Gravitational Waves Create A 'Cosmic Symphony' That Scientists Are Tuning Into

Space.com

Scientists are using pulsars to detect the gravitational wave 'hum' created from supermassive black hole mergers.  Credit: National Science Foundation (NSF)

Transcript

00:00Supermassive Black

00:29Wholes lurk in the hearts of most galaxies, and galaxies grow by merging with other

00:35galaxies. When that happens, their black holes also merge and grow, becoming more and more

00:41massive over time. How exactly this happens is not fully understood, but the universe

00:48is telling us its secrets in gravitational whispers. We just have to listen.

00:54Just as sound waves are vibrations of air molecules, gravitational waves are vibrations

00:59in the fabric of space-time. When two massive black holes spiral toward each other, they

01:05produce gravitational waves that travel through the cosmos at the speed of light.

01:10If we imagine the universe as a grand symphony, these merging supermassive black holes are

01:15the bass players. As they orbit each other, these black holes play the deep bass notes

01:21that echo throughout the cosmic concert hall. But that's not all there is to the symphony.

01:27In the background is a faint but pervasive hum produced by the collective motion of massive

01:32objects throughout the universe, from the earliest moments of the Big Bang until now.

01:38This gravitational wave background is truly a harmony of space and time.

01:44Nanograv is an NSF-funded collaboration of astronomers and astrophysicists. Our goal is to solve some

01:50of the deepest mysteries of the universe by studying the gravitational waves produced by these dancing

01:55monster black holes. These waves are light years long and can only be detected by the most

02:01extraordinary instruments. To measure these giant but subtle ripples in space-time, Nanograv created

02:09a galaxy-sized detector using some of the most incredible objects in the cosmos, rapidly rotating neutron stars, known as millisecond pulsars.

02:17Pulsars are the ultra-dense remnants left behind when massive stars reach the end of their lives

02:24and explode as supernovae. These pulsars are also cosmic beacons. They spin extraordinarily rapidly

02:30and with startling regularity, releasing pulses of radio waves with each rotation. Astronomers detect

02:38those pulses using giant radio telescopes. By monitoring the radio pulses from these ultra-precise

02:45cosmic clocks, Nanograv can detect the slightest deviations in the regularity of their time-keeping,

02:51and these deviations trace ripples in space-time. This galactic-scale detector is called a pulsar timing array.

02:57Nanograv has now observed an array of dozens of pulsars for more than 15 years, and the results are astounding.

03:07We are finally hearing the faint background hum likely coming from in-spiraling pairs of supermassive black holes.

03:15With time, astronomers expect to pick out the individual instruments in this cosmic symphony,

03:21revealing unique insights into the evolution of galaxies and the history of the cosmos.

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