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The radio source ASKAP J1935+2148 is an amazing thing. It blasts out radio waves once every 54 minutes, which is incredibly slow for a pulsar. Pulsars usually pulse somewhere between 1000 times a second and once every few seconds.

ASKAP J1935+2148 puts out 3 kinds of pulses in a rather random way: bright pulses, weak pulses, and no pulse at all. But if you fill in the missing pulses, you'll see the pulses keep the same period with an accuracy of 1/10 of a second. So I imagine it must be something quite heavy slowly spinning around, which has a patch that switches between 3 modes of radio emission.

It could be a really weird pulsar, but nobody knows how a pulsar spinning so slowly could put out radio waves. Another candidate I've read about is a 'magnetic white dwarf'. These are white dwarf stars that have strong magnetic fields. Nobody knows why! But also, nobody has seen one put out radio pulses. So this also seems like a long shot.

In short, it's a mystery! And that means we'll learn something cool.

For a nice account of this, try Astrobites:

• Magnus L'Argent, This ultra-long period radio signal can’t make up its mind, https://astrobites.org/2024/07/02/ultra-long-period-radio-signal-askap/

For even more details, try this:

• M. Caleb et al, An emission-state-switching radio transient with a 54-minute period, https://www.nature.com/articles/s41550-024-02277-w

The animated gif here shows an artist's impression of an ordinary pulsar, not ASKAP J1935+2148. It's probably been slowed down a lot.

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