Voyager 1: Is It In or Is It Out?

Nearly 18.7 billion kilometers from Earth — about 17 light-hours away — NASA’s Voyager 1 spacecraft is just about on the verge of entering interstellar space, a wild and unexplored territory of high-energy cosmic particles into which no human-made object has ever ventured. Launched in September 1977, Voyager 1 will soon become the first spacecraft to officially leave the Solar System.

Or has it already left?

I won’t pretend I haven’t heard it before: Voyager 1 has left the Solar System! Usually followed soon after by: um, no it hasn’t. And while it might all seem like an awful lot of flip-flopping by supposedly-respectable scientists, the reality is there’s not a clear boundary that defines the outer limits of our Solar System. It’s not as simple as Voyager rolling over a certain mileage, cruising past a planetary orbit, or breaking through some kind of discernible forcefield with a satisfying “pop.” (Although that would be cool.)

The outer edge of the heliosphere has been found to contain many different regions, which Voyager 1 has been passing through since 2004. (NASA/JPL-Caltech)
The outer edge of the heliosphere has been found to contain many different regions, which Voyager 1 has been passing through since 2004. (NASA/JPL-Caltech)

Rather, scientists look at Voyager’s data for evidence of a shift in the type of particles detected. Within the transitionary zone that the spacecraft has most recently been traveling through, low-energy particles from the Sun are outnumbered by higher-energy particles zipping through interstellar space, also called the local interstellar medium (LISM). Voyager’s instruments have been detecting dramatic shifts in the concentrations of each for over a year now, unmistakably trending toward the high-energy end — or at least showing a severe drop-off in solar particles — and researchers from the University of Maryland are claiming that this, along with their model of a porous solar magnetic field, indicates Voyager has broken on through to the other side.

Read more: Voyagers Find Giant Jacuzzi-like Bubbles at Edge of Solar System

“It’s a somewhat controversial view, but we think Voyager has finally left the Solar System, and is truly beginning its travels through the Milky Way,” said Marc Swisdak, UMD research scientist and lead author of a new paper published this week in The Astrophysical Journal Letters.

According to Swisdak, fellow UMD plasma physicist James F. Drake, and Merav Opher of Boston University, their model of the outer edge of the Solar System  fits recent Voyager 1 observations — both expected and unexpected. In fact, the UMD-led team says that Voyager passed the outer boundary of the Sun’s magnetic influence, aka the heliopause… last year.

Read more: Winds of Change at the Edge of the Solar System

But, like some of last year’s claims, these conclusions aren’t shared by mission scientists at NASA.

“Details of a new model have just been published that lead the scientists who created the model to argue that NASA’s Voyager 1 spacecraft data can be consistent with entering interstellar space in 2012,” said Ed Stone, Voyager project scientist at Caltech, in a press release issued today. “In describing on a fine scale how magnetic field lines from the sun and magnetic field lines from interstellar space can connect to each other, they conclude Voyager 1 has been detecting the interstellar magnetic field since July 27, 2012. Their model would mean that the interstellar magnetic field direction is the same as that which originates from our sun.

The famous "Golden Record" carried aboard both Voyager 1 and 2 contains images, sounds and greetings from Earth. (NASA)
The famous “Golden Record” carried aboard both Voyager 1 and 2 contains images, sounds and greetings from Earth. (NASA)

“Other models envision the interstellar magnetic field draped around our solar bubble and predict that the direction of the interstellar magnetic field is different from the solar magnetic field inside. By that interpretation, Voyager 1 would still be inside our solar bubble.”

Stone says that further discussion and investigation will be needed to “reconcile what may be happening on a fine scale with what happens on a larger scale.”

Whether still within the Solar System — however it’s defined — or outside of it, the bottom line is that the venerable Voyager spacecraft are still conducting groundbreaking research of our cosmic neighborhood, 36 years after their respective launches and long after their last views of the planets. And that’s something nobody can argue about.

“The Voyager 1 spacecraft is exploring a region no spacecraft has ever been to before. We will continue to look for any further developments over the coming months and years as Voyager explores an uncharted frontier.”

