Podcast: Listening for Black Holes and Neutron Stars

Gravitational waves: what are they, and what can they tell us about our universe?

From pulsar timing arrays to ground-based interferometry, there are currently many strategies and instruments in the works to capture gravitational waves over a range of frequencies. Direct detection remains a highly-anticipated–and potentially imminent!–outcome of these vast projects, but what does it really mean? On this week’s podcast, we take a look at a range of instruments and techniques designed to capture these elusive signals. First, theoretical astrophysicist Dr. Chiara Mingarelli explains how watching distant pulsars for tiny changes in the timing of their flashes can tell us about supermassive black hole mergers and the gravitational waves these violent “spacetime storms” produce.

A NASA simulation of two merging white dwarf stars and the gravitational waves they produce.
Image: NASA

Next, we catch up with Dr. Kari Alison Hodge, a recent graduate from Caltech working on the Laser Interferometer Gravitational-Wave Observatory (LIGO), which uses lasers to look for tiny distortions in the lengths of 4-kilometer-long tunnels–a calling card left by passing gravitational waves. Collisions involving pairs of black holes or neutron stars generate gravitational waves with frequencies falling largely in the audio band, and we explore what a black hole merger “sounds” like before wrapping up with a look to the future and hopes for what a direct detection will tell us about black holes, galaxy mergers, and the fundamental nature of gravity.

Here’s a fun interactive tool that lets you select various sources to create your own gravitational wave background and then see which instruments will be able to detect it!

Want to know more about how LIGO deals with noise on the ground? Take a look at Dr. Hodge’s 2012 “Dance Your PhD” entry (a finalist!).

This demonstration shows how deconstructive interference works in an interferometer like LIGO.

Want more? Check out recent work on pulsar timing arrays by Dr. Mingarelli.

The “merger sounds” (extreme mass ratio inspiral and black hole binary system) included in this podcast were created at MIT by the Scott A. Hughes group in astrophysical general relativity.

– Podcast and post by Meg Rosenburg

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