasma eruption spanned a distance over 33 times farther than the Moon is from Earth!
Filaments are long channels of solar material contained by magnetic fields that have risen up from within the Sun. They are relatively cooler than the visible face of the Sun behind them so they appear dark when silhouetted against it; when seen rising from the Sun’s limb they look bright and are called prominences.
When the magnetic field lines break apart, much of the material contained within the filaments gets flung out into space (a.k.a. a CME) while some gets pulled back down into the Sun. These events are fairly common but that doesn’t make them any less spectacular!
This same particularly long filament has also been featured as the Astronomy Picture of the Day (APOD), in a photo captured on April 27 by Göran Strand.
For more solar news follow Karl Battams on Twitter.
Image credits: ESA/NASA/SOHO & SDO/NASA and the AIA science team.
*The Sun, being a mass of incandescent gas, doesn’t have a “surface” like rocky planets do so in this case we’re referring to its photosphere and chromosphere.
Dr. Thad Szabo is a professor of physics and astronomy at Cerritos College. He’s also a regular contributor to many of our projects, like the Virtual Star Party and the Weekly Space Hangout. Thad has an encyclopedic knowledge of all things space, so we got him to explain a few fascinating concepts.
In this video, Thad explains the strange mystery of dark energy, and the even stranger idea of the Big Rip.
What is the ‘Big Rip?’
If we look at the expansion of the universe, at first it was thought that, as things are expanding while objects have mass, the mass is going to be attracted to other mass, and that should slow the expansion. Then, in the late 1990’s, you have the supernova surveys that are looking deeper into space than we’ve ever looked before, and measuring distances accurately to greater distances than we’ve ever seen before. Something really surprising came out, and that was what we’ll now use “dark energy” now to explain, and that is that the acceleration is not actually slowing down – it’s not even stopped. It’s actually getting faster, and if you look at the most distant objects, they’re actually moving away from us and the acceleration is increasing the acceleration of expansion. This is actually a huge result.
One of the ideas of trying to explain it is to use the “cosmological constant,” which is something that Einstein actually introduced to his field equations to try to keep the universe the same size. He didn’t like the idea of a universe changing, so he just kind of cooked up this term and threw it into the equations to say, alright, well if it isn’t supposed to expand or contract, if I make this little mathematical adjustment, it stays the same size.
Hubble comes along about ten years later, and is observing galaxies and measuring their red shifts and their distances, and says wait a minute – no the universe is expanding. And actually we should really credit that to Georges Lemaître, who was able to interpret Hubble’s data to come up with the idea of what we now call the Big Bang.
So, the expansion’s happening – wait, it’s getting faster. And now the attempt is to try to understand how dark energy works. Right now, most of the evidence points to this idea that the expansion will continue in the space between galaxies. That the forces of gravity, and especially magnetism and the strong nuclear force that holds protons and neutrons together in the center of an atom, would be strong enough that dark energy is never going to be able to pull those objects apart.
However, there’s a possibility that it doesn’t work like that. There’s actually a little bit of experimental evidence right now that, although it’s not well-established, that there’s a little bit of a bias with certain experiments that dark energy may get stronger over time. And, if it does so, the distances won’t matter – that any object will be pulled apart. So first, you will see all galaxies recede from each other, as space starts to grow bigger and bigger, faster and faster. Then the galaxies will start to be pulled apart. Then star systems, then planets from their stars, then stars themselves, and then other objects that would typically be held together by the much stronger forces, the electromagnetic force objects held by that will be pulled apart, and then eventually, nuclei in atoms.
So if dark energy behaves so that it gets stronger and stronger over time, it will eventually overcome everything, and you’ll have a universe with nothing left. That’s the ‘Big Rip’ – if dark energy gets stronger and stronger over time, it will eventually overcome any forces of attraction, and then everything is torn apart.
You can find more information from Dr. Thad Szabo at his YouTube channel.
If you go out hiking this weekend and somehow find yourself hopelessly lost in the wilderness, but suddenly remember you have a compass with you, you can use it to find north because the needle always points towards the Earth’s geographic north pole, which never changes… right?
Wrong, wrong, and wrong. And this video from MinutePhysics explains why.
(But still bring a compass with you. They do come in handy.)
Recently we took a look at a very unusual type of map – the Faraday Sky. Now an international team of scientists, including those at the Naval Research Laboratory, have pooled their information and created one of the most high precision maps to date of the Milky Way’s magnetic fields. Like all galaxies, ours has a magnetic “personality”, but just where these fields come from and how they are created is a genuine mystery. Researchers have always simply assumed they were created by mechanical processes like those which occur in Earth’s interior and the Sun. Now a new study will give scientists an even better understanding about the structure of galactic magnetic fields as seen throughout our galaxy.