– Ed Stone, Voyager project scientist

Built by JPL and launched in 1977, both Voyagers are still capable of returning scientific data from a full range of instruments, with adequate power and propellant to remain operating until 2020.

Read the full UMD news release here, and find out more about the Voyager mission on the NASA/JPL website here.

_____________

Note: The definition of “Solar System” used in this article is in reference to the Sun’s magnetic influence, the heliosphere, and all that falls within its outermost boundary, the heliopause (wherever that is.) Objects farther out are still gravitationally held by the Sun, such as distant KBOs and Oort Cloud comets, but orbit within the interstellar medium. 

Weekly Space Hangout – August 9, 2013

Gather round the internets for another episode of the Weekly Space Hangout. Where our experienced team of journalists, astronomers and astronomer-journalists bring you up to speed on the big happenings in the universe of space and astronomy.

Our team this week:

Reporters: Casey Dreier, David Dickinson, Amy Shira Teitel, Sondy Springmann, Nicole Gugliuci

Host: Fraser Cain

And here are the stories we covered:
Curiosity Celebrates One Year on Mars
2013 Perseids Meteor Shower
Lori Garver Leaving NASA
Kilonova Discovered
Sun’s Magnetic Field is About to Flip
Japanese HTV-4 Docked
MAVEN Update

We record the Weekly Space Hangout every Friday at Noon Pacific, 3 pm Eastern. Join us live here on Universe Today, over on our YouTube account, or on Google+. Or you can watch the archive after the fact.

An Exoplanet’s Auroral Engine


Located 880 light-years away, a massive gas giant called CoRoT-2b orbits its star at a mere 2 million miles – less than a tenth the distance of Mercury’s orbit from the Sun. At this cozy proximity the star, CoRoT-2a, continually assaults the hot, gassy exoplanet with high-powered stellar winds and magnetic storms, stripping it of millions of kilograms of mass every day… and undoubtedly creating global auroras that rival even the most energetic seen on Earth.

But CoRoT-2b isn’t merely a tragic player in this stormy stellar performance; the planet itself may also be part of the cause.

[/caption]

Almost 3 1/2 times the mass of Jupiter, CoRoT-2b (so named because it was discovered by the French Space Agency’s Convection, Rotation and planetary Transits space telescope, or CoRoT) orbits its star very rapidly, completing an orbit every 1.7 days. This in turn actually speeds up the rotation of the star itself thus generating even more magnetic activity, via a dynamo effect.

Caught up in this deadly dance, CoRoT-2b is losing mass at an estimated rate of 150 million billion kilograms of material every year! The planet would likely have a long comet-like tail of this stripped material trailing behind it.

Although this sounds like a lot, CoRoT-2b has enough mass to keep “spinning up” its star for thousands of billions of years.

Read more about CoRoT-2a and b here.

Video: [email protected]

Regular Solar Cycle Could Be Going on Hiatus

[/caption]

Are we headed into the 21st century version of the Maunder Minimum? Three researchers studying three different aspects of the Sun have all come up with the same conclusion: the Sun’s regular solar cycles could be shutting down or going into hibernation. A major decrease in solar activity is predicted to occur for the next solar cycle (cycle #25), and our current solar cycle (#24) could be the last typical one. “Three very different types of observations all pointing in the same direction is very compelling,” said Dr. Frank Hill from the National Solar Observatory, speaking at a press briefing today. “Cycle 24 may be the last normal one, and 25 may not even happen.”


Even though the Sun has been active recently as it heads towards solar maximum in 2013, there are three lines of evidence pointing to a solar cycle that may be going on hiatus. They are: a missing jet stream, slower activity near the poles of the sun and a weakening magnetic field, meaning fading sunspots. Hill, along with Dr. Richard Altrock from the Air Force Research Laboratory and Dr. Matt Penn from the National Solar Observatory independently studied the different aspects of the solar interior, the visible surface, and the corona and all concur that cycle 25, will be greatly reduced or may not happen at all.

Solar activity, including sunspot numbers, rises and falls on average about every 11 years – sometimes the cycles are as short as 9 years, other times it is as long as 13 years. The Sun’s magnetic poles reverse about every 22 years, so 11 years is half of that magnetic interval cycle.

