What Happens When Neutron Stars Get REALLY Magnetic
Welcome to the Magnetar Page! You’ve probably heard some recent news about these objects and wondered about them. Well, we’re here to talk about them.
Magnetars are highly magnetic neutron stars, which are themselves the endpoints of stellar evolution for really massive stars. Astronomers first detected these magnetic monsters by the gamma-rays and x-rays that they emit. In fact, they’re also referred to as “soft gamma repeaters” due to the type of gamma-ray emission they periodically emit.
It’s tough to imagine a magnetar, but think of it this way: a small (say 20 or so kilometer-wide) object that is so densely packed that if you could near enough to scoop up a tiny spoonful of its matter, that spoonful would weigh 100 million tons! Of course, for a number of reasons, you couldn’t get near one — first, they spin very rapidly (up to tens of times per second) and their magnetic fields are among the strongest known.
For comparison, Earth’s magnetic field ranges from 0.3 to 0.6 gauss (or 30 to 60 microteslas), and 10,000 gauss makes 1 Tesla. A magnetar’s magnetic field strength is ten gigateslas (a gigatesla is a billion teslas, so that’s ten of those billion-tesla units). Very strong, indeed!
In 2008 the Spitzer Space Telescope showed a view of a magnetar called SGR 1900+14. Spitzer is an infrared-sensitive satellite, so what it was seeing was the ring of material surrounding and being heated BY the magnetar, which is itself the leftover remnant of a massive star.
Magnetars were discovered inadvertently in 1979 during observations of Venus. Two Soviet Venera spacecraft detected a burst of gamma-rays. In short order other spacecraft detected them, too. They’ve been observed since then, although the name “magnetar” is relatively recent. There are at least 13 known magnetars, with more to be discovered and confirmed. In 2008, NASA’s Swift Observatory detected radiation from a distant magnetar, and now astronomers are reporting on studies they’ve done of that objectusing ESA’s XMM-Newton and the INTEGRAL satellite (which sniffs out gamma-ray events). This one is giving astronomers a chance to study what they term an “extreme matter object” and hopefully understand more about their formation and outburst activity.
To learn more about magnetars, pulsars and neutron stars, visit the main entry for magnetars at Wikipedia, Robert Duncan’s Magnetars page, and another cool artist’s conception of these cosmic beasts at Astronomy Picture of the Day. Phil Plait, over at Bad Astronomy also offers his unique take on these beasts. And, here’s the press release page for the latest magnetar discovered, SGR 0501+4516. Check it out!