Final Stop: Magnetars

• By Jason McCracken
• November 14, 2014
• Comments Off on Final Stop: Magnetars

We have one final blog from past summer intern Jason McCracken, wrapping up his adventures through space.

---

Remember that time when we were all like Oooooh and Aaaaah? I miss those days. Since we began exploring these voids I’ve been starting to get a little bored. I mean look over there, nothing.  And look over there, nothing.  It really is just a big void. So like a moth to a flame, let’s head to that very bright light that’s flashing in the distance! This seems promising. This seems like a neutron star, a very special neutron star, a magnetar.

*Warning* Under no circumstances should any person approach a neutron star unless under the protection of technologies that have yet to or may never be discovered. Neutron Stars may lead to burning, major trauma, and spaghetification. Do not taunt neutron star.

This is an artistic image of all that is awesome. Credit: NASA/Dana Berry

All joking aside, neutron stars are very intense objects. Created from the collapse of stars 4 to 8 times the size of our Sun, these guys are the densest things in the universe next to black holes. Black holes need the collapse of a much larger star than does a neutron star to form. During the collapse, some mass is lost, resulting in neutron stars around 1.4 to 3.2 solar masses. Our sun is 1 solar mass. So they have more mass than the sun, but they are considerably smaller. In fact, neutron stars average about 12 kilometers in diameter. Two neutron stars could sit side by side in Chicago! The sun is 60,000 times larger than this but less massive, how can that be?

A neutron star compared to Manhattan. Credit: NASA/Goddard Space Flight Center

The amount of mass in a neutron star causes an immense amount of gravity. So immense that matter can degenerate into a pool of neutrons. What does that even mean? Take a sponge for example. Use one of those cool sponges you use in the bathroom – or a loofah. A loofah would work too. Hold your sponge in your hand and observe its structure. All the holes and empty space are badly analogous to the space in atoms that build matter.

Now, there are forces at play that hold the structure of the sponge but if you take your hands, and name them gravity, and squish the sponge as hard as you can, you’ll have a much smaller object with the same mass. Similarly, our neutron star builds a strong enough gravitational force to compress all the empty space out of matter leaving a pool of neutrons that is much smaller than our sun but much more massive.

Stars can balance this gravitational compression with pressure from the nuclear reactions that occur inside of them, but when the fuel is up gravity takes over. More fun examples to blow your mind! A Boeing 747 would be smaller than the size of a grain of sand under the same circumstances. Earth would be about the size of a basketball.

Like an m&m, a chocolate neutron center with a candy shell. Credit: NASA/Marshall Space Flight Center.

Along with the tremendous gravity, neutron stars also have a strong magnetic field. Actually, that doesn’t do it justice, the magnetic field around a neutron star is ridiculous and in some situations absolutely ridiculous! So let’s talk about magnetic fields. Magnets are awesome, and you have all noticed how you can manipulate objects with a magnet without them touching, right? Magnets have this non-contact force that builds around itself that we call a magnetic field. This field begins at one end of the magnet and ends at the other.  That’s all I’m giving you, if you need a better recap click here!

Earth creates its own magnetic field, and it acts like a shield against the Sun. And the Sun has a magnetic field too. We can measure a magnetic field by the force it exerts on a charged particle; the unit scientists use for this is called the Tesla (T). And a refrigerator magnet is about 0.01T. Earth’s magnetic field is around 0.004T. An MRI can produce a magnetic field of 10T, and the strongest magnetic field created by man (without destroying anything) was 100.75T. Neutron stars average a million T (10⁶)! And under unique circumstances a neutron star can reach a billion T (10⁹), and is thus named a magnetar.

Artistic image of the magnetic field of a magnetar. Magnetic fields are actually not visible, but its effects are dire. Getting to close will cause your atoms to flatten along the field and all your credit cards will wiped! Credit: NASA/Goddard Space Flight Center Conceptual Image Lab

So what can I say about magnetars? It almost sounds straight out of science fiction. Neutron stars are born spinning really fast. To create a magnetar, we hypothesize that a neutron star is born spinning just a bit faster than your typical neutron star. This rotation sets up a “dynamo effect” that ramps up the magnetic field. As the magnetic field increases it starts to produce a drag on the star. This causes the rotation of the magnetar to slow and the magnetic field to stabilize. Even though the magnetar starts out faster than a typical neutron star, it spins down much faster since the magnetic field is so strong and provides more resistance.

There is still a lot of research needed on magnetars to fully understand them, and there aren’t too many orbiting around. Out of roughly 1000 observed neutron stars only a little over 20 have been discovered to be magnetars. Our 1^st recorded observation of a magnetar was in 1979 as a wave of gamma rays rushed through our solar system peaking instruments in satellites and causing small anomalies in our atmosphere. Over a year later it was found to originate outside our galaxy in a super novae remnant within the Large Magellanic Cloud (our neighboring galaxy). This also meant that the gamma wave was over 180,000 years old. Since then we’ve been on the lookout. 

The Setting of the Sun Over the Pacific Ocean and a Towering Thundercloud, July 21, 2003 As Seen From the International Space Station (Expedition 7); Image Science and Analysis Laboratory, NASA-Johnson Space Center.

As with all good things, we have come to our last stop on our trip through the cosmos and should return to the land of blue skies and sunshine. But don’t think of it as returning home, think of it as the next stop to the most interesting place in our known universe. Of the rarest and most unique things we’ve discovered, Earth and its history is by far most unique to it all. I want to thank everyone who came on our journey, please leave any tips in the comments below. Keep looking up!