"Butterfly diagram" shows the position of sunspots over 12 solar cycles. Sunspots emerge over a range of latitudes centered on migratory jet streams that follow a clear pattern, trending from higher latitudes to lower latitudes on the Sun. The active latitudes are associated with mobile zonal flows or "jet streams" that vary through the cycle. Credit: SWRI

The first line of evidence is a slowing of a plasma flow inside the Sun, an east/west flow of gases under the surface of the Sun detected via seismology with spacecraft like the Solar Dynamics Observatory (SDO)or SOHO and also with the Global Oscillation Network Group (GONG) observing stations, a system that measures pulsations on the solar surface to understand the internal structure of the sun. The flow of plasma normally indicates the onset of sunspot formation for the next solar cycle. While this river ebbs and flows during the cycle, the “torsional oscillations,” — which starts at mid-latitudes and migrates towards the equator — and normally begins forming for the next solar cycle has not yet been detected.

Latitude-time plots of jet streams under the Sun's surface show the surprising shutdown of the solar cycle mechanism. New jet streams typically form at about 50 degrees latitude (as in 1999 on this plot) and are associated with the following solar cycle 11 years later. New jet streams associated with a future 2018-2020 solar maximum were expected to form by 2008 but are not present even now, indicating a delayed or missing Cycle 25. Credit: SWRI

Hill said the above graphic is key for understanding the issue. “The flow for Cycle 25 should have appeared in 2008 or 2009 but it has not and we see no sign of it,” he said. “This indicates that the start of Cycle 25 may be delayed to 2021 or 2022, with a minimum great that what we just experienced, or may not happen at all.”

Plots of coronal brightness against solar latitude show a "rush to the poles" that reflects the formation of subsurface shear in the solar polar regions. The current "rush to the poles" is delayed and weak, reflecting the lack of new shear under the photosphere. Note the graph depicts both north and south hemispheres overlaid into one map of solar magnetic activity, and that the patterns correspond with the butterfly diagram above. Credit: SWRI

The second line of evidence is slowing of the “rush to the poles,” the rapid poleward march of magnetic activity observed in the Sun’s faint corona. Altrock said the activity in the solar corona follows same oscillation pattern described by Hill, and that they have been observing the pattern for about 40 years. The researchers now see a very weak and slow pattern in this movement.

“A key thing to understand is that those wonderful, delicate coronal features are actually powerful, robust magnetic structures rooted in the interior of the Sun,” Altrock said. “Changes we see in the corona reflect changes deep inside the Sun.”

In a well-known pattern, new solar activity emerges first at about 70 degrees latitude at the start of a cycle, then towards the equator as the cycle ages. At the same time, the new magnetic fields push remnants of the older cycle as far as 85 degrees poleward. “In previous solar cycles, solar maximum occurred when the rush to the poles reached an average latitude of 76 degrees,” Altrock said. “Cycle 24 started out late and slow and may not be strong enough to create a rush to the poles, indicating we’ll see a very weak solar maximum in 2013, if at all. It is not clear whether solar max as we know it.”

Altrock added that if the “rush” doesn’t occur, no one knows what will happen in the future because no one has modeled what takes place without this rush to the poles.

Average magnetic field strength in sunspot umbras has been steadily declining for over a decade. The trend includes sunspots from Cycles 22, 23, and (the current cycle) 24. Credit: SWRI

The third line of evidence is a long-term weakening trend in the strength of sunspots. Penn, along with his colleague William Livingston predict that by Cycle 25, magnetic fields erupting on the Sun will be so weak that few if any sunspots will be formed.

Using more than 13 years of sunspot data collected at the McMath-Pierce Telescope at Kitt Peak in Arizona, Penn and Livingston observed that the average field strength declined about 50 gauss per year during Cycle 23 and now in Cycle 24. They also observed that spot temperatures have risen exactly as expected for such changes in the magnetic field. If the trend continues, the field strength will drop below the 1,500 gauss threshold and spots will largely disappear as the magnetic field is no longer strong enough to overcome convective forces on the solar surface.