The team, led by the Max Planck Institute for Astrophysics (MPA), gathered their information and compiled it with theoretical simulations to create yet another detailed map of the magnetic sky. As NRL’s Dr. Tracy Clarke, a member of the research team explains, “The key to applying these new techniques is that this project brings together over 30 researchers with 26 different projects and more than 41,000 measurements across the sky. The resulting database is equivalent to peppering the entire sky with sources separated by an angular distance of two full moons.” This huge amount of data provides a new “all-sky” look which will enable scientists to measure the magnetic structure of the Milky Way in minute detail.
Just what’s so “new” about this map? This time we’re looking at a quantity called Faraday depth – an idea dependent on a line-of-sight information set on the magnetic fields. It was created by combining more than 41,000 singular measurements which were then combined using a new image reconstruction method. In this case, all the researchers at MPA are specialists in the new discipline of information field theory. Dr. Tracy Clarke, working in NRL’s Remote Sensing Division, is part of the team of international radio astronomers who provided the radio observations for the database. It’s magnetism on a grand scale… and imparts even the smallest of magnetic features which will enable scientists to further understand the nature of galactic gas turbulence.
The concept of the Faraday effect isn’t new. Scientists have been observing and measuring these fields for the last century and a half. Just how is it done? When polarized light passes through a magnetized medium, the plane of the polarization flips… a process known as Faraday rotation. The amount of rotation shows the direction and strength of the field and thereby its properties. Polarized light is also generated from radio sources. By using different frequencies, the Faraday rotation can also be measured in this alternative way. By combining all of these unique measurements, researchers can acquire information about a single path through the Milky Way. To further enhance the “big picture”, information must be gathered from a variety of sources – a need filled by 26 different observing projects that netted a total of 41,330 individual measurements. To give you a clue of the size, that ends up being about one radio source per square degree of sky!
Even with depth like this, there are still areas in the southern sky where only a few measurements have been cataloged. To fill in the gaps and give a more realistic view, researchers “have to interpolate between the existing data points that they have recorded.” However, this type of data causes some problems with accuracy. While you might think the more exact measurements would have the greatest impact on the map, scientists aren’t quite sure how reliable any single measurement could be – especially when they could be influenced by the environment around them. In this case, the most accurate measurements don’t always rank the highest in mapping points. Like Heisenberg, there’s an uncertainty associated with the process of obtaining measurements because the process is so complex. Just one small mistake could lead to a huge distortion in the map’s contents.
Thanks to an algorithm crafted by the MPA, scientists are able to face these types of difficulties with confidence as they put together the images. The algorithm, called the “extended critical filter,” employs tools from new disciplines known as information field theory – a logical and statistical method applied to fields. So far it has proven to be an effective method of weeding out errors and has even proven itself to be an asset to other scientific fields such as medicine or geography for a range of image and signal-processing applications.
Even though this new map is a great assistant for studying our own galaxy, it will help pave the way for researchers studying extragalactic magnetic fields as well. As the future provides new types of radio telescopes such as LOFAR, eVLA, ASKAP, MeerKAT and the SKA , the map will be a major resource of measurements of the Faraday effect – allowing scientists to update the image and further our understanding of the origin of galactic magnetic fields.
Original Story Source: Naval Research Laboratory News.
Although well over 40 years old, the Dunn Solar Telescope at Sunspot, New Mexico isn’t going to be looking at an early retirement. On the contrary, it has been outfitted with the new Facility Infrared Spectropolarimeter (FIRS) and is already making news on its solar findings. FIRS provides simultaneous spectral coverage at visible and infrared wavelengths through the use of a unique dual-armed spectrograph. By utilizing adaptive optics to overcome atmospheric “seeing” conditions, the team took on seven active regions on the Sun – one in 2001 and six during December 2010 to December 2011 – as Sunspot Cycle 23 faded away. The full sunspot sample has 56 observations of 23 different active regions… and showed that hydrogen might act as a type of energy dissipation device which helps the Sun get a magnetic grip on its spots.
“We think that molecular hydrogen plays an important role in the formation and evolution of sunspots,” said Dr. Sarah Jaeggli, a recent University of Hawaii at Manoa graduate whose doctoral research formed a key element of the new findings. She conducted the research with Drs. Haosheng Lin, also from the University of Hawaii at Manoa, and Han Uitenbroek of the National Solar Observatory in Sunspot, NM. Jaeggli now is a postdoctoral researcher in the solar group at Montana State University. Their work is published in the February 1, 2012, issue of The Astrophysical Journal.
You don’t have to be a solar physicist to know about the Sun’s 11 year cycle, or to understand how sunspots are cooler areas of intense magnetism. Believe it or not, even the professionals aren’t quite sure of how all the mechanisms work… especially those which cause sunspot forming areas that retard normal convective motions. Of the things we’ve learned, the spot’s inner temperature has a correlation with its magnetic field strength – with a sharp rise as the temperature cools. “This result is puzzling,” Jaeggli and her colleagues wrote. It implies some undiscovered mechanism inside the spot.
