On January 14, 2025, the largest gravitational wave so far was detected. Today, these types of findings They are much more frequent than when the first of these waves was discovered, 10 years ago now. However, the fact that it was especially intense encouraged an international team of scientists to try something they had been wanting to try for some time: delve into the event horizon of a black hole.
Less noise and a lot of intensity. Since the first gravitational wave was detected, the techniques used have been greatly refined, so background noise has been significantly reduced. Therefore, today it is possible to detect direct waves, a “jet” of gravitational radiation that occurs just when the two event horizons of the black holes that collided give rise to a single one.
The study of these waves could provide very interesting information about black holes. However, a sufficiently powerful gravitational wave was necessary. For years, the authors of the study that It was just published in Nature They were exploring options, but they knew they were looking at the ideal candidate when analyzing one that was detected in January 2025.
Important concepts. Before understanding what these scientists did we must be clear what are gravitational waves and what is the event horizon. Gravitational waves are produced by a very violent event, capable of disturbing space-time like a stone falling into the water of a pond. Normally, said violent event is the collision of two black holes, which merge to give rise to a single one.
For its part, the event horizon is the theoretical limit from which nothing approaching a black hole can escape. Not even the light. When two black holes merge, we go from having two event horizons to just one. Just when that happens, that’s when direct waves form.
The event horizon of a black hole remains a great unknown in many ways
GW250114. The gravitational wave detected on January 14, called GW250114, was formed when two very similar black holes collided, one of 33.6 solar masses and the other of 32.2 solar masses. The result was a black hole of 62.7 solar masses. This is not the exact sum of the two black holes, because there was a surplus that was released in the form of very intense energy. This is how gravitational waves arise.
Before and after. Generally, black hole collisions can be observed before and after. The vibrations of the approach and the stabilization after the formation of the new black hole are studied. There is a lot of mystery surrounding what happens in the “during.” Therefore, studying direct waves could provide a lot of interesting information.
Finding the ideal fusion, these scientists identified the direct waves and proceeded to analyze them. As they had anticipated, this allowed them to extract data about the new event horizon. In turn, this allows us to extract data that cannot normally be measured from black holes, such as their rotation frequency or surface gravity.
Was Einstein right? Scientists have been studying whether Einstein was right for years. His theory of relativity covers so many phenomena in the Universe that, with each new one that is discovered, an attempt is made to verify whether its predictions are fulfilled. Thanks to this first measurement of direct waves, it is believed that in the future it will be possible to study whether these black hole mergers obey the General Theory of Relativity. Basically, they want to check for the umpteenth time whether Einstein was right.
Although for this we will first have to check if these direct waves can be detected together with other gravitational waves and, incidentally, if the resulting measurements are consistent with those that have been made now. This is just a start, but at least it is a small thread drawn from the tangle of mysteries that surrounds black holes.
Image | NOIRLab
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