“Things are erupting on the sun,” Penn said, “but they don’t have the energy to create sunspots.”
But back in 1645-1715 was the period known as the Maunder Minimum, a 70-year period with virtually no sunspots. The Maunder Minimum coincided with the middle – and coldest part – of the Little Ice Age, during which Europe and North America experienced bitterly cold winters. It has not been proven whether there is a causal connection between low sunspot activity and cold winters. However lower earth temperatures have been observed during low sunspot activity. If the researchers are correct in their predictions, will we experience a similar downturn in temperatures?

Hill said that some researchers say that the Sun’s activity can also play a role in climate change, but in his opinion, the evidence is not clear-cut. Altrock commented he doesn’t want to stick his neck out about how the Sun’s declining activity could affect Earth’s climate, and Penn added that Cycle 25 may provide a good opportunity to find out if the activity on the Sun contributes to climate change on Earth.

Source: Southwest Research Institute, press teleconference

Lead image thanks to César Cantú in Monterrey, Mexico at the Chilidog Observatory. See more at his website, Astronomía Y Astrofotografía.

You can follow Universe Today senior editor Nancy Atkinson on Twitter: @Nancy_A. Follow Universe Today for the latest space and astronomy news on Twitter @universetoday and on Facebook.

Comet Elenin: Just Passing By

[/caption]

It starts out innocently enough: a small speck against a field of background stars, barely noticeable in the image data. But… it’s a speck that wasn’t there before. Subsequent images confirm its existence – there’s something out there. Something bright, something large, and it’s moving through our solar system very quickly. The faint blur indicates that it’s a comet, an icy visitor from the outermost reaches of the solar system. And it’s headed straight toward Earth.

Exhaustive calculations are run and re-run. Computer simulations are executed. All possibilities are taken into consideration, and yet there’s no alternative to be found; our world will face a close encounter with a comet in mere months’ time. Phone calls are made, a flurry of electronic messages fly between computer terminals across the world, consultations are held with top experts in the field. We are unprepared… what can we do? What does this mean for civilization as we know it? What will this speeding icy bullet from outer space do to our planet?

The answer? Nothing.

Nothing at all. In fact, it probably won’t even be very interesting to look at – if you can even find it when it passes by.

(Sorry for the let-down.)

There’s been a lot of buzz in the past several months regarding Comet Elenin, a.k.a. C/2010 X1,  which was discovered by Russian astronomer Leonid Elenin on December 10, 2010. Elenin spotted the comet using a telescope in New Mexico remotely from his location in Lyubertsy, Russia. At that time it was about 647 million kilometers (401 million miles) from Earth… in the time since it has closed the distance considerably, and is now around 270 million km away. Elenin is a long-period comet, which means it has a rather large orbit around the Sun… it comes in from a vast distance, swings around the Sun and heads back out to the depths of the solar system – a round trip lasting over 10,000 years. During its current trip it will pass by Earth on October 16, coming as close as 35 million km (22 million miles).

Elenin's orbit via the JPL Small-Body Database Browser

Yes, 22 million miles.

That’s pretty far.

Way too far for us to be affected by anything a comet has to offer. Especially a not-particularly-large comet like Elenin.

Some of the doomy-gloomy internet sites have been mentioning the size of Elenin as being 80,000 km across. This is a scary, exaggerated number that may be referring to the size of Elenin’s coma – a hazy cloud of icy particles that surrounds a much, much smaller nucleus. The coma can be extensive but is insubstantial; it’s akin to icy cigarette smoke. Less than that, in fact… a comet’s coma and tail are even more of a vacuum than can be reproduced in a lab on Earth! In reality most comets have a nucleus smaller than 10km…that’s less than a billionth the mass of Earth (and a far cry from 80,000 km.) We have no reason to think that Elenin is any larger than this – it’s most likely smaller.

