Help us detect 50 neutron star collisions to be able to calculate the expansion of the universe, plead the cosmoboffins • The Register

According to new research, cosmologists need gravitational wave measurements from 50 binary neutron star fusions to determine how fast our universe is expanding.

The cosmos has been swelling since its birth in the Big Bang 13.8 billion years ago. Edwin Hubble, an American astronomer, discovered that galaxies farther from our own Milky Way were moving away faster, a sign that the universe was expanding.

The rate of expansion, known as the Hubble constant, is apparently anything but constant. When scientists try to calculate it by analyzing cosmic background radiation or studying stars and supernovae, they get different answers. Now, an international team of physicists thinks the conflict can be solved by probing a new data source: the gravitational waves of neutron stars crashing into each other.

"We calculated that by observing 50 binary neutron stars over the next decade, we would have enough data on gravitational waves to independently determine the best measure of the Hubble constant," said Stephen Feeney, lead author of the paper published in Physical Review Letters. and a researcher at the Flatiron Institute in the United States.

"We should be able to detect enough mergers to answer this question in the next five to ten years."

Although gravitational waves were predicted by Albert Einstein more than a century ago, they were observed for the first time in 2016. This confirmed sighting was produced by two giant black holes, 29 and 36 times the mass of our Sun, spiraling.

Some other events have since been identified and laboratories such as LIGO (Gravitational Observatory of Laser Interferometer) and the Observatory of the Virgin have been upgraded to be more sensitive and detect smaller gravitational waves. The first collision of neutron stars was detected in 2017, but cosmologists do not have enough resources to start calculating numbers to calculate the Hubble constant.

When two neutron stars collide, a portion of the resulting energy is converted into gravitational waves that wave in space – time. They provide telltale signs of the mass and distance of stars and allow scientists to determine how quickly they move in space to determine the Hubble constant.

"This will give us a more accurate picture of the expansion of the universe and help us improve the standard cosmological model," said Hiranya Peiris, co-author of the article and professor of physics and physics. of astronomy at University College London. ®