Astronomers find double star system that keeps changing its behavior

A large cluster of stars 19,000 light-years from Earth harbors something strange: Within the cluster, a neutron star left over after a supernova explosion orbits a star not too different from our Sun.

The big picture: The Chandra observatory has been observing that star system — known as Terzan 5 CX1 — for more than a decade, and in that time, Terzan 5 CX1 has gone from looking like one type of star system to another and back again.

• As that neutron star orbits the other in the pair, its immense gravity pulls material from the companion star, forming a disk around the neutron star.
• All that material falling in on the neutron star makes it spin quickly, blowing away any extra material encircling the star and transforming it into what's known as a millisecond pulsar.

Yes, but: Chandra found this star system has gone from behaving like a more typical binary to a millisecond pulsar and then back again.

• It's not yet clear why the pair has done this dance multiple times, but scientists expect this is a phase in the evolution of these types of star systems.

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