Colossal Collisions in Space send Shockwaves through the Universe: Gravitational waves break records with new observations

Now University of Copenhagen researchers and their international collaborators have published a treasure trove of new gravitational waves that may challenge our fundamental understanding of black holes, gravity, and the universe itself. Among them the strongest signal and the largest collision ever recorded.

For millions upon millions of years, they orbited each other, bound by gravity. The distance between them grew shorter until, in a fraction of a second, they collided with velocity nearing the speed of light.

When the most compact and heavy objects in existence—black holes—merge, the forces involved are so immense that they ripple through the universe, sending waves that distort space and time.

"These are waves in spacetime itself—like ripples in water—that travel at the speed of light. They don’t move through space; they are waves of space: a rhythmic stretching and compression of the very structure of the universe," explains Jose Maria Ezquiaga from the Niels Bohr Institute, who leads NBI’s LIGO-Virgo-KAGRA group and contributed to the new scientific publications and observations.

Exactly ten years ago, Einstein’s prediction of gravitational waves was confirmed with the first measurement. Now, an almost identical black hole collision has provided gravitational wave researchers with a stronger and clearer signal than ever before: The measurement reveals two black holes, each having around 30 times the mass of the Sun.

"The properties of this merger are a type we know well from previous measurements. What makes this discovery truly exceptional is the very strong signal. It opens entirely new possibilities for testing our fundamental understanding of gravity and the nature of black holes," says Jose Maria Ezquiaga.

Already, the observation has confirmed—at more than 99% certainty—a longstanding theory by the renowned physicist Stephen Hawking, which states that a black hole formed from merging black holes must have a larger area than the combined area of its progenitors. Because gravitational waves fade quickly after a merger, it has previously been difficult to confirm the theory through observations. But the strength and clarity of the new record signal has made it possible.

The spacetime disturbances caused by gravitational waves are extremely small. To detect them, researchers must measure changes that are 700 trillion times smaller than the thickness of a human hair.

The reason the signal from GW250114 - the name given to the collision - was so strong is largely due to the advancements in measurement equipment made by the LVK collaboration. This development continues and promises a bright future for the field.

The strongest measurement vs. the biggest clash

The record-breaking measurement is part of a massive package of gravitational wave observations now released by the research coalition. Not only does it double the number of gravitational wave measurements available for study, but thanks to several remarkable observations, it marks a significant leap forward for the field.

GW250114 is not the only record among the group’s new observations. They also include a measurement of the merger of two black holes weighing approximately 100 and 140 solar masses, forming a black hole of at least 225 solar masses: the largest black hole merger ever observed.

Until now, researchers have seen that binary systems—where black holes orbit each other—typically have masses up to 50 solar masses. Beyond this, the number of observations drops significantly.

GW231123, the name of this collision, breaks that pattern. The resulting black hole may weigh up to 260 solar masses, placing it outside the normal classification of “stellar” black holes formed from stars, and instead into the range known as intermediate-mass black holes—between 150 and 100,000 solar masses. This size is extremely rare and puzzling to scientists.

"The observation challenges our understanding of how black holes form. Black holes of such large mass shouldn’t arise through ordinary stellar collapse. One possibility is that the two black holes in this system were themselves formed by previous mergers of smaller black holes, but in truth, we don’t know. It’s also possible that the signal was distorted as it traveled through the universe," says Jose Maria Ezquiaga.

In addition to their extreme masses, both black holes rotate at unusually high speeds, making the observation even more remarkable. The downside, however, is that this signal is very short and weak compared to GW250114, which makes analysis and interpretations much harder.

A research field driving innovation

Einstein predicted gravitational waves nearly 100 years ago as an inevitable aspect of his famous theory of relativity. Ten years ago, the theory became empirical reality when the first gravitational waves were measured. Now, the decade is marked by a wealth of new observations, including these two spectacular ones. Both studies are milestones that demonstrate we can not only hear the universe’s deepest resonances—we can begin to decode its structure.

As often happens in physics, the fundamental research driving these discoveries can also lead to new technologies. Already, the extremely sensitive instruments used to measure gravitational waves have led to new types of lasers and optical systems in quantum computers and atomic clocks, and AI techniques are used to reduce noise and much more.

The development is expected to continue. Future waves of observations are anticipated to eventually include all gravitational wave signals from black hole collisions that the universe has to offer. This will be achieved by expanding the LVK collaboration with a new observatory in India and through planned new instruments.

"We expect this research field to be crucial for our fundamental understanding of the universe. We’ve only just reached the end of the beginning," says Jose Ezquiaga.

The research article on the observation GW231123 has not yet passed peer review but is expected to do so very soon. The article on the first mentioned observation, GW250114, can be read in the journal Physical Review Letters.