One theory is that hydrogen atoms combining into hydrogen molecules may be responsible. As for our Sun, the majority of hydrogen is ionized atoms because the average surface temperature is assessed at 5780K (9944 deg. F). However, since Sol is considered a “cool star”, researchers have found indications of heavy-element molecules in the solar spectrum – including surprising water vapor. These type of findings might prove the umbral regions could allow hydrogen molecules to combine in the surface layers – a prediction of 5% made by the late Professor Per E. Maltby and colleagues at the University of Oslo. This type of shift could cause drastic dynamic changes where gas pressure is concerned.
“The formation of a large fraction of molecules may have important effects on the thermodynamic properties of the solar atmosphere and the physics of sunspots,” Jaeggli wrote.
With direct measurements being beyond our current capabilities, the team then measured a proxy – the hydroxyl radical made of one atom each of hydrogen and oxygen (OH). According to the National Solar Observatory, “OH dissociates (breaks into atoms) at a slightly lower temperature than H2, meaning H2 can also form in regions where OH is present. By coincidence, one of its infrared spectral lines is 1565.2nm, almost the same as the 1565nm line of iron, used for measuring magnetism in a spot and one of the lines FIRS is designed to observe.”
By combining both old and new data, the team measured magnetic fields across sunspots, and the OH intensity inside spots, judging the H2 concentrations. “We found evidence that significant quantities of hydrogen molecules form in sunspots that are able to maintain magnetic fields stronger than 2,500 Gauss,” Jaeggli commented. She also said its presence leads to a temporary “runaway” intensification of the magnetic field.
As for the anatomy of a sunspot, magnetic flux boils up from the Sun’s interior and slows surface convection – which in turns stops cooler gas which has radiated its heat into space. From there, molecular hydrogen is created, reducing the volume. Because it is more transparent than its atomic counterpart, its energy is also radiated into space allowing the gas to cool even more. At this point the hot gas primed by the flux compresses the cooler region and intensifies the magnetic field. “Eventually it levels out, partly from energy radiating in from the surrounding gas. Otherwise, the spot would grow without bounds. As the magnetic field weakens, the H2 and OH molecules heat up and dissociate back to atoms, compressing the remaining cool regions and keeping the spot from collapsing.”
For now, the team admits that additional computer modeling is required to validate their observations and that most of the active regions so far have been mild ones. They’re hoping that Sunspot Cycle 24 will give them more fuel to be “cool”…
Original Story Source: National Solar Observatory News Release.
Ever since the Apollo era, scientist have known that the Moon had some kind of magnetic field in the past, but doesn’t have one now. Understanding why is important, because it can tell us how magnetic fields are generated, how long they last, and how they shut down. New studies of Apollo lunar samples answer some of these questions, but they also create many more questions to be answered.
The lunar samples returned by the Apollo missions show evidence of magnetization. Rocks are magnetized when they are heated and then cooled in a magnetic field. As they cool below the Curie temperature (about 800 degrees C, depending on the material), the metallic particles in the rock line up along ambient magnetic fields and freeze in that position, producing a remnant magnetization.
This magnetization can also be measured from space. Studies from orbiting satellites show that the Moon’s magnetization extends well beyond the regions sampled by Apollo astronauts. All this magnetization means that the Moon must have had a magnetic field at some point in its early history.
Most of the magnetic fields we know of in the Solar System are generated by a dynamo. Basically, this involves convection in a metallic liquid core, which effectively moves the metal atoms’ electrons, creating an electric current. This current then induces a magnetic field. The convection itself is thought to be driven by cooling. As the outer core cools, the colder portions sink to the interior and let the warmer interior sections move outwards towards the exterior.
Because the Moon is so small, a magnetic dynamo that is driven by convective cooling is expected to have shut down some time around 4.2 billion years ago. So, evidence of magnetization after this time would need either 1) an energy source other than cooling to drive the motion of a liquid core, or 2) a completely different mechanism for creating magnetic fields.
Laboratory experiments have suggested one such alternate method. Large basin-forming impacts could produce short-lived magnetic fields on the Moon, which would be recorded in the hot materials ejected during the impact event. In fact, some observations of magnetization are located at the opposite side of the Moon (the antipode) from large basins.
So, how can you tell if magnetization in a rock was formed by a core dynamo or an impact event? Well, impact-induced magnetic fields last only about 1 day. If a rock cooled very slowly, it would not record such a short-lived magnetic field, so any magnetism it retains must have been produced by a dynamo. Also, rocks that have been involved in impacts show evidence of shock in their minerals.
One lunar sample, number 76535, which shows evidence of slow cooling and no shock effects, has a distinct remnant magnetization. This, along with the age of the sample, suggests that the Moon had a liquid core and a dynamo-generated magnetic field 4.2 billion years ago. Such a core dynamo is consistent with convective cooling. But, what if there are younger samples?