Ok, but how about the gravitational and/or magnetic effect of a comet passing by Earth? That’s surely got to do something, right? To Earth’s crust, or the tides? For the answer to that, I will refer to Don Yeomans, a researcher at NASA’s Near-Earth Object Program Office at JPL:

“Comet Elenin will not only be far away, it is also on the small side for comets. And comets are not the most densely-packed objects out there. They usually have the density of something akin to loosely packed icy dirt,” said Yeomans. “So you’ve got a modest-sized icy dirtball that is getting no closer than 35 million kilometers. It will have an immeasurably miniscule influence on our planet. By comparison, my subcompact automobile exerts a greater influence on the ocean’s tides than comet Elenin ever will.”

“It will have an immeasurably miniscule influence on our planet. By comparison, my subcompact automobile exerts a greater influence on the ocean’s tides than comet Elenin ever will.”

– Don Yeomans, NASA / JPL

And as far as the effect from Elenin’s magnetic field goes… well, there is no effect. Elenin, like all comets, doesn’t have a magnetic field. Not much else to say there.

But the claims surrounding Elenin have gone much further toward the absurd. That it’s going to encounter another object and change course to one that will cause it to impact Earth, or that it’s not a comet at all but actually a planet – Nibiru, perhaps? – and is on a collision course with our own. Or (and I particularly like this one) that alien spaceships are trailing Elenin in such a way as to remain undetected until it’s too late and then they’ll take over Earth, stealing our water and natural resources and turning us all into slaves and/or space munchies… or however the stories go. (Of course the government and NASA and Al Gore and Al Gore’s hamster are all in cahoots and are withholding this information from the rest of us. That’s a given.) These stories are all just that – stories – and have not a shred of science to them, other than a heaping dose of science fiction.

“We live in nervous times, and conspiracy theories and predictions of disaster are more popular than ever. I like to use the word cosmophobia for this growing fear of astronomical objects and phenomena, which periodically runs amuck on the Internet. Ironically, in pre-scientific times, comets were often thought to be harbingers of disaster, mostly because they seemed to arrive unpredictably – unlike the movements of the planets and stars, which could be tracked on a daily and yearly basis.”

– David Morrison, planetary astronomer and senior scientist at NASA’s Ames Research Center

The bottom line is this: Comet C/2010 X1 Elenin is coming, and it will pass by Earth at an extremely safe distance – 100 times the distance from Earth to the Moon. It will not be changing direction between now and then, it will not exert any gravitational effect on Earth, its magnetic field is nonexistent and there are no Star Destroyers cruising in its wake. The biggest effect it will have on Earth is what we are able to learn about it as it passes – after all, it is a visitor from the far reaches of our solar system and we won’t be seeing it again for a very, very long time.

I’m sure we’ll have found something else to be worried about long before then.

“This intrepid little traveler will offer astronomers a chance to study a relatively young comet that came here from well beyond our solar system’s planetary region. After a short while, it will be headed back out again, and we will not see or hear from Elenin for thousands of years. That’s pretty cool.”

– Don Yeomans

For more information about Elenin, check out this JPL news release featuring Don Yeomans, and there’s a special public issue of Astronomy Beat, a newsletter from the Astronomical Society of the Pacific, that features David Morrison of NASA’s Ames Research Center discussing many of the misconceptions about Elenin.

An updated chart of Elenin’s orbit and statistics can be viewed here.

Top image © Jason Major

Helmholtz Coil

Helmholtz Coil

[/caption]A magnetic field is a pretty awesome thing. As a fundamental force of the universe, they are something without which, planetary orbits, moving electrical charges, or even elementary particles could not exist. It is therefore intrinsic to scientific research that we be able to generate magnetic fields ourselves for the purpose of studying electromagnetism and its fundamental characteristics. One way to do this is with a device known as the Helmholtz Coil, an instrument that is named in honor of German physicist Hermann von Helmholtz (1821-1894), a scientist and philosopher who made fundamental contributions to the fields of physiology, optics, mathematics, and meteorology in addition to electrodynamics.

A Helmholtz coil is a device for producing a region of nearly uniform magnetic field. It consists of two identical circular magnetic coils that are placed symmetrically, one on each side of the experimental area along a common axis, and separated by a distance (h) equal to the radius (R) of the coil. Each coil carries an equal electrical current flowing in the same direction. A number of variations exist, including use of rectangular coils, and numbers of coils other than two. However, a two-coil Helmholtz pair is the standard model, with coils that are circular and in shape and flat on the sides. In such a device, electric current is passed through the coil for the purpose of creating a very uniform magnetic field.

