Date: October 24th, 2012
Title: Encore: Magnetar the Magnificent
Podcaster: Carolyn Collins Petersen
This podcast originally aired on June 20th, 2009
Description: Magnetars sound like mysterious aliens from another dimension, but they’re not. I’ll discuss these powerfully magnetic beasts and talk about what we know about them from recent research and observations.
Bio: Carolyn Collins Petersen is a science writer and show producer for Loch Ness Productions, a company that creates astronomy documentaries and other materials. She works with planetariums, science centers, and observatories on products that explain astronomy and space science to the public. Her most recent projects were the Griffith Observatory astronomy exhibits in Los Angeles and the California’s Altered State climate change exhibits for San Francisco’s California Academy of Sciences. She has co-authored several astronomy books, written many astronomy articles, and is currently working on a new documentary show for fulldome theaters, a vodcast series for MIT’s Haystack Observatory, and a podcast series for the Astronomical Society of the Pacific.
Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by No one. Please consider sponsoring an episode of 365 Days of Astronomy by clicking on the “Donate” button on the lower left.
Hi, I’m Carolyn Collins Petersen — the Spacewriter.
Magnetar! Say it with me — magnetar!
What a wonderful word! It sounds like the name of some golden age of science fiction hero — Magnetar the Mighty — wrestling with the vampires of Omicron IV… or maybe a heroine out of a 1950s space opera: Magnetar the Magnificent and her loyal subjects, who all live on the planet Epsilon Indii III and have grand adventures fighting off alien invaders from the fourth dimension!
Well… those could be grand stories featuring all the usual suspects — beautiful aliens and their weird worlds. But, there’s no such thing as Magnetar the Magnificent … is there?
As it turns out, magnetars do exist. But they’re not hunky alien heroes or gorgeous green-skinned empresses in charge of planets.
No, they’re even more weird than that.
A magnetar is ….a highly magnetic neutron star. And, it’s one of the stranger beasts in the cosmic zoo.
Imagine that you have this massive star — many times MORE massive than the Sun. It goes along living its starry life, consuming fuel, putting out heat (and other radiation), blowing a stellar wind out into space, all that stuff that stars do. Then, one day (a stellar day), the gravy train ends. It’s time for the star to die.
Such stars usually end their lives by blowing up in supernova explosions. When that happens, it sends a whole lot of stuff — clouds of gas and dust and heavy metals — out into space in a huge catastrophic explosion.
But, that’s not the end of the star. There’s still something left — something called a neutron star — a ball of neutrons packed together very tightly, and spinning very, very fast.
These are the only stars that actually have solid surfaces. Imagine such an object with a kilometer-deep crust, overlying a thick “ocean” of neutrons, all packed into a tiny dense ball. That’s a neutron star.
The neutron star’s spin generates a strong magnetic field. And, as it spins, it gives off regular pulses in radio, visible light, x-rays and sometimes gamma-rays. Astronomers call these active objects “pulsars.”
Some of the most energetic pulsars and neutron stars also send out regular gamma-ray bursts — astronomers call those soft-gamma repeaters.
Occasionally you get a neutron star that has collapsed down to about 16 kilometers across but has the equivalent of the Sun’s mass packed inside that tiny area. That thing goes way beyond the call of neutron star duty and generates the most intense magnetic field imaginable — along with regular gamma-ray pulses.
Based on the existence of that mighty magnetic field, astronomers began calling these things magnetars. They’re objects with magnetic fields a thousand trillion times the Earth’s magnetic field strength .
How strong is a magnetar’s magnetic field? Think of it this way — if a magnetar got close to our planet — say it flew between Earth and the Moon — its magnetic field would wipe out all of humanity’s stored electronic data. Think of it — your computer’s hard drive would be cleaned off. Your credit card would be useless. And that’s just for starters. On a larger scale, our planet’s magnetic field would be affected big time.
So, magnetars are not something to be trifled with; and luckily there are none of them nearby.
Now, how is it we can detect these things in radio, x-ray, visible and gamma-ray wavelengths? It’s because magnetars are extraordinarily hot. Their surfaces are about 10 million degrees Celsius. Why so hot? Because of those strong magnetic fields. They help heat the star and keep it very hot. And, extreme heat powers x-ray emissions.
As the magnetic field moves in a magnetar, it causes ripples to move across the surface of the neutron star. Those ripples are like giant star quakes, and the energy they release power the gamma-ray bursts.
Magnetars had been seen by gamma-ray detectors on satellites since 1979, although they weren’t called magnetars then. That name came later. In the late 1990s the Compton Gamma-Ray Observatory spotted radiation from an object called SGR 1806-20, in the constellation Sagittarius. The Rossi X-ray timing Explorer also caught some high-energy bursts from the same object. And, as it turned out, a Japanese satellite called ASCA (the Advanced satellite for Cosmology and Astrophysics) had studied the same object a few years earlier.
Eventually, astronomers determined that SGR 1806-20 is a magnetar. Today, the magnetar count is up to more than a dozen, and the closest is about 9,000 light-years away.
Astronomers think that only about 1 in 10 supernova explosions creates a magnetar, and there’s some evidence that a neutron star can somehow slip in and out of being a magnetar.
While we don’t know the exact number of these beasts in the Milky Way, it’s possible that there could be millions of them.
One final interesting note, though.
They don’t seem to last too long because their magnetic fields tend to decay in around 10,000 or so years. This means there could be many “dead” magnetars out there in the galaxy.
So, there you have it — the low-down on magnetars.
They may not be attractive young superheroes in space operas — but, they certainly have magnetic properties — and are a magnificent way for formerly massive stars to end their lives.
To learn more about magnetars, head on over to www.thespacewriter.com/wp and click on the 365 Days of Astronomy tab. You’ll find links to all kinds of great resources about these weird cosmic beasts.
For 365 Days of Astronomy, I’m Carolyn Collins Petersen. Thanks for listening!
End of podcast:
365 Days of Astronomy
The 365 Days of Astronomy Podcast is produced by the New Media Working Group of the International Year of Astronomy 2009. Audio post-production by Preston Gibson. Bandwidth donated by libsyn.com and wizzard media. Web design by Clockwork Active Media Systems. You may reproduce and distribute this audio for non-commercial purposes. Please consider supporting the podcast with a few dollars (or Euros!). Visit us on the web at 365DaysOfAstronomy.org or email us at info@365DaysOfAstronomy.org. Until tomorrow…goodbye.