On June 28 scientists announced the first evidence of a background of long-wavelength gravitational waves that fills the cosmos. The background ripples were detected by NANOGrav.
Key points
- These waves are thought to have been created over eons by supermassive black holes, up to billions of times the mass of our Sun, circling each other before they merge.
- Detecting the gravitational wave background is analogous to hearing the hum of a large group of people talking at a party, without distinguishing any particular voice.
- This findings prove that the motion of black holes and other massive objects through space can create ripples in the fabric of the universe, called gravitational waves.
- The background ripples could help scientists better understand how gravitational waves are created and what happens to them as they propagate through the universe.
- They could also be used to study supermassive black hole mergers, events that can last for millions of years.
- Scientists think these mergers happen in most galaxies and influence their evolution.
- The discovery complements the first-ever detection of gravitational waves in 2015 by LIGO, the Laser Interferometer Gravitational Observatory. Those signals, at a much shorter wavelength than the new discovery, were from black holes about 30 times the mass of our Sun.
- Background hum from all of the other ‘sounds’ in the Universe was incredibly challenging. But scientists were able to do it using pulsar timing arrays.
- Pulsars are a type of neutron star, the remains of once-massive stars that have died in a spectacular supernova, leaving just a dense core behind. These rotating stars act like cosmic lighthouses, with their beams of radio emissions sweeping over Earth at precise intervals.
- Gravitational wave ripples should, in theory, produce tiny irregularities in the timing of these pulsar flashes.
NANOGrav
- The background ripples were detected by NANOGrav.
- The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) is a National Science Foundation-funded Physics Frontiers Center of more than 190 scientists from the United States and Canada, including scientists at NASA’s Jet Propulsion Laboratory in Southern California and other NASA centers.