Helmholtz coils are used for a variety of purposes. In one instance, they were used in an argon tube experiment to measure the charge to mass ratio (e:m)of electrons. In addition, they are often used to measure the strength and fields of permanent magnets. In order to do this, the coil pair is connected to a fluxmeter, a device which contains measuring coils and electronics that evaluate the change of voltage in the measuring coils to calculate the overall magnetic flux.In some applications, a Helmholtz coil is used to cancel out Earth’s magnetic field, producing a region with a magnetic field intensity much closer to zero. This can be used to see how electrical charges and magnetic fields operate when not acted on by the gravitational pull of the Earth or other celestial bodies.

In a Helmholtz girl, the magnetic flux density of a field generated (represented by B) can be expressed mathematically by the equation:

Where R is the radius of the coils, n is the number of turns in each coil, I is the current flowing through the coils, and ?0 is the permeability of free space (1.26 x 10-6 T • m/A).

We have written many articles about the Helmholtz Coil for Universe Today. Here’s an article about the right hand rule magnetic field, and here’s an article about magnetic field.

If you’d like more info on the Helmholtz Coil, check out an article from Hyperphysics. Also, here’s another article about the Helmholtz Coil.

We’ve also recorded an entire episode of Astronomy Cast all about Magnetism. Listen here, Episode 42: Magnetism Everywhere.

Sources:
http://en.wikipedia.org/wiki/Helmholtz_coil
http://www.oersted.com/helmholtz_coils_1.shtml
http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/helmholtz.html
http://physicsx.pr.erau.edu/HelmholtzCoils/index.html
http://www.youtube.com/watch?v=nu5kwkmj870
http://www.circuitcellar.com/library/print/0606/Wotiz191/5.htm

Magnetic Fields on O-Class Stars

[/caption]

The primary method by which astronomers can measure magnetic field strength on stars is the Zeeman effect. This effect is the splitting of spectral lines into two due to the magnetic field’s effect on the quantum structure of the orbitals. For massive O-class stars, their spectra are largely featureless in the visual portion of the spectra due to an insufficient number of atoms with electrons in the necessary orbitals to undergo transitions which can produce visual spectral lines. Thus, determining whether or not these stars have magnetic fields has been a unique challenge. A new paper from researchers at the University of Amsterdam, led by Roald Schnerr, looks for evidence of these fields in the form of synchrotron radiation.

Synchrotron radiation is a form of light produced when relativistic, charged particles move through a magnetic field. The light emitted can be generated in any portion of the spectra from radio to gamma rays, depending on the strength of the field. Astronomically, this was first detected in 1956 by Geoffrey Burbidge in the jets of M87 and has since been used to explain emission in planetary magnetospheres, supernovae, near black holes, and around pulsars.

This form of energy distinguishes itself from other forms of light in two main fashions. The first is that it is highly polarized. This property is generated by the electric and magnetic components always being in the same planes and can be studied with filters that only allow light with its fields in appropriate planes to pass. The second is that the radiation created is “non-thermal”. In other words, it doesn’t match the distribution of wavelengths generated by a blackbody.

Models of massive, O-class stars suggest they should contain magnetic fields. Some evidence has seemed to confirm this. Previous studies have also shown that the stellar winds from some of these stars varies with timescales similar to the rotation rates of the stars which could be interpreted as winds being slowed on some faces by the magnetic field as it swept by.

Schnerr’s team attempted to bolster the evidence for magnetic fields by detecting the non-thermal radiation from these stars. The team selected 5 stars which have been shown to have strongly variable winds, some with cyclic variations and used the Westerbork Synthesis Radio Telescope, in the Netherlands to search for non-blackbody signals. The radio range was selected due to the predicted magnetic field strength.

Ultimately, only three of the five selected targets could be observed with the chosen telescope and only one of those, ξ Persei, showed evidence of a non-thermal spectrum. But while this strengthens the case for magnetic fields on the star, it raises another question: From where do the relativistic particles originate? Although O-class stars have strong stellar winds, their speeds are well studied and well below the necessary velocity.

