Date: March 3, 2010
Title: A 6 Year Old’s Question on Star Quakes
Podcaster: Brains Matter
Organization: Brains Matter podcast – http://www.brainsmatter.com
Description: My six year old asked whether magnetism could crush a star. The following podcast is the result of trying to find the answer to that!
Bio: The Brains Matter podcast has been producing and communicating science stories and interviews since September 2006. The show is based out of Melbourne, Australia, and takes an everyday person’s perspective of science in easy-to-understand language.
Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by Claes Skold and dedicated to all the great people who made 365 days of astronomy possible last year.
Transcript:
Hi all, and welcome to another episode of 365 Days of Astronomy. I’m the Ordinary Guy from the Brains Matter podcast – www.brainsmatter.com
Last year, as part of the International Year of Astronomy, I took my very young boys to see a talk at Monash University on the topic of magnetism in the universe. The talk was presented by Professor Bryan Gaensler from the University of Sydney, and he explained to the audience what magnetism was, the role of cosmic magnetic fields in the formation of stars and galaxies, how it protects life on earth, and so on.
At the end of the talk, my 6 year old had a think about what he had heard, and then excitedly put his hand up and asked “can a star crush in a magnet?” in other words – “can magnetism crush a star?”
Professor Gaensler responded: There are a special type of star called a magnetar Magnetars are the strongest magnets in the universe. They’re a star, whose magnetism is about a thousand trillion times stronger than the magnetism of the earth. The magnetism of a magnetar is so strong that it actually can cause star quakes on the star – so just like we have earthquakes on the earth, when the earth’s crust cracks and slips, the magnetism of a magnetar is so strong, that it actually causes the surface to slip and causes star quakes. Now that doesn’t destroy the star completely, but the last time one of these happened in 2004, the star quake lasted half a second, and in that half a second, the flash of light that was produced was more light than the sun gives off in 250,000 years. So you can’t completely crush a star, but these magnetic stars that are extremely rare have unbelievable amount of energy and explosiveness associated with them. That’s a pretty good question, the answer is not quite, but they can do a lot of damage.
So with that, 6 year old Ordinary Guy Junior was extremely pleased with himself and then started to ask me more about magnetars when we got home. “What’s the difference between a normal star and a magnetar?” he asked me.
The best known ‘normal’ star we know of is of course, our sun. It’s considered to be quite unremarkable. Magnetars, however, are quite different. They’re thought to be in the order of only around 20 kilometres wide. If you were fit, you could run that distance in an hour. They are, however, extremely dense. So dense, that a 1 cm cube would, if brought to earth, weigh in the order of a hundred million tonnes!
The other amazing fact about them is that they rotate very quickly – they take around 10 seconds to complete a revolution – sometimes faster.
So how do they form, you my ask? Well, it is thought that in a supernova, when a star collapses to form a dense, neutron star, and the magnetic field increases dramatically due to something known as the dynamo effect – this is whereby the rotation and convection of the neutron star maintains the strength of the magnetic field, from the order of around 10^8 tesla in a neutron star to around 10^11 tesla – then you are left with a magnetar. So basically, you can consider it to be a very highly magnetic neutron star!
It’s estimated that around one in ten supernova explosions end up in a magnetar as opposed to a normal neutron star, or pulsar.
Magnetars suffer from the James Dean syndrome though. They’re exciting for a short career span, astronomically speaking. The magnetic fields decay after around 10,000 years, putting a halt to the x-ray and other emissions
Robert Duncan from the Univeristy of Texas estimated in 2003 that there are in the order of 30 million inactive magnetars in the Milky Way alone.
And of course, as Professor Gaensler mentioned earlier in this episode, the strength of the magnetic fields and the volatility of the magnetar quite often results in star quakes.
And I hope that you, whatever age you are, enjoyed hearing about magnetars and star quakes.
If you want to hear more science and astronomy stories, please go to www.brainsmatter.com.
Bye for now.
End of podcast:
365 Days of Astronomy
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