New studies recently published in Science by Erin Shea and her colleagues suggest this may be the case. Ms Shea, a graduate student at MIT, and her team studied sample 10020, a 3.7 billion year old mare basalt brought back by the Apollo 11 astronauts. They demonstrated that sample 10020 shows no evidence of shock in its minerals. They estimated that the sample took more than 12 days to cool, which is much slower than the lifetime of an impact-induced magnetic field. And they found that the sample is very strongly magnetized.
From their studies, Ms Shea and her colleagues conclude that the Moon had a strong magnetic dynamo, and therefore a moving metallic core, around 3.7 billion years ago. This is well after the time a convective cooling dynamo would have shut down. It is not clear, however, if the dynamo was continually active since 4.2 billion years ago, or if the mechanism that moved the liquid core was the same at 4.2 and 3.8 billion years. So, what other ways are there to keep a liquid core moving?
Recent studies by a team of French and Belgian scientists, led by Dr. Le Bars, suggest that large impacts can unlock the Moon from its synchronous rotation with the Earth. This would create tides in the liquid core, much like the Earth’s oceans. These core tides would cause significant distortions at the core-mantle boundary, which could drive large-scale flows in the core, creating a dynamo.
In another recent study, Dr. Dwyer and colleagues suggested that precession of the lunar spin axis could stir the liquid core. The early Moon’s proximity to the Earth would have made the Moon’s spin axis wobble. This precession would cause different motions in the liquid core and overlying solid mantle, producing a long-lasting (longer than 1 billion years) mechanical stirring of the core. Dr. Dwyer and his team estimate that such a dynamo would naturally shut down about 2.7 billion years ago as the Moon moved away from the Earth over time, diminishing its gravitational influence.
Unfortunately, the magnetic field suggested by the study of sample 10020 doesn’t fit either of these possibilities. Both these models would provide magnetic fields that are too weak to have produced the strong magnetization observed in sample 10020. Another method for mobilizing the liquid core of the Moon will need to be found in order to explain these new findings.
A Long-Lived Lunar Core Dynamo. Shea, et al. Science 27, January 2012, 453-456. doi:10.1126/science.1215359.
A long-lived lunar dynamo driven by continuous mechanical stirring. Le Bars et al. Nature 479, November 2011, 212-214. doi:10.1038/nature10564.
An impact-driven dynamo for the early Moon. Dwyer et al. Nature 479, November 2011, 215-218. doi:10.1038/nature10565.
Superconductivity and magnetic fields are like oil and water… they don’t mix. When it can, the superconductor will push out any magnetic fields from the interior in a process called the Meissner effect. It happens when a sample is cooled below its superconducting transition temperature, where it then cancels out its magnetic flux. What’s next? A superconductor. Now the fun really begins… Continue reading “Quantum Levitation And The Superconductor”
A permanent magnet is a magnet that does not lose its magnet field. However what makes a magnet permanent? In order to understand this we need to know how magnets work. Magnetism is an aspect of the phenomenon known as the electromagnetic force a fundamental force of the physical universe. Magnetism like its other aspect electricity manifests itself as a field. What makes a magnet is when certain substances and elements are induced with a strong magnetic field. In the case of permanent magnets this field remains over time without weakening.
A permanent magnet is a magnet because of the orientation of its domains. Domains are the small magnetic field inherent in the crystalline structure of ferromagnetic materials. Ferromagnetic materials are the only substances capable of being made into magnets they are normally iron, nickel, or alloys that are made or rare-earth metals. A magnet is created when certain condition cause separate domains in a ferromagnetic item to be all aligned in the same direction. However the method used in most cases weak magnets can only be made. This is normally by direct contact with a naturally magnetic material or by running an electric current through it. However in the case of a field produced by rubbing it against a strong magnet is too weak and will fade over time as the domains return to their original positions.
The main way that permanent magnets are created is by heating a ferromagnetic material to a key high temperature. The temperature is specific to each kind of metal but it has the effect of aligning and “fixing” the domains of the magnet in a permanent position. It is conjectured that this same process inside the Earth is what creates natural permanent magnets.
Permanent magnets are important for their industrial uses especially when it comes to power generation and electric motors. The induction process for turbines and generators needs permanent magnets to turn mechanical motion into energy. They are also important for electric motors in many electronics using the reverse of the induction of electric current to make mechanical energy. As you can see without the permanent magnet we would not be able to take full advantage of the capabilities of electricity in modern devices.
We have written many articles about permanent magnets for Universe Today. Here’s an article about bar magnets, and here’s an article about super magnets.
We’ve also recorded an entire episode of Astronomy Cast all about Magnetism. Listen here, Episode 42: Magnetism Everywhere.