One clue could come from the fact that ξ Persei is a “runaway star”. These stars have velocities and plunge through the interstellar medium at 30-200 km/sec. The team suggests that a bow shock created by this motion could result in sufficiently high velocities. Whether or not ξ Per has such a bow shock is something that could be determined with additional observations.

While this research provides some interesting clues to the nature of these magnetic fields on these stars, it still relies on a small sample. This technique can certainly be expanded to a larger number of stars in the future and may help astronomers better constrain their models of stellar workings.

How Do Magnets Work

How Do Magnets Work

[/caption]
We have all played with magnets from time to time. Every time you do, you have asked yourself ‘how do magnets work?’ Many of us understand that magnets have two different charges and that like charges repel each other, but that still does not explain how a magnet works. Below is an attempt to explain the basics behind the secret inner workings of the mysterious magnet.

A magnet is any material or object that produces a magnetic field. This magnetic field is responsible for the property of a magnet: a force that pulls on other ferromagnetic materials and attracts or repels other magnets. A permanent magnet is an object made from a material that is magnetized and creates its own persistent magnetic field. Materials that can be magnetized, which are strongly attracted to a magnet, are called ferromagnetic. Although ferromagnetic materials are the only ones attracted to a magnet strongly enough to be commonly considered magnetic, all other substances respond weakly to a magnetic field.

Some facts about magnets include:

  • the north pole of the magnet points to the geomagnetic north pole (a south magnetic pole) located in Canada above the Arctic Circle.
  • north poles repel north poles
  • south poles repel south poles
  • north poles attract south poles
  • south poles attract north poles
  • the force of attraction or repulsion varies inversely with the distance squared
  • the strength of a magnet varies at different locations on the magnet
  • magnets are strongest at their poles
  • magnets strongly attract steel, iron, nickel, cobalt, gadolinium
  • magnets slightly attract liquid oxygen and other materials
  • magnets slightly repel water, carbon and boron

The mechanics of how do magnets work really breaks right down to the atomic level. When current flows in a wire a magnetic field is created around the wire. Current is simply a bunch of moving electrons, and moving electrons make a magnetic field. This is how electromagnets are made to work.

Around the nucleus of the atom there are electrons. Scientists used to think that they had circular orbits, but have discovered that things are much more complicated. Actually, the patterns of the electron within one of these orbitals takes into account Schroedinger’s wave equations. Electrons occupy certain shells that surround the nucleus of the atom. These shells have been given letter names K,L,M,N,O,P,Q. They have also been given number names, such as 1,2,3,4,5,6,7(think quantum mechanics). Within the shell, there may exist subshells or orbitals, with letter names such as s,p,d,f. Some of these orbitals look like spheres, some like an hourglass, still others like beads. The K shell contains an s orbital called a 1s orbital. The L shell contains an s and p orbital called a 2s and 2p orbital. The M shell contains an s, p and d orbital called a 3s, 3p and 3d orbital. The N, O, P and Q shells each contain an s, p, d and f orbital called a 4s, 4p, 4d, 4f, 5s, 5p, 5d, 5f, 6s, 6p, 6d, 6f, 7s, 7p, 7d and 7f orbital. These orbitals also have various sub-orbitals. Each can only contain a certain number of electrons. A maximum of 2 electrons can occupy a sub-orbital where one has a spin of up, the other has a spin of down. There can not be two electrons with spin up in the same sub-orbital(the Pauli exclusion principal). Also, when you have a pair of electrons in a sub-orbital, their combined magnetic fields will cancel each other out. If you are confuse, you are not alone. Many people get lost here and just wonder about magnets instead of researching further.

When you look at the ferromagnetic metals it is hard to see why they are so different form the elements next to them on the periodic table. It is generally accepted that ferromagnetic elements have large magnetic moments because of un-paired electrons in their outer orbitals. The spin of the electron is also thought to create a minute magnetic field. These fields have a compounding effect, so when you get a bunch of these fields together, they add up to bigger fields.

