Researchers from University College London and the University of Potsdam in Germany studied the two most massive stars in a nearby galaxy and eventually turned into black holes and collided, sending waves through space and time. The black holes we see today were formed billions of years ago, when lower levels of iron and other heavy elements were floating around in the universe. As the universe aged, the level of these elements increased, making the phenomenon of black hole mergers less common.

Orbiting a common center of gravity and known collectively as binary stars, the stars are located in the Small Magellanic Cloud, just 210,000 light-years from our Milky Way galaxy. The stars orbit each other every three days and are the largest touching stars (contact pairs) ever observed. But it was their mutually destructive relationship that caught the researchers’ attention.

Using long-term data collected by the Multi-Unit Spectroscopic Explorer (MUSE) and other telescopes on NASA’s Hubble Space Telescope and the European Southern Observatory’s (ESO) Very Large Telescope in Chile, the researchers measured different bands of light from Earth. binary system. star (spectroscopic analysis). They found that most of the outer shell of the smaller star was stripped away by the larger one.

“This binary star is the largest contact binary system ever observed,” said study co-author Daniel Pauli. “The smaller, brighter, hotter star, with 32 times the mass of the Sun, is currently losing its mass to its larger companion, which is 55 times our Sun.”

According to the researchers, in the astronomical evolution scheme, it won’t be long before the small star turns into a black hole and the star’s role changes.

“A smaller star can collapse into a black hole only after 700,000 years, either in a spectacular explosion called a supernova, or so massive that it’s not an external explosion,” said lead author Matthew Rickard. of your study. “They will be restless neighbors for about three million years, until the first black hole begins to increase its mass by taking revenge on its friend.”

Their findings were confirmed by comparing gravitational waves observations made by the Virgo interferometer and LIGO, the Laser Interferometer Gravitational-Wave Observatory, with theoretical models of binary star evolution.

“Thanks to the Virgo and LIGO gravitational wave detectors, dozens of black hole mergers have been detected over the past few years,” Rickard said. “For now, however, we have yet to observe stars predicted to collapse into black holes of this size and coalesce on timescales shorter than the age of the universe, or even roughly comparable to it.”

Gravitational waves are invisible “ripples” in time and space caused by the most violent and energetic processes in the universe. The strongest gravitational waves are produced by catastrophes such as colliding black holes that distort space-time to send cosmic waves traveling at the speed of light in all directions. These fluctuations carry information about their origin.

“In just 200,000 years, at an astronomical moment, the companion star will also become a black hole,” Pauli said. “These two massive stars will continue to orbit each other, rotating every few days for billions of years.”

According to the results of the study, we have some time before the black holes collide. But when they do, they will produce gravitational waves that can be detected on Earth.

“They will gradually lose this orbital energy through the emission of gravitational waves until they orbit each other every few seconds, and eventually merge into a massive release of energy via gravitational waves 18 billion years later,” Pauli said.