While you may never have pondered the similarity between a common bar magnet and a star, astronomers do, and they believe they have figure out why the two disparate bodies are sometimes strikingly similar.
Magnetic activity on many stars, such as our Sun, varies a lot over days, weeks and years. Magnetic fields pop in and out of existence at different spots and overall intensity changes with time. But other stars have strong, consistent magnetic fields that behave just like the smooth and static field of a bar magnet. Astronomers call them magnetic stars.
In these magnetic stars, as with bar magnets, magnetic field lines emanate from each pole, north and south, and loop outward like the skeletal lines of a perfect pumpkin, connecting one pole to the other.
There are three types of magnetic stars:
- Magnetic A-stars are otherwise normal and about two to 10 times as hefty as the Sun. One example is Alioth, the third star in on the handle of the Big Dipper.
- Some white dwarfs, which are burnt-out stellar corpses, have magnetic fields 100,000 times stronger than the typical magnetic A-star.
- Magnetars are ultra-dense neutron stars that have fields 100 billion times stronger than a commercial bar magnet.
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