To wrap things up on ‘how do magnets work?’, the atoms of ferromagnetic materials tend to have their own magnetic field created by the electrons that orbit them. Small groups of atoms tend to orient themselves in the same direction. Each of these groups is called a magnetic domain. Each domain has its own north pole and south pole. When a piece of iron is not magnetized the domains will not be pointing in the same direction, but will be pointing in random directions canceling each other out and preventing the iron from having a north or south pole or being a magnet. If you introduce current(magnetic field), the domains will start to line up with the external magnetic field. The more current applied, the higher the number of aligned domains. As the external magnetic field becomes stronger, more and more of the domains will line up with it. There will be a point where all of the domains within the iron are aligned with the external magnetic field(saturation), no matter how much stronger the magnetic field is made. After the external magnetic field is removed, soft magnetic materials will revert to randomly oriented domains; however, hard magnetic materials will keep most of their domains aligned, creating a strong permanent magnet. So, there you have it.

We have written many articles about magnets for Universe Today. Here’s an article about bar magnets, and here’s an article about super magnets.

If you’d like more info on magnets, check out some cool experiments with magnets, and here’s a link to an article about super magnets by Wise Geek.

We’ve also recorded an entire episode of Astronomy Cast all about Magnetism. Listen here, Episode 42: Magnetism Everywhere.

Sources:
Wise Geek
Wikipedia: Magnet
Wikipedia: Ferromagnetism

Electric Resistance May Make Hot Jupiters Puffy

The Sun’s magnetic field

One of the surprises coming from the discoveries of the class of exoplanets known as “Hot Jupiters” is that they are puffed up beyond what would be expected from their temperature alone. The interpretation of these inflated radii is that extra energy must be being deposited in the regions of the atmosphere with large amounts of circulation. This extra energy would be deposited as heat, causing the atmosphere to expand. But from where was this extra energy coming? New research is suggesting that ionized winds passing through magnetic fields may create this process. Continue reading “Electric Resistance May Make Hot Jupiters Puffy”

What are Magnets Made Of

Magnet

[/caption]

Magnets are the unsung heroes of the Modern Age. However most people don’t really understand what are magnets made of and how they even work. The issue is that we just know that magnets attract iron and nickel. However, magnets have a very interesting origin and can be seen as a physical manifestation of the electromagnetic force.

All magnets are made of a group of metals called the ferromagnetic metals. These are metals such as nickel and iron. Each of these metals have the special property of being able to be magnetized uniformly. When we ask how a magnet works we are simply asking how the object we call a magnet exerts it’s magnetic field. The answer is actually quite interesting.

In every material there are several small magnetic fields called domains. Most of the times these domains are independent of each other and face different directions. However, a strong magnetic field can arrange the domains of any ferromagnetic metal so that they align to make a larger and stronger magnetic field. This is how most magnets are made.

The major difference among magnets is whether they are permanent or temporary. Temporary magnets lose their larger magnetic field over time as the domains return to their original positions. The most common way that magnets are produced is by heating them to their Curie temperature or beyond. The Curie temperature is the temperature at which a ferromagnetic metals gains magnetic properties. Heating a ferromagnetic material to its given temperature will make it magnetic for a while. While heating it beyond this point can make the magnetism permanent. Ferromagnetic materials can also be categorized into soft and hard metals. Soft metals loses their magnetic field over time after being magnetized while hard metals are likely candidates for becoming permanent magnets.

Not all magnets are manmade. Some magnets occur naturally in nature such as lodestone. This mineral was used in ancient times to make the first compasses. However, magnets have other uses. With the discovery of the relation between magnetism and electricity, magnets are now a major part of every electric motor and turbine in existence. Magnets have also been used in storing computer data. There is now a type of drive called a solid state drive that allows data to still be saved more efficiently on computers.

We have written many articles about magnets for Universe Today. Here’s an article about the Earth’s magnetic field, and here’s an article about the bar magnet.

If you’d like more info on Magnets, check out NASA’s Discussion on Magnets, and here’s a link to an article about Magnetic Fields.

We’ve also recorded an entire episode of Astronomy Cast all about Magnetism. Listen here, Episode 42: Magnetism Everywhere.

Sources:
NASA
Wikipedia