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Pulsar Acceleration Used to Calculate Milky Way’s Dark Matter Density

13 Jan 2021, 23:17 UTC
Pulsar Acceleration Used to Calculate Milky Way’s Dark Matter Density
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IMAGE: The ripples in the Milky Way disk are shown, along with the tidal debris from the Sagittarius dwarf galaxy. The pulsars analyzed by Chakrabarti and collaborators to calculate galactic accelerations are shown in the inset. CREDIT: IAS; Dana Berry

Pulsars — these fast-spinning neutron stars — are essentially rotating tops that have beacons of light that are emitted toward an observer twice per rotation, like the double-sided lights in a lighthouse. Just like a top, pulsars slow down with time, but the deceleration is so slow that, for the most part, we can use the timing of the pulses as a metronome against which we can measure all kinds of phenomena.

Back in 1990, the first exoplanets ever found were discovered orbiting a pulsar, and they were found because the slight orbital motions of the pulsar and the planet going round and round affected the timing of the pulses reaching Earth. I still remember exactly where I was when that discovery was made. I was a high school student working at a spare computer next to a laser printer at Haystack Observatory. It smelled like ozone, and my advisor was super excited to explain pulsar timing to me ...

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