Astronomy

Cool hearing about NANOGrav for the first time! Looks like it is a consortium of 70 institutions that are using radio telescopes to observe 79 pulsars in the millisecond range.

The pulsar acts as the reference clock at one end of the arm sending out regular signals which are monitored by an observer on the Earth. The effect of a passing gravitational wave would be to perturb the local space-time metric and cause a change in the observed rotational frequency of the pulsar. Hellings and Downs extended this idea in 1983 to an array of pulsars and found that a stochastic background of gravitational waves would produce a correlated signal for different angular separations on the sky.^[https://en.wikipedia.org/wiki/North_American_Nanohertz_Observatory_for_Gravitational_Waves]

Their data does not show a signal for gravitational waves yet but they are getting close. The new model from the article will help predict what a "stochastic background" would look like.

This isn't about primordial black holes though as the title suggests. It's just that the new model predicts heavier galactic super-massive black holes than prior models.